Odd printer stalls

I'm suddenly seeing some unusual behavior on the Anycubic linear delta which I'm using to fabricate components for a larger delta currently under construction. The print will stall at certain points, usually for only a few seconds at a time but sometimes for more than 10 seconds (leaving a bad melt crater in the part). So far it's happening only on the particular file which I'm trying to print right now, though this did also occur on a print which I was running several months ago -- I recall only that I eventually managed to generate a G-code file which ran smoothly though I don't recall what was done in order to do so. I've tried generating new G-code a few times, changing some parameters slightly here and there each time, but no improvement yet.

Some things which I've noticed ...
It occurs, as far as I can see, only during infills (which is currently at 100%, I'm experimenting with printing some lithophanes as holiday gifts).
From layer to layer it tends to happen at the same XY coordinates, though those coordinates will drift around the print over longer periods of time.
When I checked the extruder gear during half a dozen stalls I found that it was retracting, not at anything like the normal retraction rate but at something like 5 times the normal forward extrusion rate.

I see no indication of the problem when I preview the file in S3D, nor have I been able to uncover anything by browsing the G-code file near the coordinates where the stalls have occurred. Here's a download link to the G-code and S3D Factory Files in case anybody wants to play detective ...
[www.dropbox.com]

Thanks for the help!


- Michael

Sounds like driver overheating... They pause for a while to cool down, then move on. Better cooling and less stepper current might help.

Thank you for your reply o_lampe, I appreciate it!

Would it not be unusual for all three drivers to repeatedly hit their overheating protection cutoff points simultaneously in this way? Perhaps it can happen, I wouldn't know -- I have come to realize that some pretty odd things can happen in the land of 3DP!

Based on my experience with this machine however, I'm inclined to believe that the problem lies elsewhere. Other very similar files print without issue, this being the reason for my suspecting something in the gcode or possibly in the stl file used (though after noticing the problem I did check it with Netfabb).

I have installed some fairly aggressive active cooling of the TMC2100 drivers, and once having at last managed to dial these in successfully I've not encountered a missed step or layer shift in many months, even on 20-30 hr prints. One caveat to having the TCM2100 drivers run reliably seems to be limiting speeds to 30 or 40mm/s (at least on longer prints), but I'm fine with that.


- Michael

I have managed to get the print to complete since having made that initial post, going back and regenerating a fresh stl and re-slicing.

So at this point it's just an academic matter but I'd still really like to know what happened. I'm especially most curious about those mysterious low-speed extruder retracts during the stalls! Surely there would be something in the gcode accounting for these, but it's likely that I'd fail to recognize anything even if I spotted it.


- Michael

Edited 1 time(s). Last edit at 12/19/2017 03:10PM by papilio.

Were you printing from an SD card on the printer, or from an attached PC over USB?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I'm printing from the SD card.

Edited 2 time(s). Last edit at 01/01/2018 03:41AM by papilio.

The slow retractions suggest to me either faulty GCode or a firmware bug.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thank you David!


- Michael