It appears that the x or y, or maybe both x and y steppers missed some steps.
Any recent changes to your max speeds or accelerations?
No. I have been running with these settings for days with no issue.
My first guess would be that your speeds were changed to a value in excess of what the motors are capable of doing, so when it tries to do a rapid travel move, it misses steps. After which, it no longer knows where the toolhead is, hence the drastic offset after the missed steps.
My second guess would be that there is something amiss, perhaps on your linear bearings that cause some binding, again resulting in some missed steps. Or, maybe a combination of speeds/accel too high and linear bearings not lubed, binding, dirty, etc.
Definitely looks like missed steps on a motor though. I had the same thing happen when I first built my Voron, because I inadvertently assembled a linear bearing shuttle incorrectly. It still moved freely, but had more drag than it should. It worked fine at low speeds, but whenever it tried to do a 300mm/s rapid move, the motor couldn't handle it and missed steps.
Edit to add:
I thought I had posted about the missing steps issue in the Voron thread. Here was the post
That was several days of frustration that I thought I had cured several times, and just kept coming back.
The Prusa is not enclosed, to get good quality ABS/ASA the recommendations are for 50C in the print volume. So it would have to be enclosed to get quality ABS prints (at least for parts of any size), so I've read and heard from many sources. The Prusa has many PETG parts which can barely handle...
www.hobby-machinist.com
Note that the video is real time, I did not speed it up or slow it down at any point. It shouldn't have been going any faster than 18mm/s. I am using a 0.8mm nozzle, with 0.64mm layer height and the maximum 375% height:width ratio (2.4mm width), which works out to 28mm³/s volumetric at 18mm/s. My extruder is running near its limit at this linear snail's pace. My travel is set to 250mm/s I believe, with conservative acceleration.
I have been studying my sliced file, the video, and the two parts which failed at the same layer, and either drawing more informed conclusions or talking myself into more elaborate conspiracy theories; not sure which yet.
I don't have an abundance of experience in 3D printing but I have been working with steppers for unrelated projects for a while and I agree that there was the sound of missing steps in there, but it seems to me like what happens when you apply a modest speed pulse train directly, with no acceleration. Like if you plug in a step/dir signal cable while the controller is already sending pulses. I think X and Y were hit with an instantaneous blast of pulses and that trip out into left field actually happened on the decel ramp, when the motors finally caught up to the pulse train.
In re-watching the video I notice that as soon as it got back around to the seam and finished that outer perimeter, instead of proceeding to start the next layer it went to warp speed directly away from where it should have gone. The other one that failed on this layer, seems to have done the same thing. That last layer is complete, includes the final outer perimeter. I think they both did exactly the same thing at exactly the same spot in the g-code. My layers are so tall and extrusions so thick that I can actually count the layers and rings and be reasonably confident about this.
But I have two other failure specimens that didn't fail at that spot; one that failed prior to it, and one that made it past that point and failed at about 95% completion. So what gives? I am not 100% sure that all 4 failures were from the exact same gcode file. I
think I ran the same file 4 times but I have been working on printing this part for a couple of days now, among other parts and another printer, and I have 2 versions of the file. Since I can't say beyond a reasonable doubt, I am striking those two prior failures from the record and focusing on the two I know for fact were the same file and which failed at the same layer.
Going back to slicer, there is something special about that area. I added a layer height modifier near there because I wanted the bottom layers to have more resolution because there is a bearing race at the bottom.
This failure happened not
on layer which transitions from high resolution to low resolution, but just after it; I think it failed on the very next layer, hard to tell. But I think the layer height modifier is the culprit. I suspect (conjecture warning) that the slicer told the printer to do something that it misinterpreted as "teleport to Taco Bell and finish printing this in the parking lot" and it did its best to comply.
I would expect things like this to happen if I was using a crowdsourced slicer with a DIY printer but I am using the slicer that was supplied with the printer. But technically this is still a (re-branded) crowdsourced slicer and the difference between DIY and commercial is often just aesthetic. Maybe I am being too accusatory, too early. I will try tomorrow to print the whole thing with consistent layer height and new firmware, see where that gets me. I would like to test those two things separately but I have already lost 2 days on this one part.
EDIT: oh yeah, and the linear guides have been oiled twice since I got it just over a week ago. No crunchy grindy noises.
