Vacuum hold-down issues.

[Travisty]

Well, unfortunately my first post here is regarding a problem, and not simply to say hello.

I've recently assumed command of a '96 Routech 250 with twin 5x5 beds. I'm only using the left table because, like I said, I'm so new at it. I'm using 3/4 MDF surfaced .010" for my spoil board. I have both surfaces and all edges sealed by my finisher. My issue is, I can't maintain vacuum with my parts. I will attach a picture to represent what I'm running.




*EDIT* Figured I should post that the material is 61"x8"x1" 0% Aspen. The slots are .96"x4.75" (IIRC), using a 3/4" 3-flute Auger for the initial relief, then a 1/2" Compression to finish the hole. If that helps.


The green perimeter is x61.5y61 just for reference. I initially had vacuum areas in between each of the slats, held in from the perimeter by .100", and ran vacuum cord in that channel. The problem is, it's a very firm line that doesn't allow any flex and is holding my part above the table, IF I could get a vacuum seal! The majority of the time it just leaked vacuum til it sat at .001 (psi? bar?)

What should I do? I've had problems like this in the past with other parts, but assumed it was the sheer quantity of those I was running along the table, coupled with the fact they weren't exactly straight, but this is being a pain in my backside as well!!

Is there an easy way to figure required vacuum area for a part? A general rule of thumb? Any suggestions would be much appreciated guys, thanks!

Travis

[stairgod]

Sorry I really don't understand what you are cutting but I had a problem with hold down of my material and went to Schmalz website and ordered a rubber flange to set my material on to create a pod effect. When the vacuum kicks on it pulls the material tight to the table. If I cut through the rubber flange it loses a little vacuum but not all of it. I have since had my rubber flanges made by a private company as it cost 90% less and I go through several flanges a week. the flange I first used was on they use for matieral lifting and routered it into my table. the part number is 10.07.04.0014 sealing profile DI-MOS 11 x23 1k-MOS-20-DL sealing lip. Hope that helps. By the way if I stick my hand under the matieral between the pods and turn on the vacuum it would probably break my fingers, it works that well.

[rubianroaddog]

Your problem could be the MDF, it is quite porous, and often will leak more than enough to kill your vac. Try varnishing it after you have machined it, that should help some.

Cheers
Mick

[Travisty]

I've been playing with different spoil board setups for the last couple months and we seem to have found something that works well enough for us.

Rubian: Exactly! We were losing more than half of the vacuum just through bleed-out. I surface my spoil boards and then have my finish department shoot them with a top coat just to seal them. Any area I machine afterwards will allow the vacuum to bleed through, and on some of the projects this alone is enough to hold them.

Another method we have come up with is the same as above, but around the perimeter of the work piece, held in by about .250", we run some weather-stripping. It's soft enough that it compacts down to about .06", which is plenty thin for me to make up in my programming. This seals any surface imperfections and allows for absolutely NO movement with my work pieces...

This still isn't perfect as I would prefer to have my work piece sit flat on to the spoil board and not have to compensate for it, but for now this is much better than what we were running.

Thanks for the heads up and suggestions guys!

Travis

[Santa Fe Al]

[QUOTE=Travisty;698116]

Another method we have come up with is the same as above, but around the perimeter of the work piece, held in by about .250", we run some weather-stripping. It's soft enough that it compacts down to about .06", which is plenty thin for me to make up in my programming. This seals any surface imperfections and allows for absolutely NO movement with my work pieces...

Hi Travis,

Welcome to the ZONE. Just a thought, could you slot the spoil board to the depth (.06") that will help keep the seal and allow your material to be on the actual surface?

Al

[ger21]

Get some gasket material from All Star Adhesives. They have material that will fully compress .