Spoil board question

[toad]

I recently installed a Vacuum to my table. Table is divided into six sections. with rubber ring around each section. Pulls the spoil board down real tight. I have not put a gauge in the suction line, so I do not know what the inches of vacuum are.
I am using 2 (Lighthouse Lh676565-OD-240 Shopbot motors for my Vacuum system. I am not getting enough suction through the spoil board to hold down the material.
I am using 3/4 MDF that has been planed 1/16th off each side. I am getting some suction, but very little. Doesn't matter how many I turn off, suction doesn't increase.
It is just a MDF board that came from Home Depot. nothing special.
If I lay a piece of plastic over the board, it will suck it down, so I know I am getting some suction.
Any suggestions?
Thanks
Toad

[domino11]

Most of the guys are using lightweight MDF called Trupan for the
vacuum systems. Your mdf might be too dense for vacuum use.

[bradm]

What Heath said. Also, have you double checked the bottom and edges to ensure you are getting a good seal, so that all the vacuum pulls through the top? In particular, sealing the spoilboard edges (paint, or even just tape) is important.

[toad]

Hi all, All is sealed and painted.
I found a lightweight MDF that is I am told the same as TruPan.
It has to be ordered, but Hardwoods Store in Gibsonville can get it. I will let you know how it turns out.
Toad

[Gerald D]

[QUOTE=toad;69650]. . . . . with rubber ring around each section. . . . . . /QUOTE]

Brad & Domino, it sounds as if his design does not want any bleeding through the board at all?

[toad]

Hi Gerald,
The seal is around the perimeter of each divided section.
When you turn on the Vacuum, it sucks down the spoil board
and only vacuum loss should be through the spoil board. Correct?
If I am missing something, let me know. I done this so I would not have to glue down the spoil board. Your assistance and guidance is always appreciated.
Toad

[Gerald D]

It is the opposite of what Heath said (and to which Brad agreed). You need non-porous board, or boards (top and bottom) made non-porous by paint/sealer. The dividers must also not leak.

[bradm]

How about a picture? Do you have a spoilboard for each zone, or just one big sheet sitting on top of all of the zones?

[domino11]

Usually the ones I have seen have a sealed bottom board that usually have zones and a square hatch pattern cut into them. These are completely sealed, top, bottom and edges and form the support board. This does not have to be Trupan as it will be sealed This is where the vacuum lines attach to the zones. The guys mention using a 50/50 mix of titebond and water to do the sealing.
Then a porous board, usually trupan, is put on top as a spoil board which only has the edges sealed. The vacuum is pulled through the trupan to suck the material being cut to the spoil board. This way your spoilboard is one piece.

Im not sure that is the same system Gerald is recommending though.

[KenC]

Guessing work is a waste of time. go get a vacuum gauge & find out what vacuum you are getting & where.

[Gerald D]

I am not recommending any particular system, I was just concerned that his system was misunderstood. If he uses the rubber ring method, then he must not have any porosity anywhere.

[toad]

Here are two photo's the plenum.
Picked up the lightweight MDF Today, Now I will see what happens, and also install a gauge to see what's going on at the pump.
Toad

[alan254]

Has the bottom of the plenum board been sealed since the top does not appeared to be sealed ?

Al

[KenC]

It is most advisable to taper/countersunk the pipe/duct opening on the bottom plenum board to encourage air-flow.

Must paint/coat/seal the bottom plenum.

[toad]

top and bottom have both been sealed.

I thinned down wood glue and let it soak in and recoated it again to be sure.

Coated all edges also.

I should have the edges sealed on the spoil lightweight board today and get it resurfaced. I will give it a try tomorrow. Hope the issue was just the Lowes MDF.

Toad

[KenC]

For the top, yo only seal the edges, i.e. the vertical portion of the board when laying flat on the table. If you seal the top & bottom side of the top sheet. where do you thing vacuum will form.?
I prefer applying any kind of varnish thin down by at least 1:5 I never trust glue to stay on long enough without a top coat.

