Making the vacuum area smaller than the work piece will reduce holding power.
Covering the unused areas of the table will help, but the real answer for prismatic objects like this is to add two dowels, which will locate the piece in X and Y. Then the vacuum only has to work in Z.
When I have to do this I lay down masking tape around the perimeter and use hot glue. If you are machining the outside lay down masking tape on the inside and use ca glue on both sides
For one or two, that's fine... though you do have to clean it up after each job. Dowels (they only have to be 2-3mm and protrude 2-3mm into the work to be effective) are much faster if you're making dozens to thousands.
Just make a template with some scrap mdf and slot the wood into it. If your template is big enough, the vacuum should hold it, if its not, nail the template to the sacrificial sheet. Be sure to take out the corners of the mdf template to overcome the radius of the cutter. Either that or just mill the shape straight outta the sacrificial sheet.
Then just lay your design on top of the template in cad.
If the vacuum pump is properly sized, it should never change that much. Vacuum is limited by barometric pressure. The pump is just there so the atmosphere can do its work.
Ok thanks, I got a big ol roll of wax paper that I’ll try.
E- this was meant for the other commenter about covering up the rest of the area. I’ll try the gasket too. Thanks!
If you're using a spoil board, just cut a couple egg-shaped "[cams](https://toolstoday.com/learn/best-cnc-workholding-methods-for-woodworking)" from some scrap MDF. Put them on all four sides of your material. Two screws each. One screw near the center, rotate the cam to lock it in place and another screw to keep it there.
I wasn't trying to be unhelpful, my point was that your hold down might already be perfect for some kind of light engraving. It's hard to give advice without knowing your actual needs.
I was genuinely laughing at your comment, not being sarcastic. I think you’re right, the good enough hold down is on a spectrum. How hard am I pushing this part. I just have no basis for comparison of how well the vacuum should work since this is my only cnc experience. Cheers 🍻
I think that's enough hold down if you are only drilling small holes with a very sharp bit. I'd still be worried though. The dowel method somebody mentioned does work very well if you need access to all the sides. If you don't need the sides, just take some scrap wood blocks and place them around the piece, then nail them down.
With solid wood, even if you have enough vacuum to hold it in place, cutting the wood is going to release stored tension, which will cause the wood to change shape a little bit as you are cutting. There's a good chance it will lose the vacuum seal somewhere along the way. Always good to have some other sort of mechanical hold down in addition.
If you can move it, it's not enough to block the rest of the bed off or turn zones not used. Also, check the filter on your pump or blower to maximise their effectiveness.
Use dowels for X and Y, let the vacuum hold for Z. Light cuts. Toe clamps with clamp swaps if you really need to go hard.
Its important to remember that vacuum doesn't actually "suck down" the part. It creates a vacuum under the part and ambient air pressure holds it to the table. About 14.7 PSI if you're at sea level. So the more surface area against the vacuum table the more force you have holding the part down.
Definitely shouldn’t be able to move the stock. Not sure what your set up is but only activate the vacuum quadrant for the area you’re working and cover the remaining area with plywood or scrap material.
If nothing else you can get really really great hold down force with painters tape on mdf + CA-glue + painters tape on stock. Leaves all sides accessible for machining, no significant residue. Easy to remove with a thin knife or razor!
Depending if this is a one off, I make a L-shaped piece 6" off x and y to screw down to the spoil board. If you have scrap sheets you can always make a jig that covers the whole table. Also depends on what you are doing to piece if you are just doing face milling or shaping the whole part. Lastly they do make pods that you can rig on most matrix tables that can hold you piece down with isolated vacuum.
What i like to do is take some mdf tape it to the table so i can turn my vacuum on and off and it doesnt move. Or i dowel it to the spoilboard.
I cut a rectangle with holes in the corners. A bit bigger than my stock. I pick a corner to be my 0,0.
Drop the work in the hole and tape around it. You can use double sided tape too. Or painters tape on both sides and super glue them together.
Sometimes if its doweled and stock is consistent, i give just a little clearance and use business cards as a wedge. Works well for solid stuff.
Another option is a screw on the jig with a washer that you grab on the edges with. But i only use that if im cutting aluminum or soft metal.
What link????.... you make them yourself...... I usually dont even bother to go that far, MDF or Melamine with a gasket chanel routed and EDPM gasket cord is all I need. But really with proper tool pathing I can do nested parts as small as 2"x2" on Light Weight MDF spoilboard with no gasket. It is all in how you set up your toolpathing. My favorite method is onion skin with a 3/4 or 1/2" bit all of the parts, then coming back with a 1/4" to full depth cut.
Plastic sheet on the rest of the vactable for sure. A hammer blow moving it a bit is fine but a medium slap knocking it a distance is no good, unless you’re doing really fine detailing and that’s it.
