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Hi Walt,
One of the GCode start commands on the BIBO2 E1 right profile is causing a small problem. At times the filament will retract out of the nozzle at the start of a print.

I can recreate this by:

1. Using Octoprint and the LCD, Before print, extrude between 20 and 50 mm of filament (I do this to ensure there is no previously cooled brittle filament in the head).
2. Load up gcode and print.

It seems like the positing of E is not handled well or reset to 0 before a print, causing the filament to unload if it was loaded earlier for whatever reason.

Under some situations the Z-seam has blobs. need to determine if it is at the start or end and adjust the profile settings to correct the issue.

Note: this is a 32bit sensorless homing specific issue
Follows comments in #1 by @InitialJC

I am not exactly sure what is going on with this starting Gcode or why it needs to be as complicated as it is however I have gotten much better results by priming the extruder with the following Gcode.

The current release GCode seems to crash my extruder to the left hand side without properly identifying the home/ origin point. The below Gcode will set appropriate absolute position for every print.

G21 ;metric values
G90 ;absolute positioning
M107 ;start with the fan off
G28 X0 Y0 ;move X/Y to min endstops
G28 Z0 ;move Z to min endstops
G1 Z2.0 F400 ;move the platform down 15mm
T0
G92 E0 ; reset extruder
M117 Purge Extruder 1
G1 X-50.0 Y-92.3 Z0.0 F2400.0
G1 X50.0 Y-92.3 Z0.0 F1000.0 E10 ; draw 1st line
G1 X50.0 Y-92 Z0.0 F3000.0 ; move to side a little
G1 X-50.0 Y-92 Z0.0 F1000.0 E20 ; draw 2nd line
G1 E19.5 F3000 ; retract filament 0.5mm
G92 E0
M117 BIBO Printing...

Response in #1

The start gcode is mostly adopted from the BIBO provided Cura start gcode and was originally modified that way based on issues reported in the Facebook BIBO group. One of the big issues with the code you listed above is the lack of temperature preheating of the nozzles and bed which caused failures to print for some people.

There are some things that can be done to simplify the start gcode, but that's probably something to put in a different issue for consideration as there are a lot of things to consider such as how it's implemented for dual extrusion, E1 only, E2 only, Ditto printing printers, etc.

As for your specific left-hand crash issue ... I have noticed that when I'm consecutively printing if I don't move the print head slightly away from the homing switches, before printing occasionally the printer will start off-center. It doesn't have to be much just enough to keep the switches from being clicked before starting. the off-centered start seems to happen occasionally with cura as well.

This Issue is most for discussing direction to consider simplifications of the start gcode and potentially address the issue with the extruder head occasionally crashing.

Note: this is a 32bit sensorless homing specific issue