Blobs/Zits on Walls with Octoprint

[dfrez 21]

Hi All, I've got a UM2+ running TinkerFW 19.03 connected to Octoprint 1.5.3. It's loaded onto an older Raspberry Pi 2. I've been using it for awhile without any issues. But lately I've noticed that printing from Octoprint will cause blobs/zits to appear on outer walls. I've watched it happen, the printhead will pause momentarily, depositing a small amount of material. Same g-code printed from the SD does not cause this issue. Sliced with Cura 4.2. 

 

An initial search shows that this is due to a buffer issue, that Cura creates a lot of small move commands which basically overwhelms the Octoprint server feeding  the UM2+. 

 

It's not a power issue since I'm powering the RPi with an iPad charger (12W). 

 

Only thing I can think is that the RPi2 is too slow for newer versions of Octoprint? I had been using it for some time without any issues so it's odd that it recently started. 

Edited February 2, 2021 by dfrez

[dfrez 21]

Bump

[Cuq 198]

https://community.ultimaker.com/topic/34888-arc-welder-anti-stutter-plugin/   ?

[dfrez 21]

4 hours ago, Cuq said:

https://community.ultimaker.com/topic/34888-arc-welder-anti-stutter-plugin/   ?

When I saw that thread title before making this post, I (stupidly) assumed it was actually for an arc welder 🤦‍♂️... looking closer, I think this is solving my exact problem! 

 

The buffer underrun that is caused by too many g-code commands, do you think that would be mitigated by a newer Raspberry Pi? I figured my 2 is a bit long in the tooth anyway.

 

or is it more of a bottleneck caused by the USB protocol itself?  

Edited February 3, 2021 by dfrez

[Cuq 198]

I would say : a bottleneck caused by the USB protocol itself

[ahoeben 1,948]

You could also try lowering the tessellation of the model when exporting it from the modeller you use.

[dfrez 21]

Since I wanted to be able to access both of my UM2's through Octoprint, I ended up getting a Raspberry Pi 4 (didn't want to mess with trying to run two instances on the same Pi). I printed the same exact models that caused blobs on the RPi2 and they came out flawless with the RPi4. So FWIW, it does seem that part of the issue can be caused by an older Pi. No post processing with the Arc Welder plugin on either set. 

 

RPi2 on the left and RPi4 on the right.

Edited February 4, 2021 by dfrez