i just bought a 40 hp dekker oil ring with vfd to use on my 5x13 multicam cnc router. the problem i have been trying to resolve for 3 days is.
i can close all valves on system & get 28.5hg so i now know vac is working.
i removed spoilboard & plugged all vac holes with rubber stoppers & get 28.5hg so that tells me i dont have a plumbing issue.

i am using 1.5" ldf with edges sealed & faced on both sides. with my old 20hp roots blower pump i could get 14-15hg. with the 40hp dekker all i can get is 16hg.

i have a slotted table that is .180 deep & .500 wide. i am using .250 x .500 wide gasket from all star cnc. i have tried medium & soft but no luck yet.
i have removed all gasketing & cleaned very well & installed all new gasket. still cant get good vacuum.

does anyone have any advice for me to try?

Try using MDF in place of LDF. LDF allows more air flow.

Agree with Jim. I have tried LDF and I don't care for it. The thinner it gets from milling, the more vacuum loss there is. I get much better holding ability with just shop grade MDF at 3/4" thick. I usually replace when the board gets between 0.480 and 0.50" thick. That gives me around 25 table mills before I have to replace.

thanks for the advice . i will give that a try.

the main issue i am having is when i put material on top of the spoilboard the loss i am getting is between the spolboard gasket & the table top , not really losing thru edges.

seems i have overbought on my 40hp vac to me

thx
mike

Seems to me, a 40 hp Dekker is a big step up from a smaller blower. How do you know the loss is between the gasket and the LDF? If that was the case, losing so much vacuum, I imagine you would hear it. If I recall, you said you replaced the gasket. Something isn't adding up. If you try the MDF, let us know the results on your machine.

mike
i took smoke & ran along the edge. just cant tell if leaking between the bed & gasket or gasket & spoil board. but to me it just doesn't seem like its that much air loss. i have also noticed that air is coming from between the spoil board & the sheet of 1" acetal. the edges are really sealed good at this point.
when i 1st started trying to figure this mess out i was like u. i would have thought losing this much air would be really loud. but i have to turn off any fan blowing to be able to hear any air leakage.

I'm assuming the table gasket between the LDF and the table is 8mm or 5/16" cord gasket and in good shape. The only thing you haven't been able to try is standard MDF that has been face milled both sides. I also have a 40h.p. liquid ring pump. Tavaini, but those are similar to Dekker and I have very good holding power with both of mine. My configuration is Aluminum table with Aluminum grid top attached. Resting on that is my 0.5"-.75" MDF spoilboard.

i have been working on this for a week now with little success.

dekker has not been much help other than saying we will get someone to call you. & still have not heard from them.

i have not tried the mdf but have ordered a 1 x 48 x120 sheet of mdf since majority of my plastic is 4x10 & it will be here next tuesday. only getting the 1' because that is what they had. if that is bad pls let me know & i will mill down to .750. other than that i will mill both sides as usual before trying to use it..
i have tried nylon screws to help seal but no better
i have even tried putting 1" pc of plastic on top of spoil board& running vac , then adding hot hot glue to edges to help seal it down.
my grooves are .500 wide x .187 deep for .250 x .500 rectangle gasket.

Once we drilled and tapped the table and started bolting down the spoilboard with nylon screws all our vacuum issues went away....

I think the real problem is that the spoilboard doesn't machine flat. Bolting down the spoilboard solves that issue.

1" seems like a pretty thick slab to pull vacuum thru, but give it a try. You can always mill it down later. I screw the boards down in the corners. Helps keep it from curling since we keep milling the same face.

We found that the corners are not enough. We have over 20 screws in a 5X10 table.

I've been told thicker is better - it acts like a chamber. I've never used thicker than 1" but I know from experience that thinner is bad.

You don;t mention what size table and what size material you are cutting. 4X8 on a 5X10 table will be harder no matter how much vacuum you have. One of our 5X10 machines is gasketed for a 4X8 spoilboard cause all we run is plywood.

Oops - see you did mention 5X13 table - 65 square feet. 4X8 ply is 32 square feet, less than 1/2 that. Even 5X10 at 50 square feet leaves 23% of the table uncovered.

It's likely an airflow issue - try covering up any empty space on the table and see what happens.

We surface both sides of a 5x10 x 3/4" regular MDF and screw the corners to the phenolic table. On top of that I surface both sides of a 4x8 sheet of 5/8 MDF. I use the same 5/8 MDF as we use for door panels, so it is usually dual refined Plum Creek (Weyerhaeuser now).

We only cut 4x8 material so this works really well for us. I cover the unused part of the 5 x 10 with plastic laminate sheets.

This way I am only replacing the 4x8. It usually gets replaced when it is 3/8 to 1/4" thick.

We have a 15hp oil flooded Busch vane pump.

I would guess you have too much air flow thru the LDF and uncovered parts of the table. Your roots blower likely moved more CFM than the oil ring pump, but will not produce as hard of a vacuum if the table is completely covered with either the material you are cutting or plastic cover sheets.

some additional info that may help

https://www.cnc-tool.com/technical-white-pages-cnc-part-fixturing.html#/

thanks everyone for your opinions
i did about everything that was mentioned above

sealed edges 2 times
went to mdf
milled both sides flat
screwed mdf to table
i have been cutting parts today
& it seems much better.
where i am getting confused is
it won't hardly pull down a slightly bowed
pc of laminate i am using to cover open
area past parts i am routing.
my vacuum is really good @ 23.8 hgv
but dont understand why laminate is not pulling down.

with an open sheet of mdf on top what should the hgv
be approx.

thx
mike

I don't hit nearly those numbers for vacuum. I have to look at the gauge to be certain.

4x8 table. I've got 3 pumps totaling about 11hp.

I seal the edges with plastidip. It comes in a rattle can, I hit all edges 4-5 times.

Surface both faces.

I do not screw it down. I don't see the point. If it starts to potato chip, I just grab another guy and we flip it. It usually only happens once or twice in the life of the spoilboard.
Convex, they suck down easily. Concave, not so much.

I change them out around ¼" thick. The thinner they are, the less issues I have with parts moving. I do a return skin on everything, to help with that, and to also make the dust collection more effective.

I start with a ¾" sheet, but have been considering starting with ½".

I try to penetrate the spoilboard .002" when cutting, and surfacing we take .1mm (.004").

Dylon sent me this, (i had to copy & paste on web page to open it)

https://www.cnc-tool.com/technical-white-pages-cnc-part-fixturing.html#/ >if anyone is having issues & you have the time take a look at it.
there is alot of stuff in it that is way over my pay grade but,
i learned a lot from reading thru what i could somewhat understand.
as far as the screws, they really helped me as they pulled the gasket down around the outer edges so thickness stayed the same as middle of sheet.

a blower works great in LDF because it has a lot of air moving

a vac works best on mdf because it is using vacuum to hold parts

had no clue how they worked differently

the blower eats up a ton of a/c & spits it outside

vac has minimum air going outside since the vacuum is holding the part

as of now it really holds parts much more firm than blower & cuts are much better also. as in no vibration marks

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i think i have been snake bit on this 1.
70 hours use & now when i start the vac up
i get this noise. can anyone maybe point me in the right
direction on what it might be? thx mike

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