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Heatbed thermal expansion??  

New Member
Heatbed thermal expansion??

Lately I'm printing a lot with ABS and ASA that needs bed temps over 100C. My prints are fine without problems BUT one thing is really strange both my printers MK2S and MK3S are calibrated using PLA on 60C bead temp for perfect first layer. But when i switch to ABS or ASA I have to manualy change Live Z from -0.660 to -0.600 on MK2S and for MK3S from -0.930 to -0.850. 

I know about PINDA temperature drift in MK2S so no questions, ( but you know that you can actually move hot end before print high above heatbed to avoid this right ?)

BUT MK3S has built in temperature sensor to avoid this problem and it still needs to be corected, so I thought that maybe it is thermal expansion of heatbed and steel sheet with PEI that is causing this, what you think?

Is there any way in MK3S software to set this change in height on Z axis for hight temps to avoid doing this by hand?

Posted : 13/05/2021 8:47 am
Illustrious Member
RE: Heatbed thermal expansion??

The Mk3S PINDA is horribly temperature sensitive and the internal thermistor is virtually useless as used by the firmware. Even running the cal also has known issues.

Many of us use a gcode script to normalize the temperature before we run bed level.

; cool down PINDA
M106 S255 ; turn on fan
M104 S0 ; turn off nozzle heat
M140 S0 ; turn off bed heat
M860 S35 ; wait until PINDA is less than 35C
M106 S0 ; turn off fan

; preheat nozzle to a low temp, get plastic mushy before driving into the bed with G28
M140 S[first_layer_bed_temperature] ; set bed temp
M109 R175 ; wait for extruder temp
M190 R[first_layer_bed_temperature] ; set & wait for bed temp
G28 W ; home all without mesh bed level

; soak PINDA then level
G0 X50 Y50 Z1 F3000; this is a good PINDA heating position
M860 S37.5 ; wait until PINDA is >= 35C in winter, 37.5C spring/fall, 40C summer
G80 N7 R5; mesh bed leveling


This post was modified 1 year ago by --
Posted : 13/05/2021 9:01 am