Has anyone built/used a vacuum table top?

[309cnc]

Curious if anyone has designed / built / used a vacuum table on their machine?

Not talking about the pucks Axiom offers. Thinking more along the lines of a reasonably thin 'contraption' that mounts (mechanical / vacuum) to the bed and covers more or less the entire surface.

Lots on the net but something (although perhaps less complicated) like this:


Source: Ralf Klaassen

[Mezalick]

I have,,,,a real simple yet effective solution..

carveddetails.com/vac/

Michael

[309cnc]

Thanks Mike. Good idea. Also thanks again for a good class in Columbus last week.....

[arsystems]

The one pictured above seemed very complicated... I recently designed, built and am currently using a vac table I made with HDPE. It amazing how well it works, and I hopefully will never use a clamp again.

Can post pics here if need be, but can check it out on my instagram there are pics and vids. @advancedretentionsystems

http://instagr.am/p/BfWoiY6nj5Z

http://instagr.am/p/BfVx7YtHu7n

http://instagr.am/p/BfWn9TuHj6E

http://instagr.am/p/BfrrKa8HYd4

[309cnc]

Very nice, thanks for posting. Agree that the one I showed above is WAY to complicated. Like yours much better.

Couple questions:

I thought about HDPE as well but what I have is very 'slick' and I wondered if a different material might be better. Have you encountered any issues you would associate with how 'slippery' HDPE is?

Curious: Your vacuum pump in the first video sounded familiar. Is it a rotary vane type pump?



The other reason for asking about the pump is air flow. I use these rotary vane pumps for vacuum chucks on lathes and I know they can create great vacuum. However, the ones I have don't produce very much air flow. So, as long as you don't have any leaks, great! But in case of leaks the holding power goes down quite a bit. In other words, what happens if you wanted to hold down a work piece that you actually cut through as part of the design? You create a leak.... Any experience with this yet? I assume this is when higher air flow reserves might keep the pieces securely held down....

[arsystems]

The HDPE I have is also very "slick", and before I machined anything I faced both side using a facing tool path to make sure it is completely level with my also faced spoil board. I then machined the grooves with a 1/8 flat end mill. I have had no issues, I believe the surface of the plate does not matter. The rubber gasket that forms the seal is what matters.

Also, I have a Robinair 15800 that I use for various things. It creates a lot of mist and I don't like it at all. So I bought the pump in the link below. It is oil less and continuous run. I have had nothing but a great experience with it so far. If there is a leak between the material and fixture it won't matter what pump you have, your work piece is gonna get chucked.

I typically cut at least 2mm from the bottom of my model to avoid possibly going too deep and breaking the seal. I then flush trim whatever my part is on a router table. It is easier and safer this way. Have had great success with that as well.

Any other questions just let me know.


www.veneersupplies.com/products/Excel-5-Continuous-Run-Vacuum-Press-System.html

[309cnc]

Lots of info. Thanks.....

Yes, I know about the oil mist. Mine produces lots of it if I run the pump without building a vacuum. I then get plenty of air coming out the exhaust and it definitely carries oil mist with it.... It gets much better when I connect the intake to whatever I try to evacuate as the airflow goes way down once the vacuum builds.
Anyway, here is what I did about that: Removed the little 'muffler' piece form the exhaust hole of the pump housing and put a barb fitting in its place. From there I used a short piece of vinyl hose to connect an inline automotive fuel filter and then, using a long piece, terminated the tubing - don't laugh - into the side of a toilet paper roll. Occasionally I replace the $4 filter and the toilet paper. No more noticeable mist.... ;-)

Not exactly a professional solution but it seems to work for me until I can justify buying another (more expensive) pump.

[arsystems]

They sell mist filters for mine, I have one... it does not work. Any mist at all is annoying to me, the oil less is the way to go.

[traindriver]

arsystems, that is SWEET! I played around with a different design without much luck. Once I get some free time, I'm going to give that a try. Thanks also for posting the link to the oil-less vacuum pump.

[arsystems]

Mar 1, 2018 20:02:57 GMT -5 traindriver said:

arsystems, that is SWEET! I played around with a different design without much luck. Once I get some free time, I'm going to give that a try. Thanks also for posting the link to the oil-less vacuum pump.

let me know when you're going to do it... can give you some measurements that I used for the channel. 

[buildswithbrian]

I made one for the AR8pro, from MDF using a shop-vac for the suction
it works quite well for sheet products (high flow vac systems have their pros and cons
I have a video of it on Youtube if anyone is interested

[arsystems]

Saw that video the other day, nice job - on both the table and video

[grg]

I'm in the process of designing one now and have spent a good deal of time researching vacuum sources.  I use one of those vane pumps for doing fiber composite work when vacuum bagging pieces under pressure.  I would not expect one of those to move nearly enough air to sufficiently hold down parts on a CNC bed.  You are correct in that you will need considerably more air flow.  Finding the right system that balances air flow and achievable vacuum while being adequate when powered with residential single phase voltage is tough.  Using a shop vac is probably pretty decent for short term use but they're really made to have constant air flow for proper cooling of the motor and bearings.  Ideally, your hold down table won't leak too much air so you can achieve the highest possible vacuum level and holding power - but it's going to leak.

After poking around a lot and talking to a couple of people with experience, I think I found a solid vacuum motor source.  These still draw a good bit of amperage so I'm designing my system around 240V single phase to reduce the amperage demand on the service line to my shop a little.  I just received my first test motor yesterday but haven't had a chance to do anything with it yet.

This motor comes highly recommended for this application by the owner of that website.  I spoke to him at length about the various motors he has available.  The one in question is the second one listed on that page, p/n 122178-18
centralvacuummotor.com/shopbot.htm

According to the website owner, one of these motors is enough capacity to power a 2'x4' hold down table.  Two are sufficient for a 4'x4' table, 3 for a 4'x8' table and 4 would be needed for a 5'x12' table.  I'm designing my system with the capacity for three of these motors and I'll probably build with two in it for now.

I'll have a check valve for each motor and a small processor that monitors the manifold vacuum and will cycle on additional motors as necessary to maintain a particular setpoint.  Once I get going with it, I'll be glad to share details.

This was round 1 of my design when I had selected the wrong motors - I'm just starting again with the larger 8" motor.