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Help resurfacing mdf spoil board


Homag BOF 311 CNC, BIG vacuum pump with matrix table.

Cannot get enough vacuum through mdf to run a resurfacing program. Breaths too well, software will not run if vacuum requirements are not met. WoodWop programming language (version 5).

Any ideas?

12/4/15       #2: Help resurfacing mdf spoil board ...
Chuck Hicks  Member


Have you sealed the edges with paint or a sanding sealer yet?

Catalog page

12/4/15       #3: Help resurfacing mdf spoil board ...

Yes, with an end grain sealer, multiple coats. My issue isn't when using the spoilboard with something (plywood) over it, it's trying to resurface it empty.

12/4/15       #4: Help resurfacing mdf spoil board ...
Chuck Hicks  Member


What is type and HP of Vacuum?

12/4/15       #5: Help resurfacing mdf spoil board ...

Dekker VMax, not sure of HP, 300 CFM.

12/4/15       #6: Help resurfacing mdf spoil board ...

550 cfm, 40hp, my mistake.

12/4/15       #7: Help resurfacing mdf spoil board ...

You should contact tech service. You get the alarm due to insufficient vacuum threshold set by the factory. That is adjustable(at least it is on other machines I have worked on). Find out how and dial it down.

12/4/15       #8: Help resurfacing mdf spoil board ...
Chuck Hicks  Member


You should not have a problem with that. May want to contact your machine or software company to see if there is a issue there.

12/4/15       #9: Help resurfacing mdf spoil board ...

Are you using LDF by chance.
LDF allows to much air flow MDF is the best option.

12/4/15       #10: Help resurfacing mdf spoil board ...

MDF. As of now we resort to simply buying a new piece when needed.

12/4/15       #11: Help resurfacing mdf spoil board ...
J Wilson  Member

How thick is your spoil board? We can surface ours down to around 5/16-3/8" before we have to replace it with a new 3/4" thk mdf panel

12/4/15       #12: Help resurfacing mdf spoil board ...


I have the same problem with all mdf other than plumb dbl refined.I'm hoping to find a solution also. I can't find 5 x 12, so I have to cut 4 x 10s to cove table. It's doable but a pain.

12/5/15       #13: Help resurfacing mdf spoil board ...
stvnhrmn Member

We have been buying 1/2" but I'm going to try 3/4" from here on out. I had another CNC machine my last 1/2" to 3/8" and I get better holding power on my 1/2" so I'll try 3/4" to see how it holds. My tooling and machine are VERY accurate so I can make a new sheet last for months.

12/5/15       #14: Help resurfacing mdf spoil board ...
Jerry Member

Is there a way to close off some of your vacuum to mimic that your spoil board is covered

12/5/15       #15: Help resurfacing mdf spoil board ...
stvnhrmn Member

I've pursued that a little. Seems the less ports I open on the matrix table the more concentrated the suction is where it is open...and again, the mdf is so open it shows even less vacuum overall. I almost wish I could turn down the HP on my pump. I think I'll just resort to getting a new piece when needed.

Thanks for all the feedback!

12/5/15       #16: Help resurfacing mdf spoil board ...
Kerry Fullington



On Thermwood machines we use a 3/4" Table Board (32Lb per cubic foot recommended density) as a base with a 1/4" Wasteboard (48 lb per cubic foot density) on top This eliminates a lot of the bleed through. We replace the wasteboard when it is surfaced to .17"

You should probably look at the CFM of your pump to see if it is moving enough volume of air. The piping to the pump and the table matrix are also factors. The pump can be rated for a lot of suction but if it can't move enough volume of air it won't hold your parts.

Dirty air filters in the pump can also reduce its efficiency.

12/5/15       #17: Help resurfacing mdf spoil board ...
Kerry Fullington

Forgot to mention, make sure your pipe connectors and valves aren't constricting the air flow to the pump. How long is the pipe run to the pump?

12/5/15       #18: Help resurfacing mdf spoil board ...
stvnhrmn Member

Not to be rude, but my problem lies in having too much suction. The mdf I'm trying to resurface isn't even seen by the machine as my pump sucks THRU it so well.

Apparently this isn't a big issue for smaller pumps (like the four other CNC machines at our other facility).

I can't just make a massive spoil board as most of what I do runs on pvc/uhmw pods directly on the table and I have to take my spoil board on and off as necessary. 90% without it so making it massive isn't going to work as I have to lift it off and on manually.

12/5/15       #19: Help resurfacing mdf spoil board ...
Kerry Fullington

Is your gasket material to the matrix table properly sized and sealing properly?

12/5/15       #20: Help resurfacing mdf spoil board ...
Kerry Fullington


Suction, is what happens when you restrict the flow of air through your spoilboard.
If your spoilboard is allowing too much flow of air through it then the pump needs to move a greater volume of air (CFM) to create suction.
Give us some more info about the pump.

12/5/15       #21: Help resurfacing mdf spoil board ...

If this is a low plenum pressure alarm, I would really look at the simple and most likely things first because 3/4 standard MDF should be working just fine with just about any pump and any machine.
Have you carefully and thoroughly checked for leaks in your vacuum line? Like Kerry says blockage can reduce the pressure and set off this alarm, but the opposite is true as well, leaks reduce the pressure and the sensor will trigger the alarm. If you have really eliminated this possibility Mike and Chuck are dead on, your sensor may be bad or mis-set. Contact tech and get the real answer, your problem is not likely the MDF.

12/5/15       #22: Help resurfacing mdf spoil board ...
Kerry Fullington


I missed reading above where you gave the pump specs. 550 CFM should be more than enough.

12/5/15       #23: Help resurfacing mdf spoil board ...
Dropout Member

I went from a 10HP Becker to a 30HP rotary screw. I had to lower the switch setting with the rotary screw to get rid of the low vacuum errors. It's likely the high cfm that is causing you the problem.

If you can't adjust the vacuum switch, jumper it out when resurfacing, or, depending on where the switch is, put a ball valve between the switch and the table so you can restrict the flow and increase the vacuum the switch sees.

12/6/15       #24: Help resurfacing mdf spoil board ...

Check your gaskets make sure you have a dood seal on the edges. Sometimes our board will start to warp and won't lay flat and leak, so i have jumped up on the table to weight the high spots, once it grabs it will hold.

12/7/15       #25: Help resurfacing mdf spoil board ...
kevin waldron


Change brands of material. We had something similar and discovered the material was the culprit along with a bow in the product. If we have vacuum problems we often will cover the table with a roll of polyethylene to find out where our leaks or problems exist. It becomes fairly easy to trace whistle sound when you restrict the draw with the poly.

12/9/15       #26: Help resurfacing mdf spoil board ...
Gerry W

Place 1/2 sheet of laminate on the table to seal off some area. As surfacing tool works its way to the laminate swap positions and let tool finish.

12/9/15       #27: Help resurfacing mdf spoil board ...
stvnhrmn Member

Gerry, that's been my workaround so far. It's a pain, but it works.

12/14/15       #28: Help resurfacing mdf spoil board ...
Mike McClaran

There's an awful lot of talk here for just a simple 1/2 turn of your vacuum sensor.

12/4/20       #29: Help resurfacing mdf spoil board ...

I use the Aluranger from Casadei. Its an upright. We had the same issue first time we tried to plain a new Spoil board. Turns out that they actually recommended NOT to plane the back side of the spoil board, only the front. tried it and it worked like a charm. went against everything I knew but I was able to plain it empty and it still held my parts like they were fastened to the table. It may not work for your table but it is worth trying. you can always plane it after if it doesn't work.

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