I have seen significant differences in calibrations when the bed is cold versus when the bed is hot.
Please either add heated bed and nozzle temperature controls to the calibration screen OR add a Heated Calibration that first takes the bed and nozzle set temperatures from the user and then starts calibration when those temperatures are reached. If you feel that you must, you can display a warning that this mode is only recommended for advanced users who will be responsible for their own safety while these temperatures can burn them if they come into contact with heated components.
Either way, I’d really like to not have to “start a print” and cancel it just to have the bed warmed up enough to do a good calibration. I have prints that will not stick no matter what I do when I print on a bed that was calibrated cold. The very same prints will stick every time when I calibrate with a heated bed.
About 15 seconds of this video at this point will show you how much a hot plate flexes as it goes through it’s normal heating cycles. Hot plates run on a duty cycle meaning that they reach their set temperature based on running for X seconds and off for Y seconds before repeating the cycles. As the hot plate cycles you can see the plate flex one way and then the other. The heated bed flexes a little bit when it heats up and I would like to calibrate it at the temperature of the print, but currently the controls do not make that easy without a work around. See this moment in the video for about 14 second: https://youtu.be/E2zS8MyvJxU?t=398 to see what I am talking about.
(Starting a print and cancelling it when it reaches the set temperature gets you “close enough” when calibrating even though the temperature is rapidly decreasing. Using OctoPi or the control software through a USB cable is another work around, but I really like just printing straight from the touch screen, so I would really like to see this be a touchscreen calibration feature.)