How to use z_thermal_adjust to compensate hotend expansion?

General Discussion
1

Basic Information:

Printer Model: Voron 2.4
MCU / Printerboard: SpiderV2.3
Host / SBC: RPI4B
klippy.log
klippy (3).log (68.4 KB)

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Describe your issue:

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I found out that I need to adjust SET_GCODE_OFFSET Z_ADJUST=+0.075 every time I’m printing at 275°C instead of 215°C to get a perfect first layer.

I tried configuring temp_coeff to negative and hardcoding ref_temp to be 215, but I got stuck when it told me I could not use the same temperature sensor twice. I guess it’s designed to compensate for frame expansion, not hotend expansion. But still, I need a way to compensate my hotend expansion.

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Sorry, where is this gone?

grafik
grafik624×268 7.5 KB

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Added, didn’t think it was relevant, sorry for that

4

As far as I know, there is no built in possibility.

FWIW, you could probably write a macro that calculates the needed compensation and call it via PRINT_START or similar.

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Is it possible to duplicate one sensor to use as if there are two virtual sensors?

6

Not sure what you are trying to achieve.
You can get the extruder’s target temperature in a macro and from this target temperature calculate your needed offset. Then pass the offset to SET_GCODE_OFFSET

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It’s because I’m really not familiar with the coding language used for macros, and I want to see if it’s possible to work around the limitation of [z_thermal_adjust], which is that it can only be used with a brand new, unused sensor.