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.
I have good results with "shaved" MDF as well. It is amazing how permeable it becomes with the hard faces milled off. For blocking unused areas, I use thin plastic sheeting like the .5 mill painters drop cloths.
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.
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.
What you need is an actuating part that blocks the holes not in use for your run. This may be a manual switch that you have to actuate from the sides or top or bottom of the table. Ideally your CNC program would run the actuation automatically when you located your part and hit the "go" button...but that's a different set of circumstances. Good stuff, as alway, Frank. Thanks for doing what you do.
Even if you're not totally pleased with it as a vacuum hold-down, you've made yourself a darned nice downdraft table. Perfect for sanding on to keep dust to a minimum. We've got a couple of these in our shop for this.
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!
Great video. Thanks. MDF is porous anyway, so it may not be necessary to drill all those holes (if you have enough vacuum). If you cut 1/8" / 3mm from each face of the MDF sheet it removes the most dense part of the MDF and makes the vacuum significantly more efficient. I use scraps of plastic sheet to cover the remaining area when I need more vacuum on the job piece. A vacuum cleaner is not designed to be dead ended as the air going through it is intended to cool the motor. Using it for a vacuum table may not allow it to have a long and happy life!
Hi Frank just a few pointer I used to program CNC machines.the Matrix machine works better if you seal the sides of the mdf your vacuum with increase, you will have air leakage at the side until it's sealed, you could put a sacrificial board on top so you can cut right through I set the cutter depth to -.2mm we put 25mm mdf on top of our plenum which we would skim every day until its about 6mm we skim both sides so we get airflow and seal the edges. we do exactly what you are doing by covering the unused bed with melamine covered 6mm ply we tried various method but for speed we found this to be the best way but mostly we used 8x4f sheets. Great build of the CNC liked the way you overcame all the problems.
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.
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)
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.
I used to work on a 4x8 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.
A friend has a vacuum table for all his CNC, he doesn't have holes in his vacuum table only a piece of MDF with a 64th trimmed off each side to open up the pores. This does a great job doesn't have the loss issue that you're trying to deal with by putting boards over the unused holes
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
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.
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.
Paint the sides to help. MDF and particleboard allow air to flow through. At the maker space I go to the have MDF on their CNC to clamp plywood sheets down.
I'll second that. A company I work for uses sacrificial 6mm/1/4in MDF sheets on the bed to hold blanks of polyethylene foam. We sometimes use it with plywood and MDF blanks.
I recall with the CNC that my school had, you could get a vacuum bed that you put a 6mm piece of MDF onto as a sacrificial board and then in theory you could still clamp wood to it as it created a vacuum through the 6mm sacrifice board. I was a little skeptical, but my school never bought one so I don't know if it worked. They used the T-slots in the metal bed to clamp sacrifice boards to and then used carpet tape to hold the wood/plastic that was being cut.
Hey Frank, great build, what i use on my vac table is a plastic bag and just lay it over the open areas, not as sexy for sure but gets the holes covered!!
A commercial vacuum table I saw years ago had several dozen ball bearing valves with a grid of rubber/foam gaskets; just slap a workpiece anywhere on the table and it stuck. The springs holding each ball bearing in place were just strong enough to resist a shop vac, but any weight on top would break the seal and start the vacuum effect. I thought it was pretty neat, but always thought that a huge workbench sized version would be more awesome.
I really like your videos. I have built a number of vacuum tables before. The only recommendation that I will make is smaller holes. Like 1/16 to 1/8 in size. The vacuum hold down for this size is much stronger then the 3/8 inch holes that you used. They would be closer together and you don't need as large of vacuum. For the tables that I build I use dowels instead of raceways. I have found using raceways over time you get scalloping of the surface where it is not supported underneath. I also use a much smaller chamber size. No more then an inch between the sandwich. The smaller the area of volume produces more suction.
NICE ! And as a professional photographer, it reminds me of the smaller, peg board topped vacuum box I made "back in the FILM day" - to hold down sheets of 16x20 photographic paper below my enlarger. That way I could expose the entire sheet to easily create a borderless image... ( it worked great.)
Hi frank, make sure you have enough air flow to allow the shop vac to stay cool. They rely on air flow to cool the bearings and motor. I've seen people use motors from ducted vacuum systems and drill a small hole in the hose so it leaks just enough to keep the motor cool. Love your work
We had a thermwood in high school with a built in vacuum table and what we did is cut custom waste boards for each project. We'd cut a 1/4" groove was offset to the inside of the outline of the piece (if that makes sense). And a grid pattern of the same size/depth cut inside that outline along with small holes drilled periodically to allow the air flow. Then we'd fill the the outline with a 1/4" rubber strip. Once the piece was in place and the vacuum turned on, the suction would fill that grid pattern and apply even pressure across the entire piece. This was especially effective pieces that needed to be mass produced but even for small one-off projects it was fine because the work bed 8'x8' so you could simply grab an old waste board with some room on it and use that. I hope at some least of that was coherent. It's early and I haven't finished my coffee lol
Frank, may I say you are an inspiration and ambitious. Your vacuum table. My experience is that you’re never the right size and cover pieces. Rather than trying to make one big one, make many small one’s. A round piece of wood say 3” and 2” thick with an O ring grove cut into top and bottom with a hole through the side. Make several with a ball valve on each. Small flexible hose to each all piped individually back to the vacuum pump. Place them under your work piece, open valves only to the ones you going to use. Switch on vacuum pump. Suction cups fix to bottom and work piece at the same time. Job done. Many thanks for your entertaining videos. Johnathan
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 :-)
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
I own/run a commercial CNC in a millwork shop. Not sure how well the information would transfer to a smaller CNC, but here are a few ideas: Our CNC has an aluminum table with holes for vacuum. Instead of having so many holes (ours are about 4" apart), our machine has channels around each hole to spread the vacuum of each hole. Would reduce cutting time, and allows for realistic plugging of individual holes. Ontop of that we put a "spoilboard" solid 4x8 sheet of 3/4" MDF (no holes). We prep the sheet by running all edges through the edge bander. This stops air from leaking out the sides. Once that is done, I use a 3" cutter to mill off about .2mm from one side of the sheet. No only makes it very flat, but the surface is now much more "open" for airflow. Flip the sheet, and repeat. The sheet is now perfectly paralel to your gantry and open for airflow. I'm not sure if a vacuum should have enough power to do the same (pulling through MDF) on your scale. Our pump is 10hp, but it is capable of 5x12 cutting area (usually setup for 4x8). I can cut a 24" x 24" piece of MDF sitting in a corner of the sheet without blocking the rest of the sheet off.
