Zits/Bumps print surface issues - need help troubleshooting
 
Notifications
Clear all

[Solved] Zits/Bumps print surface issues - need help troubleshooting  

  RSS
Yair Maimon
(@yair-maimon)
Member
Zits/Bumps print surface issues - need help troubleshooting

Hey, I've had my Prusa Mini for almost a year but as this is very much a side hobby for me, I haven't had a ton of hands on troubleshooting experience with it yet.Lately I've been printing a lot more and noticed I have a ton of surface artifacts that looks like bumps (or "zits") on large parts of the print surfaces.I'm printing via Octoprint (running on RPi 3) on FW 5.1.2 and using Input Shaper. I'm using Prusament PLA, fresh out of the box.

I've also attached a view of the sliced gcode with tool speed displayed. You can see that in parts with bumps, the tool speed is lower, and in smoother parts, the speed is higher (though not always the case, like the neck area is graphed as high speed but still has some bumps).

At first I thought it was a seam/retraction issue, but if you look at the pic above I don't have any seams or retractions at those points. besides you can see my very existent seam problem here (I'll hopefully get to that too sometime) and it doesn't seem to correlate to the bumps in any way.

It feels a bit like an extrusion issue, but I'm still somewhat of a novice so not really sure how to troubleshoot this myself, so I would really appreciate any help finding the root-cause of this issue.

Here are the topics I came up with as possibly having something to do with these blobs, after browsing the internet for similar cases and my thoughts on how to proceed\the probability they are relevant in this case:

  • The printer has been sitting unused for a while, so I might need to clean the nozzle or the hotend PTFE tube - Maybe do a cold pull? (would be my first, so I'm kind of hesitant and nervous)
  • Extrusion multiplier issue - maybe, but I'm not convinced since it's only in certain areas, and not others.
  • Adjusting the resolution - I'm referring to this video by CNC Kitchen which is talking exactly about these artifacts I am observing. basically caused by too many tiny move commands making the tool spend an extra fraction of a second at points between those points, causing extra extruding there.
    • I think this might be a good candidate but I'm unsure how to adjust these setting properly in PrusaSlicer without messing up my model. and besides, for a round model like this - shouldn't 2.7's arc welder feature convert most of these to G2/G3 and fix most of these issues?
  • Tool hangups due to bandwidth - I saw some places talking about how the serial interface of Octoprint sometimes isn't fast enough to deal with fast printers. could it be that the new input shaper profile is too fast for octoprint and these are just signs of the tool waiting for a milisec for the next command to come along from the serial bus?
    • This should be rather easy to test - maybe just run the same g-code straight from a usb stick?

Any more ideas I haven't thought about? Comments on my ideas so far?

Here's the gcode if you want to have a closer look.
Also here's the Imgur page with all of my examples, if you want to see more angles of the bumps/print.

 

Best Answer by sandysasmita:

Some people have problem using octoprint on MINI, and one of the problem is because BAD usb cable. Try changing the cable with a good one.

This topic was modified 3 months ago by Yair Maimon
Posted : 03/01/2024 11:04 pm
Yair Maimon
(@yair-maimon)
Member
Topic starter answered:
RE: Zits/Bumps print surface issues - need help troubleshooting

I also forgot one idea I saw being thrown around this forum:

  • Adjusting Extruder Idler tension and print temp - Basically since input shaper is enabled I might need to help the Mini perform extrusion adjustments quicker, specifically to avoid lagging retractions/detractions causing either gaps or bumps from extra material
    • Sounds like a sound idea overall, it seems to also match up with the fact that I have what seems like a bit of under extrusion in my first layer but the more I think about it the more it seems to me like something that would have been tested and mentioned by Prusa when they released the Input Shaper profiles (at least the increased print temp).
Posted : 03/01/2024 11:20 pm
Tysonsw
(@tysonsw)
Trusted Member
RE: Zits/Bumps print surface issues - need help troubleshooting

It might be worth looking into tuning volumetric slope.

https://help.prusa3d.com/article/pressure-equalizer_331504

But it looks more like over extrusion so could be that you need to adjust your multiplier. Doesn't hurt to try.

 

Printer: Original Prusa Mini+
Nozzles: E3D 0.25, E3D Nozzle X 0.4 , E3D 0.4, Bondtech 0.6 CHL
Printables: Tysonsw
Mastodon: [email protected]
.

Posted : 04/01/2024 10:40 am
sandysasmita
(@sandysasmita)
Estimable Member
RE: Zits/Bumps print surface issues - need help troubleshooting

Some people have problem using octoprint on MINI, and one of the problem is because BAD usb cable. Try changing the cable with a good one.

Posted : 09/01/2024 1:35 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Zits/Bumps print surface issues - need help troubleshooting

I would consider a problem with the hotend. Either the heatbreak is not absorbing the heat properly or the PTFE in the hotend needs to be replaced (cracked, melted, filament debris). Both problems could cause irregular extrusion or partial clogging.

wbr,

Karl

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.

Posted : 09/01/2024 4:47 pm
Yair Maimon
(@yair-maimon)
Member
Topic starter answered:
RE: Zits/Bumps print surface issues - need help troubleshooting
Posted by: @sandysasmita

Some people have problem using octoprint on MINI, and one of the problem is because BAD usb cable. Try changing the cable with a good one.

This is actually exactly on point!
I managed to solve this myself a few days ago - as I mentioned I HAD heard that Octoprint could cause some stuttering and artifacts and decided to test it out quite simply by printing the exact same gcode with the exact same filament but from the USB Stick and it worked!

Below you can see some examples of quality comparison between the bumpy Octoprint product and the smooth USB one. literally solved the entire issue.
I now need to figure out if it's simply a USB cable thing with Octoprint or if my Octoprint setup is just unable to manage the rate of commands issued by the Input Shaper profile for the MINI (I actually stumbled upon a video talking about a similar issue of buffer size. He even talks directly about the Octoprint issues at the conclusion of the video. It's also the only proper reference I've seen for this issue when looking up for solutions!)

Posted : 10/01/2024 8:09 am
Share: