I had seen on the HeatSync Slack that we were having some issues with the 3D printers. The next time I stopped at at Heat Sync, I saw the Ultimaker 2 just had a note:

Underextruding :(

So the next week I made a date with the UM2 to see what was going on. First thing was first: test print. As a first test for just about any FFF printer I like to slice the following gcode

  • 20mm Cube
  • Vase Mode*
  • 1 base layer
  • 0 top layers
  • ~.2 layer height
*A.K.A. Corkscrew mode A.K.A. single perimeter A.K.A. spiraled contour mode

I like this kind of print since it's fast, and you can get a lot of information from it. In this case I wanted to see how bad the underextrusion was, and with the first print I got this:


First thing's first, check the basics. PLA was loaded, settings on the printer matched. Cooling fans were working correctly and running unload/reload showed that the extruder itself was (probably) working fine. But once the filament hit the hotend the extruder started having a hard time pushing, which meant that there was be a problem with the extruder or that there was a jam in the hotend. As the latter was far more likely, I started with some basic operations to try to unclog the hotend.

Just incase the printer had been loaded with ABS or another material that needs a higher temp, I heated up the extruder to 265 and extruded several hundred millimeters or plastic. When that didn't help much, I tried Ultimaker's Atomic Method (which is more or less a manual cold-pull). While this did pull out a bunch of dirt, The printer was still having extrusion problems.


At this point if I had a new nozzle I would have tried that - but if there are any spares, I don't know where they are. So I took apart the hotend

  • Remove the 4 phillips screws connecting the fan shroud to the toolhead
  • Remove the 4 hand screws to disconnect the heatsink/hotend from the toolhead
  • Remove the 2 M2.5 bolts from the top plate that connects to the heatsink
  • Remove the phillips screw what goes through the hotend into the bottom heatsink plate
  • Unscrew the heater block from the coupler on the other side of the heatsink plate

Note: The heater cartridge and RTD are held in with friction and hope, so they may pop out on you.

Once I had the hotend free I used the hot air rework gun to heat the inside of the nozzle. A mix of cold pulls, tiny picks, a tiny drill and some percussive maintenance left me with a clean(er) nozzle.

I reassembled the hotend and re-ran my cube. Finally, there was a vast improvement over the original. There was still one spot that had some small underextrusion, but I saw a similar spot on the second print at the same spot, which makes me think there could be an overflow in the firmare or the extrusion just needs some fine tuning (rather than continued nozzle jamming). Though we should still get some new hotends to be safe.


The other problem with the print was that the first layer was awful. I'm guessing that when I reassembled the toolhead, I inadvertently changed the height.

Running the UM2's bed adjustment (on the LCD menu, Maintenance -> Build Plate) was very easy. At first I decided not to mess with the set screws, but after my first print showed up lopsided I went through the whole thing and was pretty happy with the results - for my final print I did the same cube, except wider (100mm in X/Y) and about twice height (40mm in Z).


So I'll leave it to run overday with a "real" test print. Hopefully it stays working for me to see what's going on with my nemesis The Choocher.