Setting correct parameters to print in Ultimaker 2+ with Bondtech DDG

Hi all,

I've got an Ultimarker 2+ with a Bondtech DDG feeder. It is working like a charm when I print using the SD card but that is boring. I've installed octoprint without problems and connected it to the UM2+. So far so good. The problem comes when I print.

What is the problem?

The Bondtech feeder requires a special firmware to print, which just modifies two parameters of the printer. From their manual ( :

" The following is changed when compared to the original:
E-step is now 311 and Loading speed is 50 mm/sec"

If those changes are not done, the feeder creates too much force on the filament, until it slides with a big worrying noise. I can see visually that the amount of plastic coming out the nozzle is too much.

What did you already try to solve it?

I've set up this initial gcode script:

M109 S210 M109 S210 ; Extruder temperature
M190 S60 ;Bed temperature
M92 E311 ; Set sep * may be wrong *
M203 X50.00 Y50.00 Z40.00 E45.00 ; My try with loading speed * may be wrong *
G28 ; home all axes
G1 X5 Y10 F3000 ; bring extruder to front
G92 E0 ; zero the extruded length
G1 Z10 ; lower
G1 E19 F200 ; purge nozzle quickly
G1 E26 F60 ; purge nozzle slowly
G92 E0 ; zero the extruded length again
G1 E-5.5 F400 ; retract
G1 X190 Z0 F9000 ; pull away filament
G1 X210 F9000 ; wipe
G1 Y20 F9000 ; wipe
G1 E0 ; feed filament back

This is latest octoprint, 2019-09-26-octopi-buster-lite-0.17.0.img and the ultimaker tuned with the custom firmware from bondtech.

I think I should be able to solve it with a proper gcode init script. Any help will be much appreciated.

You state that your setup requires specific firmware. Did you install that firmware? If so, there is nothing you have to do in your (start) gcode; the default start gcode should still work fine because the setting is adjusted in the firmware.

I did install that firmware... In fact it works perfectly when running the job from an SD card. What surprises me is that the same gcode file, launched from the Octopi produces that strange behaviour.

It is interesting to note that when launching jobs from SD card, the UM2 does a starting task (going to the front-left corner, pushing out some material) before the actual print. This is not in the gcode produced by cura.

My guess is that the UM2+ pushes some init parameters in that starting task that I emulate, somehow, with the init gcode script. But I am missing something, as the results are quite different.

You need to set the gcode flavor to Marlin (instead of Ultimaker 2) if you want to print with OctoPrint (or other methods that involve the USB port)

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That did the trick. It is working without noises now, with good results.

Thanks very much for your kind help!