Many people find it useful to add insulation between the Y carriage platform and the heat bed. This allows the bed to heat up a little faster and retain heat better. It also reduces the thermal gradient in the wooden bed and reduces the warping. Without the insulation, the bed starts to warp as the top surface heats up, tightening the wheels on the extrusions. Then, as the heat soaks through the bed, it relaxes, loosening the fit of the wheels against the extrusions. With insulation, the heat flow rate is lower, and the gradient (hence the warping) is reduced.

I looked around for thin ceramic wool fabric, but ended up just cutting a piece of corrugated cardboard, and it's been working fine. The sheet has small holes in it to clear the various screw heads.

You may wish to keep an eye on it or use a more heat-resistant material, depending on how hot you run your bed.

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