I thought about doing the method where you suck right thought the mdf, but it looked like you need a big suction motor for that. A lot of flow and pressure.
in our shop we just used two pieces of mdf and routed a center groove that branched out on top and bottom pieces and glued them together so they made an air channel and had holes on the top piece. when you wand to use a small section we just put a peg in one of the center holes and it stops the air from going to the other branches. works pretty well
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.
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 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.
I used to run a graphic arts camera that had a vacuum film back. To allow different sizes of sheet film there was a sliding valve that would close off the area around the edge allowing smaller and smaller sizes of vacuum area. The sizes were marked off in red so you could align the film where the vacuum was, worked quite nicely and I'm sure you could do the same thing and not even need those pieces for blocking off the air flow but the pieces for alignment might be nice.
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.
Hey Frank I put a 1/4" piece of mdf on top of the holes and your vacuum will suck through the mdf and hold your piece down (depending on how strong your vacuum is) then put trash bags on the part of the mdf that's not been used to direct the suction to the work piece. You might try that and see if it would work for you.
I'm hardly qualified to make a suggestion, but I can think of a couple of things. 1. Actually just use perf-board. 2. Make an external PVC manifold to go between chambers, rather than the holes in the supports. By doing this, you only draw vacuum on the chambers you need. 3. A thin film of plastic would work as well as plywood to block the holes you aren't using. Just suggestions. You are waaaaaay better at this than I could ever be. Love the channel.
What i would suggest (when you make a lot of pieces which don't take a lot of time to cut) that you build a foot pedal to switch the vacuum on and off! I also would find another solution fpr covering the holes cause that looks not good and is inefficient. I work as a carpenter and at work we have a big CNC and we also use suction to hold it. For that we have a few rails where you can put some rubbes "boxes" on which have a few holes in it and every time we step on the foot pedal, the "boxes" get the suction to hold the piece somehow through the rails. Maybe membranes are used . Maybe you thought about the same thing with the suctionboxes. Respect and love 4 wood from Germany
Seems more like the modular peg board pieces are holding the work piece in place by surrounding it and then the router cut pushing down from the top. How much is the suction real doing? Would your logo have been cut just as well with the vacuum off?
Hi mate. What do you think about just using some plastic sheeting, bags or tarps to shield off the area that you're not using? You can just cut a hole where you put the workpiece. You might even be able to use some butcher's paper.
I do commercial large format printing on an Océ Arizona which features a 3050x2500mm vacuum table separated into multiple zones. If you made some of the baffles solid, then split your vac run with valves, you can turn on/off the individual zones and lessen the need to cover the unused areas. Also the space inside need not be so cavernous, its just a pathway from the vac hose to the holes in the top. You could make it much lower profile by using a thick sheet of polycarbonate/aluminium/sealed MDF and route a series of channels only 3-5mm deep, then add your spoil board with the holes directly sandwiched on top. Our table is 2 sheets of aluminium with only a 3mm space between them. Also the holes are barely 2mm in diameter at 30mm centres. You'd be surprised at the hold down force it can generate. Your table does what you need it to do, so I don't imagine we'll be seeing Mk II anytime soon. But I just thought I'd share incase anyone else can benefit.
Small note if you make another. Your inner baffles are perfect, what I've see in other is having a second mirror piece then you slide them shut to block of sections of the holes so it's just a little easier.
Hey Frank, not sure on the vacuum required but some of the CNC router companies I've come across draw vacuum directly through the MDF w/out the peg board design needed. You can isolate this surface area with thin plastic sheet i.e. trash bags. Love your videos.
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 9x8 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.
industrial cnc table saws have that, but the opposite.. it helps slide heavy sheets across the surface.. there are little ball bearings in every hole that opens (is pushed down) whenever the workpiece slides over it, making it float across, kinda like on an air- hockey table.. Now in order to do that with a vacuum table, each ball bearing would have to be spring loaded, with more force than the vacuum generates, or else the vacuum would just suck the bearing down, closing the hole.. It might be possible, but I'm not intelligent enough to know how.
you might be more successful by just creating sections with valves that you can shut off and keep it in parts that have higher vacuum then a floating valve would work in theory but as said... the force pushing on it would be a bit too much to make it work... practically impossible... industrial vacuum fixture plates for CNC machines use some rubber seal that you put in a square pattern milled plate so only the sections needed create negative pressure in that case you could work with only 4 or 6 holes in total on the plate but you would need several lengths of rubber slings to actually create the seals themself... pretty complicated stuff tho
How about little rubber balls in depressions. When the air flow is great it would pull the rubber balls down sealing the hole. Holes covered by work pieces wouldn't generate any airflow so would not pull the balls down.
