With a hell a lot of effort I bent bare heater plate to <0.05mm flatness. Really tough job without having some sort of press to apply a lot of force in controlled manner. Plate is very stiff, certainly not some soft aluminum alloy. Now when hot plate stays dead flat in X direction where it previously became concave and becomes slightly concave (~0.05mm) in Y direction where it previously was somewhat bulged.
Also with thermal camera I noticed that sides/corners are noticeable colder than center of the plate. Which of course contributes to warping. It’s not surprising all due to how copper traces are laid out without making center more sparse and edges more dense. It’s exactly opposite, same density everywhere and no traces on corners where screw holes are located. This is without plastic base, so maybe some thermal insulation it provides makes the difference smaller. Did not check temperature uniformity before taking it apart. Disregard temperature reading in red color since it’s measures black screw temperature while readings are corrected for lower emissivity of aluminum plate.
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