First extrusion after changing e-steps is a mistery

[AndiJ 0]

Hello community,

 

a while back I calibrated my extruder because I had slight underextrusion. I used pronterface to extrude the filament and directly inserted the new steps via the command bar using M92 Exx.xx. I then extruded again to get the most accurate steps. But the printer would then retract the filament and would also retract a lot more than I wanted to (extrude). It was like it had multiplied the amount by 10, when I wanted to extrude 100mm he retracted what felt like 1000mm. When it finished I could then extrude normally it was always just the first extrude.

I inserted the new steps into my gcode back then and I fixed the underextrusion, he extruded fine. So recently I changed my start gcode and it includes a line in which he should extrude 5mm at the beginning to compensate the molten filament but it retracts like crazy and then keeps going normal without filament in the hotend. I am not sure why it didnt do it with the old start gcode I had, maybe I had a mistake in the code. Did this occur to anyone else yet? It really is a mistery to me at the moment.

 

Start g-code:

G21 ;metric values

G90 ;absolute positioning

M82 ;set extruder to absolute mode

M140 S{material_bed_temperature} ;set bed temperature

M104 S{material_print_temperature} ;set extruder temperature

M190 S{material_bed_temperature} ;wait for bed temperature

M92 E115.00 ;Esteps

M107 ;start with the fan off

G1 Z10 F8000 ;avoid collision

G28 X0 Y0 ;Home Axis X Y

G28 Z0 ; Home Axis Z

G1 Z15 E5 F8000 ;move 15 mm up while extruding 5mm (this is where it retracts)

G92 E0 ;reset extruder

 

thanks in advance

Andy

[gr5 2,229]

When you first start a print the extruder could be at any position.  So you need to do a G92 E0 after the M92 but before you first move the extruder.  Not only could the extruder be in a random position but also I think it stores the position internally in *steps*.  So anytime you change steps/mm you need to do a M92.

 

In addition consider doing a M500 which will store the M92 steps/mm value permanently.  Then you can get rid of that M92 command from your gcode start script.

 

More details here on gcodes: http://reprap.org/wiki/G-code#G92:_Set_Position