# Under extrusion with Cura 3.1

I upgraded from Cura 2.7 to 3.1.0 and I'm getting horrible under extrusion, I'm sure this is the software because I rolled back to 2.7 and everything is working fine again.

My printing is a Robo3D R1+ using the "custom FDM printer" profile.

Is there any new setting or a setting that isn't migrated properly that causes this?

• Maybe give your custom profile parameter so we can have a guess at what could be wrong ? I don't think someone here has enough divination skills to guess the parameters on your software. Dec 21 '17 at 13:09
• This may be a bug, because my new install of latest Cura is creating the same problem AND I saw 2.85 one of the settings, so I changed it to 1.75 and it continued to under extrude severely. All was well with a Repetier print. Now reading above I need to also check both the machine settings and material section of the print settings. Jun 30 '19 at 10:45
• This is not a bug, Ultimaker default filament diameter is 2.85 mm, so that is what they default to.
– 0scar
Jun 30 '19 at 12:03

I hit this issue again in January 2019 with CuraEngine 3.6+git. Since support for multiple extruders was added, it now auto-loads a per-extruder settings file that overrides the main settings file and the command line, so -s material_diameter=1.75 on the command line did not help. Given $foo.def.json, it seems to construct the filename %$foo_extruder_0.def.json, and if that does not exist, loads fdmextruder.def.json, which sets material_width to a default of 2.85.
I was able to solve the problem by either patching fdmextruder.def.json, or making a copy of it named to match my printer's settings file, with the 2.85 changed to 1.75.
Update: There should already be extruder files for supported printers, but they're in a different directory, so they won't be found when invoking CuraEngine from the command line unless you've set the CURA_ENGINE_SEARCH_PATH environment variable to include the path they're in. Alternatively you can copy them to the same directory as the main printer json files.