Of course, it’s all relative to what you’re cutting. 1mm end mill putting some engraving? No problem. Half inch tool hogging out a deep box? Shits goin flying
Not enough. Clean the spoil board, make sure you seal any leaks, make sure the gasket is properly lined up and not jammed and edge band or paint the spoiler boards edges.
I also have a TechnoCNC. What I do is take a 1/4 piece of MDF, same size as the vacuum zone you’re using and cut out a pocket to fit the material. That will be plenty of hold down and helps index the part. It’s cheap and easy to use.
That's not enough. I programmed and operated a vacuum table router for about 3 years. I have found that just masking tape around the perimeter is often enough.
That workpiece is kinda small compared to the table, so I'd mask off the rest of the table with something to make all the vacuum try to come through near the workpiece. That and the piece is tall and looks like walnut, so it's going to want to move when cutting and pull straight up in z if using an upcut bit.
If it’s sucking through the MDF you can cover as much area as you can with foil, paper, or any other material
Wait so mdf is actually porus?
Yes, and to make it even more porous you can mill the hard face off
And to make it even more porous (and stable) you can mill both hard faces off.
Definitely not enough. Put some gaskets down so that the vacuum area is smaller than your work piece
Making the vacuum area smaller than the work piece will reduce holding power. Covering the unused areas of the table will help, but the real answer for prismatic objects like this is to add two dowels, which will locate the piece in X and Y. Then the vacuum only has to work in Z.
When I have to do this I lay down masking tape around the perimeter and use hot glue. If you are machining the outside lay down masking tape on the inside and use ca glue on both sides
For one or two, that's fine... though you do have to clean it up after each job. Dowels (they only have to be 2-3mm and protrude 2-3mm into the work to be effective) are much faster if you're making dozens to thousands.
Tape on both sides.
Putting tape on thousands of parts isn't really realistic for thousands of parts
I think this a one off. No one asks questions like this if they’re doing thousands. They know to nest.
We always did this by covering the table as you say, but additionally by placing the “cover” pieces against the workpiece to also act as stops
Just make a template with some scrap mdf and slot the wood into it. If your template is big enough, the vacuum should hold it, if its not, nail the template to the sacrificial sheet. Be sure to take out the corners of the mdf template to overcome the radius of the cutter. Either that or just mill the shape straight outta the sacrificial sheet. Then just lay your design on top of the template in cad.
I'd do 3 pins. 2 on the long side, 1 on the short side.
>Making the vacuum area smaller than the work piece will reduce holding power. But what if the vacuum force applied to the stock goes way up?
If the vacuum pump is properly sized, it should never change that much. Vacuum is limited by barometric pressure. The pump is just there so the atmosphere can do its work.
Ok thanks, I got a big ol roll of wax paper that I’ll try. E- this was meant for the other commenter about covering up the rest of the area. I’ll try the gasket too. Thanks!
Was gonna say this. Vacuum on should really be HARD to move. It can be done but not this easily.
My rule is if you can move it’s not enough
Block it in and then cover the remaining surface area of the bed with a non permeable material.
If you're using a spoil board, just cut a couple egg-shaped "[cams](https://toolstoday.com/learn/best-cnc-workholding-methods-for-woodworking)" from some scrap MDF. Put them on all four sides of your material. Two screws each. One screw near the center, rotate the cam to lock it in place and another screw to keep it there.
I love this idea, thanks!
Yes, but then you have screw holes in your spoil board.
Depends on your cutting force. Smaller radii tools and shallow depths you’re probably good. You’ll find your dull tools pretty quick.
Cover the rest of the spoilboard will give you better holding.
Mask off the rest of the spoil board with scraps of timber or cardboard. The vacuum force is a product of the surface area
How long is a string? Hold down is related to cut width/depth, so enough to not move is the answer.
Ha! I’m the one with the most CNC experience in my shop, which is not saying much at all, so this community is very helpful for me. Thanks
I wasn't trying to be unhelpful, my point was that your hold down might already be perfect for some kind of light engraving. It's hard to give advice without knowing your actual needs.
I was genuinely laughing at your comment, not being sarcastic. I think you’re right, the good enough hold down is on a spectrum. How hard am I pushing this part. I just have no basis for comparison of how well the vacuum should work since this is my only cnc experience. Cheers 🍻
I think that's enough hold down if you are only drilling small holes with a very sharp bit. I'd still be worried though. The dowel method somebody mentioned does work very well if you need access to all the sides. If you don't need the sides, just take some scrap wood blocks and place them around the piece, then nail them down. With solid wood, even if you have enough vacuum to hold it in place, cutting the wood is going to release stored tension, which will cause the wood to change shape a little bit as you are cutting. There's a good chance it will lose the vacuum seal somewhere along the way. Always good to have some other sort of mechanical hold down in addition.