To get better suction you want to make a larger number of smaller holes. Big holes like what you have or pegboard for example don't make very good tops for suction tables. I'd suggest looking at some videos related to making vacuum forming or vacuform tables - they're extremely similar in build and are used for holding down forms to molded, while a hot pliable plastic is placed over top that then gets sucked tightly over the form to make a mold of it.
That could be handy for something that can't be clamped with classic clamps. But otherwise, the classic clamps you might use more often than that table, classic clamps are faster and easier for parts that have plenty of clamping room. I forgot what you call them, but little connection points in your work piece so the part you cut out don't move, then you just use utility knife to snip the tiny tabs, no need to mess with a vacuum clamp. you might find it more convenient, but from here it looks like traditional clamps have it beat. Nice experiment, thanks for the share.
For an example of vacuum fictures in use on cncs on another scale I come to think of John Grimsmos channel (metal/knifes cnc). His setup was consisting of multiple fixtures stacked with one having groves cut around a central air vent which would be sealed with an rubber string to form the perimeter of the vacuum to form. maybe easier to setup than the holes and chamber even if the vacuum might take longer to form. The tricky part would be to get the ratio of rubber compression, deformation and groove dimentions just right so that you get an air tight seal and have the workpiece rest on the ridges instead of the rubber.
That's a lot different than the conventional grid plenum with MDF spoilboard top, cool concept!. You may find you have better performance with the tried and true with the addition of a few whole house vacs. There is a lot of good information on making these in shopbots forums. If you are interested I have some of these vacs and a homemade manifold that I could send some pics of. Trupan MDF is ideal for your spoilboard. I run an 8hp vac on my CNC and I think the whole house vacs are nearly as effective.
so we have a very expensie cnc mill at school that uses a vacuum table but instead of relying on holes in the mdf the vacuum is strong enough to actually penetrate the mdf without any holes which means that there isnt that much loss of suction of parts of the vacuum table arent covered of course the larger the area of the piece the better it will be held down but it does a pretty good job and if the piece is small we sometimes just hot glue it down the the mdf which really holds it well
I remember a magazine article from way back in the day where they used a roll-up window blind to cover part of a down draft sanding table. As someone else suggested, a roll of craft paper would work and you could cut the opening you needed.
I suppose you can add in some adjustable sliders, or pluggable tubes, to create multiple zones to vacuum. For example, you could create a box with 2 full depth dividers inside it to create a box with 3 zones, then drill 3 holes in the sides and externally have some sort of elbow mechanism as needed, or have one vacuum hole, then additional holes to connect the side to the center. Or have some more elaborate dividers that slide internally with offset holes so that if you move them a few inches, the holes are aligned to combine the 3 zones into one, and a few inches the other way closes the holes.
friend of mine build a vacuum table with 9 chambers (3x3), simple internal piping and a few valves to connect to the vacuum... easy to focus the suction on a specific area
MDF is porous and doesnt need holes drilled for air to pass through. On CNCs we use in the millwork and cabinet industry we have vacuum tables built in and we use MDF spoilboards and the parts are held down to the mdf with suction. sometimes you can tape the edges of the mdf to improve the suction and also put laminate or another non porous material around the parts similar to what you are doing. Also just using a 3/8" bit and drilling with your CNC. instead of routing a circle for every hole would speed up your running time significantly.
I know this might be too simple and not noteworthy, but perhaps covering the open holes with plastic such as thick mill roll plastic? 4 sheets that the excess would just hang over or fold when vacuum applied to the covering pieces. Just a thought. Will be very interested in what you finally come up with.
I have a 5'x10 ' table and it takes about five hours to drill all the holes. I use a 1/4" end mill but do a straight peck. Last thing I do after drilling is to put in a 1" bit and surface the entire bed. It takes off any high spots and makes precise Z cutting.
Peter Collin suggested making each hole into a valve so you don't need to seal it. I have a dirt-cheap way to do this. Replace the round clear hole with a blind slot, 3/8"W x 3/8"D x 1"L. Near one end, drill a 1/8" through hole for the air to pass through. The valve consists of a little lollipop: a flat disk with a stick that is bent out of the plane of the disk. When you pop the lollipop into the slot, the disk covers the through hole, and the end of the stick protrudes above the top surface. Vacuum on: the disk is sucked down and seals the hole. Place an object on the table: it pushes down on the end of the stick, levering open the valve (this takes about 2oz of force). I don't know a simple way to make the lollipop, but it has to be cheap.
You can make channels on the bottom piece for the airflow with cnc. Just glue the top piece with the holes airtight and your complete design is 2 layer thick only. You don't really need a 10cm high monster.
One suggestion. On the supports inside put slides with pulls on the outside to close off areas that are not used. Then use the boards on top to cover what is left of the open areas. Make sure the slides are on the opposite side of where the vacuum is so they are pulled in to help seal.
1/4" holes are sufficient for the vac hold down. If in your software you have a feature called Convert circles to drill points then it will do a straight plunge instead of walking around. When I have to drill mine it's about 5500 holes and takes about five hours. I just turn off the lights and go do something else for a while.
what if you cut out a larger recess at each hole then dropped a washer blank or some other stamped disc in it? quick and easy to pull out with a small magnet.
You can also use this with a large plastic sheet to glue inlays or veneers that need constant and equal pressure. The pressure will compress the glue up together.
hi frank I live in England and where i work we have a CNC ( Multicam 3000 series ) we use a vacuum table and we use stock MDF no holes the air can get thot the MDF just fine but we do have a big vacuum pump so may be somtink worth looking in to and just google the CNC ( multicam 3000 ) your find videos on how there table are set up .