[toad]

Hi all:
Ok, finally received the lightweight MDF and got it on the table, resurfaced both sides and sealed the edges and gave it a try. With all valves open, am pulling 8 inches of Vacuum at the pump. with back section closed off, have 11 inches. Placed a small piece of MDF on the table, and it sucked down. Went all the way down to a 12 X 14 and still held good.
Must have been the MDF from Home Depot that was the problem.
Still amazed at how well it works.
Thanks for your assistance once again.

Toad

[Tom Ayres]

Cool Beans! You may have mentioned it but what size is your plumbing? I have a huge heap of that stuff up in the rafters of the shop. I should go ahead and make mine as well

[KenC]

Well done!!! Anything above 8" should handle items larger then 2'x2' with confidence..
A note of precaution, turbo fan will fry if there are totally no air flow, hence it is mandatory to allow some air leakages to keep the fan cool.

[Fox]

Manditory airleak: you can use a sintered bronze blow off used in pneumatics for that. Just screw it in your pipes somewhere.

[KenC]

Airleak : just don't cover up all the leakages religiously will do the job.

[Fox]

It sounded like he has done that :)

[toad]

Hi all;
I have a couple 1/4 I holes in the pipe for air to get to the bearings.
I am surprised on how good it does.
The pipes are 1 1/4. Going into a 4" PVC Plenum with a 2" from the plenum to the pump.
Have a wonderful day, Raining here, buts that's OK.
Toad

[Fox]

Nice ! I still need to do mine, but got the same motors from lighthouse already waiting. Only just got my spindle coolant pump after three attempts from the idiots where I ordered it ( last time I ordered something there). Hope to get a first cut this weekend.

Ps. I would still use some of these sintered bronze blow off valves (or something else you like to use) to filter the inrushing air.
Right now (open holes) you're not only cooling your bearings but also sucking them full with dust and other debree, which does not help for longlivety.

[Tom Ayres]

Coffee filter...just kidding;)

[Fox]

You might create even more vacuum when it's put on a on a caffeine diet :p

At least a cloth, better something that stops finer particles without restricting air too much ( it'll get sucked in quickly)

[danilom]

Vacuum inlet should have its own some kind of filter anyway already so any hole should do the job.

[Fox]

He's using vacuum cleaner motors, Danilo. Not a pump.
I agree he better put a bigger filter somewhere in the main line for all the holes in his table if that is what you mean. He might be putting his spoilboard on semi permanently, and sealing those holes that way, and hope to not cut trough it entirely.
I am going to flip my grid upside down, don't seal the bottom (which will be the top ) and let it suck trough the table, to avoid pollution. and put a thin layer of spoil on top of that.

[danilom]

Yes I mean filter all the vacuum inlet air. And vacuum motor is just the same thing as vacuum pump in regards of dust or debris that get sucked.

Brady from shopbot forum (bradywatson) on black box vacuum subject.

You should most definitely run filtration on those motors. An automotive air filter or cylindrical shopvac filter (Rigid brand ones work well) to keep anything the bleeder misses or chunks/debris when you first fire up your system. Also, put a little filter/breather on your bleeder holes for the vac cooling holes so that junk doesn't get into the pump that way. Cheap insurance...Few even think about the little PVC chips that are stuck to the inside of pipes when you cut them while plumbing the system the first time...

My small pump inside inlet has a synthetic felt (don't know exact name) and it works. Large water ring pumps tolerate some dust as it gets in the tank but have a inlet filter anyway.

[KenC]

I'm running without filter. no problem as long as the plenum & spoil board don't have big holes on them. IMHO, the spoil board is the filter.
If you must have some sort of filtration. a fine mesh screen should keep bolts & nuts or other foreign object big enough to damage the vacuum cleaner fan.

[toad]

I have seen some people put pool filters inline, not sure how that works.
I have not put anything in line, and just cheap filter media over the holes for air.
If I do need to do filtering in the main line, I would have to build a box for the shopvac type filter unless someone knows of a better way to filter it.