Extira Vacuum Plenum

[anthonyjules]

Hi,

I have had my Bot for over 2 years and have used it and this forum quite extensively, but this is my first post. I would like to first off thank all the members for their contributions and all of the experience and knowledge that is shared on this forum. It has been invaluable to me over the last 2 years.

Now on to my Question:

I am about to create a new vacuum plenum, similar in design to Gary Campbell's original PVC plenum with T track. For cost reasons (and since I have some) I was thinking of using Extira. The last posts I have found on this topic are a couple years old so I wanted to see what people's experiences have been since then.

There were a couple different choices for how to do this. Some people have coated it (with epoxy) others have not. For anyone who has tried an Extira plenum, how has it worked and what have you learned?

Thank you in advance.

-Anthony Jules

[Gary Campbell]

Anthony...
Most of us keep trying different things to make the better mousetrap, as far as plenums go. My first was from PVC. Expensive but good. Unfortunately when I went to a dual Z config, I had to remake. I had Extira in stock and used that. I also used a much more open design that allowed better flow. I made a few posts that showed how I did this, but didnt find the thread.

Although many like the stuff, I personally wouldnt use Extira for the bottom of a litterbox. It may work will for cut out parts that are sealed on all sides, but I have found that it swells and delaminates just about as much as regular mdf, and when placed in water, will almost swell to double its size. Many glues, except epoxy dont hold well and the dust is bordering on toxic. I have had it delaminate from everything I have tried to adhere it to, using different single and 2 part products.

This is not to say that you may hit on the correct combination, but to say that I havent.

[dlcw]

Anthony,

I used two sheets of 3/4" baltic birch glued together with yellow glue to form my spoil board. I cut out the 4 plenums with the Shopbot, leveled the area for the spoil board and sealed everything with a couple of heavy coats of 3lbs. shellac. I then mounted the motors directly to the plenum and also drilled a small hole for the vacuum tube going to the meters.

So far I've been very please with the performance of the BB. I do, however, live in a very dry climate. Our humidity changes amount to about a 10% swing over the course of the entire year. If you live in a humid area, I would suspect you would have problems with the BB moving on you a bunch.

[anthonyjules]

Thank you Gary & Don.

Gary, I did manage to find your posts and pictures from your latest Extira + Epoxy Plenum. Based on your response and the amount of epoxy/sealing involved I think I will steer away from the Extira.

I just found a local distributor for Expanded PVC (Komatex). I can get a 3/4 inch sheet for about $150. I think I will go this route. The time I save on sealing the plenum and the added dimensional stability (even over BB) makes it worth the extra $$$ for me.

Gary, I also saw that you didn't do T-track in the center of your new plenum. Did you find that you just didn't use it?

Thanks Again.
-Anthony Jules

[Gary Campbell]

Anthony...
Our last version was geared to cutting mostly sheetgoods as this is where our business was. The t track in the center caused an area of no hold down. Since we have been doing mostly nested parts, we need every inch we can get.