[SteveChlupsa]

Hey Guys-

I have a CNCRP 48x48- great machine. I am cutting small parts from 12mm foamed PVC board and 1/8" polypropylene sheets.
I am designing a vacuum hold down table using 2 Lighthouse vacuum motors. As I was beginning to design the plenum grid something came to me-

My machine sits on a 4x8 table with MDF top. Is there any reason why I can't treat the areas between the machine's 5 base extrusions as vacuum zones?

If one was to seal the tabletop and then seal the outer extrusions to the table (RTV?) and seal any air leaks on the corners it seams the framework/table would be an airtight compartment after spoilboard is attached.

The vac motors could be attached under the MDF table under 2 of the "zones".

I'd use some MDF pieces against the inner inside corner brackets that are sealed to the table. An ultralight MDF spoilboard would glue directly to these parts.

If needed a couple holes could be drilled through the inner extrusions to let vacuum pass through all 4 zones.

This should allow full vacuum to the whole table. W/O a plenum grid maybe it could hold smaller parts.

Am I nuts or could this possibly work?

THX for any input.

[nlancaster]

You would have to build sealed chambers between the aluminum rail.

Also you probably won't get enough suction thru the LDF. Gerry runs a heavy duty CNC router for a living and I believe he said that machine uses a 10HP vacuum pump to pull thru the MDF or LDF surface sheets.

[ger21]

Probably not, for 2 reasons.

1) Most people use 4 motors on a 4x8 table.

2) The table will sag in between the rails, because the vacuum will be pulling it down.

Thin, flexible materials can be hard to hold, because if a corner lifts up, you lose vacuum on the part pretty quickly.

[SteveChlupsa]

You would have to build sealed chambers between the aluminum rail.

Also you probably won't get enough suction thru the LDF. Gerry runs a heavy duty CNC router for a living and I believe he said that machine uses a 10HP vacuum pump to pull thru the MDF or LDF surface sheets.

I would use MDF spacers along inside of rail side extrusions- so it would be sealed chambers. Many guys are using the "Hurricane" vacuum setup by BlackBoxVac.com with great results on 4x8 tables.
The Hurricane uses 4 Lighthouse motors.
Since mine is 4x4 2 motors might do the job.

[SteveChlupsa]

Probably not, for 2 reasons.

1) Most people use 4 motors on a 4x8 table.

2) The table will sag in between the rails, because the vacuum will be pulling it down.

Thin, flexible materials can be hard to hold, because if a corner lifts up, you lose vacuum on the part pretty quickly.

Gerry- My machine is 4x4, (it is bolted to a 4x8 table)
I could add extra bracing between extrusions to prevent sagging....
Actually thin materials with smooth surfaces and no porosity vacuum down better than anything.

[ger21]

I saw the 4x8 table, but missed the 4x4 machine.

Actually thin materials with smooth surfaces and no porosity vacuum down better than anything.

They also can be lifted from the vacuum easier than anything.

There are a lot of factors involved when using vacuum. Smaller tools and slower speeds can help if you have problems.

[SteveChlupsa]

I'm gonna give it a shot-will take pics and update thread on results. Hopefully it'll suck lol.....
THX guys for the input!

Nlancaster- I saw your build thread on your CNCRP 48x48....how's the machine doing these days?

[nlancaster]

Machine is doing great! Upgraded last summer to 48x96!

[Rover31]

Steve,
Could you update this post?
Did it work?

Thanks

[SteveChlupsa]

Steve,
Could you update this post?
Did it work?

Thanks

Rover-
Totally works. I'm cutting 4" circles no problem. I'm having some slight sagging issues with the ultralight mdf...but I am planning to pull it off and add a few support bolts that will go through the base table and be adjustable.
Then I can run a straightedge across the table and adjust the bolt heights to be flush. Should cure the sagging. Once a piece of material is vacuumed down (even a 2x4 piece) I can't pull it sideways with all my strength. My suggestion is one lighthouse motor per 2x4 foot zone.