I am thinking have pieces that have matching holes that is under the top. if your want to seal an area you could slide the lower piece half an inch so the holes no longer line up.
in between the two top layers you can glue a "rail" system in which 2 wood stripes for each row would be inserted from two opposing sides meeting in the middle. do that for every row and u have a convenient way to activated each hole individually by pulling out the stripes sometimes more sometimes less. or one side more than the other.
On our CNC, the vacuum table has a grid cut in it in between all the holes, cut with a rounded bit, so that we can put tubular gasket type stuff around the piece being cut, and then everywhere else, we just use freezer paper and tape to cover. Also, it helps to put sawdust on the line where the work piece and the table meet, cause it helps seal it off.
and when the work piece is a weird shape (we build skis, so you have that parabolic shape on both sides), we cut that shape into a squared piece of MDF, and drill the holes in that for the vacuum to come through that. It works much better, if a bit tedious.
If you could figure out a way to block the holes in the struts on the unused parts of the table with out sacrificing suction, that would take away the need to cover the holes with other boards. Maybe a sliding cover on the struts and a small box that seals air tight to go over a know that actuates the slides? This idea does mean making a new box though.
if you have something odd-shaped, you can use plain old newspaper to cover up the rest. That said, your modular covers with registration pegs are very nice :-)
Hey Frank, great design. Always enjoy your videos. I was wondering would be an idea to make blocks, kind of like Lego, say strips of 6 pegs x 2 pegs, fill the whole vacuum table with the blocks. Then only remove the sections required for the size of the piece you need to hold? You could have different strip lengths available for odd shaped work pieces? This way your only removing and replacing small sections as you use them ? Like I said just thinking out load :-) Thanks for sharing, regards Steve.
I run a vacuum bed at cnc at my work. I would recommend sealing the sides to restrict air flow through them. I was wondering, does the end furthest from the side with the vacuum port have enough suction to hold strong?
You can make the holes just at the center of the table, and then you make hails from right to left and front to back, when you need to machine one small piece you can use one rubber ring to limit the area of the vacuum
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 have some videos of a similar inc with a 5'x12' bed we used a large vacuum and a sealed table with mdf on top the pdf was ports enough to allow very good suction. it helps to cover the unused space with rubber mats to increase suction where you want it
Well, if the test piece at the end is surrounded by other boards it surely helps keeping it in place... not sure you proved this is working as intended.
nice project. I'm sure you could just use some pieces of paper to block off the holes as well. A shop vac can't deliver enough vacuum to tear most paper with only a 3/8in hole.
You could use a sheet of plastic to cover the holes when you have an odd or round shape. Just cover the table with the plastic, then cut and remove the plastic from the hole that you need to hold the work in place.
Great idea... But how strong it is... Did you make some tests? For example How many force you need to move a piece of wood, or how is the seal... The air that flows between the fixtures and the machined piece... I really like your videos.. But I think is missing something tests sometimes... :/ Anyway! You are great, Frank! :)
Hey frank, I've gone thru a bunch of hold down options but the best solution I've found is the ultimate cantilever clamps...mother great and you can efficiently hold down any size or shape. Search for Marius Hornerberger's channel and look up ultimate cantilever clamps I know you'll looooooove them as much as I do. Shout out to Marius ....!!
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.
Question: Under what circumstances would you be using all the holes all the way to the edges? It seems that you could just drill a few larger holes in the center and, even if the piece is large, the suction from the few central holes would be sufficient to hold the entire piece down. Would it not? Even if you were to mill multiple smaller pieces at once, drill more holes as needed and, thus, discover the most efficient hole pattern without over doing it and drilling hundreds of extra holes you may never actually need. That would also negate the need for all these modular dams and hundreds of points of potential leakage.
On Amazon here in the UK, you can buy cheap silicon baking sheets. Sticky rubber and rinse-able with no embossed pattern 62cm x 41cm for £10. You could use a few cut to different sizes as necessary and reuse.
Hey Frank. Heres an idea. cover the table with rosin paper then poke holes where you need suction. Simple and cheap.
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.
I have good results with "shaved" MDF as well. It is amazing how permeable it becomes with the hard faces milled off. For blocking unused areas, I use thin plastic sheeting like the .5 mill painters drop cloths.
jmick.art
Good idea using drop cloth. I've tried using stretch wrap but that was a pain because it sticks to itself...
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 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.
What you need is an actuating part that blocks the holes not in use for your run. This may be a manual switch that you have to actuate from the sides or top or bottom of the table. Ideally your CNC program would run the actuation automatically when you located your part and hit the "go" button...but that's a different set of circumstances. Good stuff, as alway, Frank. Thanks for doing what you do.
Even if you're not totally pleased with it as a vacuum hold-down, you've made yourself a darned nice downdraft table. Perfect for sanding on to keep dust to a minimum. We've got a couple of these in our shop for this.
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!
Great video. Thanks.
MDF is porous anyway, so it may not be necessary to drill all those holes (if you have enough vacuum). If you cut 1/8" / 3mm from each face of the MDF sheet it removes the most dense part of the MDF and makes the vacuum significantly more efficient.
I use scraps of plastic sheet to cover the remaining area when I need more vacuum on the job piece.
A vacuum cleaner is not designed to be dead ended as the air going through it is intended to cool the motor. Using it for a vacuum table may not allow it to have a long and happy life!
