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post #1 of 5 (permalink) Old 03-06-2012, 08:15 AM Thread Starter
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Default It wasn't me...

In our climate we have significant issues with humidity making the panels swell and flare at the edges, but I've never seen anything like this. When we leave panels after they have been cut and the humidity is high, the edges of the panel flare out as the chipboard absorbs the humidity, and in normal circumstances this flaring is between 0.2 - 0.4mm (approx 0.008" - 0.016"). Not enough to be seen by the naked eye, but 0.4mm is outside the range of the edge bander, and it starts cutting the panel itself when it trims the edge tape.

Not this morning - the flare was so big it was visible to the naked eye and when I measured it, the flare was 0.8mm. Enough to gouge a strip about 2mm wide down the length of the panel. It really looks like water damage, but I can vouch that it hasn't been out in the rain at all. The job left the CNC after cutting and was held in the waiting area until I picked it up this morning to edge. Totally out of the weather and totally dry - no leaks in the roof etc. It has been very humid over the last few days, and that appears to be the only source of moisture in contact with these panels, but even that is far in excess of anything we've had before.

Any ideas???

The first photo shows the edge of the panel. The next two show the calipers measuring the panel at the edge and as far away from the edge as the calipers could reach. The difference is 0.81mm.

Darryl
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post #2 of 5 (permalink) Old 03-06-2012, 08:58 AM
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How about applying some sort of coating to the raw cut edge after you make the cut? Since chip board material edges don't glue all that well anyway, maybe just applying a clear varnish would keep the moisture out. Your project would need to depend a bit more on fasteners, but the edges of the stock should be more resistant to moisture. I've never had to deal with this, so I'm just guessing at a possible solution.

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post #3 of 5 (permalink) Old 03-06-2012, 09:36 AM
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Darryl, was the board sitting on the [swollen] edge on a moist surface or concrete slab prior to the swelling?

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post #4 of 5 (permalink) Old 03-06-2012, 11:20 AM
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If you're in a closed shop, how about installing a dehumidifier? Sounds like it'll be running 24/7! Another thought; build a store room and put an air conditioner in one of the walls, pulling the cooled air into the storeroom...remember to allow for a drain pipe to carry away the condensate...and also a filter to prevent dust from plugging the radiator.
Store your stock and work-in-progress in the room.
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post #5 of 5 (permalink) Old 03-07-2012, 02:31 AM Thread Starter
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Thanks for your responses, all of you. My responses to you...

Charley,

I was actually in the process of sealing the edge. What you say is correct, but we use industrial grade glue at 200C to glue tape on to the side of the board. It is a well proven process and provided it is done correctly does stand the test of time and protects the board.

Dan,

nice idea, but that costs money and you know what management do when that subject comes up.

Otis,

The panel standing on something wet was one of our thoughts, but we can find any candidates for that "something wet". There were about 5 panels out of 50 that were effected, and they were spread through the job. Panels next to the one in the photo had more normal swelling in the 0.2-0.3mm range so the trolley they were on appears unlikely to be an issue. I then wondered if they were all cut from the same sheet of whiteboard, which was already effected before hitting the CNC. I know they went straight from the CNC to the trolley - I watched them - so the damage would then have to have been before hitting the CNC. Possibly, but we never use the very edge of the sheet as it is nearly always damaged in some way from transport. So if the full sheet from which they were cut was effected by moisture, then it was likely that the effected edges would have been cut away just as part of the standard cutting procedure. Having said that, it is one of two theories that I favour. The other is a fault in the manufacture of the full sheet of whiteboard which made it more susceptible to humidity.

Darryl
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