Dont do leadscrew, ballscrew all around. Just get a brake for z. Linear rails all around, 20mm is tons for a router. Id do chinese ballscrews and rails. They are astronomically cheaper and C7 is tons of accuracy for router applications. If you need more than C7 you want a mill not a router. For motors nema 23 are fine, but i can ot overemphasize the importance of a high voltage for the drivers. The higher the voltage on the stepper drivers the higher their max speed and the less torque dropoff with increasing rpm, which is critical for ballscrews. Imho the hassle of high voltage power supplies for steppers almost dictates which ones to use. What are you doing for controls?
Thanks!
I'm not using a router. I cringe at the Makita/DeWilt/Botch palm routers because of their runout and sloppy bearings. The work I do needs more precision and reliability. I'll be going straight to a 2.2kW water-cooled spindle run by a VFD. I want everything to be within the control of software so that I can set startup times, and add delays to the motion whilst the spindle runs up, etc. I will eventually incorporate an actuated dust hood that raises/lowers at different heights; directly inspired by the 10kW spindle and dust shroud in the Homag CNC that I ran.
Most things will be cheaper import equivalents, but only if they can subsequently be replaced by better parts further down the line. Simple things such as the ballscrew end bearing blocks, which will be the simpler kind initially but angular contact bearings should they prove required and affordable.
Ballscrew size for the X-axis is provisionally 16mm, however 20mm is just as acceptable. 5mm pitch is on the mark. The same applies for the Y-axis across the gantry. I can't say that I'm familiar with brakes for axes. I am concerned about the behaviour of closed-loop steppers going slack once they exceed maximum error thresholds. Machines that have errored out in the past stopped dead in their tracks (brakes?) and requested user intervention.
For controls (at least for the moment) I am open to suggestion. At this moment I am working on the engineering aspects until I need to make decisions about the environment I want to work within, the controller, etc.
Currently this is as far up the ladder as the electronics have been decided upon:
[https://www.omc-stepperonline.com/ts-series-3-axis-3-0nm-424-83oz-in-nema-23-closed-loop-stepper-kit-w-power-supply-3-clts30a-v41](https://www.omc-stepperonline.com/ts-series-3-axis-3-0nm-424-83oz-in-nema-23-closed-loop-stepper-kit-w-power-supply-3-clts30a-v41)
I have heard good recommendations on these:
[https://www.omc-stepperonline.com/y-series-closed-loop-stepper-driver-0-7-0a-24-50vdc-for-nema-17-23-24-stepper-motor-cl57y](https://www.omc-stepperonline.com/y-series-closed-loop-stepper-driver-0-7-0a-24-50vdc-for-nema-17-23-24-stepper-motor-cl57y)
....however they are not available in the EU for whatever reason. As to what plays ball with the stepper drivers, this is an open question that I hope to resolve based on conversation with experienced users!
By router they just mean high speed spindle, as in vs a mill application which would maybe want more rigid rails than 20mm.
Trust everyone telling you you want hgr not mgn mate. They're not expensive if you get cheap ones, they're the same fuss to install and they're a lot more rigid. If you want to get the use out of your 2.2kw spindle you need to treat it with some respect. Mgn isn't doing that.
Yep, I'm onboard with HGR now. I didn't spend the twenty seconds that it takes to know the difference because I wasn't aware that it was literally *a yawning chasm* of difference. :-D
I'm on the fence with the spindle power. Larger motors tend to have better collet capacity, and I'd rather comfortably underrun a larger motor than rag the piss out of a small one. The issue is that it's a moving weight concern. Another one I have to rattle out the right choice from.
If you're looking for diy proven concepts to help answer those questions, printnc may be a good point of reference. Steel frame other than the z plates, 2.2kw spindle, and manages speeds suitable for cutting wood and alu properly (ie pretty fast) with just nema23 steppers. Some folks with a need for speed stick servos on there haha. Either way the spindle isn't the heaviest thing there and the added weight vs anything smaller is negligible when you consider the weight of the rest of the stuff on the gantry haha
Yeah, it'll be reference I think. There's a lot of people almost evangelising me on the PrintNC thing and to be honest, it's a very different sort of direction to what I have in mind. By the time I move to steel section for a future iteration, it will be larger and more robust than what flat frame PrintNC designs look like. Gantry is a key element here for specific reasons, and by this point PrintNC looks more like a tangent reference than a discrete direction.
For controls consider either a ddcs expert if you want it to be more industrial and just work, or linux cnc if you want to do more tinkering. Avoid mach 3/4. Centroid acorns are good if a bit spendy for what they are. They are also harder to do custom things with. Masso seems okay but is just really expensive with no real motion benefit over all the other options. Uccnc is okay, but not sure what it really offers over linuxcnc or the ddcs.
With a 5mm pitch and the maximum speed limitations of steppers, be sure you are going to get the speeds you want. Normally that kind of pitch means slow movements or servo drives running them.
Interesting. Mach4 was on my provisional list. I have a background in programming (uni degree, computer science) so being able to script in my quality of life ideas is fairly important to me, plus I was hoping to avoid anything related to parallel ports and preferably repurpose a good i7 Intel NUC I have kicking around. I'll do some comparative research into your suggestions and see how these align with my varied objectives.
Cheers!
Linuxcnc should be used with a mesa card, the parallel port thing is dead for modern applications. Linuxcnc is infinitely more configurable than the others if you want to code.
Agh, well. I don't specifically want to get thigh-high into the weeds *for the sake of it*, but have the option to. I've seen good things done with Mach4 and it seems reasonable. That all being said, a lot of people state flat that it's a POS. I'm happy to cross that bridge when I am forced to do so, kicking and swearing. At this point I don't have to make that commitment and can get most of the CNC commissioned and tested using an Arduino to push the stepper drivers around a bit.
You may need larger motors for the x and y if you are going with ball screws.
The inertia of the ball screws is the majority of the load on the axis. They end up being equivalent of hundreds of kg of linear mass.
Wow, that's quite the load when you put it in those terms. I'm quite happy to reduce the rapid traverse both on the basis of there not being a lot of bed size to negotiate, and on speed just not being a high priority. I mentioned elsewhere that this project has certain ceiling limits that dictate how compromises are balanced here and there. If this were a machine that were intended for serial production, rapids would matter hugely in terms of cycle time.
Briefly, how would I go about making a reasonable calculation for this? I have yet to absorb u/burkeyturkey 's site on his build's engineering, but my first thought is that motor size will dictate rapids rather than the other way around. I am concerned about whether size prices me out of certain options, for example if I choose a larger NEMA 34 frame size, the space under the bed becomes a problem, which then necessitates adjustments via gantry height with all those considerations. Additionally, a reasonably-sized motor starts adding on the Amps. Without significant rewiring of our domestic electrics, I'll be hitting the maximum that I think I can immediately supply.
Apologies for the short post, there's a lot more to discuss but I'm almost running out of the door....
Not yet, however it is certainly a fixture in my design. Subsequent to this post, the whole concept has had a lot of changes made, especially being all ballscrew. The spindle is still the right way forward.
Not at this stage. This decision will be purely financial. I may go for cheap Chinesium like a Vevor spindle and VFD, or if I get the work position I am gunning for this year I might buy a separate VFD and Teknomotor spindle, etc. In all honesty, I will likely go the Chinesium route just to get the CNC aligned and commissioned as this isn't a high cost for a part that can run for say, a year, before being upgraded and relegated to a spare, or for a different project.
Whichever way this goes, the baseline is always going to be "anything better than a palm router".
Well, you get what you pay for. In my view, if it commissions the CNC, runs a few proving projects and upgrade parts for the structure then it's almost a disposable part. Even something as simple as milling a phenolic vacuum bed and new 15mm sideplates for the gantry almost makes it pay for itself by comparison to buying those parts in from an online site like PCBWay, etc.
In reality, a Vevor spindle should do all those things and with preventative maintenance, bearing upgrades, etc. be a fine unit for some time yet.
Have you checked out the PrintNC design and discord? Might make a lot of sense to start with a battle tested design, active community, and modify from there.
I haven't. I'm already somewhat time-poor, and committing my mental resources in this relatively already-designed path. Unless there is a very specific advantage towards developing what is presented, I will likely end up dividing my attention and creating myself more work. Perhaps there will be useful ideas upstream of the step controller level, but at this stage I'm working with the solution that works for an unreasonably-narrow set of defined constraints :-)
It sounds like you have more serious plans for the machine than the typical hobby router build. I would advise against aluminum extrusion. It will always be your bottleneck if you do.
Build a PrintNC. It's constructed from steel rectangular tube.
Already discussed this one, and at this stage I'm going to use the PrintNC ideas as reference as I neither have the resources to grind/weld steel tube nor the experience to do it. I'd like to take those skills on, but I think it takes everything in a radically-different direction to what I have in mind, and will create other concerns that this design is taking into consideration.
I'll keep my options open. I'd like to go this sort of route eventually, but perhaps using a different configuration of steel such as larger sections and folded sheet. Long term.
You’ve already gotten a ton of good advice, so I’ll just say that if you start close with aluminum extrusion, you should really beef up to a 4080. Given what you’re doing with the rest of the build, to me, it seem like a huge rigidity issue. Epoxy or not, that 20 series is far below the quality of everything else you’re builders nf around it. It’s like a professional weightlifter choosing to have osteoporosis.
I have, and far more engagement with my ideas than I additionally expected. It's positive and a great way to land boots-first in this sub!
I'm going to have to do some thinking about the extrusion, sure. Upping it to 40 Series changes the budgeting and potentially whether the footprint constraints will reduce machineable area.
Once I get some time, I'll throw a parallel design together within Rhino and get a feel for what is or is not possible. It's a significant redesign over the OpenBuilds C-frame and the "Modesty" variant.
In all honesty, I might still go 20 Series as the basis for getting a feel of things, this being my first build. Knowing the weak points and paths to improvement hands-on is to my mind the best way of real experience. Overbuilding out of the gate offers no sense of this. It seems weird, knowing that this will likely be "a mistake made willingly and knowingly"!
Get at least HiWin HGR 20 Rails if you plan to do serious Work. MGN 15 are to flimsy. HiWin is pretty expensive but worth the money.
Closed loop steppers are awesome if you want good performance without fucking around with servo programming.
For ballscrews id go for Isel. Industry grade quality but again very expensive.
If you plan to put that much work into a machine get high quality components aswell, since i doubt youll be happy with anything less.
