Shift in print (Y direction)

[sshwarts]

I've been seeing all of a sudden a shift in Y direction. The attached shows how this rectangular piece has decided to be a stair step. This shift happened in this case at about layer 27-28. The Gcode preview fine. When this happened before I tried resetting the Y belt and tightening the pulley on the shaft which afterwards I did get a good print but now its back again.

Strange thing with this one is that once it shifts, the shifted layers are all good. The only thing I've done fairly recently was to upgrade the firmware to Marline firmware that cmenard forked (for Viki support). I might add that I'm printing with Octopi. Is it possible this is a communications issue? If GCodes get missed can the rest of the layers be shifted?

I know other have reported a shift in X which was put down to the extruder motor turning, but I've not seen anyone else with a Y shift. Any ideas?

Scott

[jimc]

In the past i have had shifts in x and y. They are few and far between. Assuming the set screw is thight on your motor shafts then be sure you dont have warping in your model where the hot end can get caught on the corner or something and knock it out a few steps. Also check over the stepper harness. Wiggle connections and wire while the bed is moving to see if it jumps. If so try and track down the location of the loose connection or bad wire.

[sshwarts]

In follow up to my post, I did a number of things such as reflash firmware so can't definitely point to a cause, however I re-ran the same gcode file with repetier directly connected instead of octoprint on pi and it printed fine. We'll see if this remains the case.

[jimc]

You will find this to be a common issue will all 3d printer makes and models. Sometimes a cause can be found and sometimes its just one if those odd flukes that occurs once in a while where you just never find anything wrong. Just a slight glitch on occasion.

[markb]

I use Octopi also I had this happen like twice but I recent had it happen on a 13 hour print at the end if it.
Then the very next print it happened again about 1 hour in. I immediately printed the exact same files but using the built in SD card. No issues at all.
The first print I was streaming more video than I usually do.
I was printing directly from the Pi SD card. I have printed those same parts many times using Octopi before I never had a issue.
I never had back to back issues before.

[jdacal]

If its happening on every print I can try running it on mine. I have Octopi, Vicki, and S3D.

[markb]

Thanks but I had printed it many times before without an issue with Octopi. I printed it another 10 times with the SD card no issues at all. I really wonder if it had to do with video streaming.

[jdacal]

I had been getting terrible streaming, or CPU performance on the first Raspberry I received, not sure which it was. Then it started to intermittently re-boot. Returned it and ordered the B+ and streaming is incredible. The uploads are happening about 8 times faster than they were before. Not sure if the better wi-fi performance is due to the different wi-fi adapter that came with the new one, but the web interface and uploads are impressive compared to the original one I received. Difference between night and day type of thing if you know what I mean.

[chuskamp]

Has anyone root caused this issue. I am having the same thing particularly in the Y axis. I have checked for loose connections and tightened fasteners. It happens randomly in taller, long build time builds (16.5 hours and it happened 4 times in the last 1.5 inches of a 3.0 inch build.) Frustrating. Any thoughts are appreciated. X/Y Axis Movement Speed is 18000.0 mm/min for those concerned about steppers skipping counts.

Also the measured offset is consistent with offsets at 1.53mm/0.060".

Thanks in advance,
Chris

[jimc]

Run the print again but turn down your movement speed. I know thats default but it really doesnt need to be that high. Mine is 9000. Also turn your accelleration down from the stock 3000 to maybe 1200. Youll get cleaner prints this way too. Of course check all your usual things like belt tension and ight set screws on the pullleys. You should be able to get the belts fairly tight but too tight can cause skips as well. Too loose and you can jump teeth.