Squawking extruder problem... seems to be software.

[sixdeuces]

So in the last two weeks I've been having an issue with my extruder. During a print, about every 30 seconds or so I get a an awful "squawk" from the motor. It seemed the motor was stalling. Previous to this I'd been producing great prints with no problems for months, so the machine itself is fairly proven and solid.

I thought the issue was mechanical, and that it was having trouble during retractions. I'd get a big blob of extruded filament after the sound. I figured the filament wasn't being retracted properly, and that when pushing forward again after the retract it was sending out all the filament it thought it had retracted. I blew the whole extruder apart, really looked everything over and got it all back together, certain that it was 100%. I also did a de-clog on the nozzle, in case that was the issue. The problem persisted, even with very conservative retract settings.

So, I ran another print, and watched it carefully. It really looks like retracts are actually working fine, and that the real issue is that at random times the extruder seems to try and jump forward about 5mm or so at very high speed with no retract. It's simply moving along at the normal fill rate, then suddenly trying to extrude way faster than it's able for short bursts.

I figure this must be an issue with a software setting, but for the life of me don't know what it could be. I don't know what to look for in the gcode, or I'd try and track it down that way.

Suggestions?

[RomeFallsAgain]

It might be software.

But have you ever lubricated the moving parts? If I don't lubricate the rails on mine about every 20 hours of printing it starts to shudder and can make blobs.

Friction.

[sixdeuces]

The machine is a Kossel Mini delta. The linear rails are lubed. The extruder is a direct-drive bowden. I also occasionally use some light oil on the filament to keep the bowden tube nice and free. Everything seems OK. It's definitley the extruder motor making the noise.

[sixdeuces]

Progress update:

Through trial and error, I have narrowed it down to the "wipe nozzle" feature under the Retraction dialog. As soon as I enable it, the problem starts. Currently it's set to 1.5mm. I'll play with the settings and see if that matters.

[martinkopplow]

Why would you want to wipe the nozzle on a single extruder kossel during a print at all?

There is a setting for the max extrusion speed, you may want to set it to a speed your extruder is actually capable of extruding at, so no matter what length of filament feed you get at wipe nozzle, it will not overload your extruder drive.

[MikeO]

It's apparently a software bug in S3D 3.0.2 (better minds than mine found it). If you search the forums you'll find some posts about it.

I had the same thing hit me two days ago, but I could see the extrude/retract gear running on my TAZ5 printer, and could see it sometimes was doing really fast, very big retractions, apparently randomly.

To save you some time, if you go to the G-Code tab and enable "Relative Extrusion Distances" the problem goes away (if your firmware supports that). I did that change yesterday, and it absolutely fixed the problem.

[edit] And for the problem to happen you have to have Wipe enabled AND have "Perform Retraction During Wipe Movement" enabled on the Advanced tab.