Hi Frank just a few pointer I used to program CNC machines.the Matrix machine works better if you seal the sides of the mdf your vacuum with increase, you will have air leakage at the side until it's sealed, you could put a sacrificial board on top so you can cut right through I set the cutter depth to -.2mm we put 25mm mdf on top of our plenum which we would skim every day until its about 6mm we skim both sides so we get airflow and seal the edges.
we do exactly what you are doing by covering the unused bed with melamine covered 6mm ply we tried various method but for speed we found this to be the best way but mostly we used 8x4f sheets.
Great build of the CNC liked the way you overcame all the problems.
I was very skeptical about a shop-vac being able to hold a board down, but you've proved me wrong! Kudos! :)
This kind of movies should be at the Oscar awards. Thanks, Frank
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)
Frank your vacuum working table is fantastic.
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.
I used to work on a 4x8 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
A friend has a vacuum table for all his CNC, he doesn't have holes in his vacuum table only a piece of MDF with a 64th trimmed off each side to open up the pores. This does a great job doesn't have the loss issue that you're trying to deal with by putting boards over the unused holes
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.
Paint the sides to help. MDF and particleboard allow air to flow through. At the maker space I go to the have MDF on their CNC to clamp plywood sheets down.
I'll second that. A company I work for uses sacrificial 6mm/1/4in MDF sheets on the bed to hold blanks of polyethylene foam. We sometimes use it with plywood and MDF blanks.
Or laminate it.
I recall with the CNC that my school had, you could get a vacuum bed that you put a 6mm piece of MDF onto as a sacrificial board and then in theory you could still clamp wood to it as it created a vacuum through the 6mm sacrifice board. I was a little skeptical, but my school never bought one so I don't know if it worked. They used the T-slots in the metal bed to clamp sacrifice boards to and then used carpet tape to hold the wood/plastic that was being cut.
Jared S z
this works
very cool. your cnc seems to be the best one I've seen yet. at least that is home work shop size.
I was kicking around making something but I was no where close to this idea. Gonna give it a try for my small ShopBot. Thanks Frank.
Hey Frank, great build, what i use on my vac table is a plastic bag and just lay it over the open areas, not as sexy for sure but gets the holes covered!!
Wow. That fade into the outro is genius
Agreed!
A commercial vacuum table I saw years ago had several dozen ball bearing valves with a grid of rubber/foam gaskets; just slap a workpiece anywhere on the table and it stuck.
The springs holding each ball bearing in place were just strong enough to resist a shop vac, but any weight on top would break the seal and start the vacuum effect.
I thought it was pretty neat, but always thought that a huge workbench sized version would be more awesome.
That "peg board" making part was cool to watch!!! Great project!
I really like your videos. I have built a number of vacuum tables before. The only recommendation that I will make is smaller holes. Like 1/16 to 1/8 in size. The vacuum hold down for this size is much stronger then the 3/8 inch holes that you used. They would be closer together and you don't need as large of vacuum. For the tables that I build I use dowels instead of raceways. I have found using raceways over time you get scalloping of the surface where it is not supported underneath. I also use a much smaller chamber size. No more then an inch between the sandwich. The smaller the area of volume produces more suction.
NICE ! And as a professional photographer, it reminds me of the smaller, peg board topped vacuum box I made "back in the FILM day" - to hold down sheets of 16x20 photographic paper below my enlarger. That way I could expose the entire sheet to easily create a borderless image... ( it worked great.)
Hi frank, make sure you have enough air flow to allow the shop vac to stay cool. They rely on air flow to cool the bearings and motor.
I've seen people use motors from ducted vacuum systems and drill a small hole in the hose so it leaks just enough to keep the motor cool.
Love your work
Good idea. There is a cut in the hose, maybe I won't fix it.
frank howarth perfect
We had a thermwood in high school with a built in vacuum table and what we did is cut custom waste boards for each project. We'd cut a 1/4" groove was offset to the inside of the outline of the piece (if that makes sense). And a grid pattern of the same size/depth cut inside that outline along with small holes drilled periodically to allow the air flow. Then we'd fill the the outline with a 1/4" rubber strip. Once the piece was in place and the vacuum turned on, the suction would fill that grid pattern and apply even pressure across the entire piece. This was especially effective pieces that needed to be mass produced but even for small one-off projects it was fine because the work bed 8'x8' so you could simply grab an old waste board with some room on it and use that. I hope at some least of that was coherent. It's early and I haven't finished my coffee lol
Very nicely done! Not sure why this video didn't come up when I was researching my own vac table. Enjoyed the video - thanks for posting!
Frank, may I say you are an inspiration and ambitious. Your vacuum table.
My experience is that you’re never the right size and cover pieces. Rather than trying to make one big one, make many small one’s. A round piece of wood say 3” and 2” thick with an O ring grove cut into top and bottom with a hole through the side. Make several with a ball valve on each. Small flexible hose to each all piped individually back to the vacuum pump. Place them under your work piece, open valves only to the ones you going to use. Switch on vacuum pump. Suction cups fix to bottom and work piece at the same time. Job done.
Many thanks for your entertaining videos.
Johnathan
Super interesting stuff, Frank. The test piece at the end was very cool to see emerging! Thanks for makin' !
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
I own/run a commercial CNC in a millwork shop. Not sure how well the information would transfer to a smaller CNC, but here are a few ideas:
Our CNC has an aluminum table with holes for vacuum. Instead of having so many holes (ours are about 4" apart), our machine has channels around each hole to spread the vacuum of each hole. Would reduce cutting time, and allows for realistic plugging of individual holes.
Ontop of that we put a "spoilboard" solid 4x8 sheet of 3/4" MDF (no holes).
We prep the sheet by running all edges through the edge bander. This stops air from leaking out the sides.
