What causes these blobby corners


Contrary to a lot of other corner related problems (where the corners are bulging), I seem to have a different problem where the corners (ONLY) seem to stick out and appear blobby in the x/y plane. This only happens for corners/edges with a fillet radius greater than 3-4mm and only in the x/y plane. Anything smaller than that radius (such a sharp corner/edge) seems to be fine.

Any ideas what could be causing this?


  • CR-10s
  • Ultimaker Cura v4.2.1
  • Material: ABS
  • Nozzle size: 0.4mm
  • Bed temp: 80 °C (I can't go any higher than this)
  • Nozzle temp: 250 °C

What I've tried already

  • increasing nozzle temp from 240 to 250 °C (seemed to help slightly?)
  • reduced flow rate from 100 % to 80 % - had a negative effect on overall print quality

Thank in advance for any ideas/suggestions

blobby corners

more blobby corners


Posted 2019-09-19T01:26:06.760

Reputation: 25

Hi Dane, welcome to 3DPrinting.SE! Have you calibrated the filament extrusion (e.g. over-extrusion can cause blobs) and what print speed are you using? From the rounded cube it appears that the speed is too high, the individual lines in the shell are not touching. Please update the question by [edit] rather than replying in a comment. Thanks! – 0scar – 2019-09-19T06:43:32.773

The corners are actually the only part of the second print that looks right - the straight paths in between are extremely under-extruded. – R.. GitHub STOP HELPING ICE – 2019-09-20T04:40:38.640



I suspect you are printing through a usb or network connection, and the communication rate it's to slow for any of many reasons. A curve consists of many tiny linear movements, each requiring a command exchange between the PC and printer.

If you can, try printing from an sd card plugged into the printer (I'd the printer is so equipped).

This could be worse if the uses a Bowden extruder, since there is now compression and windup in the filament.


Posted 2019-09-19T01:26:06.760

Reputation: 4 180

This solved the issue. However, I'm very surprised as to why. I have been printing with the Octoprint OS on the raspberry pi for several months now without any dramas. I feel like there must be something more to the story here. Perhaps a recent Octoprint firmware upgrade or similar which has slowed the baud rate? or increased the amount of processing required per head move? – dlenno89 – 2019-10-15T05:10:02.547


150 °C is way too low for pretty much any material commonly used in 3D printing, especially ABS. I'm quite surprised anything comes out of the nozzle at all rather than just griding in the extruder gear. Most ABS filament manufacturers recommend a nozzle temperature in the range 210-250 °C. From your images, it looks like you have a lot of serious extrusion problems aside from the corners that should all go away if you print with the right temperature.


Posted 2019-09-19T01:26:06.760

Reputation: 5 311

Sorry. I meant 250degC. Typo. – dlenno89 – 2019-09-19T05:50:31.733

So I have the hot end set to 250degC. It was originally 240degC. increasing it marginally helped. But I feel like the issue is more than just a temperature problem. Why would this only be shown in the corners (and not appearing at sharp corners, only filleted corners) – dlenno89 – 2019-09-19T05:52:18.773

You think I should up the temp again? – dlenno89 – 2019-09-19T05:53:38.940

Your temperature doesn't seem too bad. Make sure not to use layer cooling / only very little of it. How fast are you printing? – towe – 2019-09-19T07:13:51.820