The Woodshop Shed

Panel warpage

Furnished content.
(from WoodNet.net)


Working on the set of kitchen cabinets.
Two sections they went with 1/4 sawn WO.
On the Island, they went with walnut.

I shop cut the veneer, sanded them to a hair more than 1/16"
I used Unibond 800 glue.
I used 7 ply 1/4" plywood as the core and of course veneered both sides.
I book matched the veneer.

The oak door panels came out great, nice and flat. With it being 1/4 sawn, that did not surprise me.
The walnut panels with highly figured front face veneer and just normal veneer on the back came out of the vacuum press looking good.
It did not take long before the walnut panels started to bow and warp.
In both the width and height the panels cup towards the figured face.

One set of panels approximately 17" wide cup enough that if you put a straight edge from side to side, there would be almost a 1/2" gap in the middle.
I tried to put a panel on a jig that bent the panel the opposite of the bow. Left the panel in there for 2 1/2 days.
When I removed it, it was flat for about 4 hours!

Some door panels are 18" wide and 28" high. They need to be flat!

First of all, I can not understand why this happened. Any speculation?
All I can come up with is I should have made the veneer maybe closer to 1/32" instead of the 1/16".
Should I have used MDF instead of plywood?

Second, any good ideas that would flatten the panels permanently?

Any information or help will be greatly appreciated!

Toney

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