Cura 2.7 - Filament Grinding / Uneven Extrusion on Prusa i3 MK2S

[Vespyr 0]

I'm new to Cura and am having trouble getting prints sliced on the software to work on my Prusa i3 MK2S. The files slice fine in Cura without any problems, but as soon as I send them over to the printer, the extruder goes haywire and, for lack of a better term, spurts out flattened blobs of filament while making clicking/grinding noises that sound alarming enough that I immediately stop the print for fear of causing any damage to either the nozzle, bed, or extruder gear. The 3D model that I'm trying to print requires supports and I was able to slice the same file and print it successfully without any of the aforementioned issues using Slic3r PE. I want to give Cura a try as I've heard it does a better job at generating supports than Slic3r does, but I can't get far enough to actually print anything I've sliced because of this issue.

In the interest of full disclosure, I have modified my start gcode in Cura to include my calibrated Estep value and an anti-ooze preheating/nozzle priming routine, as I also did in Slic3r PE. I copy/pasted some of the gcode that I had set in Slic3r to Cura and the initial preheating and nozzle priming phase works without a hitch, but once the print gets started, the extruder goes all out of whack on the skirt and first layer. Does this have something to do with my Estep setting? I also lowered the flow setting in Cura to 90% to match my setting in Slic3r of 0.9 extrusion multiplier (unless I misunderstood how Flow works and shouldn't have done this at all...?). All the other settings were only adjusted slightly to my preference (0.2 layer height, printing temps slightly lower at 205°C/55°C, 10% infill, 3 top/bottom layers, supports enabled, speed at default) and I don't think should have contributed to this issue.

 

M115 U3.0.12 ; tell printer latest fw versionM83 ; relative modeM92 E187.60 ; set extruder steps to calibrated value [user added]M500 ; save new E-steps until restartG28 W ; home all without mesh bed levelG0 Z60 ; get head above bed to keep it coolM140 S{material_bed_temperature} ; set bed tempM104 S170 ; preheat extruder to 170°CM190 S{material_bed_temperature} ; wait for bed tempG28 W ; home all without mesh bed levelG80 ; mesh bed levelingM104 S{material_print_temperature} ; set extruder tempM109 S{material_print_temperature} ; wait for extruder tempG1 Y-3.0 F1000.0 ; go outside print areaG1 X60.0 E9.0 F1000.0 ; intro lineG1 X100.0 E12.5 F1000.0 ; intro line

 

I'm relatively new to 3D printing and am still learning the ropes, so I wouldn't be surprised if this problem is simply due to user error, but any help/advice would be appreciated. I'd really like to give Cura a fair chance and see what it's capable of. Thanks!

[tinkergnome 927]

Welcome @Vespyr!

Cura always uses absolute coordinates for the extruder axis (at least i see no option to change this). I assume, an M82 at the end of your start script would be a good idea...

[burtoogle 513]

Hi, the next release of Cura adds a setting to choose either relative or absolute extrusion mode. By default, it will stay as absolute for all gcode flavours except RepRap which will be relative mode by default. Be aware that not all printer firmwares can cope with relative extrusion (the Ultimaker machines being an example!)

[Vespyr 0]

Thank you both for the help! I changed the extrusion mode from relative back to absolute and that solved the problem. I'm now able to print normally, but I notice the nozzle seems to be clogging much more frequently than before I used Cura. I slowed down print speeds to around 40mm/s (which was Slic3r's default setting) but it hasn't made much of a difference in preventing clogs. Do I have to adjust my retraction settings as well?

In any case, I'll look forward to the next version that will allow me to use relative mode as I think that may work better for the MK2S. Thanks again for the help!