Troubleshooting Warping and Delaminating

Using a heat tunnel during fabrication of laminate tops can cause the top to warp because of temperature-related expansion and contraction of the laminate. March 13, 2009

I am getting a fair amount of warping and cupping on my tops. I am roll coating with a PVA. My tops are flat coming off the line but warp and cup overnight. The tops are warping up on the edges, resulting in a concave top which I believe is called negative warping. When doing a peel test, I have a fair amount of fiber pull but if the top is left to sit for over a week (single roll bars) the laminate will pop loose. Can anyone give me any feedback?

Forum Responses
(Laminate and Solid Surfacing Forum)
From contributor D:
What is your process - heat tunnel, hot press, cold press, pinch rollers? What brand of adhesive are you using?

From contributor B:
You didn't mention backer - they will warp for sure without backer, itís the same thickness as the laminate.

From the original questioner:
I am roll coating both the laminate and board separately with Forbo PA318 PVA, running them through a heat tunnel at low temps to partially flash some of the moisture out of the glue, laying the laminate then running through a pinch roller. This process is creating a very strong bond which I verify on a regular basis with peel tests and plug tests.

From contributor D:
Try laminating without the heat tunnel; the heat causes the laminate to expand. As the top cools, the laminate contracts, pulls the board, and causes the board to curl or "warp". The cupping causes a lot of stress on the bond and that's why they peel after a week. You can use heat only if the panel is balanced, as Ben stated. Thicker board (3cm) works quite well with Gatorply and similar balance sheet materials.