The flat earthers of the 3D printing hobby tell us that heated beds don't expand in the heat. They measure the bed hot and cold at the mounting screws and see no change in the measurement. "SEE!" They say. "Its the same. BED EXPANSION IS A MYTH!" Well, they are wrong. So, let's make an effort to actually understand the complicated behavior of expanding 3D printer beds.
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https://www.youtube.com/watch?v=DsaSvoFqvxA