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Potato Chip in MDF7/29
Anyone have any experience with eliminating or reducing this by machining the glaze off the backside prior to milling?
We ran some very large panels with deep profiles using 1 1/8" MDF and they turned out great other than the fact that they potato chipped in both directions. The panel cupped in the 49" dimension AND in the 97". The profile milled down in some places to 1/2" to 7/16" of material remaining. The panels are still super rugged and not fragile at all but the corners would try to pull off the table my as much as 3/4" if we didnt fixture them down.
We had a feeling going in that hogging this much material off one face material movement would be inevitable even in MDF. This makes installation (on a flat wall) a bit of a chore.
I have had similar experiences with MDF.To dramatically reduce the distortion I glued subsequent panels from several thinner sheets and vacuum bagged them together.Not all jobs will justify the extra work though.
Never tried it but I've heard that cutting a diamond shape pattern on the back first will take the tension out. I think it was James McGrew who suggested that.
I do not have direct experience with this, but I do agree that machining a relief pattern in the back should help substantially with this.
It's the same thing done to hardwood flooring, you can see the relief dados cut on the back of each piece to eliminate cupping.
I don't think you need to flycut the underside to remove the wax coating. In fact, that might not work since there's still a pure flat surface on the back. I think the relief cuts/dados are what you will need.
Have you tried Plum Creek MDF we use it and it is a lot more stable