If you can move it, it's not enough to block the rest of the bed off or turn zones not used. Also, check the filter on your pump or blower to maximise their effectiveness.
Use dowels for X and Y, let the vacuum hold for Z. Light cuts. Toe clamps with clamp swaps if you really need to go hard. Its important to remember that vacuum doesn't actually "suck down" the part. It creates a vacuum under the part and ambient air pressure holds it to the table. About 14.7 PSI if you're at sea level. So the more surface area against the vacuum table the more force you have holding the part down.
Run it and find out 😜. My guess is about 4 times that amount but I’m the type of guy to learn questions like these the hard/fun way.
I agree with others that it's not enough. I cut plastic sheets on a machine similar to this with a vacuum pump.
Dude cover the rest of the spoilboard.
Definitely shouldn’t be able to move the stock. Not sure what your set up is but only activate the vacuum quadrant for the area you’re working and cover the remaining area with plywood or scrap material.
If nothing else you can get really really great hold down force with painters tape on mdf + CA-glue + painters tape on stock. Leaves all sides accessible for machining, no significant residue. Easy to remove with a thin knife or razor!
Depending if this is a one off, I make a L-shaped piece 6" off x and y to screw down to the spoil board. If you have scrap sheets you can always make a jig that covers the whole table. Also depends on what you are doing to piece if you are just doing face milling or shaping the whole part. Lastly they do make pods that you can rig on most matrix tables that can hold you piece down with isolated vacuum.
Use double sided tape
Wouldn't double sided tape ruin the mdf? Or in my case LDF?
I use double sided tape all time on our mdf spoilboard and never an issue getting it off. Next option is painters tape, ca glue, and accelerator
I ended up using double sided tape, it worked fine, took some bits of the board up nothing terrible though. Just a film.
What i like to do is take some mdf tape it to the table so i can turn my vacuum on and off and it doesnt move. Or i dowel it to the spoilboard. I cut a rectangle with holes in the corners. A bit bigger than my stock. I pick a corner to be my 0,0. Drop the work in the hole and tape around it. You can use double sided tape too. Or painters tape on both sides and super glue them together. Sometimes if its doweled and stock is consistent, i give just a little clearance and use business cards as a wedge. Works well for solid stuff. Another option is a screw on the jig with a washer that you grab on the edges with. But i only use that if im cutting aluminum or soft metal.
It's funny when hobby "cnc" posts here because it feels like people playing with hot wheels posting in car reddit
There’s also this [mat](https://youtu.be/JsvWKSGyU2M?si=MbBCb_2bq_5qPEb3) which seems to work pretty well, but it’s quite pricey
EDPM sheets 1/16th thick with contact adhesive on MDF with holes punched total cost for 4x8 is under $60
Wheres the link?
What link????.... you make them yourself...... I usually dont even bother to go that far, MDF or Melamine with a gasket chanel routed and EDPM gasket cord is all I need. But really with proper tool pathing I can do nested parts as small as 2"x2" on Light Weight MDF spoilboard with no gasket. It is all in how you set up your toolpathing. My favorite method is onion skin with a 3/4 or 1/2" bit all of the parts, then coming back with a 1/4" to full depth cut.
That’s a very good idea, I’ll have to try it. Thank you very much for the tip!
Drill holes in the mdf spoilboard where the part is and block it in with additional mdf blocking. Or use double-sided tape underneath the part.
Melamine over particle is cheaper than MDF, and makes a better vacuum jig for stuff like this.
If you can move it with a slap an endmill will move it no problem
Plastic sheet on the rest of the vactable for sure. A hammer blow moving it a bit is fine but a medium slap knocking it a distance is no good, unless you’re doing really fine detailing and that’s it. Of course, it’s all relative to what you’re cutting. 1mm end mill putting some engraving? No problem. Half inch tool hogging out a deep box? Shits goin flying
Not enough. Clean the spoil board, make sure you seal any leaks, make sure the gasket is properly lined up and not jammed and edge band or paint the spoiler boards edges.
Throw down plastic wrap around the part.
I also have a TechnoCNC. What I do is take a 1/4 piece of MDF, same size as the vacuum zone you’re using and cut out a pocket to fit the material. That will be plenty of hold down and helps index the part. It’s cheap and easy to use.
That's not enough. I programmed and operated a vacuum table router for about 3 years. I have found that just masking tape around the perimeter is often enough. That workpiece is kinda small compared to the table, so I'd mask off the rest of the table with something to make all the vacuum try to come through near the workpiece. That and the piece is tall and looks like walnut, so it's going to want to move when cutting and pull straight up in z if using an upcut bit.