Cura 4.8 Why unload all the filament after initial positioning

[Doxena 0]

I have a problem when i try to send a print via USB. For some reason every time after the initial positioning the printer unload all the filament and start to print (while it try to load the filament since it's now empty).

It only happen when i use the print via usb option but if i create the .gcode it works perfectly. It happen also to anyone else ?

Printer : Longer lk4pro
Cura : 4.8.0

AU30_earbudholder_left_shell_repaired.gcode

[GregValiant 1,251]

Did you install the printer in Cura as a "custom" printer or did you use a definition and alter it?  I think the problem you are experiencing is more related to "when did I turn on the machine and what did I do" than to USB/SD card.

 

This is from the startup Gcode in that file:

 

G28 X0 Y0  ;move X/Y to min endstops
G28 Z0     ;move Z to min endstops
G1 Z1 F1000             ;move up slightly
G1 Y60.0 Z0 E9.0 F1000.0;intro line
G1 Y100.0 E21.5 F1000.0 ;continue line
G92 E0                  ;zero the extruded length again

 

There is no G92 E0 before the first line of extrusion.  If the extruder has a previous location, it is moving to E9 before it does anything else.  If it is starting out for example at E456 then yes, it is going to do a very long retraction before starting to print.  If you turn on the printer and it's fresh the E is at 0 so the Gcode works as expected whether it's via USB or from the SD card.

In regards to that first extrusion line - it starts at X0 Y0 Z1.0 and extrudes 9mm of plastic to X0 Y60.0 Z0.  Then the second part of the extrusion in the next line is 40mm long but also at a Z of 0.  The printer is being asked to squeeze 12.5mm of filament into a space of zero volume.  Not good.

I suggest that you go into "Machine Settings / Start-Up Gcode" and make the following changes:

 

G28 X0 Y0  ;move X/Y to min endstops
G28 Z0     ;move Z to min endstops

G92 E-5            ; Add this line to set E location to a slight retraction
G1 Z0.2 F1000             ;move up slightly  ;Change this line

G1 F3000 E0                ;Add this line to prime the nozzle - it may leave a little puddle.

G1 Y60.0 Z0.2 E3.0 F1500.0;intro line ;Change this line.  The 3.0 is for a .4 nozzle at 150% flow.

G1 Y100.0 E5.0 F1500.0 ;continue line ;Change this line to continue at a decent flow.

Edited November 16, 2020 by GregValiant