Once that is done, I use a 3" cutter to mill off about .2mm from one side of the sheet. No only makes it very flat, but the surface is now much more "open" for airflow. Flip the sheet, and repeat. The sheet is now perfectly paralel to your gantry and open for airflow.
I'm not sure if a vacuum should have enough power to do the same (pulling through MDF) on your scale. Our pump is 10hp, but it is capable of 5x12 cutting area (usually setup for 4x8). I can cut a 24" x 24" piece of MDF sitting in a corner of the sheet without blocking the rest of the sheet off.
I thought about doing the method where you suck right thought the mdf, but it looked like you need a big suction motor for that. A lot of flow and pressure.
in our shop we just used two pieces of mdf and routed a center groove that branched out on top and bottom pieces and glued them together so they made an air channel and had holes on the top piece. when you wand to use a small section we just put a peg in one of the center holes and it stops the air from going to the other branches. works pretty well
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.
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 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.
I used to run a graphic arts camera that had a vacuum film back. To allow different sizes of sheet film there was a sliding valve that would close off the area around the edge allowing smaller and smaller sizes of vacuum area. The sizes were marked off in red so you could align the film where the vacuum was, worked quite nicely and I'm sure you could do the same thing and not even need those pieces for blocking off the air flow but the pieces for alignment might be nice.
That is the coolest large setup have ever seen, so jealous!
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.
Hey Frank I put a 1/4" piece of mdf on top of the holes and your vacuum will suck through the mdf and hold your piece down (depending on how strong your vacuum is) then put trash bags on the part of the mdf that's not been used to direct the suction to the work piece. You might try that and see if it would work for you.
I'm hardly qualified to make a suggestion, but I can think of a couple of things. 1. Actually just use perf-board. 2. Make an external PVC manifold to go between chambers, rather than the holes in the supports. By doing this, you only draw vacuum on the chambers you need. 3. A thin film of plastic would work as well as plywood to block the holes you aren't using. Just suggestions. You are waaaaaay better at this than I could ever be. Love the channel.
What i would suggest (when you make a lot of pieces which don't take a lot of time to cut) that you build a foot pedal to switch the vacuum on and off! I also would find another solution fpr covering the holes cause that looks not good and is inefficient. I work as a carpenter and at work we have a big CNC and we also use suction to hold it. For that we have a few rails where you can put some rubbes "boxes" on which have a few holes in it and every time we step on the foot pedal, the "boxes" get the suction to hold the piece somehow through the rails. Maybe membranes are used . Maybe you thought about the same thing with the suctionboxes.
Respect and love 4 wood from Germany
Mr. Howarth, appreciate all your videos, very impressive skills!
Seems more like the modular peg board pieces are holding the work piece in place by surrounding it and then the router cut pushing down from the top. How much is the suction real doing? Would your logo have been cut just as well with the vacuum off?
Every time you said struts I took a shot and now I’m hammered hahaha!!
Hi mate. What do you think about just using some plastic sheeting, bags or tarps to shield off the area that you're not using? You can just cut a hole where you put the workpiece. You might even be able to use some butcher's paper.
I do commercial large format printing on an Océ Arizona which features a 3050x2500mm vacuum table separated into multiple zones. If you made some of the baffles solid, then split your vac run with valves, you can turn on/off the individual zones and lessen the need to cover the unused areas.
Also the space inside need not be so cavernous, its just a pathway from the vac hose to the holes in the top. You could make it much lower profile by using a thick sheet of polycarbonate/aluminium/sealed MDF and route a series of channels only 3-5mm deep, then add your spoil board with the holes directly sandwiched on top. Our table is 2 sheets of aluminium with only a 3mm space between them. Also the holes are barely 2mm in diameter at 30mm centres. You'd be surprised at the hold down force it can generate.
Your table does what you need it to do, so I don't imagine we'll be seeing Mk II anytime soon. But I just thought I'd share incase anyone else can benefit.
Small note if you make another. Your inner baffles are perfect, what I've see in other is having a second mirror piece then you slide them shut to block of sections of the holes so it's just a little easier.
You could create slides that slide along the venting on the inside to make your work area larger and smaller depending on need.
Hey Frank, not sure on the vacuum required but some of the CNC router companies I've come across draw vacuum directly through the MDF w/out the peg board design needed. You can isolate this surface area with thin plastic sheet i.e. trash bags. Love your videos.
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 9x8 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
What if each hole had some kind of floating valve? The weight of the workpiece would open only the holes needed.
industrial cnc table saws have that, but the opposite.. it helps slide heavy sheets across the surface.. there are little ball bearings in every hole that opens (is pushed down) whenever the workpiece slides over it, making it float across, kinda like on an air- hockey table.. Now in order to do that with a vacuum table, each ball bearing would have to be spring loaded, with more force than the vacuum generates, or else the vacuum would just suck the bearing down, closing the hole.. It might be possible, but I'm not intelligent enough to know how.
you might be more successful by just creating sections with valves that you can shut off and keep it in parts that have higher vacuum then
a floating valve would work in theory but as said... the force pushing on it would be a bit too much to make it work... practically impossible...
industrial vacuum fixture plates for CNC machines use some rubber seal that you put in a square pattern milled plate so only the sections needed create negative pressure
in that case you could work with only 4 or 6 holes in total on the plate but you would need several lengths of rubber slings to actually create the seals themself...
pretty complicated stuff tho
check valves in reverse......
How about little rubber balls in depressions. When the air flow is great it would pull the rubber balls down sealing the hole. Holes covered by work pieces wouldn't generate any airflow so would not pull the balls down.
That would just suck all the balls down, regardless if a workpiece was above one or not.