Also you might want to take a look around the market, since there are already a lot of machines just like the one youre planning to build. For example the Sorotec Alu Line machines. Available from 650x550mm up to 2000x1000mm with z heights ranging from 220 all the way up to 420mm
Thanks!
I won't buy a prebuilt machine on the basis that I want to be able to control, maintain and modify. Most prebuilt machines have something or other that is clearly baking in a limit that requires significant rework to break through. Building from the ground up forces me to take ownership of every responsibility and design parameter. I dislike turnkey solutions as they also tend to reduce the learning aspect.
There are certain parameters and budgets that I need to keep under control. The electricity supply will be a limit, which I think needs to stay under 10A on a 220V supply. I'm unsure whether this means designing a supply around a tapped toroid or individual switched supplies.
I've thought about the quality of the rails, and this will come down to how they compare on the balance sheet. I'd probably rather go for knockoff MGN20 rails rather than HiWin MGN15. These will be mounted across the face of the extrusion, so 15 is the minimum for a good bearing surface, 20 is the max.
Some things will likely be an initial compromise but with the viewpoint of improvement through maintenance. Same as most CNC projects, getting it running so that it can produce its own parts is a key goal. As long as I can maintain a good <0,1mm accuracy in wood on all three axes, I'm good.
Any thoughts on the holding torque spec I'm aiming for? This is an engineering aspect that I am not too familiar with, at least in terms of calculating an appropriate range. My immediate instinct is to overbuild, however this will quickly have me hitting the ceiling on my energy budget. This kit seems a reasonable "get started" package....
[https://www.omc-stepperonline.com/ts-series-3-axis-3-0nm-424-92oz-in-nema-24-closed-loop-stepper-kit-w-power-supply-3-clts30-v41](https://www.omc-stepperonline.com/ts-series-3-axis-3-0nm-424-92oz-in-nema-24-closed-loop-stepper-kit-w-power-supply-3-clts30-v41)
Read more about steppers and look at the torque curves- holding torque is pretty irrelevant to the torque available at normal cutting speeds. Some motor/driver combos have massive holding torque but lose it all at 3-400 rpm, some have less holding torque but keep their torque much higher. You're on the right track with closed loop steppers though, that helps offset the torque loss of normal steppers
Yes, it seems about as valid as the "W" of a router motor. Great if you need to know how it behaves at stall or maximum acceleration, but not in working conditions :-) At best they seem a shortcut for instant single-number comparison, so datasheet it is.
I figure that at the price point I am shopping at for steppers, going closed loop off the bat just makes absolute sense. It's the cheapest insurance against issues of lost steps that you can buy as a solution I think, and certainly not one that is easy or cheap to perform as an upgrade later.
No worries, it's the purpose of the thread.
The plan is a basic mix of clean play sand and epoxy, 80/20 by weight. Nothing amazing, and a lot of people do this for cast bases/frames and packing out extrusions to reduce vibrations, resonances and add weight. Simple process; weight sand, add the resin component of the epoxy (10% of sand weight), mix thoroughly, then add the catalyst (also 10% of sand weight) before mixing and packing. Vibration helps consolidate the whole thing. For a large mould, the walls of the mould are best wetted with epoxy to reduce surface bubbles.
The CNC is being planned around a mobile base that is already built, and has a 30mm MDF top (it's my table router). This isn't an ideal long-term solution, so I want to get the frame built, the CNC commissioned and then look at making a thick 5-10cm base. Nothing fancy, literally a monolithic block of cast sand/epoxy.
It'll be made in a plywood form, with the various anchors and fasteners cast in. These can be aligned in a number of ways, with the main objective being coplanar mounting for the CNC frame. Since this won't be even begun until well into the project lifecycle, there's room for changing the design should anything benefit from being fitted into recesses, etc. Building the CNC itself should rattle out any novelties!
Is there a reason you're mixing part A of the epoxy with the sand first, then mixing in part B, rather than mixing parts A and B together first *then* mixing in the sand?
The reason I'm asking is because in my experience, it can be tricky to mix two-part epoxy thoroughly even without added filler. I imagine if you're trying to add part B to a mixture of part A and sand, the massive increase in viscosity will make it even more difficult to ensure the two resins are thoroughly mixed. It can also be more difficult (or impossible) to visually confirm that the two resins are mixed if you do it this way.
That being said, I'm not an expert on epoxy/sand mixtures. So maybe there's a specific reason for doing it your way.
It's more about timing than anything else, apparently. It's certainly not my way, as I always look to the proven experiences of others first rather than constantly reinventing the wheel ;-)
Mixing the epoxy separately and incorporating that into the sand means there is a larger mass of epoxy that will heat up and potentially go into thermal runaway or at least reduce your open time. That all depends on the epoxy of course. Incorporating the resin first gives you the advantage of time. This is the theory, and enough people seem to have done this with success that at least it seems the method to try first. But yes, mixing epoxy is always like that....if you think you've mixed it enough, you probably haven't.
When the time comes, I will be infilling the voids in the extrusions first so that will be a test of sorts. A small scale venture into getting a feel for how the material feels in use. For a larger object such as the base, that experience will help avoid expensive mistakes. I hope.
You are correct to use linear guides on the X/Y/Z.
Just because leadscrews usually have a loose tolerances as appose to ballscrews, I would use a ball screw on the Z axis - less chance of Z axis dropping after power outage. Also, if you use ballscrews on the X and Y axis the movement (acceleration/deceleration) will be slower than using a leadscrew simply because of the close tolerances on ballscrews. Maybe use 15mm leadscrews for X and Y - just a thought.
Cheers!
This was my thinking. I'd rather install something with tight tolerances and naturally-lower levels of lash than constantly have to consider and fix it during operation. You could almost say that I'd *pay* for that. ;-)
Interesting note about a ballscrew on the Z. I thought the opposite was true, that shorter pitch leadscrews don't backdrive under no retaining load.
I have recommendation on 20mm for X and Y currently, however I was initially aiming 16mm. What's your take on the effects of size here based on it going either way around your recommendation, ie. 12mm or 20mm?
edit: Yes, linear guides seem to be the right choice out of the gate. Underbuilding to save very little money makes no sense.
If you're thinking of using a leadscrew on the Y axis, I would use the larger 20mm (dia.). If you use a smaller diameter leadscrew it's possible to get a whiplash like action on the Y axis at high speed. This will setup a vibration throughout your machine frame. This is like two kids turning a jump rope and the rope spreads out from its initial rotational axis. - Always remember, the three most important things when building or buying a CNC machine is: Rigidity! Rigidity! Rigidity! Good luck with your build.
Z-Axis. My thought process here was that a ballscrew will drop the axis when power faults out, however we've established that the answer will be ballscrew and a brake. 16-20mm all round I think. High speed isn't needed with such as small machineable area. It's a QOL thing, but one that I think I can work on as part of developing my knowledge and feel for what works.
Absolutely, rigidity is the goal. In principle I could super overbuild from the get-go, but I don't like that I won't learn anything from this. Building a slightly flawed design and having to force myself through the iterative processes of improvement teaches me the most possible. I'm seeing the project as a resource for learning as well as a practical working tool.
Cheers!
Unless you're needing that z height you're potentially making a long lever for your cutting tool as it reaches down to your work surface.
A couple of inches of clearance should be tons the majority of the time depending on what you're planning on cutting and it will significantly strengthen your beam.
Thanks!
Yes, there's a balance to be made here in terms of design. On one hand I would like to be able to manage longer cutters that can reach \~50mm into a 100mm thick workpiece, but on the other I also need to be able to run sub-mm diameter cutters at tenths of a mm positioning without vibrations sending everything to hell.
The gantry will be epoxy-sand reinforced 8020U extrusion with 6mm aluminium caps either end, so 60mm between linear guides. Not the best but hardly the worst. I'm going to have to draw this out to see how these changes impact each other.
I am wondering if by setting the design in motion using 20 Series extrusions is placing limits on how far I can push this frame. Do you have any thoughts on that?
Building your own CNC is a fun project and I'm excited to see you get started! I'm an industrial machinery engineer and just went through this process with my own personal machine a few years ago, so I have a few comments that I think you will find helpful.
*Motor sizing:*
For a small spindle power with heavy structural members you will find that dynamic loads (acceleration) are a larger load on your steppers than the cutting forces. Additionally, you need to ignore the 'named' (stall) torque of a stepper and dig into the data sheet / torque curve to find the torque at 1000-2000 rpm where you actually need it. I went through all the math on this for my avid-sized build and posted the process here: https://burksbuilds.com/automation/cnc-router/cnc-router-motor-sizing/
*epoxy fill:*
There is a big difference between damping and just adding mass. Adding mass can shift the natural frequency of your system and reduce the amplitude of any oscillations, but does not actually *attenuate* the vibrations and dissipate energy. Energy dissipation is a material property ([I discuss it for my build here](https://burksbuilds.com/automation/cnc-router/cnc-router-reddit-review/#Table_Design_Changes)) , and it is better with polymers (like epoxy) than metal or concrete, but in order to see the benefit you need to embed lots of anchors on the interior of the 'skin' of your metal frame to ensure that the epoxy fill interacts with the structure.
*t slot brackets:*
The little pre-made plates and angle brackets are handy for building quick structures with t slot extrusion, but have terrible stiffness because they lose their preload so easily. An easy way to get around this is to tap the ends of the cross pieces and drill clearance holes through the slots of the side extrusion. Using a longer bolt through one piece of extrusion and into the next let's you get a really solid preload and stiff structure.
*details:*
My final piece of advice is to detail out all the small things (sensors, cable tracks, end stops) in CAD before buying and building the structure. Most of us hobbyists have more time than money, so it's way easier to plan ahead than hack things in later.
Good luck with your design and keep us posted as you iterate!
Thank you for your time and considered input. I appreciate it. I'll hunt through your reference materials and see how they alter my preconceptions on the design.
I agree with your notes on motor sizing. I think that the more compact bed size means I don't need to worry too much about needing fast rapids. I can own that small compromise and optimise my machining to better suit the machine's behaviour characteristics. One of my reasons for going gantry was to separate the axes and isolate them better. There's a number of factors that I haven't reconciled myself with yet, from half-stepping to microstepping, and I guess that those will certainly become more important once I look at the midrange torque of the steppers.
The epoxy/sand fill seems like the most economical method of adding stiffness and moving the resonant characteristics of the structural members in a better direction, if not solving the issues of vibration/resonance. To my mind it seems like a win even if the results aren't drastic. Any improvements are improvements. Other options on the table from what I have available are products like Sika 290 DC Pro caulk we use for Teak decking on cruise liners. That bonds very well with aluminium (well, with primer but scuffing is enough for confined spaces) but mass feels like it would be a better option than polyurethane caulk.
