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Start Gcode M92 command & retraction issue

extrusion gcode

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Firstly in case anyone can spot a conflict, here's my startup gcode in Cura 4.0 using BL Touch:

G21 ; (metric values)
G90 ; (absolute positioning)
M82 ; (set extruder to absolute mode)
M203 E80 ; (set extruder max to 80)
G28 ; (home all axis)
G29 ; (Auto Level)
G92 E0 ; (reset extruder)
G1 Z1.0 F3000 ; (move z up little to prevent scratching of surface)
G1 X0.1 Y20 Z0.2 F5000.0 ; (move to start-line position)
G1 X0.1 Y200.0 Z0.2 F1500.0 E15 ; (draw 1st line)
G1 X0.4 Y200.0 Z0.2 F5000.0 ; (move to side a little)
G1 X0.4 Y20 Z0.2 F1500.0 E30 ; (draw 2nd line)
; G1 E27 F1000 ; (retract filament 1mm)
G92 E0 ; (reset extruder)
G1 Z1.0 F3000 ; (move z up little to prevent scratching of surface) M117 Printing...
M92 E87.92

My main issue is the M92 command, after measuring I was over extruding 7mm so change the gcode and it did improve my print, my next issue was stringing so onto my retraction settings, I used:
reducing it to 20mm high for a faster print.

The main body came out pretty good but produced lumps at the edge of the posts where it started retracting (no strings as such).
I started with extrusion settings:
6mm at 60mm/s same results.

Changed to 6mm at 25mms which I spotted on a Makers Muse video, this made zero difference, the towers were identical.

Trying to see what was going on I pushed the envelope and changed my M92 command to 85 - guess what, identical results, then tried 90 and the same results - I am baffled.

Any tips appreciated, feel free to make me suck eggs as I feel like I've done something silly!

Basic Stringing Test
by Loohney


M92 E87.92 vs M92 85 vs M92 90
could lead to the same results regarding stringing, the only difference could be in the resulting diameter of the towers, and/or you can notice some gap, or not, between the outer and the inner layers.