Plastic or HDPE vac plenum?

[ByronConnDesign]

Hey Eric,
I just replaced my table to PVC. I have baltic ply bolted to the frame and epoxied the pvc to that. I cut slots for aluminum extrusions which I use to hold fixtures and such. Any bleeders or additional plenums I seal with gasket rod and have had much better vacuum with this setup.

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[EricSchimel]

I saw that picture in another thread, really nice looking setup! What kind of PVC did you use? Sintra or something else?

[waynelocke]

Here is an HDPE vacuum table I recently built. It exceeds all of my expectations - to this point. I use a single Fein and it holds down much better than the shellacked mdf. I use round Home Depot weatherstripping and the T Track as stops.

[EricSchimel]

That looks fantastic. I love how you're able to pull up the strips and move them around for different work.

It looks like you've got that HDPE glued down to a base layer of regular plywood. What did you use for that? Wood glue or something else?

[waynelocke]

I did not glue it. I screwed with thee rows in the x direction spaced about 8" (I think) apart.

[EricSchimel]

Not sure where you're located but have you been through some heating and cooling cycles with that setup? Have you seen any lifting or curling?

You've sold me. I think I'll do an HDPE plenum, silicone and screw it down to the base layer and call it good.

Right now my spoilboard is glued down to my plenum. I'm thinking that glue won't grab to the HDPE very well. Perhaps I'll just dowel it in place. Do those gaskets provide a lot of side to side grip as well? I'm wondering if I don't glue my spoilboard down if a lot of sideways force would cause it to slip on the X and Y....

[waynelocke]

My shop has AC and heat so that is less of an issue. I read but don't remember the coefficient of expansion of the hdpe but it seemed small over a 40 degree change in temperature for the 2' X 4' pieces. I put the screws through larger holes in the hdpe so that it can move a bit. It has only been a month so who knows maybe in another month I will be screaming obscenities at it.

[wwaldner]

Eric
What did you end up going with for your plenum MDF, HDPE, or PVC? I am poised on making a new vac table, but undecided on whether to go with MDF for the plenum or just go with PVC. I can get a 1" sheet of PVC that I could cut ttracks into, but a bit worried about how stable it would be. My shop is well heated, but could get hot/humid in the summer. Just curious as to what you ended up doing.

To add the discussion, person sourcing the PVC said they taped their PVC to their table with double-sided tape. Anyone else have any experience with that?
wayne

[EricSchimel]

I haven't done anything just yet. I'm about to replace my spoilboard once again and I think I'm leaning towards keeping my MDF plenum and just re-coating it again...

[Brady Watson]

MDF + epoxy sealed is probably both your cheapest and best solution.

Unfortunately with anything other than phenolic, it just isn't reliable enough for large tables to stay flat and keep the bleeder flat. You can't reliably glue the bleeder down.

US Composites 635 Thin is decent and a good value for the money. I've laminated a lot of glass in the past with it. Get the pumps.

-B