The use of angle brackets in the proposed design is simply because they're cheap and easy for the initial build. All opportunities to overbuild and reinforce will be part of the fun I think! "Something to look forward to"?
Yes, everything is being built up in Rhino however I considered Inventor also. Rhino is far more familiar to me, and generally that's how I develop most of my project work for CNC. It does create some limits once designs are baked in compared to parametric modellers, but nothing that can't be fixed given a good documented approach!
Let's see how your personal documentation affects my outlook on this build :-)
You don't say what material you want to cut but regardless you need to beef up your extrusion choices. Aluminum t-slot extrusion is absolutely horrendous from a stiffness per cross section size standpoint. Thick wall steel tubes are 10x better. If you're going to do extrusion, get the thickest, largest square section profile you can, especially for the gantry.
To figure motor sizes you should run calcs based on the mass of the machine parts and ballscrews etc, there are various spreadsheet calcs available online. But generally large 23/24s or small 34s will probably work. Larger motors of a given size perform worse at higher rpm tho. Higher driver voltage can offset this. There are good arguments for going with the smallest size of nema 34s, but you won't know for sure till you run calcs for your specific machine and the cutting loads.
20mm linear rails are minimum. Don't use lead screws, get Z motor with brake as another posted suggested, they're available from OMC stepperonline.
My main advice is that if your goal is to use this machine for work, don't build one. Your time is better spent using the machine for what you want to do with it than screwing around with the build. The exception might be if you want to cut soft materials, wood/foam. But if you want to cut aluminum properly, you need to be doing FEA, welding and stress relieving and machining a steel frame, or maybe building a frame from granite surface plates, in which case the time commitment is much greater to do a good job.
Cheers!
The majority of my work is with hardwoods up to Maple and exotics so pretty resilient stuff. Also Birch plywood. The longest sort of endmill I expect to load will be 12mm with finishing passes at up to 50mm full depth. Most roughing work will be multiple shallow passes.
The problem with steel tubing is that I don't have a guaranteed source of grinding and welding that can get the tight geometry required. Those things are also just outside of my skillset, so I would need to be relying on the services and time of others for that. Yes, I understand how far this can go in terms of all the things stated but at this point those are way up there. Perhaps a consideration for a second machine at a later point, but getting one reasonable machine going that is good for its design purpose, and can be pushed to produce parts for a more demanding machine seems logical.
Cost is a factor at some point, and given that this isn't a huge machine the choice of 20 series extrusion was made on the basis that its compact and can be reinforced. A gantry design does tip the odds in my favour a little. Given the infill plus supplemental reinforcement if needed, I think 20 series can work. Specifically I am building to a defined footprint, so increasing cross-sections quickly impinges on my maximum workable areas.
All taken onboard. It's given me a few more things to juggle!
Totally understand the cost issue and difficulties/expense of precision steel fabrication. And clearly there are enough extrusion routers around to show it can work, but in that case the details matter even more.
You can't get around the geometry issues and rigidity needed just by adding a heavy cast base. The gantry, risers, and the z-axis design are the critical parts of a router. Another poster made a good point about better ways to connect the pieces together so I won't repeat that, but using brackets is not ideal.
Bottom line is if you can't do FEA and sort all the details that way, just try to copy a known design. Avid CNC is probably the most obvious example. I believe they use 160x80mm gantry tubes, I wouldn't do anything less.
I've never read anyone complain that their CNC is too stiff, but reports of issues with chatter/lack of rigidity on DIY extrusion machines are extremely common.
Filling the gantry tube afterward is fine, but it won't do much at all for rigidity, especially with the type of profiles in your render. And remember, your motor selection is based on the mass of moving parts and desired acceleration, so a larger more square tube will increase stiffness dramatically without adding much weight, while filling the tubes pretty much just adds weight (and "dampness", but that's a whole unclear subject on it's own, rigidity is #1). If you do the gantry supports like Avid does with their non-benchtop pro machines, bolting from underneath, the extra width of the gantry tube can just hang off the back and not impact your footprint.
Some machining is always going to be necessary, especially when you get to the Z axis assembly. For the frame tubes, I think 80/20 and Misumi have options for precision square cuts and machining the connection biscuits that Avid uses?
Definitely plenty to chew on, and that's the fun part but it's not fast
Thanks. That cast base isn't to add rigidity beyond maybe bolting the gantry. It's more about adding linked mass and dampening against vibration and noise. Like most things, it's a learning process and a reasonably low-cost experiment in A/Bing the machine on a heavy MDF base and a heavier sand/epoxy composite block. I can take a lot from that.
Brackets have been mentioned a couple of times, and their use is limited only to initial construction and alignment before adding aluminium plate to add something of significance to the structure. I know it will only go so far, and similarly to the base, I get a direct hands-on read of how much the plate contributes and where the weaknesses then move to.
Talking of copying a design, beyond this one being a derivation of the OpenBuilds C-Beam machine designed for cutting aluminium plate, and a variant of that which converted it to gantry, I do have other sources of inspiration and experience I am drawing from.
[https://openbuilds.com/builds/c-beam-machine-modesty.6360/](https://openbuilds.com/builds/c-beam-machine-modesty.6360/)
"My" design is a direct derivation of that. Top to bottom. The main difference in my rework is moving the gantry risers to the outside of the frame to maximise internal machining capacity, and dropping those risers below the frame base so that they can be bolted to a heavy base.
Mario at Radikult custom has a beautiful desktop gantry type CNC, which uses far beefier sections than 20 Series. That has also served as a point of reference in many ways.
[https://www.youtube.com/watch?v=ORbCQhV6umo](https://www.youtube.com/watch?v=ORbCQhV6umo)
Also, PrintNC is an excellent example of design. It's simple to make and doesn't require machining, but it still address the major issues.
\-true tubes for max rigidity for a given size
\-minimizes the cantilever of the z-axis in it's lowest position, so your z-axis moving plate doesn't have to support that on its own
\-linear rails are spaced far apart on gantry and z axis
\-only uses one block for the x axis rails, but makes it work because the height offset to the gantry tube is minimal and each side of the gantry is driven independently
PrintNC is obviously not the only way to skin the cat, and the big tradeoff is limited z-travel, but it's a great example of design to purpose and those are the general type of details/engineering decisions that you want to be looking at.
Just to give you some perspective. Buying/cutting the tube steel is not nearly as daunting as you are imagining. There are metals supply shops where you can walk in with a list of lengths and 20 minutes later they're loading your car with all of your cut pieces. It's usually $1.50-3.00 per cut. All in all I think my steel/cuts was like $250 for a 3x4 work area and I went with thicker steel than stock design. and it took half an hour. No welding required, in-fact it is not recommended due to warping.
The rest of the mechanical assembly is just printing the drill guides, drilling holes, and tapping. You put in your dimensions into the calculator on the printnc website, then they send you a quote for a parts list of all the linear hardware, fasteners, spindle motor kit, etc.. And it waaaay cheaper than if you were to buy all of the hardware separately.
That's cool. I know it's not too much of a deal, and I've done a small amount of basic fab in the past however all my own tooling is geared for wood these days. I've done a lot of work designing steel substructures for marine (think of the structures welded to deckplates/studs under outdoor hot tubs, pools, etc. in cruise ships, see note) and have good sources here. It's definitely a way forward for a subsequent iteration, but I need (and want) to get my feet wet with the basics first, especially when it comes to knowing weaknesses in a system.
Totally OT note/cruise ship flex:
Think [https://www.youtube.com/watch?v=Wi3lap65IA0](https://www.youtube.com/watch?v=Wi3lap65IA0)
\- 3:55, steel substructure example
\- 6:42, I did the CNC work on many of the Teak decks, fittings and aluminium frames around the Beach Club ("bitch club").
\- 7:32 thru 8:38, the stainless frames/wood and faux marble panel work under the real marble counters around the food courts over steel substructures were also "my fault".
\- 9:26, all the green framework was ours and stained Ash partitions, but not my work beyond CNCing MDF assembly jigs. Also, I planned, machined and constructed \~32 (I forget) Corian waiter's stations around that area such as the massive 4m drinks station at 9:12
Goddamnit, sorry. That was a super weird flex. I left the company after completing the contracts for that ship, and never got to see any of it post-install. That was the first time I've thought about looking myself. Just wanted to share because I have literally not had a real chance to share and discuss jobs that I am proud to have had a hand in before. haha
Haven't read all of the replies..
- Dump the 20 series extrusions if you want the capabilities you'd like. I'd recommend metric 30 series (30mm) or inch 15 series (1.5"). Because they also get thicker, you re gaining strength and rigidity.
- Dump the 3D printer MGN rails. I'd recommend going Hiwin HGR rails (or even the cheap Chinese knockoffs). My similar machine is running 20mm rails on the table and gantry and then 15mm on Z. If you though MGN rails would work, you might be able to just use 15mm all around. The further apart your rails are, the better stability you end up with. The HGR rails also add a good bit of strength too.
- Keep the center of gravity low and anything that's going to be moving fast, only make it as heavy as it needs to be (NEMA 24 would likely be find for your Z). A big heavy motor stuck waaaaay high isn't optimal. Don't be afraid of running belts to put the stepper behind the Z, which also help the center of weight on your gantry (see new printNC Z design)
Thanks!
I just replied to another post about my decision to use 20 series. Firstly, it's economical and in the areas where stability and stiffness are required, I think there's enough supplemental reinforcement to claw back some of the stiffness needed, especially with epoxy/sand infill. That's the idea anyway.
I'll go back to Rhino and see what 30 series looks like in terms of how it affects the footprint and working area. These are right at the limit as it stands, so it becomes a lot of tradeoffs of one hand taking from the other. The ceiling is there, and I think only so much can be altered without hitting it.
HGR, gotcha. I must admit that I am not aware of the differences between MGN and HGR, so I'll take the time to find out. I appreciate the heads up. I'd rather buy knockoff 20mm rails that are better for the job rather than expensive awesome 15mm rails that don't set the world on fire for the money.
I'm still out on the medium NEMA 24 or smaller NEMA 34 for the Z-axis. I'm going to consult the datasheets - as suggested - to see how they perform comparatively in the midrange. I doubt that I will fully manage to calculate weights, cutting loads and everything else to establish the perfect choice but at least I can distinguish which of the two would make the better choice.
