CNC Multicam Vacuum Issue

Tried to use the CNC and the vacuum pressure was really poor, the MDF pieces also just slide all around now where it seems they used to be taped down. Anyone else experience any issues?

The spoilboard pieces have been “floating” since before the lockout. The table vacuum seemed to be working fine last week. Are you pulling out the correct stops for the vacuum zones you were using?

Do we have anyone there able to check the filter on the blower motor? @cghaly thought it may be a part of the issue.


Yes, the vacuum was enough to pull down the panels but that’s about all it had.

When I refinished the spoilboards, I added foam backer rod in the grooves of the grid underneath to seal the boards, make sure those backer rods are sealing all the way around. Also blow out both vacuum pump filters before you use it because thats what caused the pump to blow up the last time.


Thanks Mitch!

Backer rods and no tape was chosen as the path forward back in Feb. It’s a good method in an environment with a regular CNC operations crew and is used in most commercial shops. Not sure about it at DMS where oversight and TLC are both in short supply. My comment at the time:

There are two other related issues with no tape: MDF moves a lot due to humidity difference top to bottom. If you do anything to cause the top surface to dry out more than the bottom surface, it will curl upward on the edges. Often it will lay back down as the board equilibrates, but in the meantime, contact is lost with the gasket resulting in poor vacuum holddown and dust bypassing to the blower filter. This tendency to curl becomes more pronounced as the spoilboard gets thinner.
The second issue is that having separate boards for the zones means more gasket length, so more places for a bypass to happen.

Tape was my way of fighting the curl. Doesn’t hold forever and once it comes up, it’s hard to address without doing a replacement.

On the separate zone boards, my initial impression that Makers would be damaging a single zone and zone replacements would save on MDF cost didn’t really pan out. Too many Makers don’t realize they are carving up the spoilboard quickly and stop to make adjustments. As a result, most of the time multiple zones were damaged. That minimized the possible savings.

Something I never got to, but might be worth testing is to lay down a full sheet of the MDF and use a 1/4" or smaller bit to cut divider grooves to outline the zones (but not along the outer table perimeter). The grooves would be almost, but not completely through the board. Then clean the grooves out and fill with Bondo All Purpose Putty or similar product to create a barrier for air to flow sideways through the board between zones. If that works, then all that is left to worry with is the seal at the table perimeter and I’d use double sided tape and then single sided tape to further seal the gap between table and spoilboard.

My 2 cents.


When I took the Multicam class last year, I seem to remember a practice of laying down butcher paper around our work to so that the vacuum would be concentrated on holding the work in place and not just sucking air through the surrounding spoil board. Is this practice no longer recommended? If it is still a good idea, could we hang a roll of butcher paper on the backside of the room divider separating the Multicam from the Jet lathes?

Also, there is an extensive collection of scraps (mostly MDF) piled up behind, under and around the Multicam. A few look like have adjustable screws in them that make them look like crude, simple jigs. What is all of this junk? Can I toss it all in the dumpster and clean up the area around the Multicam?

I sometimes use those to locate pieces when I’m cutting multiple, identical boards. I’ll micro-pin (23 gauge) two of them to the spoilboard to locate the corner of my work. Subsequent workpieces can then be slapped down into the same exact location with no fiddling to find zero.

Prefer to not get rid of all of them.

The paper used was freezer paper which differs from butcher paper in that it has a plastic coating on one side to make it impermeable.

The pieces of MDF with blocks and bolts were provided as additional holddown aids. These are explained in Video #3 here:

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@bertberaht Good to know. Next time I’m there, I’ll label the hold downs like some of the other jigs around the Multicam are labeled. I’ll also bring some freezer paper.

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@mdredmond I didn’t really intend to throw everything away, but I would like to clear out the excess. It makes it hard to keep the area around the Multicam clean. And like several other places in the woodshop–in corners and under tools–most of this stuff looks like it was just tossed there instead of carrying it out or disposing of it properly.

I’d the old spoilboards can definitely go. I’d keep the undamaged MDF that has the blocks and screws. Everything else is probably trashable.

Matt & Jim,

Actually, I would like for you to leave some of the old spoilboards if you can. I have used them under pieces that I wanted to profile-cut completely through.

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I had planned on leaving some of the larger pieces that still look usable for that purpose. The problem is that people see a couple of scraps laying around and they see it as an invitation to throw their trash scraps in the pile with them.

When I was in there yesterday, it was much better than it was when I took the pictures. There was a guy there–his name escapes me–that had done a great job of sweeping and vacuuming up. But there is still a lot of junk under the table that needs to be tossed. I’ll take care of it next time I’m there.

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Thanks Jim. I wish I could be there to help out, but I’m trying to restrict my public access until this Covid-19 thing does an about face.

No worries. It won’t be that big of job. It’s just been bugging me.

This is what it looked like when I left Tuesday evening 6pm


Thank you Jim!

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Thanks for taking care of all the junk!

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