Vacuum Table

[JMCS]

Finally time to build my vacuum table. Black box is ready to go. Just wondering about cutting my plenum, sealing it up, and using a gasket between plenum and spoil board (Tupan),seal up the edges and pop in a few dowels to keep the spoil board aligned. Any thoughts? 99% of my work is panel processing for cabinets. Or would gluing the spoil board on be the better way to go?

[Kyle Stapleton]

We glue ours on, works well.

[Keith Larrett]

I glue mine on. The last time I changed my spoil board I glued it down with Loctite Powergrab. It gave me a lot more time to place the adhesive on all the "hills" of the plenum and around the perimeter than the previous times when I used Titbond.

[jerry_stanek]

I have the 4 zone vac plenum that is in the SB files. I divide my spoil board into 4 sections and put a piece of 6 mill Sintra between each section to stop bleed over. When I first got my Shopbot I used the whole sheet and one day when I was only using one zone I had a piece of plexi sitting on the table at the opposite corner and went to push it so I could do some other work and noticed that it was being held there by the bleed over.

[fredtoo]

I sealed my plenum with watered down Titebond II. It has served me well.

[mcgoo]

Jerry...what kind of vacuum are you using

[dlcw]

Finally time to build my vacuum table. Black box is ready to go. Just wondering about cutting my plenum, sealing it up, and using a gasket between plenum and spoil board (Tupan),seal up the edges and pop in a few dowels to keep the spoil board aligned. Any thoughts? 99% of my work is panel processing for cabinets. Or would gluing the spoil board on be the better way to go?

I use a bead of caulk to secure the 3/4" spoil board to the plenum. Then run the vacuum for a couple hours to holde the spoil board flat until caulk sets up. I have 7 zones in my table (using a black box with valves for each zone) and each zone is a separate sheet of Trupan with plastic (melamine) edgebanding to seal the edges. When all the zone pieces are in, I caulk all the way around the outside of the spoil board to seal it up. I mark with a red marker where I put caulk down in the plenum field to hold the zone pieces. When my spoil board gets down to about 1/4" I grind it off until I see the red marks. At that point I am ready to put a new spoil board on. Since 2009 I've replaced my spoil board twice (and using the current one since early 2014). For small parts I use a 1" thick piece of MDO with T-tracks to hold the material. The MDO is held in place with the vacuum system. I haven't cut into my spoil board directly in about 5 years.

95% of my work is panel processing. I don't cut directly on the spoil board. I use 1/8" MDF ($5.00 from my local supplier) skinned both sides as a sacrificial board on top of the spoil board. When cutting is complete I slide the panel and sacrificial board onto an outfeed table, load up another sacrificial board and material to cut and get it started while my helper is labeling and processing parts from the previous sheet. Another benefit is that when I am going to be cutting a sheet of smaller parts, I can use a new sacrificial board (like resurfacing your spoil board) so I get really good hold down from the vacuum. When cutting sheets with larger parts I can use an older sacrificial board and still hold the parts in place with no problem. I can normally cut 10 to 15 plywood panels (depending on size of parts being cut) per side of the sacrificial board, sometimes more. For a typical cabinet job (25 to 35 cabinets), I might purchase 5 or 6 of the 1/8" MDF sacrificial boards.

Using this method, I only surface my spoil board at the start of each panel processing job. So I limit my surfacing to about 10 to 12 times a year (start of each cabinet job) taking at most 1/32" off the spoil board directly. This is done to account for seasonal climate changes and any movement in the CNC.

[jerry_stanek]

I have 2 Fein vacs. My plenum is 1 inch sintra that I skinned to level it and give it some bite for the Tite bond III

[knight_toolworks]

I have the 4 zone vac plenum that is in the SB files. I divide my spoil board into 4 sections and put a piece of 6 mill Sintra between each section to stop bleed over. When I first got my Shopbot I used the whole sheet and one day when I was only using one zone I had a piece of plexi sitting on the table at the opposite corner and went to push it so I could do some other work and noticed that it was being held there by the bleed over.I do the same but just coat the inside edges with the glue to seal them its easier.

[jerry_stanek]

I do the same but just coat the inside edges with the glue to seal them its easier.

The reason I use the sintra is I have tons of scrape pieces and the edges get a coat of glue when I install it. I use the sintra to register the piece also

[Ajcoholic]

For my 4'x4' plenum I used a half sheet of 3/4" starboard and over the past 2.5 yrs it's been awesome.

Bolted to my table, it has the zones sectioned off with U shaped neoprene CNC foam (sits in a round bottomed 1/4" groove).

I use regular 3/4" mdf for my spoilboard. Generally I cut about 5 to 10 thou into the spoilboard and resurface just to clean it up. I flip the spoilboard every few weeks so both sides get cut.

Not having it glued down hasn't been an issue. When the vacuum is turned on the spoilboard gets sucked firmly to the starboard plenum and won't move.

I do sometimes throw a second piece of mdf on the spoilboard if I don't want to cut into the sb. I stopped sealing the edges of the spoilboard since I wasn't seeing much difference, but I use a 10hp regen blower.

Other than cost I'm not sure why using plastic for the plenum isn't more common.

[EricSchimel]

Funny I was just thinking about using HDPE for a new plenum next time I get through my spoilboard. Did you have an MDF plenum prior? If so, how much more suction are you getting now?

[Ajcoholic]

Funny I was just thinking about using HDPE for a new plenum next time I get through my spoilboard. Did you have an MDF plenum prior? If so, how much more suction are you getting now?

I have a better groove system with the starboard. Deeper and more grooves closer together. I'd assume it's better hold down than the lacquered mdf board I started with. But I didn't do any real tests.

The starboard one should outlast me though, and is super stable. I go use 12 machine screws to hold it to the aluminum top on my shopbot. It's a home brew setup.

[waynelocke]

I am just redoing my vacuum table this week and am going to use HDPE. A 3/4", 4' X 8' piece is $225.00. I use a Fein and am going to a couple of lighthouse motors. My plenum has four zones and I use Home Depot round weatherstripping to further refine the vacuum area when needed.

The guy at All Star Adhesive convinced me a few years ago not to use mdf for the plenum. His argument, which made sense to me, was that, especially when using a smaller vacuum source, the vacuum needs all of the help it can get and no mdf , no matter how well it is sealed, is going to be as effective as the plastic.

The difference in price is not that great and I would have gladly paid more while I was sealing my current plenum with a brush and shellac. It was not a thrilling use of my time.

[MogulTx]

Wayne- who in the local area is offering 3/4" HDPE for that amount? I was just looking at 1/2" at Allied in 54 x 96 for $250. I need three sheets for a project.... (Thanks in advance) Monty

[waynelocke]

I am not at my desk but I am pretty sure that it is Austin Plastic and Supply (512-836-1025 (tel:512-836-1025)). They quoted me that price last week. If that is not the right place, I will repost tomorrow.

[curtiss]

In my table, I drilled a number of 17/64 holes through the “high spots” of the vac plenum. This allows lag bolts from below to hold about anything using “pull down” rather than hold down. (you do have to miss the bolts)

Holes are 5 1/2 inches on center. Did not see any major leak problems when using the vac table, I tape the bottom of the holes which are not used often..

I use some “threaded T nuts” on the bottom of several holes which can be used for threaded screws / clamps from above.