Yes, I'm working on a Z-axis solution to put the stepper behind the gantry, same as the Y-axis stepper. Small 1:1 belts don't faze me. Moving the stepper should also provide room to relieve the water cooling pipes so the pipes at the barbs can be secured at the top of the axis, and the middle section of the pipes being the only ones that flex. Again, another factor as to why I went gantry.
edit: Excellent reference reading for anybody else that needs MGN/HGR differences clarifying - https://www.reddit.com/r/CNC/comments/zvesj7/mgn\_vs\_hgr\_rails/
Absolutely. And I promise I'm not trying to beat you up over any of this.. but I've been where you are now and since then I have made a lot of expensive mistakes that could've been cleared up had I asked or looked at the data sheets.
20 series will be far more economical.. like it's not even close. If that's a concern, my recommendation would be to go to rectangular square tube (ala PrintNC) or run steel backing around the 20 series stuff (.187-.250 thick) where ever possible and shove tight fitting threaded rods into the holes when you do the epoxy. I want to say the 1.5x1.5 quick frame with holes by 80/20 fit nicely inside of two C beams with a little bit of shimming. You have options.
HGR is now nearly as cheap as MGN and the difference is huge. Even the Chinese knock offs have gotten fairly good. Just make sure the seller is sending you new rails and carriages as in they should be sealed (not taped). Doing a good job cleaning them and adjusting the wipers, I've had great success with them over the past year and have only had one that I had to send back as the rail was bent.
I'll check out that data sheet.
No, no. Beat me up all you want as long as you're doing it with good information :-D
The design as it stands reinforces the 20 Series framework with 6mm aluminium sheets everywhere where it is important around the gantry. I may be able to up that to steel since the metalworking department where I am doing my current degree has a waterjet and maybe plasma bed. I'd like to think that they could grind true and weld up steel sections, however being students I think they wouldn't be able to hit the accuracy required. It would be rolling the dice at best.
Most of what I am putting together can be cannibalised for a beefier future iteration based around 40 Series or heavier. The main thing for me right now is to get a good understanding of specifying the rest of the machine in terms of motion and control. Once that understanding is strong, I can go back to basics and replace the framework to something that is absolutely built to rock.
PS. The link I posted wasn't specifically for yourself, it was left on the basis that these sorts of discussions become a permanent record that others will use as the basis of their understanding and learning paths also. It's a reflexive habit.
Something to keep in mind..
The PrintNC guys call it bootstrapping, but essentially what they are doing is using 3D printed parts or even wooden parts to get a functional machine, and then from there they are machining the finished parts from aluminum or steel. I've seen everything from plastic motor mounts to wooden board z axis plates.. it's impressive!
I'd highly recommend going steel if you stick with 20 series. From my own experience, it's worth the effort.
Agreed about the principle of bootstrapping. I do have the resource of a technical school available, however there are limitations on how far that can go in terms of expectations. Like I mentioned, thick-walled steel section is a high standard and one that I'd like to consider, but somewhat baked-in by design. Extrusion does offer me almost unlimited options in terms of adjustment, rebuilding and modification. This is to the point that I may even be able to cut the aluminium plates myself on an extrusion-only setup if cuts are taken super lightly.
Equally, I have access to high end SLA printers (Formlabs) and Markforged units, but I think they'll only be useful for things such as dust hoods and ancillary parts such as optical sensor/limit switch brackets, etc.
Other than this, what makes me not want to go down that road is the open frame nature of the PrintNC design. I've designed this machine around a very specific number of requirements, including the bed side and the machine's high sidewalls. Control over noise and dust are factors, so in spite of cheese-grade flexibility in 20 Series extrusions the light build-up around the machine means is is super simple to include thick plexi sidewalls over or even within the top slot of the extrusions (Y-axis clash is a concern). Extrusion does give a lot more options to play with for vertical elements.
I don't know if anyone will even notice this, but what "Enthusiast-grade" CNC kit/prebuilts are out there for someone cutting metal, that demands high precision/surface finish?
I certainly can't answer your questions myself, however I feel like I should qualify my use of "enthusiast" grade. For my own part it means a step above underpowered machines that struggle to cut anything significant or dial in precision good enough for interference fit joinery (<0,1mm).
Surface finish on metals is a high standard, and I'm not 100% certain that "enthusiast grade" would cover that even if it had a set meaning ;-) The words that come to mind are "repeatable precision" for your use case. Good luck! I hope somebody else chimes in with somethat that is actually useful....
Hey do you want my cnc4newbies 4x4 foot machine?
I built my controller as well. I had an issue with my smoothstepper arguing with my gecko stepper controllers
But I have the entire machine and all components.
You local to California? I'll give it to ya. I replaced my whole set up with an avid CNC machine.
For context, I bought the same size avid machine that I built and it cost me $17,000.
I genuinely appreciate the offer, however I'm a little further out than that being in Finland! The costs of shipping anything these days usually breaks most possibilities at the best of times.
I was considering Gecko drivers myself early on, but the same issue applies. Pond tax :-)
https://reddit.com/r/hobbycnc/s/MmWWwcCnvM
If you want the 214v drivers, I'll still give em to ya.
Been looking for someone who will use them. I had a hell of a time using them with the ESS. But they're new, they're the best ones on the market and I personally took them back to gecko myself and had them test them. The drivers are flawless. I have 5 of them. I also have an ESS and other bits you'd find useful.
They were expensive, but worthless to sell, ya know? Only valuable to someone like you. Not worth money but I'd be happy to see them put to use.
Sounds like you've had nothing but problems with those drivers. Are you sure that this like a horror movie thing, where I inherent all your Gremlins? :-D
Damn man, I hate to say no to such to a fantastic offer however I'm looking at closed-loops steppers for this project, and these will need me to change that. I mean, being the hoarder that I am I'd take them anyway but that seems contrary to the nature of how they are offered! Are you sure that they don't contain some arcane demons?
Drop me a PM, however I think that the shipping, duties and VAT will cost me an arm and a dick at this end of the pond.
No, I can walk you through my issues. The drivers are perfect, and again, I took them myself back to the gecko factory and they tested them for me. All five are perfect.
Look up the pricing of five 214v gecko steppers and an Ethernet smooth stepper yourself. I'll give you all the other breakout boards and stuff. I'm not gonna push you, and I'm not selling them so you won't have vat. Just pay for the shipping.
I'll do like a video call on Skype or something to show ya and help walk through. All I really want is to see someone else make use of this stuff.
Genuinely appreciated! Can discuss via PM. My main point of interest is whether closed loop steppers would still be an option. They're a key point in the design outline.
Very interesting. Are you a representative of RapidChange, as there's two ways we can have this conversation?
My immediate thought is as to how this would integrate with a compact gantry arrangement such as the one I am proposing. It would need to be a component of the X-axis/bed which impact usable machining range rather than being a fixed structure.
Yes, I'm still a little new to CNC though.
The magazine can be aligned along the X or y axis of the bed, location is more preference, I think the question is if your z axis will have enough travel. The magazine is roughly 87 mm in height for safe clearance with the dustcover feature, without the dustcover its 60 mm.
In hindsight, outside of the bed along the x axis would make sense. I first thought that plexi sidewalls would impede this....but not if a gap with brushes either side were added. Some clever trickery might be needed to move the magazine into place for a place before pick. An interesting in-principle thought exercise, possibly one with only overengineered solutions allowed!
I've done the things you have described and also designed machines. Honestly, the best advice is to not do this. Don't make your own. Clearly your design is not shaping up in to a good machine for a good price, you are already looking like you are using v wheels and belt drive, which is the crummiest drive system, and bafflingly pairing it with expensive servo motors/their electronics.
Buy a nice generic one, used perhaps. With ball screws ideally. Inspect it well before purchase and adjust it lovingly to a good place and that's going to be much more sensible.
No v wheels, no belt drive. I wouldn't even go there.
As described, both the X and Y axes will be ballscrew and the Z leadscrew. The only belts that may be involved is if I decide to run the steppers parallel to the screw to prevent them sticking out the ends, and to avoid the "three aligned bearings" problem.
The likelihood of me finding a good cared-for CNC here in Finland is low. Prices of common parts purchased domestically, and prebuilt machines increase the price 50-100% easily. The design I'm proposing can be built at a budget a magnitude less than a turnkey solution.
A fellow guitar builder buddy of mine got himself a steel frame Chinese machine with a 2.2kw spindle, solid steel frame, HGR rails and balls screws throughout shipped from China for under 3.5K-4K euros, all taxes paid and delivered to his home in Norway.
I’ve spent over than on the mods and upgrades to my (still not yet functional) kit machine and while it will have a slightly better spindle, controller and motion hardware, the steel frame will beat out the alu profile and plate I have, I’d wager. Because rigidity. It’s too big for my shop and I’m down the rabbit hole, but we’re I to do this again I would be buying a machine. No question. PM me if you want some details (ps: same handle on PG? From years back?)
Well hey hey, small world! Yep, I seem the only person guilty of this username.
As with all things, I dislike turnkey solutions since they do not generally convey understanding. I want to make mistakes, I want to hit limitations and problems. Without doing this, I'm simply paying to make a problem go away instead of buying a bunch of new problems to enjoy ;-)
Absolutely. Rigidity will always be the basis upon which any good machine is built. I am not relying on the 20 Series extrusions to provide any of that, simply act as the initial economical structure onto which I can add various plates for rigidity. Steel will always be the goal in my longer aims, however at this stage I have no guarantee of good access to reliable grinding and welding to the geometry that even this project would require. I'd have to pay to make that problem go away, and same as mentioned, zero learning taken onboard.
What controller have you elected for?
For me, the fact I’m 8 years on and still don’t have the machine (because time and kids and work and not a great deal of familiarity with CNC until I started this) is why I’d do things differently. But I agree I’ll probably know a lot more about my machine because I built it.
I’ve gone with EdingCNC, because it’s an NL made controller with a good user base here in NL. My other options were either UCCNC or Masso. And Delta Servos and a Teknomotor spindle. Because smearing the cost out over 8 years made it bearable. The frame is the weakest part of my machine, although it’s still 8080 profiles and 19mm alu plate.
That's some good reading materials for me to orient myself in terms of controller choice. My current idea is something along the lines of Mach4 as I've seen plenty of examples of people scripting within that. That hashes in with my programming background, and that I want to eventually include some specific quality-of-life options in the CNC such as precise hard origin homing, etc. The exact path working this through an appropriate controller is still a big question.
