Plastic or HDPE vac plenum?

[EricSchimel]

Hey all, in searching around the forum it looks like some of you have used plastic, PVC or HDPE vacuum plenums for your vacuum setups.

I have a 4x8 machine with 8 zones. The work that I do is really varied so having a universal vacuum that I can switch from the full table all the way down to a small 24" x 24" zone works well for me.

You can see my setup here: https://goo.gl/photos/MUq1RJaKRV2xxrFk7

I'm getting near the point of having to replace my spoilboard again and I'm thinking of switching my plenum out for something that's made out of plastic. My current MDF plenum has several coats of glue and Shellac on it, but I can't help but think that totally non porus plastic will work even better.

For those that use plastic plenums, what did you use exactly (PVC, HDPE, something else) and if you did switch from MDF, did you notice a good performance boost?

[knight_toolworks]

you would not want hdpe it is so heavy and so slippery it would be horrible. sintra would work but still attaching the top to it will be a pain. I use Baltic birch of apple ply.

[EricSchimel]

I was thinking HDPE for the plenum, and then gluing LDF (Trupan) to the top of it. HDPE is heavy but I deal with it all the time so lifting it on to the table is no problem...

[jerry_stanek]

I have a 1 inch thick sintra top on mine. I counter sunk some screws around the edges and then cut my plenum and drilled holes and counter sunk screws in the high blocks. I then surfaced it to give it some bite for glue. I then surfaced one side of my trupan spoil board then flipped it and glued it down with tite bond III

[EricSchimel]

Did you have an MDF plenun before? I'm wondering what the vacuum increase (if any) there would be..

[knight_toolworks]

I was thinking HDPE for the plenum, and then gluing LDF (Trupan) to the top of it. HDPE is heavy but I deal with it all the time so lifting it on to the table is no problem...

How are you going to attach anything to it? there are a few glues that may work but maybe not.plus iti s not really all that stable when you start removing material from one side.

[EricSchimel]

I was thinking about building this like a traditional ShopBot vacuum system.

I'd have a bottom layer of plywood bolted to the frame, I'd cover that with glue and then glue my HDPE or PVC plenum to that, and then the LDF to the top of the Plenum, like this:

https://goo.gl/photos/2Y2gQi9u4mQbJiA1A

[jerry_stanek]

I was thinking about building this like a traditional ShopBot vacuum system.

I'd have a bottom layer of plywood bolted to the frame, I'd cover that with glue and then glue my HDPE or PVC plenum to that, and then the LDF to the top of the Plenum, like this:

https://goo.gl/photos/2Y2gQi9u4mQbJiA1A

That is how mine is but I glued and screwed the PVC down If you surface the PVC in grabs the glue better. Also I found Tite bond III is better than Tite Bond II for PVC

[EricSchimel]

Thanks for the tips Jerry. How do you find the PVC working? Better than MDF?

[tomkk]

Hi Eric
I am setting up my new PRS Alpha 5 x 10. In another thread I was asking for advice on using 3/4 Phenolic for my table and plenum. I think this should minimize leakage and be resistant to humidity.
Sure its heavy, but I only have to do it once. Any thoughts?

Tom