Hi all, i'm attempting to convert a 3d printer into a bioprinter. It's an ender 3 pro.

Since the extruder motor is being used to drive a syringe pump, i'm needing to bypass some things like extruder temp as well as printing cold.

I've disconnected the extrusion thermistor and am attempting to set the temp of the nozzle to zero using T0 in the cura printer profile. Unfortunately, the LCD display is showing the extruder reading the temp as -14.

I then tried to tell cura to print at -14 but it comes up as -13 on the attempted temp. When i try -15, it won't let me hit the Print option. I'm using TH3D firmware for the ender 3 4.2.2 board.

Here is the gCode i'm using

M302 ; Enable cold-extrusion

G92 X73.5 Y70.5 Z0.00 E0.00 ; Tell the printer that the nozzle is homed and at a height of zero in Z to enable printing to begin at the manually-selected point. The X and Y values used correspond to one half the length of the X and Y build dimensions of the printer platform; the values used here are for a PrintrBot Simple Metal.

T0 ; Set the nozzle temperature to zero.

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Any ideas?