Tuesday, 8 April 2008

Fantastic PLAstic

I have managed to get the GM3 to extrude PLA reliably with the following tweaks: -
  • I locked the clutch as per Solarbotics instructions.
  • I lubricated the GM3 with silicon grease as per Adrian Bowers suggestion.
  • I sharpened the thread a bit with a half round file following Vik Olliver's instructions.
  • I spaced the top half of the pump slightly further apart with some thicker washers. That gives the thread a gentle lead in.
  • Plenty of oil on the filament.
  • I throttled back the flow rate to 3/4 of the rate I normally use (π mm3/s).
The motor runs warm, but not alarmingly so. For some reason the filament is no longer rotating in the extruder.

My first attempt curled away from the MDF bed so I used 2mm balsa wood as Adrian has been using for PCL. That worked well so it's good that we can use it for both. I have yet to try it with HDPE and ABS.

I made my standard test block with 0.5mm filament extruded at 180°C (at the nozzle), layer height 0.4mm, pitch 0.6mm, fan on constantly. The results are excellent: very good filament compliance, i.e. sharp corners and flat sides, excellent layer bonding.

It is slightly more warped than my first test. That is probably because balsa is softer than MDF.

No warts on this one!


  1. LOL! Well, there goes my objections about PLA having a lousy surface treatment. I'm beginning to wonder if there is a problem on plastics extrusion that you CAN'T crack. :-D

  2. Once I stopped the clutch slipping the surface is certainly as good as any of the other three plastics, possibly better. There are a few internal blemishes which I think are some ABS remenants being flushed through.

  3. http://youtube.com/watch?v=WfKZRjL_jHo