My buddy (retired a/c ) says that the size of the pump only matters for speed, this little 3.5 cfm pump he gave me has been on jobs that took 24 hrs to pull a vacuum, but when it did, it was a vacuum, hence pulling a vacuum doesn;t take a monster pump, pulling a vacuum in seconds rather than minutes does take a larger pump. Of course no one wants to wait half an hour to suck the project piece down to the table. Think of calculating how many cubic feet of air could be held in the grooves and if the sealing is good than that should be how long it should take depending on the cfm of your pump. My hdpe test was almost instant. My pump is old and needs new seals but I don’t care right now (can’t afford repairing ) so I will just let it run and maintain the vacuum. The Joe’s wood working designs are great and when I can afford it I will make that one. But for now I will just use what I have . Your spiral groove only downside IMO is closing off the spiral outside a square work piece. But on doing that it should not require a large pump IMO. Hope this helps, Jude
YES my thoughts exactly “Plenum” is the key!
Please share your experiences
I test glues 2 pcs of hdpe together with contact cement the other day and checked it out today. The pcs are securely glued, would take lots of prying to separate them and would warp them like a potato chip. They can’t be slid apart but I don’t believe the contact cement can fully cure because it can’t get any air. It was just tacky when I put them together. I think contact cement would hold them together fine because they are absolutely sealed together like a vacuum seal, if I pry them hard air may get between them but why would I pry them apart? I’m switching to pvc panels with plumbing glue, home depot 1/2" sheet 4’ x 8’ for 68$'s, lots cheaper than even hdpe cutting boards at sam cluub for 9$'s, pvc works out to 3 1/2 $'s for approx same size.
Re HDPE, I’m not sure, but it seems like some 8x8" HDPE pieces have curled a little sitting in my very hot garage (>100 degrees probably). Don’t know if that’s even possible and I haven’t measured it, but does any know offhand if that would be a risk with using HDPE for a plenum?
My hdpe waste board after I surfaced it once, like 0.1 mm off, warped like a potato chip from the heat just like in your garage. Someone mentioned that once you cut onto the surface of hdpe it has that tendency and I agree. I am switching to ovc board for that reason and it’s also cheaper than hdpe.
I’m interested in the pvc sheets, only seen boards about 5.5" wide so far in my area
Home depot has had it for a long time, I;d never seen it either but it’s in aisle 22 down here in bldg supplies, it’s for trim. I guess you have to look for it, I asked them and there it was. Maybe your’s does also. It was on the bottom shelf maybe that’s why I never saw it before…
You can check local availability online.
half the size but workable. I have the 4’ x 8’ panel here
Unfortunately that is not available anywhere near me.
You can order it online and have it delivered to your local store for pickup. That option is available to me from the website.
A few minutes later…when I tried to get it shipped to the local store, that’s not available. You can’t haz this, it says.
If you can’t get it at your local HD, You can try to check with local plastic suppliers, it looks like PVC foam sheet, make sure to request closed cell foam.
I haven’t had much success in my efforts to get a working vacuum table using a veneer press pump. It should work; I think my design scheme is fatally flawed due mostly to a health amount of ignorance. So I’m going to try something entirely different. I was on veneersupplies.com and noticed that he sells some ball valves. http://www.veneersupplies.com/products/Mach-Ball-Valve-For-Vacuum-Clamping.html . So I ordered a bunch and some vacuum tape and I’m going to have another go at it. Just the other day I started thinking about something like a ball valve that would activate only when something was pushed down to open it. So this right along the lines of my faulty thought process.