To get better suction you want to make a larger number of smaller holes. Big holes like what you have or pegboard for example don't make very good tops for suction tables. I'd suggest looking at some videos related to making vacuum forming or vacuform tables - they're extremely similar in build and are used for holding down forms to molded, while a hot pliable plastic is placed over top that then gets sucked tightly over the form to make a mold of it.
That could be handy for something that can't be clamped with classic clamps. But otherwise, the classic clamps you might use more often than that table, classic clamps are faster and easier for parts that have plenty of clamping room.
I forgot what you call them, but little connection points in your work piece so the part you cut out don't move, then you just use utility knife to snip the tiny tabs, no need to mess with a vacuum clamp. you might find it more convenient, but from here it looks like traditional clamps have it beat. Nice experiment, thanks for the share.
For an example of vacuum fictures in use on cncs on another scale I come to think of John Grimsmos channel (metal/knifes cnc).
His setup was consisting of multiple fixtures stacked with one having groves cut around a central air vent which would be sealed with an rubber string to form the perimeter of the vacuum to form. maybe easier to setup than the holes and chamber even if the vacuum might take longer to form. The tricky part would be to get the ratio of rubber compression, deformation and groove dimentions just right so that you get an air tight seal and have the workpiece rest on the ridges instead of the rubber.
That's a lot different than the conventional grid plenum with MDF spoilboard top, cool concept!. You may find you have better performance with the tried and true with the addition of a few whole house vacs. There is a lot of good information on making these in shopbots forums. If you are interested I have some of these vacs and a homemade manifold that I could send some pics of. Trupan MDF is ideal for your spoilboard. I run an 8hp vac on my CNC and I think the whole house vacs are nearly as effective.
so we have a very expensie cnc mill at school that uses a vacuum table but instead of relying on holes in the mdf the vacuum is strong enough to actually penetrate the mdf without any holes which means that there isnt that much loss of suction of parts of the vacuum table arent covered of course the larger the area of the piece the better it will be held down but it does a pretty good job and if the piece is small we sometimes just hot glue it down the the mdf which really holds it well
I remember a magazine article from way back in the day where they used a roll-up window blind to cover part of a down draft sanding table. As someone else suggested, a roll of craft paper would work and you could cut the opening you needed.
I suppose you can add in some adjustable sliders, or pluggable tubes, to create multiple zones to vacuum. For example, you could create a box with 2 full depth dividers inside it to create a box with 3 zones, then drill 3 holes in the sides and externally have some sort of elbow mechanism as needed, or have one vacuum hole, then additional holes to connect the side to the center. Or have some more elaborate dividers that slide internally with offset holes so that if you move them a few inches, the holes are aligned to combine the 3 zones into one, and a few inches the other way closes the holes.
friend of mine build a vacuum table with 9 chambers (3x3), simple internal piping and a few valves to connect to the vacuum... easy to focus the suction on a specific area
MDF is porous and doesnt need holes drilled for air to pass through. On CNCs we use in the millwork and cabinet industry we have vacuum tables built in and we use MDF spoilboards and the parts are held down to the mdf with suction. sometimes you can tape the edges of the mdf to improve the suction and also put laminate or another non porous material around the parts similar to what you are doing. Also just using a 3/8" bit and drilling with your CNC. instead of routing a circle for every hole would speed up your running time significantly.
thank you Frank wonderful as normal . question if you dont mind could you not use some sheet plastic and just cut out to size the part size ?
I know this might be too simple and not noteworthy, but perhaps covering the open holes with plastic such as thick mill roll plastic? 4 sheets that the excess would just hang over or fold when vacuum applied to the covering pieces. Just a thought. Will be very interested in what you finally come up with.
I have a 5'x10 ' table and it takes about five hours to drill all the holes.
I use a 1/4" end mill but do a straight peck. Last thing I do after drilling
is to put in a 1" bit and surface the entire bed. It takes off any high spots
and makes precise Z cutting.
Nice build Frank!
Peter Collin suggested making each hole into a valve so you don't need to seal it. I have a dirt-cheap way to do this. Replace the round clear hole with a blind slot, 3/8"W x 3/8"D x 1"L. Near one end, drill a 1/8" through hole for the air to pass through. The valve consists of a little lollipop: a flat disk with a stick that is bent out of the plane of the disk. When you pop the lollipop into the slot, the disk covers the through hole, and the end of the stick protrudes above the top surface. Vacuum on: the disk is sucked down and seals the hole. Place an object on the table: it pushes down on the end of the stick, levering open the valve (this takes about 2oz of force). I don't know a simple way to make the lollipop, but it has to be cheap.
Great idea! A sub vacuum table. I think that's the way I'll go at first. Although I am quite happy with my downdraft table.
You can make channels on the bottom piece for the airflow with cnc. Just glue the top piece with the holes airtight and your complete design is 2 layer thick only. You don't really need a 10cm high monster.
Very cool I just ordered a 4x8 router and was thinking about a full size vacuum table as well but I like this idea much more!
One suggestion. On the supports inside put slides with pulls on the outside to close off areas that are not used. Then use the boards on top to cover what is left of the open areas. Make sure the slides are on the opposite side of where the vacuum is so they are pulled in to help seal.
1/4" holes are sufficient for the vac hold down. If in your software
you have a feature called Convert circles to drill points then it will
do a straight plunge instead of walking around. When I have to drill
mine it's about 5500 holes and takes about five hours. I just turn off
the lights and go do something else for a while.
what if you cut out a larger recess at each hole then dropped a washer blank or some other stamped disc in it? quick and easy to pull out with a small magnet.