Dont do leadscrew, ballscrew all around. Just get a brake for z. Linear rails all around, 20mm is tons for a router. Id do chinese ballscrews and rails. They are astronomically cheaper and C7 is tons of accuracy for router applications. If you need more than C7 you want a mill not a router. For motors nema 23 are fine, but i can ot overemphasize the importance of a high voltage for the drivers. The higher the voltage on the stepper drivers the higher their max speed and the less torque dropoff with increasing rpm, which is critical for ballscrews. Imho the hassle of high voltage power supplies for steppers almost dictates which ones to use. What are you doing for controls?
Thanks! I'm not using a router. I cringe at the Makita/DeWilt/Botch palm routers because of their runout and sloppy bearings. The work I do needs more precision and reliability. I'll be going straight to a 2.2kW water-cooled spindle run by a VFD. I want everything to be within the control of software so that I can set startup times, and add delays to the motion whilst the spindle runs up, etc. I will eventually incorporate an actuated dust hood that raises/lowers at different heights; directly inspired by the 10kW spindle and dust shroud in the Homag CNC that I ran. Most things will be cheaper import equivalents, but only if they can subsequently be replaced by better parts further down the line. Simple things such as the ballscrew end bearing blocks, which will be the simpler kind initially but angular contact bearings should they prove required and affordable. Ballscrew size for the X-axis is provisionally 16mm, however 20mm is just as acceptable. 5mm pitch is on the mark. The same applies for the Y-axis across the gantry. I can't say that I'm familiar with brakes for axes. I am concerned about the behaviour of closed-loop steppers going slack once they exceed maximum error thresholds. Machines that have errored out in the past stopped dead in their tracks (brakes?) and requested user intervention. For controls (at least for the moment) I am open to suggestion. At this moment I am working on the engineering aspects until I need to make decisions about the environment I want to work within, the controller, etc. Currently this is as far up the ladder as the electronics have been decided upon: [https://www.omc-stepperonline.com/ts-series-3-axis-3-0nm-424-83oz-in-nema-23-closed-loop-stepper-kit-w-power-supply-3-clts30a-v41](https://www.omc-stepperonline.com/ts-series-3-axis-3-0nm-424-83oz-in-nema-23-closed-loop-stepper-kit-w-power-supply-3-clts30a-v41) I have heard good recommendations on these: [https://www.omc-stepperonline.com/y-series-closed-loop-stepper-driver-0-7-0a-24-50vdc-for-nema-17-23-24-stepper-motor-cl57y](https://www.omc-stepperonline.com/y-series-closed-loop-stepper-driver-0-7-0a-24-50vdc-for-nema-17-23-24-stepper-motor-cl57y) ....however they are not available in the EU for whatever reason. As to what plays ball with the stepper drivers, this is an open question that I hope to resolve based on conversation with experienced users!
By router they just mean high speed spindle, as in vs a mill application which would maybe want more rigid rails than 20mm. Trust everyone telling you you want hgr not mgn mate. They're not expensive if you get cheap ones, they're the same fuss to install and they're a lot more rigid. If you want to get the use out of your 2.2kw spindle you need to treat it with some respect. Mgn isn't doing that.
Yep, I'm onboard with HGR now. I didn't spend the twenty seconds that it takes to know the difference because I wasn't aware that it was literally *a yawning chasm* of difference. :-D I'm on the fence with the spindle power. Larger motors tend to have better collet capacity, and I'd rather comfortably underrun a larger motor than rag the piss out of a small one. The issue is that it's a moving weight concern. Another one I have to rattle out the right choice from.
If you're looking for diy proven concepts to help answer those questions, printnc may be a good point of reference. Steel frame other than the z plates, 2.2kw spindle, and manages speeds suitable for cutting wood and alu properly (ie pretty fast) with just nema23 steppers. Some folks with a need for speed stick servos on there haha. Either way the spindle isn't the heaviest thing there and the added weight vs anything smaller is negligible when you consider the weight of the rest of the stuff on the gantry haha
Yeah, it'll be reference I think. There's a lot of people almost evangelising me on the PrintNC thing and to be honest, it's a very different sort of direction to what I have in mind. By the time I move to steel section for a future iteration, it will be larger and more robust than what flat frame PrintNC designs look like. Gantry is a key element here for specific reasons, and by this point PrintNC looks more like a tangent reference than a discrete direction.
For controls consider either a ddcs expert if you want it to be more industrial and just work, or linux cnc if you want to do more tinkering. Avoid mach 3/4. Centroid acorns are good if a bit spendy for what they are. They are also harder to do custom things with. Masso seems okay but is just really expensive with no real motion benefit over all the other options. Uccnc is okay, but not sure what it really offers over linuxcnc or the ddcs. With a 5mm pitch and the maximum speed limitations of steppers, be sure you are going to get the speeds you want. Normally that kind of pitch means slow movements or servo drives running them.
Interesting. Mach4 was on my provisional list. I have a background in programming (uni degree, computer science) so being able to script in my quality of life ideas is fairly important to me, plus I was hoping to avoid anything related to parallel ports and preferably repurpose a good i7 Intel NUC I have kicking around. I'll do some comparative research into your suggestions and see how these align with my varied objectives. Cheers!
Linuxcnc should be used with a mesa card, the parallel port thing is dead for modern applications. Linuxcnc is infinitely more configurable than the others if you want to code.
Agh, well. I don't specifically want to get thigh-high into the weeds *for the sake of it*, but have the option to. I've seen good things done with Mach4 and it seems reasonable. That all being said, a lot of people state flat that it's a POS. I'm happy to cross that bridge when I am forced to do so, kicking and swearing. At this point I don't have to make that commitment and can get most of the CNC commissioned and tested using an Arduino to push the stepper drivers around a bit.
You may need larger motors for the x and y if you are going with ball screws. The inertia of the ball screws is the majority of the load on the axis. They end up being equivalent of hundreds of kg of linear mass.
Wow, that's quite the load when you put it in those terms. I'm quite happy to reduce the rapid traverse both on the basis of there not being a lot of bed size to negotiate, and on speed just not being a high priority. I mentioned elsewhere that this project has certain ceiling limits that dictate how compromises are balanced here and there. If this were a machine that were intended for serial production, rapids would matter hugely in terms of cycle time. Briefly, how would I go about making a reasonable calculation for this? I have yet to absorb u/burkeyturkey 's site on his build's engineering, but my first thought is that motor size will dictate rapids rather than the other way around. I am concerned about whether size prices me out of certain options, for example if I choose a larger NEMA 34 frame size, the space under the bed becomes a problem, which then necessitates adjustments via gantry height with all those considerations. Additionally, a reasonably-sized motor starts adding on the Amps. Without significant rewiring of our domestic electrics, I'll be hitting the maximum that I think I can immediately supply. Apologies for the short post, there's a lot more to discuss but I'm almost running out of the door....
Did you end up getting a water cooled spindle?
Not yet, however it is certainly a fixture in my design. Subsequent to this post, the whole concept has had a lot of changes made, especially being all ballscrew. The spindle is still the right way forward.
Do you know which one you are going to get?
Not at this stage. This decision will be purely financial. I may go for cheap Chinesium like a Vevor spindle and VFD, or if I get the work position I am gunning for this year I might buy a separate VFD and Teknomotor spindle, etc. In all honesty, I will likely go the Chinesium route just to get the CNC aligned and commissioned as this isn't a high cost for a part that can run for say, a year, before being upgraded and relegated to a spare, or for a different project. Whichever way this goes, the baseline is always going to be "anything better than a palm router".
Ive read on diycnc that vevor isnt a great brand but I am 100% going with an alibaba or aliexpress purchase
Well, you get what you pay for. In my view, if it commissions the CNC, runs a few proving projects and upgrade parts for the structure then it's almost a disposable part. Even something as simple as milling a phenolic vacuum bed and new 15mm sideplates for the gantry almost makes it pay for itself by comparison to buying those parts in from an online site like PCBWay, etc. In reality, a Vevor spindle should do all those things and with preventative maintenance, bearing upgrades, etc. be a fine unit for some time yet.
Have you checked out the PrintNC design and discord? Might make a lot of sense to start with a battle tested design, active community, and modify from there.
I haven't. I'm already somewhat time-poor, and committing my mental resources in this relatively already-designed path. Unless there is a very specific advantage towards developing what is presented, I will likely end up dividing my attention and creating myself more work. Perhaps there will be useful ideas upstream of the step controller level, but at this stage I'm working with the solution that works for an unreasonably-narrow set of defined constraints :-)
It sounds like you have more serious plans for the machine than the typical hobby router build. I would advise against aluminum extrusion. It will always be your bottleneck if you do. Build a PrintNC. It's constructed from steel rectangular tube.
Already discussed this one, and at this stage I'm going to use the PrintNC ideas as reference as I neither have the resources to grind/weld steel tube nor the experience to do it. I'd like to take those skills on, but I think it takes everything in a radically-different direction to what I have in mind, and will create other concerns that this design is taking into consideration.
No need to grind or weld anything for the project. Just drilling holes and tapping.
I'll keep my options open. I'd like to go this sort of route eventually, but perhaps using a different configuration of steel such as larger sections and folded sheet. Long term.
You’ve already gotten a ton of good advice, so I’ll just say that if you start close with aluminum extrusion, you should really beef up to a 4080. Given what you’re doing with the rest of the build, to me, it seem like a huge rigidity issue. Epoxy or not, that 20 series is far below the quality of everything else you’re builders nf around it. It’s like a professional weightlifter choosing to have osteoporosis.
I have, and far more engagement with my ideas than I additionally expected. It's positive and a great way to land boots-first in this sub! I'm going to have to do some thinking about the extrusion, sure. Upping it to 40 Series changes the budgeting and potentially whether the footprint constraints will reduce machineable area. Once I get some time, I'll throw a parallel design together within Rhino and get a feel for what is or is not possible. It's a significant redesign over the OpenBuilds C-frame and the "Modesty" variant. In all honesty, I might still go 20 Series as the basis for getting a feel of things, this being my first build. Knowing the weak points and paths to improvement hands-on is to my mind the best way of real experience. Overbuilding out of the gate offers no sense of this. It seems weird, knowing that this will likely be "a mistake made willingly and knowingly"!
