I have made a portable vacuum hold down table for the CNC router. The hold down table is a wood box with a grid of little holes on the top with a larger hole on one side to link my shop vacuum. When the vacuum is turned on, it pulls air through the plenum within the box which produces suction through the grid of little holes on the top. This suction will hold a flat work piece on the top of the box in position.
The CNC router develop:
A few of the tools utilized in this project
Cantilever Clamps:
DEWALT DW618 2-1/4 HP Router:
Milwaukee 18-volt Compact Drill:
Whiteside Router Bit 1/8-Inch:
Whiteside Router Bit 1/4-Inch:
Oshlun 8-1/2- Inch Unfavorable Hook Finishing ATB Saw Blade:
FastCap Glu-Bot Glue Bottle:
3M Peltor H10A Optime 105 Earmuff:
3M Reusable Respirator:
3M Particulate Filter P100:
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Looks like it does the job well Frank, and nicely made as always. The only suggestion I can think of (and it is only a suggestion which may well prove impractical) would be to make some sort of sliding boards within the table itself. Sliding them back and forth would close and open the holes withing the struts, rather than you having to use boards on top. I don’t think it would work any better than the system you’ve already devised but the idea may prove to be food for thought 🙂
Matt Jones I had the same idea right before I read your comment.
I’d actually consider taking this one step further. Drill matching holes in the Dampers (sliding boards as mentioned by Matt) and then you could gain better control of airflow throughout the box by adjusting the openings. Of course this might require removal of the top or bottom to install guides for the dampers.
Also you realize you have created a base for a vacuform machine!
Make a grid of struts and have the holes along the X axis be half as tall and be on the top half of the strut. Make holes on the Y axis be half the height of the strut and go along the bottom half of the struts. Then you could slide closed whatever partitions you want along both axis’ in order to go from a very small square in one corner to whole lines or rectangles of whatever size you need. The only down side would be that you couldn’t position the items to be cut wherever you want, you’d have to keep them near the 0,0 location. I don’t imagine that would usually be a problem though.
Alternatively, maybe you could just use heavy duty plastic sheeting on areas that you want to block off. And that would let you cut it to whatever shape you need though it would be a little wasteful potentially
Frank, this is really clever! At the end of the video though I couldn’t help but wonder – is the vacuum really doing much of the “holding?” Or is it the boards with pegs covering up the remaining holes. I’d be curious if you did an identical piece to your test piece with the vacuum turned off if it wouldn’t have the same result. My guess would be that the pegs on those boards are more than strong enough to hold the piece in place themselves without the vacuum even on. What do you think?
The vacuum is definitely holding the board it place. I did not show that so well in the video.
Matthias would defo do some pulling or quantative measuring of how much force it would take to ‘unstick’ a workpeice from the vacumm table.
Hi Frank. Very nice video and work you did there again. A small hint for the next top surface. Normally the holes in a vacuum table are made in two steps. Larger diameter pockets in the top that doesn’t go through. In these pockets there are smaller diameter holes drilled (1/16″ or smaller), this time through the top. That way you have a large area for hold down force but only a small hole to limit the airflow. In case there are some leaks you don’t lose your vacuum at once. Thanks for sharing your work with us. I’ll keep following your channel. Greetings from Belgium. Julien
I did not think of this, but it makes perfect sense. Thanks
Worth comparing the area of the vacuum hose to the total area of all the holes in the table. Assuming a 3″ hose and 1000 holes you could get away with a sizing of 1/8″ and match the suction power with a work piece of 50% table area . 1/16″ might cause too much strain on the vaccum with half the holes covered. If the vacuum can handle that then no problem. Great video as always, and much appreciated.
That is a good Idea. Sounds just like when Mythbusters lifted a car with a vacuum.
When the sound of the vacuum blade goes up in pitch we think its working harder. Actually its working easier; the blade is ‘free wheeling” in a vacuum.
