I want a vacuum table!

[mekanik]

Glad to hear it Tenson, continue with the experiments.
Mike

[Tenson]

Ahh, now how about your collective thoughts on this - My bed is HDPE so had low friction. Is there a paint or similar I can coat the bed with to give it better grip? How would any paint stick to the HDPE though?! Perhaps just affix a thin rubber sheet with contact adhesive.

[GEOFFREY]

Hi Tenson, I presume that you will still be using an mdf sacrificial board on top of your new board, so why not write a program to drill a couple of screw/boltholes and secure the sacrificial board ensuring that you show to fixing position on your table to prevent hitting the fixings. I have arranged a series of clamps along the front of my table which secure both the sacrificial board and my material. these clamps are just outside the cutting area and will hold the work in the event of a vacuum failure (fingers crossed has not happened yet). the vacuum holds the job securely and I get a far better cut as the job is always held tight to the table ensuring that there is no sawdust build-up under the cut. My clamps are simply tightened with wing nuts and take only seconds to secure?release. Glad you are getting there with tour vac bed. G.

[Tenson]

Hmm yeah I guess the solution is to clamp / screw down an MDF bed then spray that with a grippy paint. I found something here - PlastiDip - Plasti Dip / Plastic Rubber Paint - Aerosol Can - 400ml Matt Black | eBay

Whatever I go for it should be cheap so I can afford to do it each time I re-surface the board.

Maybe just a coating of bitumin paint.

[Tenson]

Hi guys, sorry for such a long time with no feedback. Allow me to update this thread.

I'd say the project was a success. Firstly I'll say the vacuum pump was a waste of time for the vacuum table. It doesn't draw enough air flow so even tiny leaks reduce the pull down force. On the other hand the old vacuum cleaner I have works a charm :)

I think these pictures will mainly explain what I did. but basically I caped each end of the steel supporting tubes under my machine table. I then drilled holes into these from the top. Rather than cut channels into the machine bed directly I place a 24mm sheet of MDF on top with the channels cut into it and this bolts down on the bed at 5 points.

I started cutting that as a 12mm sheet but as I cut the channels 6mm deep it warped. So I glued it to another sheet that kept it flat.

When cutting material that is smaller than the vacuum table I use some decorators dust sheet to cover the unused area and seal it.

Additionally if I'm cutting lots of small parts I throw sheets of paper over them once complete, to keep the suction up.

I try to cut just shy of the material thickness to leave something to keep the vacuum seal but there tend to be little areas where it breaks, hence the above.

Here are my images, sorry I've got to dash out so no time to write lots.

Oh, it also makes a downdraught table for sanding and part cleanup. It doesn't such strongly with only those few holes, but it helps. Good thing about using a vacuum cleaner for suction is I don't need to worry about dust and dirt getting in there. Also it has an adjustable power knob so I can keep it turned down when there are no leaks and stop overheating the motor.















Below you can see were the cut was very nearly through the material, but not quite. Any dust helps to block up small breaks in the seal. I also use a downcut mill, which helps keep the material down and block up gaps in the material skin.


Below are some small parts I cut out, and then covered with paper sheets to help seal. Although there was a thin skin left, it was so thin at some points the vacuum pulled through.

[GEOFFREY]

Well done Tenson. The covering of part of the table with an impervious sheet works well. A friend of mine has arranged a polythene "roller blind" which extends from one end of the table - he just pulls it out to whatever length he needs and that works well. To improve your suction you could use a round rubber neoprene gasket seal around the edges of the mdf sacrificial board. I know that you will find having a vac table a big advantage. G.

[Tenson]

Thanks Geoffrey. I like the way the very thin dust sheet can wrap around the edges of an unusual shape. Sometimes like in the image above the edge of the sock material is not actually a straight edge. I do also have a silicon seal around the edge of the table. I bought some 6mm dia silicon tube on eBay. I also have some smaller peices that I can use to section off areas of the table. I threaded the holes in the steel tube that feeds the vacuum so I can also put a bolt in any of the 18 holes.

I can also confirm that painting the table with a thin coating of 'liquid rubber' helps reduce parts sliding about. I used Isoflex. I then surfaced the table and haven't put it back on since it is slow to set and very smelly, lol.

I'm moving workshops soon and will need to make the machine quieter not to annoy neighbours, so next will be a big sound-proof box for the whole machine. That's not too hard, but making it easy to access the machine when needed will be more tricky since doors and windows tend to break a sound-proof seal.

Oh and those part drawings I posted earlier in the thread were to be cut from Acrylic. That didn't work well on the vacuum bed directly because it doesn't take well to 'skinning' due to not being easy to remove the final part cleanly with a knife. What I did find worked well, much to my surprise is just putting a flat sheet of MDF on the vacuum table and then sticking the acrylic sheet on there with lots of double sided tape. I keep the protective cover in place on both sides of the acrylic too. I thought that would be far too weak to hold, but it isn't and it's far easier than removing the double sided tape from the acrylic sheet itself.

[Jonathan]

then sticking the acrylic sheet on there with lots of double sided tape. I keep the protective cover in place on both sides of the acrylic too. I thought that would be far too weak to hold, but it isn't and it's far easier than removing the double sided tape from the acrylic sheet itself.

Double sided tape is invaluable for thin material, like PCBs. If you're having trouble removing it then I found that WD-40 takes tape off PCB material (SRPB or FR4) very easily, so that might be worth a go assuming it doesn't do anything nasty to the acrylic.

[Tenson]

Ahh I tried that too :) Yes it does work, and actually I found soaking the part in white spirit for 15min worked even better. Trouble is even a kitchen tissue will scratch the acrylic slightly. A cotton make-up removing pad works best. Better still to keep the protective sheet in place IME though. How do they stick that stuff on, is it just static? There is no residue from adhesive?

[Clive S]

Wouldn't it be nice to have these Vacuum mats Vacuum Work Holding Chucks - YouTube but the mats of throw away. ..Clive