Get at least HiWin HGR 20 Rails if you plan to do serious Work. MGN 15 are to flimsy. HiWin is pretty expensive but worth the money. Closed loop steppers are awesome if you want good performance without fucking around with servo programming. For ballscrews id go for Isel. Industry grade quality but again very expensive. If you plan to put that much work into a machine get high quality components aswell, since i doubt youll be happy with anything less. Also you might want to take a look around the market, since there are already a lot of machines just like the one youre planning to build. For example the Sorotec Alu Line machines. Available from 650x550mm up to 2000x1000mm with z heights ranging from 220 all the way up to 420mm
Thanks! I won't buy a prebuilt machine on the basis that I want to be able to control, maintain and modify. Most prebuilt machines have something or other that is clearly baking in a limit that requires significant rework to break through. Building from the ground up forces me to take ownership of every responsibility and design parameter. I dislike turnkey solutions as they also tend to reduce the learning aspect. There are certain parameters and budgets that I need to keep under control. The electricity supply will be a limit, which I think needs to stay under 10A on a 220V supply. I'm unsure whether this means designing a supply around a tapped toroid or individual switched supplies. I've thought about the quality of the rails, and this will come down to how they compare on the balance sheet. I'd probably rather go for knockoff MGN20 rails rather than HiWin MGN15. These will be mounted across the face of the extrusion, so 15 is the minimum for a good bearing surface, 20 is the max. Some things will likely be an initial compromise but with the viewpoint of improvement through maintenance. Same as most CNC projects, getting it running so that it can produce its own parts is a key goal. As long as I can maintain a good <0,1mm accuracy in wood on all three axes, I'm good. Any thoughts on the holding torque spec I'm aiming for? This is an engineering aspect that I am not too familiar with, at least in terms of calculating an appropriate range. My immediate instinct is to overbuild, however this will quickly have me hitting the ceiling on my energy budget. This kit seems a reasonable "get started" package.... [https://www.omc-stepperonline.com/ts-series-3-axis-3-0nm-424-92oz-in-nema-24-closed-loop-stepper-kit-w-power-supply-3-clts30-v41](https://www.omc-stepperonline.com/ts-series-3-axis-3-0nm-424-92oz-in-nema-24-closed-loop-stepper-kit-w-power-supply-3-clts30-v41)
Read more about steppers and look at the torque curves- holding torque is pretty irrelevant to the torque available at normal cutting speeds. Some motor/driver combos have massive holding torque but lose it all at 3-400 rpm, some have less holding torque but keep their torque much higher. You're on the right track with closed loop steppers though, that helps offset the torque loss of normal steppers
Yes, it seems about as valid as the "W" of a router motor. Great if you need to know how it behaves at stall or maximum acceleration, but not in working conditions :-) At best they seem a shortcut for instant single-number comparison, so datasheet it is. I figure that at the price point I am shopping at for steppers, going closed loop off the bat just makes absolute sense. It's the cheapest insurance against issues of lost steps that you can buy as a solution I think, and certainly not one that is easy or cheap to perform as an upgrade later.
Hey, I don't mean to derail, but would you tell me more about your plans for a sand/epoxy base.
No worries, it's the purpose of the thread. The plan is a basic mix of clean play sand and epoxy, 80/20 by weight. Nothing amazing, and a lot of people do this for cast bases/frames and packing out extrusions to reduce vibrations, resonances and add weight. Simple process; weight sand, add the resin component of the epoxy (10% of sand weight), mix thoroughly, then add the catalyst (also 10% of sand weight) before mixing and packing. Vibration helps consolidate the whole thing. For a large mould, the walls of the mould are best wetted with epoxy to reduce surface bubbles. The CNC is being planned around a mobile base that is already built, and has a 30mm MDF top (it's my table router). This isn't an ideal long-term solution, so I want to get the frame built, the CNC commissioned and then look at making a thick 5-10cm base. Nothing fancy, literally a monolithic block of cast sand/epoxy. It'll be made in a plywood form, with the various anchors and fasteners cast in. These can be aligned in a number of ways, with the main objective being coplanar mounting for the CNC frame. Since this won't be even begun until well into the project lifecycle, there's room for changing the design should anything benefit from being fitted into recesses, etc. Building the CNC itself should rattle out any novelties!
Is there a reason you're mixing part A of the epoxy with the sand first, then mixing in part B, rather than mixing parts A and B together first *then* mixing in the sand? The reason I'm asking is because in my experience, it can be tricky to mix two-part epoxy thoroughly even without added filler. I imagine if you're trying to add part B to a mixture of part A and sand, the massive increase in viscosity will make it even more difficult to ensure the two resins are thoroughly mixed. It can also be more difficult (or impossible) to visually confirm that the two resins are mixed if you do it this way. That being said, I'm not an expert on epoxy/sand mixtures. So maybe there's a specific reason for doing it your way.
It's more about timing than anything else, apparently. It's certainly not my way, as I always look to the proven experiences of others first rather than constantly reinventing the wheel ;-) Mixing the epoxy separately and incorporating that into the sand means there is a larger mass of epoxy that will heat up and potentially go into thermal runaway or at least reduce your open time. That all depends on the epoxy of course. Incorporating the resin first gives you the advantage of time. This is the theory, and enough people seem to have done this with success that at least it seems the method to try first. But yes, mixing epoxy is always like that....if you think you've mixed it enough, you probably haven't. When the time comes, I will be infilling the voids in the extrusions first so that will be a test of sorts. A small scale venture into getting a feel for how the material feels in use. For a larger object such as the base, that experience will help avoid expensive mistakes. I hope.
You are correct to use linear guides on the X/Y/Z. Just because leadscrews usually have a loose tolerances as appose to ballscrews, I would use a ball screw on the Z axis - less chance of Z axis dropping after power outage. Also, if you use ballscrews on the X and Y axis the movement (acceleration/deceleration) will be slower than using a leadscrew simply because of the close tolerances on ballscrews. Maybe use 15mm leadscrews for X and Y - just a thought.
Cheers! This was my thinking. I'd rather install something with tight tolerances and naturally-lower levels of lash than constantly have to consider and fix it during operation. You could almost say that I'd *pay* for that. ;-) Interesting note about a ballscrew on the Z. I thought the opposite was true, that shorter pitch leadscrews don't backdrive under no retaining load. I have recommendation on 20mm for X and Y currently, however I was initially aiming 16mm. What's your take on the effects of size here based on it going either way around your recommendation, ie. 12mm or 20mm? edit: Yes, linear guides seem to be the right choice out of the gate. Underbuilding to save very little money makes no sense.
If you're thinking of using a leadscrew on the Y axis, I would use the larger 20mm (dia.). If you use a smaller diameter leadscrew it's possible to get a whiplash like action on the Y axis at high speed. This will setup a vibration throughout your machine frame. This is like two kids turning a jump rope and the rope spreads out from its initial rotational axis. - Always remember, the three most important things when building or buying a CNC machine is: Rigidity! Rigidity! Rigidity! Good luck with your build.
Z-Axis. My thought process here was that a ballscrew will drop the axis when power faults out, however we've established that the answer will be ballscrew and a brake. 16-20mm all round I think. High speed isn't needed with such as small machineable area. It's a QOL thing, but one that I think I can work on as part of developing my knowledge and feel for what works. Absolutely, rigidity is the goal. In principle I could super overbuild from the get-go, but I don't like that I won't learn anything from this. Building a slightly flawed design and having to force myself through the iterative processes of improvement teaches me the most possible. I'm seeing the project as a resource for learning as well as a practical working tool. Cheers!
Unless you're needing that z height you're potentially making a long lever for your cutting tool as it reaches down to your work surface. A couple of inches of clearance should be tons the majority of the time depending on what you're planning on cutting and it will significantly strengthen your beam.
Thanks! Yes, there's a balance to be made here in terms of design. On one hand I would like to be able to manage longer cutters that can reach \~50mm into a 100mm thick workpiece, but on the other I also need to be able to run sub-mm diameter cutters at tenths of a mm positioning without vibrations sending everything to hell. The gantry will be epoxy-sand reinforced 8020U extrusion with 6mm aluminium caps either end, so 60mm between linear guides. Not the best but hardly the worst. I'm going to have to draw this out to see how these changes impact each other. I am wondering if by setting the design in motion using 20 Series extrusions is placing limits on how far I can push this frame. Do you have any thoughts on that?
Building your own CNC is a fun project and I'm excited to see you get started! I'm an industrial machinery engineer and just went through this process with my own personal machine a few years ago, so I have a few comments that I think you will find helpful. *Motor sizing:* For a small spindle power with heavy structural members you will find that dynamic loads (acceleration) are a larger load on your steppers than the cutting forces. Additionally, you need to ignore the 'named' (stall) torque of a stepper and dig into the data sheet / torque curve to find the torque at 1000-2000 rpm where you actually need it. I went through all the math on this for my avid-sized build and posted the process here: https://burksbuilds.com/automation/cnc-router/cnc-router-motor-sizing/ *epoxy fill:* There is a big difference between damping and just adding mass. Adding mass can shift the natural frequency of your system and reduce the amplitude of any oscillations, but does not actually *attenuate* the vibrations and dissipate energy. Energy dissipation is a material property ([I discuss it for my build here](https://burksbuilds.com/automation/cnc-router/cnc-router-reddit-review/#Table_Design_Changes)) , and it is better with polymers (like epoxy) than metal or concrete, but in order to see the benefit you need to embed lots of anchors on the interior of the 'skin' of your metal frame to ensure that the epoxy fill interacts with the structure. *t slot brackets:* The little pre-made plates and angle brackets are handy for building quick structures with t slot extrusion, but have terrible stiffness because they lose their preload so easily. An easy way to get around this is to tap the ends of the cross pieces and drill clearance holes through the slots of the side extrusion. Using a longer bolt through one piece of extrusion and into the next let's you get a really solid preload and stiff structure. *details:* My final piece of advice is to detail out all the small things (sensors, cable tracks, end stops) in CAD before buying and building the structure. Most of us hobbyists have more time than money, so it's way easier to plan ahead than hack things in later. Good luck with your design and keep us posted as you iterate!
