UM2+ cannot print Marlin/Reprap (SOLVED)

[user978537432 1]

I need to print a temperature tower with an Ultimaker 2+ Ext, which is impossible with 'ultigcode'. In order to change the temperature multiple times at custom layers, marlin or reprap are required, both of which are being completely rejected by the printer. Sometimes (but not always) the hotend fails to heat up, usually the first layer starts a full extra layer above the (levelled) bed, and it always fails to extrude anything. None of these behaviours occur with ultigcode. Something is massively wrong with how the UM2+ is reading (or refusing to) anything other than ultigcode.

I have compiled the marlin/reprap files under several different versions of cura, dozens of different print profiles, attempted printing via usb and sd card, nothing at all works.

[Smithy 1,145]

It is or should be easy, just go to the printer setup in Cura, change gcode flavor to Marlin and that's it.

I use Marlin on my UM2+ and UM2Go without any problems. In fact ultigcode and marlin is nearly the same, the only difference is that with Marlin you can choose the material and temp in Cura.

[user978537432 1]

In the gcode generated by cura, both marlin and reprap extrude only a tiny fraction of filament for each move compared to ultigcode. The difference is not constant (and yes I use identical material settings for both marlin and ultigcode)

 

Below is a snippet of the ultigcode file which prints properly:

Quote

G1 F1200 X88.494 Y91.863 E0.05013
G1 X88.938 Y91.573 E0.10025
G1 X89.421 Y91.353 E0.1504
G1 X89.932 Y91.208 E0.2006
G1 X90.537 Y91.138 E0.25815
G1 X90.957 Y91.128 E0.29785

 

Below is a snippet of a marlin file with identical material settings, identical profile, identical model, identical printer.

Quote

G1 F1200 X88.494 Y91.863 E0.00786
G1 X88.938 Y91.573 E0.01571
G1 X89.421 Y91.353 E0.02358
G1 X89.932 Y91.208 E0.03144
G1 X90.537 Y91.138 E0.04047
G1 X90.957 Y91.128 E0.04669

 

This is only one of a list of problems that make marlin/reprap unusable on the UM2+. A single click on the "gcode flavour" dropdown in cura makes the entire file useless junk.

Edited September 22, 2020 by user978537432

[Smithy 1,145]

Strange, it works well for me and all others, so it would be interesting what's different to your setup.

 

I haven't changed anything except the gcode flavor dropdown. I printed long time with ultigcode, then changed the flavor to marlin, sliced the file and printed it with the same result. Now mainly via Octoprint, but it was the same with SD card.

 

A difference could be that I use the Tinkergnome FW on my UM2 printers, but don't know if this makes a difference.

[tinkergnome 927]

4 hours ago, user978537432 said:

In the gcode generated by cura, both marlin and reprap extrude only a tiny fraction of filament for each move compared to ultigcode.

 

UltiGCode uses volumetric values for the extruder, all extrusion amounts are specified in mm³ (cubic millimetres).

That's approx. a factor of 6,38 compared to the linear movement of 2.85mm filament.

The values in your example show exactly this factor - so that should be fine.

 

Just take sure that you don't set the extruder to volumetric mode (no M200 in the start script) and restart the printer between prints with different gcode flavors (just to be sure).

 

[ahoeben 1,981]

In addition to what @tinkergnome says, the UM2+ detects what gcode flavor the file is sliced and uses either volumetric extrusion amounts (in the case of UltiGcode) or lengths (in the case of Marlin or Reprap).

[user978537432 1]

So I just installed a brand new linux mint OS on a completely different laptop, installed a brand new instance of the latest cura and, again, using completely identical settings for all 3, compiled to ultigcode, marlin and marlin (volumetric). I made no tweaks whatsoever, this is cura's own Ultimaker 2+ Ext default settings out-of-the-box. I allowed each to print 1 layer of an overhang test.

The results are as follows:

 

Utligcode (correct outcome):

 

Marlin (severe underextrusion):

 

Marlin volumetric (severe overextrusion):

 

Note: marlin was printed FIRST, after a reset of the machine, so that appears to make no difference.

Edited September 24, 2020 by user978537432

[Smithy 1,145]

The problem with the under extrusion is in your start gcode (or the default one)

Filament is retracted too far away from the nozzle from your last print or after loading and the start code primes not enough. So the Print starts in fact without filament. You can modify your start gcode to prime more filament, then the print will be fine.

[Smithy 1,145]

These codes should work:

 

Start GCode

;### UM2Ext Start GCode ###
M42 S255		;turn led on
G21 		;metric values
G90 		;absolute positioning
M82 		;set extruder to absolute mode
M107 		;start with the fan off
G28 Z0 		;move Z to bottom endstops
G28 X0 Y0 		;move X/Y to endstops
G1 X10 Y10 F4000	;move X/Y to front of printer
G1 Z40.0 F9000 	;move platform up
G92 E0 		;zero the extruded length
G1 E20 F200 		;purge nozzle quickly
G1 E30 F100 		;purge nozzle slower
G1 E35 F30 		;purge nozzle slowly
G92 E0 		;zero the extruded length again
G1 F9000		;set speed
M117 Printing...


End GCode

;### UM2Ext End GCode ###
M104 S0 		;extruder heater off
M140 S0 		;heated bed heater off
G91 		;relative positioning
G1 E-1 F300 		;retract the filament a bit before lifting the nozzle to release some of the pressure
G1 Z+1 E-19 X-20 Y-20 F9000	;move Z up a bit and retract filament even more
G28 X0 Y0 		;move X/Y to endstops
G28 Z0		;move Z to bottom endstops
M84 		;steppers off
G90 		;absolute positioning
M107 		;turn fans off
M42 S0 		;turn led off

 

[user978537432 1]

22 hours ago, Smithy said:

The problem with the under extrusion is in your start gcode (or the default one)

Filament is retracted too far away from the nozzle from your last print or after loading and the start code primes not enough. So the Print starts in fact without filament. You can modify your start gcode to prime more filament, then the print will be fine.

Yes, that worked, thanks so much. I just doubled the default purge amount from 10mm to 20mm and added a retract to clip the prime blob and the first layer of Marlin now works great.

 

For any googlers out there, here's what I did (changes from default settings in bold, edit the textbox in machine settings labelled "start g-code") :

Quote

G21 ;metric values
G90 ;absolute positioning
M82 ;set extruder to absolute mode
M107 ;start with the fan off
G28 Z0 ;move Z to bottom endstops
G28 X0 Y0 ;move X/Y to endstops
G1 X15 Y0 F4000 ;move X/Y to front of printer
G1 Z15.0 F9000 ;move the platform to 15mm
G92 E0 ;zero the extruded length
G1 F200 E20 ;extrude 20 mm of feed stock
G92 E0 ;zero the extruded length again
G1 E-1 F500 ;retract to snip prime blob
G1 Y50 F9000 ;fast wipe away from prime blob
;Put printing message on LCD screen
M117 Printing...

 

I'm sure I can figure out some tweaks to get marlin volumetric working too.

[Smithy 1,145]

I am glad that it works and thanks for the feedback.