# Spoilboard Curling Problem



## HK7 (May 25, 2016)

Hey all,

We're having a problem at the shop with our 3/4 medium density mdf spoilboard curling at their corners as soon as we resurface it. This has happened with low density as well, and we have tried material from various suppliers. Has this happened to anyone else? How did you resolve it?

Bonus info: It hasn't been more humid in the shop than usual.

Thanks in advance!


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## Semipro (Mar 22, 2013)

Hello and welcome to the router forum.


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## DesertRatTom (Jul 3, 2012)

Resurfacing? Using glue? That could be part of it as some glue can cause mdf to expand. Could also be a handling problem which would require monitoring the process to see if someone is dropping or bumping it against something. Any way, welcome to the Forum.


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## 4DThinker (Feb 16, 2014)

Unfortunately, as soon as you skim off the top you open up the new surface to humidity/swelling, with the edges getting more and the corners a triple dose. Thus the corner curling. You could try sealing the edges with poly or even white glue before surfacing to slow down moisture from penetrating the edges. 

4D


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## Stick486 (Jan 4, 2013)

welcome to the forums...
the surface tension of MDF is way different than it's core... 
when you resurfaced the MDF on one side the opposing side began to release tension and your pieces began to move...


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## HK7 (May 25, 2016)

Thank you everyone! This is what we suspected--how do you avoid this problem? Do you skim off both sides?


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## 4DThinker (Feb 16, 2014)

On out multicam that uses a vacuum to hold parts down we do skim both sides. At least when the MDF is brand new.


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## Stick486 (Jan 4, 2013)

HK7 said:


> Thank you everyone! This is what we suspected--how do you avoid this problem? Do you skim off both sides?


don't use MDF...
skimming both sides will just hasten it's self destruction...

3/4" MDF, surface both sides with a 4" fly cutter before use and edgeband with PVC...

use LDF airboard instead....
seal the edges and increase vacuum...
no surfacing required...


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## phillip.c (Aug 9, 2012)

Is your space climate controlled?


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## HK7 (May 25, 2016)

Thanks *Stick486* for the info! 

We actually started out with LDF and had the same problem, then bumped it up to MDF to see if it would help. Not sure why we have this consistent problem..


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## HK7 (May 25, 2016)

*Phillipdanbury*, no unfortunately it's not. My assumption was that humidity is going to be a battle, but our CNC mechanic says most people do not have this problem consistently. Couldn't shake the feeling that we weren't the only one's with this issue.


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## tacomamacxtech (Mar 31, 2009)

Goggling the topic "spoil board curls" got me to this...

"Brad McIntosh posted this to a thread in 2008 that I found really interesting."

"by Brad McIntosh » Sat, Aug 02 2008, 10:52AM

Nick,

Main Spoil Board-
Our experience here in Canada with our customers indicates that a new main spoil board should always be machined on BOTH sides. The surfaces on both sides of the sheet are somewhat "sealed" in the manufacturing process. The surfacing of both sides opens up the fibers and allows a greater flow through the material.

Waste Boards (SPACERs)-
Experience has also lead us to suggesting to our clients that they start off with a SPACER (or waste board) with an initial thickness of 3/8" (9.5-10 mm). 1/4" becomes too flimsy too fast and begins to curl up at the corners. The 3/8" material allows for a couple more "re-surfacings" before the curl effect makes them unusable.

A couple of other notes:

Periodic Re-Surfacing of the Main Spoil Board-
Since the main spoil board does not get machined into on a "regular" basis by your normal production, some of our clients have gone months without "touching up" the top of it by re-surfacing and removing 0.010" (0.254 mm) or so. What these clients also found was that they would start to have the following issues: 1. The efficiency of the hold down would decrease -and- 2. Their depths of cut would become non-uniform.

We recommend that the main spoil board be re-surfaced once a month at a minimum. This levels it out from thickness variations that can be caused by uneven thickness expansion due to humidity changes, etc. The main spoil board also acts as a filter for the fine particules/dust that is constantly being pulled into it - slowly clogging the top surface. Manipulating waste boards (SPACERs) -sliding them on and off, flipping them over, etc - also can close off the porousness of the top surface. The re-surfacing opens up the top surface and can help to rejuvenate your vacuum efficiency.

Alternating the "Face-Up" of the Waste Board (SPACER)-
Some of our clients will run X number of sheets with one side of the waste board and then flip it over and run another Y number of sheets before re-machining both sides. Although this does not reduce the amount of re-surfacing, it can extend the continuous working cycle between re-surfacing operations. Another side benefit is that curl that can develop in the waste board is minimized by the uniform machining of both sides towards the core of the sheet. This seems to work well with a waste board (SPACER) that starts off with 3/8" material."


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