I worked a huge flat bed beam saw once that had the opposite the bed had ball bearing vents that when pushed down blow air up and lifted the board which meant one could move a 9×8 board with one finger. I wonder if you could use the same principle in reverse so to localise the vacuum to the work area? Love your videos thanks for sharing your time and adventures.
That is a nice idea, had not thought of that. everyone talks about air hockey, this is uesfull
Great build. A couple of things,
One: paint any MDF to seal it from air leakage. MDF is basically a sponge with micro-channels all the way through it. Either latex paint or similar, or just PVA glue diluted half glue half water should do the trick. I heard the glue trick to seal the edges of MDF to keep it absorbing to much moisture even in storage or when ‘fresh cut’ parts coming off CNC machines.
Second: Zone the hold down. If you are having a permanent vacuum hold down, make it into zones, say divided in thirds along the sides, and in half down the center length wise, making 6 segments that could be turned on or off individually with a simple 3″ PVC manifold and ball valves.
It works pretty well now but sealing up the side of the box and mdf will help.
That was just what I had seen others do with ‘full size’ CNC machines (like Shopbot or MechMate)
I would have suggested the opposite thing.
If we use small router bits (so the force on the workpiece is not to strong) we sometimes just take a natural mdf board as a sacrificial board. without any holes. mdf is so spongy, that the air will suck through it anyway.
to have even vacuum distribution, we also have a 1mm thick foam between the table and the workpiece.
you can also just use soft pvc sheets to cover up any unused area (then you don’t have any trouble with bowing wood pieces)
Pretty good design, though the boards used to cover the unused holes at the end might be a little overkill, since they don’t have to be structural and are essentially there to simply block the vacuum you could use something much more lightweight like tape or paper even, that way it would be easier to get them into the exact shape you needed. Though it’s hard to tell how strong the vacuum is from the video so maybe something thicker is needed.
Frank, love your work, always a good watch. I have a suggestion if you remake your table. Rather than making a torsion box, if you simply laminate together 2 sheets of ply or MDF you can route a deep criss-cross pattern into the surface to act as air flow channels. Then a third lamination with holes through it to act as the surface, where the through holes meet the channels below. This would be just as heavy as the torsion box, and easier to make and maintain the vacuum.
I just literally ordered my 3mt by 2mt cnc router this week… Been watching your video’s for years. I love the way you work and edit them, but this could be the most useful yet!!!
1 question, what software do you use? Like vector to G code?
Hey Frank – Cool Idea & great video! Perhaps instead of the ‘wood dams’ that you made, you could use a heavy/cardboard paper. The vacuum should hold it down just fine, and you could cut out the paper where the work piece is allowing you to do virtually any shape/size that fits on the table.
Awesome Frank! I use a biesse cnc at work that uses vacuum as the hold down. Not sure how powerful your vacuum is, but I use 3/4 mdf as a spoil board. The holes are all under that, the way I get it to suck down parts is to plane both sides of the mdf. You be surprised at how porous mdf is after removing the protective layer.
I’ve messed around with vacuum tables quite a lot, and what I found to work best is just sucking the air through the MDF. You have to machine off about 1/16″ from both surfaces to get rid of the hard outside layer, but the core of the MDF is porous enough for the air to pass through. Some guests in the shop have been really surprised to see how well it holds when there is seemingly nowhere for the vacuum to get at the workpiece!
I also found that if you have the entire surface covered it takes very little airflow to keep up, so you need surprisingly little space inside for the air to flow. My most successful vacuum table was simply one piece of 3/4″ MDF with a tree-like pattern of 5/16″ channels CNC cut into the bottom, with a piece of 1/4″ MDF glued to the bottom of that. The bottom and edges were sealed with varnish to prevent any leaks.
All of my vacuum table experiments were using a central vac motor (similar to a shopvac in performance) providing about 60 inches of water.
jmick.art
Good idea using drop cloth. I’ve tried using stretch wrap but that was a pain because it sticks to itself…
have you ever used the lightweight MDF? Same price as the regular stuff its just hard to find, but it does allow for a little more suction through the spoil board.