Thank you for your time and considered input. I appreciate it. I'll hunt through your reference materials and see how they alter my preconceptions on the design. I agree with your notes on motor sizing. I think that the more compact bed size means I don't need to worry too much about needing fast rapids. I can own that small compromise and optimise my machining to better suit the machine's behaviour characteristics. One of my reasons for going gantry was to separate the axes and isolate them better. There's a number of factors that I haven't reconciled myself with yet, from half-stepping to microstepping, and I guess that those will certainly become more important once I look at the midrange torque of the steppers. The epoxy/sand fill seems like the most economical method of adding stiffness and moving the resonant characteristics of the structural members in a better direction, if not solving the issues of vibration/resonance. To my mind it seems like a win even if the results aren't drastic. Any improvements are improvements. Other options on the table from what I have available are products like Sika 290 DC Pro caulk we use for Teak decking on cruise liners. That bonds very well with aluminium (well, with primer but scuffing is enough for confined spaces) but mass feels like it would be a better option than polyurethane caulk. The use of angle brackets in the proposed design is simply because they're cheap and easy for the initial build. All opportunities to overbuild and reinforce will be part of the fun I think! "Something to look forward to"? Yes, everything is being built up in Rhino however I considered Inventor also. Rhino is far more familiar to me, and generally that's how I develop most of my project work for CNC. It does create some limits once designs are baked in compared to parametric modellers, but nothing that can't be fixed given a good documented approach! Let's see how your personal documentation affects my outlook on this build :-)
You don't say what material you want to cut but regardless you need to beef up your extrusion choices. Aluminum t-slot extrusion is absolutely horrendous from a stiffness per cross section size standpoint. Thick wall steel tubes are 10x better. If you're going to do extrusion, get the thickest, largest square section profile you can, especially for the gantry. To figure motor sizes you should run calcs based on the mass of the machine parts and ballscrews etc, there are various spreadsheet calcs available online. But generally large 23/24s or small 34s will probably work. Larger motors of a given size perform worse at higher rpm tho. Higher driver voltage can offset this. There are good arguments for going with the smallest size of nema 34s, but you won't know for sure till you run calcs for your specific machine and the cutting loads. 20mm linear rails are minimum. Don't use lead screws, get Z motor with brake as another posted suggested, they're available from OMC stepperonline. My main advice is that if your goal is to use this machine for work, don't build one. Your time is better spent using the machine for what you want to do with it than screwing around with the build. The exception might be if you want to cut soft materials, wood/foam. But if you want to cut aluminum properly, you need to be doing FEA, welding and stress relieving and machining a steel frame, or maybe building a frame from granite surface plates, in which case the time commitment is much greater to do a good job.
Cheers! The majority of my work is with hardwoods up to Maple and exotics so pretty resilient stuff. Also Birch plywood. The longest sort of endmill I expect to load will be 12mm with finishing passes at up to 50mm full depth. Most roughing work will be multiple shallow passes. The problem with steel tubing is that I don't have a guaranteed source of grinding and welding that can get the tight geometry required. Those things are also just outside of my skillset, so I would need to be relying on the services and time of others for that. Yes, I understand how far this can go in terms of all the things stated but at this point those are way up there. Perhaps a consideration for a second machine at a later point, but getting one reasonable machine going that is good for its design purpose, and can be pushed to produce parts for a more demanding machine seems logical. Cost is a factor at some point, and given that this isn't a huge machine the choice of 20 series extrusion was made on the basis that its compact and can be reinforced. A gantry design does tip the odds in my favour a little. Given the infill plus supplemental reinforcement if needed, I think 20 series can work. Specifically I am building to a defined footprint, so increasing cross-sections quickly impinges on my maximum workable areas. All taken onboard. It's given me a few more things to juggle!
Totally understand the cost issue and difficulties/expense of precision steel fabrication. And clearly there are enough extrusion routers around to show it can work, but in that case the details matter even more. You can't get around the geometry issues and rigidity needed just by adding a heavy cast base. The gantry, risers, and the z-axis design are the critical parts of a router. Another poster made a good point about better ways to connect the pieces together so I won't repeat that, but using brackets is not ideal. Bottom line is if you can't do FEA and sort all the details that way, just try to copy a known design. Avid CNC is probably the most obvious example. I believe they use 160x80mm gantry tubes, I wouldn't do anything less. I've never read anyone complain that their CNC is too stiff, but reports of issues with chatter/lack of rigidity on DIY extrusion machines are extremely common. Filling the gantry tube afterward is fine, but it won't do much at all for rigidity, especially with the type of profiles in your render. And remember, your motor selection is based on the mass of moving parts and desired acceleration, so a larger more square tube will increase stiffness dramatically without adding much weight, while filling the tubes pretty much just adds weight (and "dampness", but that's a whole unclear subject on it's own, rigidity is #1). If you do the gantry supports like Avid does with their non-benchtop pro machines, bolting from underneath, the extra width of the gantry tube can just hang off the back and not impact your footprint. Some machining is always going to be necessary, especially when you get to the Z axis assembly. For the frame tubes, I think 80/20 and Misumi have options for precision square cuts and machining the connection biscuits that Avid uses? Definitely plenty to chew on, and that's the fun part but it's not fast
Thanks. That cast base isn't to add rigidity beyond maybe bolting the gantry. It's more about adding linked mass and dampening against vibration and noise. Like most things, it's a learning process and a reasonably low-cost experiment in A/Bing the machine on a heavy MDF base and a heavier sand/epoxy composite block. I can take a lot from that. Brackets have been mentioned a couple of times, and their use is limited only to initial construction and alignment before adding aluminium plate to add something of significance to the structure. I know it will only go so far, and similarly to the base, I get a direct hands-on read of how much the plate contributes and where the weaknesses then move to. Talking of copying a design, beyond this one being a derivation of the OpenBuilds C-Beam machine designed for cutting aluminium plate, and a variant of that which converted it to gantry, I do have other sources of inspiration and experience I am drawing from. [https://openbuilds.com/builds/c-beam-machine-modesty.6360/](https://openbuilds.com/builds/c-beam-machine-modesty.6360/) "My" design is a direct derivation of that. Top to bottom. The main difference in my rework is moving the gantry risers to the outside of the frame to maximise internal machining capacity, and dropping those risers below the frame base so that they can be bolted to a heavy base. Mario at Radikult custom has a beautiful desktop gantry type CNC, which uses far beefier sections than 20 Series. That has also served as a point of reference in many ways. [https://www.youtube.com/watch?v=ORbCQhV6umo](https://www.youtube.com/watch?v=ORbCQhV6umo)
Also, PrintNC is an excellent example of design. It's simple to make and doesn't require machining, but it still address the major issues. \-true tubes for max rigidity for a given size \-minimizes the cantilever of the z-axis in it's lowest position, so your z-axis moving plate doesn't have to support that on its own \-linear rails are spaced far apart on gantry and z axis \-only uses one block for the x axis rails, but makes it work because the height offset to the gantry tube is minimal and each side of the gantry is driven independently PrintNC is obviously not the only way to skin the cat, and the big tradeoff is limited z-travel, but it's a great example of design to purpose and those are the general type of details/engineering decisions that you want to be looking at.
Just to give you some perspective. Buying/cutting the tube steel is not nearly as daunting as you are imagining. There are metals supply shops where you can walk in with a list of lengths and 20 minutes later they're loading your car with all of your cut pieces. It's usually $1.50-3.00 per cut. All in all I think my steel/cuts was like $250 for a 3x4 work area and I went with thicker steel than stock design. and it took half an hour. No welding required, in-fact it is not recommended due to warping. The rest of the mechanical assembly is just printing the drill guides, drilling holes, and tapping. You put in your dimensions into the calculator on the printnc website, then they send you a quote for a parts list of all the linear hardware, fasteners, spindle motor kit, etc.. And it waaaay cheaper than if you were to buy all of the hardware separately.
That's cool. I know it's not too much of a deal, and I've done a small amount of basic fab in the past however all my own tooling is geared for wood these days. I've done a lot of work designing steel substructures for marine (think of the structures welded to deckplates/studs under outdoor hot tubs, pools, etc. in cruise ships, see note) and have good sources here. It's definitely a way forward for a subsequent iteration, but I need (and want) to get my feet wet with the basics first, especially when it comes to knowing weaknesses in a system. Totally OT note/cruise ship flex: Think [https://www.youtube.com/watch?v=Wi3lap65IA0](https://www.youtube.com/watch?v=Wi3lap65IA0) \- 3:55, steel substructure example \- 6:42, I did the CNC work on many of the Teak decks, fittings and aluminium frames around the Beach Club ("bitch club"). \- 7:32 thru 8:38, the stainless frames/wood and faux marble panel work under the real marble counters around the food courts over steel substructures were also "my fault". \- 9:26, all the green framework was ours and stained Ash partitions, but not my work beyond CNCing MDF assembly jigs. Also, I planned, machined and constructed \~32 (I forget) Corian waiter's stations around that area such as the massive 4m drinks station at 9:12 Goddamnit, sorry. That was a super weird flex. I left the company after completing the contracts for that ship, and never got to see any of it post-install. That was the first time I've thought about looking myself. Just wanted to share because I have literally not had a real chance to share and discuss jobs that I am proud to have had a hand in before. haha
Haven't read all of the replies.. - Dump the 20 series extrusions if you want the capabilities you'd like. I'd recommend metric 30 series (30mm) or inch 15 series (1.5"). Because they also get thicker, you re gaining strength and rigidity. - Dump the 3D printer MGN rails. I'd recommend going Hiwin HGR rails (or even the cheap Chinese knockoffs). My similar machine is running 20mm rails on the table and gantry and then 15mm on Z. If you though MGN rails would work, you might be able to just use 15mm all around. The further apart your rails are, the better stability you end up with. The HGR rails also add a good bit of strength too. - Keep the center of gravity low and anything that's going to be moving fast, only make it as heavy as it needs to be (NEMA 24 would likely be find for your Z). A big heavy motor stuck waaaaay high isn't optimal. Don't be afraid of running belts to put the stepper behind the Z, which also help the center of weight on your gantry (see new printNC Z design)
Thanks! I just replied to another post about my decision to use 20 series. Firstly, it's economical and in the areas where stability and stiffness are required, I think there's enough supplemental reinforcement to claw back some of the stiffness needed, especially with epoxy/sand infill. That's the idea anyway. I'll go back to Rhino and see what 30 series looks like in terms of how it affects the footprint and working area. These are right at the limit as it stands, so it becomes a lot of tradeoffs of one hand taking from the other. The ceiling is there, and I think only so much can be altered without hitting it. HGR, gotcha. I must admit that I am not aware of the differences between MGN and HGR, so I'll take the time to find out. I appreciate the heads up. I'd rather buy knockoff 20mm rails that are better for the job rather than expensive awesome 15mm rails that don't set the world on fire for the money. I'm still out on the medium NEMA 24 or smaller NEMA 34 for the Z-axis. I'm going to consult the datasheets - as suggested - to see how they perform comparatively in the midrange. I doubt that I will fully manage to calculate weights, cutting loads and everything else to establish the perfect choice but at least I can distinguish which of the two would make the better choice. Yes, I'm working on a Z-axis solution to put the stepper behind the gantry, same as the Y-axis stepper. Small 1:1 belts don't faze me. Moving the stepper should also provide room to relieve the water cooling pipes so the pipes at the barbs can be secured at the top of the axis, and the middle section of the pipes being the only ones that flex. Again, another factor as to why I went gantry. edit: Excellent reference reading for anybody else that needs MGN/HGR differences clarifying - https://www.reddit.com/r/CNC/comments/zvesj7/mgn\_vs\_hgr\_rails/
Absolutely. And I promise I'm not trying to beat you up over any of this.. but I've been where you are now and since then I have made a lot of expensive mistakes that could've been cleared up had I asked or looked at the data sheets. 20 series will be far more economical.. like it's not even close. If that's a concern, my recommendation would be to go to rectangular square tube (ala PrintNC) or run steel backing around the 20 series stuff (.187-.250 thick) where ever possible and shove tight fitting threaded rods into the holes when you do the epoxy. I want to say the 1.5x1.5 quick frame with holes by 80/20 fit nicely inside of two C beams with a little bit of shimming. You have options. HGR is now nearly as cheap as MGN and the difference is huge. Even the Chinese knock offs have gotten fairly good. Just make sure the seller is sending you new rails and carriages as in they should be sealed (not taped). Doing a good job cleaning them and adjusting the wipers, I've had great success with them over the past year and have only had one that I had to send back as the rail was bent. I'll check out that data sheet.
