Glue or no glue under spoil board?

[john_l]

I have been using my vac table for a while now and my motto is always if it aint broke dont fix it. It has been holding well.

My setup is; plywood bolted to steel table frame, MDF plenum sealed with polyurethane and glued to plywood, Trupan spoilboard surfaced both sides and just laying on the plenum.

Couple things I have been wondering.. I never glued or siliconed my spilboard to the plenum. I felt that I didnt want to mess up the pretty plenum by glueing the spoilboard down. It has always stayed put, and is super simple to replace.. I re-plane it smooth until it's about 1/4" thick and then toss it off. Am I missing or risking something in regards to not glueing down the spoilboard?

I've also never sealed the edges of any of my spoilboards. I am sure I have some loss at the edges but I didnt like the idea of running duct tape around the edge as I was reading. I have some epoxy paint leftover from a job.. as long as it sticks, would that be good for sealing the edges? The reason I ask is that I remember I had to recoat the plenum 4-5 times with poly before I was comfortable it was sealed.

Thanks

[myxpykalix]

John get some silicone caulk and apply it to the edges. It forms a rubbery seal and closes off any airflow. It will help your suction increase.
Paint will just be sucked into the edges and won't seal as well as the silicone.

[john_hartman]

I followed Brady's tip on this an used HVAC Foil tape. Seals the perimeter and holds everything together very well.

[cnc_works]

John, I don't have a vacuum setup on my SB yet and I like the convenience you have of replacing your spoil board. But, not everything I do can be held down by vacuum (may be held by screws, clamps, etc) so in that case do you have to run the vacuum anyway to keep a consistent Z?

Donn

[gene]

Jack and John offer good advise , also what i did was to use the bot to drill a series of holes thru the spoilboard into the plentium for wood dowells. This keeps the spoilboard from shifting and the dowells can be machined smooth .When you want to replace the spoilboard just run the drill file and it drills out the old dowells for new ones. You will be amazed at the suction you are loosing by not sealing the edges.

[myxpykalix]

THe only thing I would say is, tube of silicone $1.50, roll of foil tape $10.00, you do the math, lol.

[jhicks]

John, I have exactly the same set up with one addition. I cut a .031" deep x .250" dado around each zone on the plenum. Then place .062" x .25" gasket tape from Allstar Gaskets in the grooves to isolate each zone between the plenum and the spoil board as much as possible. The gasket tape compresses that extra .031 proud gasket height when the vac is on so its flat to the plenum. It doesn't prevent vacuum from going through the spoil board laterally but does tend to help contain as much as possible vertically up to the top of the spoil board within each zone when its turned on.
End result is lay on an ultra light spoil board surface both sides, then resurface alternating sides to reduce cupping and abuse it until its about 1/4" to 1/8" thick, toss it and start fresh with a new 3/4" spoil board as needed.
No glue, no silicone, no messing around when changing over.
Works 4 Me for 3 years so far and I can't believe I delayed making a vac system for 2 years. I'll never go back to mechanical hold downs. When I do need mechanical assist, I lay down a sheet of melimine and screw the piece to it so the vac holds the melimine and screws hold the part to the melamine. No screws ever go into the spoil board.

[john_hartman]

I like Gene's idea best. The dowels is a brillant idea. I don't know about the foil tape costing $10; maybe $5, but its the time savings which count for me. My plenum and spoilboard are all in one. Mill the grid on one side then flip it over. Again, I'll give credit to Brady W. for that one. Easy allows 1 Fien vac to hold a sheet of ply or whatever and cut all the way through.

[frank134]

Hi Has anyone heard of an air gun that shoot plastic nails. I am a new to all this and just got my bot 60 x 120 Prs A. A friend of mind came over with one. so I shot plenum with that. It shoot plastic finishing nail. I found the bot cut them off and you can't even see then or find them after that. the name of the gun is omer susegana. I have gone to there site but can't seem to find the gun that shoot the nails or the nails. I ask my friend and he doesn't know eather. the person the got it for the school he work is no longer their. It great for holding thing down.

[nailzscott]

John, I have a setup similar to Jerry's, but my Allstar gasket is thicker. I've been thinking about glueing or screwing the plenum because with the current setup, I have to run the vac all the time to keep the spoil board flat (compressing gaskets). It just seems to be a waste to run the vacs constantly.

[fmihm]

Plastic nails -- what a marvelous idea! You're a blooming genius.

Here's a source I found for plastic nails and staples. They even come in colors. There's also a link for the Omer/Raptor guns. See:
http://www.raptornails.com/english/firstframe.html

Anybody know of other sources for guns and plastic nails?

[Gary Campbell]

Guys...
I have tried 3 or 4 different methods of bleeder/spoilboard hold down. Tapes, adhesives and gaskets. Nothing works as well as a fully glued down spoilboard. Nothing!

We now glue the spoilboard down to the plenum with Urethane Glue (Gorilla). The additional vacuum that we have at the sheet has allowed us to almost double our 3/4" sheet cutting speed from 3-4 ips with a few moves to 6+ full pass with none.

The extra half hour of removing the glued spoilboard is nothing compared to the lost time we had with the unsealed or gasketed versions over the life of the spoilboard. This applies to primarily sheet and lumber cutting.
Gary

[ljdm]

Gary - how do you remove the old glued spoilboard? Scraping old glue/silicone - or machine it off? If machining to remove, doesn't that tend to remove some of the top of the plenum? I mask off unused areas of the spoilboard, and foil tape edges - you think gluing will increase vac? I max out at about 6-7
" vac with 2 feins.

[Gary Campbell]

Lou...
When the spoilboad gets thin we simply break it off in pieces and use a scraper to remove the Urethane from the Resin coating on the plenum.

If we need to surface the plenum in the future, we will take off a few thousanths, but dont wish to as then a recoat of resin will be required.

We tried silicone, it seemed to stick to the Trupan, but not so well to the plenum. Spoilboards still lifted and curled in our humidity.

I think that in our case, versus the 4 quadrant, gasketed zones, we have increased vacuum. We have also installed motors with higher vac capability, usually starting with a full sheet close to 10 inHg.

If you have 6-7 inHg, then you are at the max of the Fein.
Gary

[gene]

John,
I wish i could take the credit for that idea but the truth is that someone here on the forum told me about it and thats the way i have done it since. I wish i could remember who it was to give the credit where it belongs but i just cant. I do have the mind of a calculator,,,, the problem is that the Batteries are NOT included...