That wouldn’t work with the sacrificial layer glued on top though, right?
I have a 2 foot by 4 foot CNC router and I am planning on replacing the MDF spoil board with a three-quarter inch piece of plastic, probably PVC , with channels routed for vacuum to flow and then a piece of 1/2 inch thick MDF on top of that as a porous vacuum table. I’ll skim cut the top and bottom sides to increase the porosity and I’m planning on having four corner screw down holes with tapped inserts for rough material that will not vacuum well to the vacuum table.
Do you have a section/drawing that describes exactly what worked best for you?
I used to do a lot of screen printing and the table we used had this vacuum system. We just used sheets of paper to block the other holes. We also had an upright copy camera that used similar system to hold down the film and it used an empty canister between the vacuum and the area to be held by vacuum, it was about the volume or a little less of a 4 litre paint can. I think its purpose was to give you instant vacuum after throwing a lever or switch as the canister would be in vacuum and as soon as you threw the lever the work was held instantly and you didn’t have to wait for vacuum build up. Hope this vaguely remembered stuff helps in some way.
Thank you Frank! My dad and I have been working on a cnc table design and one thing that we’ve been dancing around is a vacuum hold down surface. Thank you for showing how easy it can be!
how about covering the whole table, workpiece included, into a disposable sheet of plastic, the kind of plastic garbage bags are made from. the cnc should easily cut the workpiece trough the sheet.
always entertaining Frank, always!
Looks nice! I always thought about using little spring-loaded ball bearings in the bottom of each hole to act as automatic valves. You just toss your workpiece on indiscriminately, and every hole that it doesn’t cover will shut itself as the ball gets pulled downward. (Unfortunately, the holes probably would get full of sawdust in a hurry…)
I used to work as a CNC operator at a local shop, I recommend routing a small groove midway between all the holes both X and Y directions and using a closed cell foam tube gasket/foam backer rod to seal the area below your work piece (If you plan to continue using boards to cover the “extra/ unused” holes then you would need to put the gasket in the groves around the edges of these pieces as well) This will allow the vacuum to pull the piece down onto the table and create an air tight seal. Also you may want to consider routing a ledge around each hole and creating “mushroom top” pegs that you can drop into unused holes so you dont need all the extra wood on the table. This will allow you to cut irregular shaped stock (we had rubber pegs that we placed into the unused holes but I’m sure you could make something out of wood). Good luck with you CNC machine! Love the videos.
A few things I did differently on my vacuum assisted cnc router table; 1. I ported the vacuum areas onto zones table and had discrete holding zones. 2. MDF is porous and a vacuum can be pulled through it. 3. I gridded the top into 1.5 inch squares and I can add 1/8 inch rubber gasket line between the squares to custom seal the zones. it takes little more effort to re-add the grid when I reface the bed.
I used to work on a 4×8 cnc that had a built in vacuum table. There were a bunch of grooves in the table and we inserted rubber gaskets in a rectangular shape the size of the piece we were working on (this would localize the suction just to our work piece). Also, we would sometimes just install a piece of MDF large enough for our work surface – it’s porous enough that the vacuum would pull right through it, especially for cuts on large sheets. Maybe try some 1/2″ or 1/4″ MDF on top of your setup and see if that gives you enough suction when you put pieces on top of that.
Just read through a bunch of comments, that’s a wealth of info down there! lol
Where I used to work, we had a 4′ x 8′ CNC router and we laid 1″ x 4′ x 8′ sheets of foam as the sacrificial layer. It breathes amazingly well, so the vacuum still holds powerfully. You then cover up the ‘non work’ areas with some cheap plastic sheet (Coroplast, etc). After a while, you flip the foam sheet and use the other side. Once both sides are too marked up, you replace the sheet. Cheap and easy.