vacuum plenum

[james mcgrew]

i am gonna make a new plenum fot the router, last one was 1.5" squares .5 wide and .375 deep in four zones.


are smaller channels better, is there a formula, we use high cfm blower are there advantages between aluminum and phenolic (grade) as the last one i made from mdf and sealed well.

[John McClanahan]

From what I understand, larger holes or slots (or more of them) provide more holding power than small ones.

If you ever see a vacuum cleaner advertisement where they brag about suction by picking up a bowling ball, they always have a funnel shaped hose adapter at the ball. The adapter that they don't talk about increases the square inches of suction surface area. No vacuum cleaner can pick up a bowling ball with the standard hose only.

John

[Nicholas Bukky]

Jim did you post this on the Zone too?

I am also interested in this!!!!

Thanks,
Nick

[james mcgrew]

john is right it is about volume, just is a great effort to do this and i would like to improve if i can
jim

[Scott Shepherd]

James, I hope you'll post your results. I'm in the process of trying to figure out the same thing. We have a lot of problems with our Trupan spoilboard compressing all over the place. It makes it impossible to cut a depth accurately, and I'm convinced it's because of the plenum design we have. My gut tells me there is a better way to direct the vacuum through the plenum that will give a more even compression. I know people say that once the vacuum is on, then it's all the same across the workpiece, but my experience says that's not true. If I cut something really close to the edge, I can pull it off the table, but if I cut something that's deeper into the table, I can't. So again, that tells me that the vacuum is not uniform, and again, I attribute that to a design that's probably not the most efficient. I'm not sure what the design that is efficient would look like, but I'd like to try something different this next time around.

[james mcgrew]

will do, i have had several private responses and posted on several forums. i intend to document this for future use

thanks

jim

[John Teichman]

very interesting i am building new table as we speak the plan i came up with is a grid .25 deep x .25 wide on 1.25 centers w/ 2 zones and 5 hp. becker pump for 50in x48in. table as for material .25x.3125 high gaskets, and thinking of using some free corian i have. lateral slip is a problem? my friend in Canada uses .25x1. slats on edge in slots to stop this. and builds a lot of jigs..

[Nicholas Bukky]

I just cut mine into my table for 4x8 .5wide .125 deep and glued the spoil sheet down with wood glue using a BIG bead around the perimiter and a little dab on each square every other row.

Used it yesterday and it worked just fine. I think I still may seal the edge with glue or silicone

(i use .75 mdf for my spoil sheet)


Nick

[Steve knight]

I use 1/2" wide and as deep as I can get with the material. mine is about 1.5" squares. but I am thinking og going with round patches. they would be less likely to break off. I think it is more important to have even airflow since there is not a lot of air moving when all is said and done.

[Michael Kowalczyk]

I think Komo and a few other CNC's actually use a flattened pyramid shape as their grid pattern and thought if I ever need to make a new one that's how i would probably try one. You can probably make the pyramids 1 3/4" and use a 1/2" downshear to clear the path in between them and your final perimeter seal. (depends on what you use for a seal I use 1/2" and 1/4" seals) So if you space them 4" on center you could still have a 2" square grid which will support your MDF spoil board very well and give good air flow under it and allow for more actual air to flow through the MDF.

[Steve knight]

I use 1/2" wide and as deep as I can get with the material. mine is about 1.5" squares. but I am thinking of going with round patches. they would be less likely to break off. I think it is more important to have even airflow since there is not a lot of air moving when all is said and done.

[james mcgrew]

steve i like the sound of the rounds airflow and smooth is paramount.

joey just showed me some pics of the stinger vac table that fits in the t tracks and works with the shop vac/fien or vac of choice

[Michael Kowalczyk]

Airflow travels better in a straight line. If all the supports are round then I would think there would be more turbulence. Not that you would be able to detect it under the spoil board but when you open the valve to hold your material, IMHO, the initial flood of air being evacuated would be quicker with straight lines rather than round. Round supports, as well as pyramid ones, also limit your ability to shrink/reconfigure your sealed area.

If you are using MDF for your grid, then I don't think it matters whether they are round or square, there is still the chance of them breaking loose.

I made my 5'x8' table out of full sheet of 1/2" gray PVC with 2" OC grids. PVC is great because it is stable and does not warp when you cut only one side. My grid lines are 1/2" wide and 5/16" deep. You can find 4x8 sheets all day but 5x8 are harder to find but they are out there.

[Ed Lang]

Jim or Joey,

I would like to see close up pictures of the Stinger vacuum table where the grid stops and the double thickness starts. This is the end where you connect the vacuum source.

My concerns are about sealing the bleeder board and preventing leaks.

Thanks
Ed

[Dennis OBrien]

steve i like the sound of the rounds airflow and smooth is paramount.

joey just showed me some pics of the stinger vac table that fits in the t tracks and works with the shop vac/fien or vac of choice

Wow, hadn't been thinking much about a vac table - but as we say here in Mass. - That's Pissah!