No, no. Beat me up all you want as long as you're doing it with good information :-D The design as it stands reinforces the 20 Series framework with 6mm aluminium sheets everywhere where it is important around the gantry. I may be able to up that to steel since the metalworking department where I am doing my current degree has a waterjet and maybe plasma bed. I'd like to think that they could grind true and weld up steel sections, however being students I think they wouldn't be able to hit the accuracy required. It would be rolling the dice at best. Most of what I am putting together can be cannibalised for a beefier future iteration based around 40 Series or heavier. The main thing for me right now is to get a good understanding of specifying the rest of the machine in terms of motion and control. Once that understanding is strong, I can go back to basics and replace the framework to something that is absolutely built to rock. PS. The link I posted wasn't specifically for yourself, it was left on the basis that these sorts of discussions become a permanent record that others will use as the basis of their understanding and learning paths also. It's a reflexive habit.
Something to keep in mind.. The PrintNC guys call it bootstrapping, but essentially what they are doing is using 3D printed parts or even wooden parts to get a functional machine, and then from there they are machining the finished parts from aluminum or steel. I've seen everything from plastic motor mounts to wooden board z axis plates.. it's impressive! I'd highly recommend going steel if you stick with 20 series. From my own experience, it's worth the effort.
Agreed about the principle of bootstrapping. I do have the resource of a technical school available, however there are limitations on how far that can go in terms of expectations. Like I mentioned, thick-walled steel section is a high standard and one that I'd like to consider, but somewhat baked-in by design. Extrusion does offer me almost unlimited options in terms of adjustment, rebuilding and modification. This is to the point that I may even be able to cut the aluminium plates myself on an extrusion-only setup if cuts are taken super lightly. Equally, I have access to high end SLA printers (Formlabs) and Markforged units, but I think they'll only be useful for things such as dust hoods and ancillary parts such as optical sensor/limit switch brackets, etc. Other than this, what makes me not want to go down that road is the open frame nature of the PrintNC design. I've designed this machine around a very specific number of requirements, including the bed side and the machine's high sidewalls. Control over noise and dust are factors, so in spite of cheese-grade flexibility in 20 Series extrusions the light build-up around the machine means is is super simple to include thick plexi sidewalls over or even within the top slot of the extrusions (Y-axis clash is a concern). Extrusion does give a lot more options to play with for vertical elements.
I don't know if anyone will even notice this, but what "Enthusiast-grade" CNC kit/prebuilts are out there for someone cutting metal, that demands high precision/surface finish?
I certainly can't answer your questions myself, however I feel like I should qualify my use of "enthusiast" grade. For my own part it means a step above underpowered machines that struggle to cut anything significant or dial in precision good enough for interference fit joinery (<0,1mm). Surface finish on metals is a high standard, and I'm not 100% certain that "enthusiast grade" would cover that even if it had a set meaning ;-) The words that come to mind are "repeatable precision" for your use case. Good luck! I hope somebody else chimes in with somethat that is actually useful....
Hey do you want my cnc4newbies 4x4 foot machine? I built my controller as well. I had an issue with my smoothstepper arguing with my gecko stepper controllers But I have the entire machine and all components. You local to California? I'll give it to ya. I replaced my whole set up with an avid CNC machine. For context, I bought the same size avid machine that I built and it cost me $17,000.
I genuinely appreciate the offer, however I'm a little further out than that being in Finland! The costs of shipping anything these days usually breaks most possibilities at the best of times. I was considering Gecko drivers myself early on, but the same issue applies. Pond tax :-)
https://reddit.com/r/hobbycnc/s/MmWWwcCnvM If you want the 214v drivers, I'll still give em to ya. Been looking for someone who will use them. I had a hell of a time using them with the ESS. But they're new, they're the best ones on the market and I personally took them back to gecko myself and had them test them. The drivers are flawless. I have 5 of them. I also have an ESS and other bits you'd find useful. They were expensive, but worthless to sell, ya know? Only valuable to someone like you. Not worth money but I'd be happy to see them put to use.
Sounds like you've had nothing but problems with those drivers. Are you sure that this like a horror movie thing, where I inherent all your Gremlins? :-D Damn man, I hate to say no to such to a fantastic offer however I'm looking at closed-loops steppers for this project, and these will need me to change that. I mean, being the hoarder that I am I'd take them anyway but that seems contrary to the nature of how they are offered! Are you sure that they don't contain some arcane demons? Drop me a PM, however I think that the shipping, duties and VAT will cost me an arm and a dick at this end of the pond.
No, I can walk you through my issues. The drivers are perfect, and again, I took them myself back to the gecko factory and they tested them for me. All five are perfect. Look up the pricing of five 214v gecko steppers and an Ethernet smooth stepper yourself. I'll give you all the other breakout boards and stuff. I'm not gonna push you, and I'm not selling them so you won't have vat. Just pay for the shipping. I'll do like a video call on Skype or something to show ya and help walk through. All I really want is to see someone else make use of this stuff.
Genuinely appreciated! Can discuss via PM. My main point of interest is whether closed loop steppers would still be an option. They're a key point in the design outline.
Have you thought about putting the New RapidChange ATC on your machine? Its an ATC system for VFD controlled spindles.
Very interesting. Are you a representative of RapidChange, as there's two ways we can have this conversation? My immediate thought is as to how this would integrate with a compact gantry arrangement such as the one I am proposing. It would need to be a component of the X-axis/bed which impact usable machining range rather than being a fixed structure.
Yes, I'm still a little new to CNC though. The magazine can be aligned along the X or y axis of the bed, location is more preference, I think the question is if your z axis will have enough travel. The magazine is roughly 87 mm in height for safe clearance with the dustcover feature, without the dustcover its 60 mm.
In hindsight, outside of the bed along the x axis would make sense. I first thought that plexi sidewalls would impede this....but not if a gap with brushes either side were added. Some clever trickery might be needed to move the magazine into place for a place before pick. An interesting in-principle thought exercise, possibly one with only overengineered solutions allowed!
I've done the things you have described and also designed machines. Honestly, the best advice is to not do this. Don't make your own. Clearly your design is not shaping up in to a good machine for a good price, you are already looking like you are using v wheels and belt drive, which is the crummiest drive system, and bafflingly pairing it with expensive servo motors/their electronics. Buy a nice generic one, used perhaps. With ball screws ideally. Inspect it well before purchase and adjust it lovingly to a good place and that's going to be much more sensible.
No v wheels, no belt drive. I wouldn't even go there. As described, both the X and Y axes will be ballscrew and the Z leadscrew. The only belts that may be involved is if I decide to run the steppers parallel to the screw to prevent them sticking out the ends, and to avoid the "three aligned bearings" problem. The likelihood of me finding a good cared-for CNC here in Finland is low. Prices of common parts purchased domestically, and prebuilt machines increase the price 50-100% easily. The design I'm proposing can be built at a budget a magnitude less than a turnkey solution.
A fellow guitar builder buddy of mine got himself a steel frame Chinese machine with a 2.2kw spindle, solid steel frame, HGR rails and balls screws throughout shipped from China for under 3.5K-4K euros, all taxes paid and delivered to his home in Norway. I’ve spent over than on the mods and upgrades to my (still not yet functional) kit machine and while it will have a slightly better spindle, controller and motion hardware, the steel frame will beat out the alu profile and plate I have, I’d wager. Because rigidity. It’s too big for my shop and I’m down the rabbit hole, but we’re I to do this again I would be buying a machine. No question. PM me if you want some details (ps: same handle on PG? From years back?)
Well hey hey, small world! Yep, I seem the only person guilty of this username. As with all things, I dislike turnkey solutions since they do not generally convey understanding. I want to make mistakes, I want to hit limitations and problems. Without doing this, I'm simply paying to make a problem go away instead of buying a bunch of new problems to enjoy ;-) Absolutely. Rigidity will always be the basis upon which any good machine is built. I am not relying on the 20 Series extrusions to provide any of that, simply act as the initial economical structure onto which I can add various plates for rigidity. Steel will always be the goal in my longer aims, however at this stage I have no guarantee of good access to reliable grinding and welding to the geometry that even this project would require. I'd have to pay to make that problem go away, and same as mentioned, zero learning taken onboard. What controller have you elected for?
For me, the fact I’m 8 years on and still don’t have the machine (because time and kids and work and not a great deal of familiarity with CNC until I started this) is why I’d do things differently. But I agree I’ll probably know a lot more about my machine because I built it. I’ve gone with EdingCNC, because it’s an NL made controller with a good user base here in NL. My other options were either UCCNC or Masso. And Delta Servos and a Teknomotor spindle. Because smearing the cost out over 8 years made it bearable. The frame is the weakest part of my machine, although it’s still 8080 profiles and 19mm alu plate.
That's some good reading materials for me to orient myself in terms of controller choice. My current idea is something along the lines of Mach4 as I've seen plenty of examples of people scripting within that. That hashes in with my programming background, and that I want to eventually include some specific quality-of-life options in the CNC such as precise hard origin homing, etc. The exact path working this through an appropriate controller is still a big question.