You can also use this with a large plastic sheet to glue inlays or veneers that need constant and equal pressure. The pressure will compress the glue up together.
hi frank
I live in England and where i work we have a CNC ( Multicam 3000 series ) we use a vacuum table and we use stock MDF no holes the air can get thot the MDF just fine but we do have a big vacuum pump so may be somtink worth looking in to and just google the CNC ( multicam 3000 ) your find videos on how there table are set up .
I am thinking have pieces that have matching holes that is under the top. if your want to seal an area you could slide the lower piece half an inch so the holes no longer line up.
in between the two top layers you can glue a "rail" system in which 2 wood stripes for each row would be inserted from two opposing sides meeting in the middle. do that for every row and u have a convenient way to activated each hole individually by pulling out the stripes sometimes more sometimes less. or one side more than the other.
On our CNC, the vacuum table has a grid cut in it in between all the holes, cut with a rounded bit, so that we can put tubular gasket type stuff around the piece being cut, and then everywhere else, we just use freezer paper and tape to cover. Also, it helps to put sawdust on the line where the work piece and the table meet, cause it helps seal it off.
and when the work piece is a weird shape (we build skis, so you have that parabolic shape on both sides), we cut that shape into a squared piece of MDF, and drill the holes in that for the vacuum to come through that. It works much better, if a bit tedious.
Frank, could you make some type of manifold system that allows you to shut off certain sections of the table instead of plugging them from the top?
If you could figure out a way to block the holes in the struts on the unused parts of the table with out sacrificing suction, that would take away the need to cover the holes with other boards. Maybe a sliding cover on the struts and a small box that seals air tight to go over a know that actuates the slides? This idea does mean making a new box though.
I have always pulled the vacuum thru the mdf sheet. The routers I have used always have large industrial vacuum pumps.
Most machines I’ve used have milled aluminum tables and gasket is used to seal the mdf spoilboard or parts/jigs/fixtures to the table
if you have something odd-shaped, you can use plain old newspaper to cover up the rest. That said, your modular covers with registration pegs are very nice :-)
Hey Frank, great design. Always enjoy your videos.
I was wondering would be an idea to make blocks, kind of like Lego, say strips of 6 pegs x 2 pegs, fill the whole vacuum table with the blocks.
Then only remove the sections required for the size of the piece you need to hold?
You could have different strip lengths available for odd shaped work pieces?
This way your only removing and replacing small sections as you use them ?
Like I said just thinking out load :-)
Thanks for sharing, regards
Steve.
That would work. something in between individual pegs and the bigger pieces I made
Exactly yes, you could even incorporate curved pieces for holding rounded work pieces ?
I run a vacuum bed at cnc at my work. I would recommend sealing the sides to restrict air flow through them. I was wondering, does the end furthest from the side with the vacuum port have enough suction to hold strong?
Have you given thought to adding blast gates of sorts along the struts to section off the area of suction?
You can make the holes just at the center of the table, and then you make hails from right to left and front to back, when you need to machine one small piece you can use one rubber ring to limit the area of the vacuum
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 have some videos of a similar inc with a 5'x12' bed we used a large vacuum and a sealed table with mdf on top the pdf was ports enough to allow very good suction. it helps to cover the unused space with rubber mats to increase suction where you want it
Well, if the test piece at the end is surrounded by other boards it surely helps keeping it in place... not sure you proved this is working as intended.
I had the same thought. the workpiece ends up being held in place by the "modular pieces" and makes all the vacuum table pretty much useless
But the vacuum is needed to hold the modular pieces as well
+Don Johnson ah yes those vacuum pegs
Don Johnson isn't the vacuum for cleaning up the bits of wood? If you don't have a way to get rid of the wood particles from the CNC it'll catch fire.
+sample text its so you dont have to screw/clamp the object you are cncing to the table
What about placing the appropriate sized marbles to plug the non-used holes..........might that work?
nice project. I'm sure you could just use some pieces of paper to block off the holes as well. A shop vac can't deliver enough vacuum to tear most paper with only a 3/8in hole.
Yeah, that's exactly what occurred to me too. A few sheets of poster board would work really well for this.
awesome job frank
As always, super idea.. well done frank
Great work as usual, but why not make all the drilling with the sacrificial board from the start?
You could use a sheet of plastic to cover the holes when you have an odd or round shape.
Just cover the table with the plastic, then cut and remove the plastic from the hole that you need to hold the work in place.
Great idea... But how strong it is... Did you make some tests? For example How many force you need to move a piece of wood, or how is the seal... The air that flows between the fixtures and the machined piece...
I really like your videos.. But I think is missing something tests sometimes... :/
Anyway! You are great, Frank! :)
you can also use plastic sheeting or trash bags to plug the exposed holes
Hey frank, I've gone thru a bunch of hold down options but the best solution I've found is the ultimate cantilever clamps...mother great and you can efficiently hold down any size or shape. Search for Marius Hornerberger's channel and look up ultimate cantilever clamps I know you'll looooooove them as much as I do. Shout out to Marius ....!!
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.
Question: Under what circumstances would you be using all the holes all the way to the edges?
It seems that you could just drill a few larger holes in the center and, even if the piece is large, the suction from the few central holes would be sufficient to hold the entire piece down. Would it not? Even if you were to mill multiple smaller pieces at once, drill more holes as needed and, thus, discover the most efficient hole pattern without over doing it and drilling hundreds of extra holes you may never actually need.
That would also negate the need for all these modular dams and hundreds of points of potential leakage.
good point.
On Amazon here in the UK, you can buy cheap silicon baking sheets. Sticky rubber and rinse-able with no embossed pattern 62cm x 41cm for £10. You could use a few cut to different sizes as necessary and reuse.