Fighting with computers

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Sunday, April 14, 2013

Running in circles with the extruders

While my Wade-type extruder works nicely in my old Prusa, I planned to use a smaller geared stepper motor for my new Prusa i3 3D printer. But the road to a reliable extruder that is lighter and smaller is paved with many different trouble.

The first problem was to source PG35L-048 motors that Josef Prusa was using for his compact extruder and shown in different youtube videos. Sourcing it in Europe was not easy but I was lucky buying some units from an Austrian supplier called Neuhold Elektronik. But my joy was brief, once I could not easily extract the gear of the motor and I ended up sawing it off, because the shaft of my motor was shorter than the version used by Prusa, so I had to adapt the 3D design of the extruder to fit my motor. I got that extruder eventually working, but in order to get consistent extrusion the motor needed a bit more current than its specs so it was overheating. An aluminium piece, part of a heat-sink of an Intel processor took care of the extra heat. Still, I was not impressed with that extruder performance, though part of the fault might be caused by a not so great hotend.


Once I saw that even Josef have moved away from that stepper, I bought a unit of the new one he was using from 2engineers.com. The motor was more or less the same price of a regular nema17 but delivered much more torque due to a 50:1 reduction gearbot. User OhmEye complained of some gears early failure on an extruder of his own design but once I got the extruder working it was all good. Or so I thought, till I noticed some banding on my prints. It ended up not to be a fault of the extruder but of my hotend that was incapable to handle speeds above 40mm/sec and it started to stutter.


This new motor did not overheat and it works ok, but I was not impressed with the results due to the additional delay introduced by the gear box, that did not allowed fast retracts.  



So I took an modified Wade extruder and I made a small change for it to fit the x-carriage part of the Prusa i3 and this is what is working the best for me. The added advantage is that you can do the hobbed bolt at home, which leads to a quite cheaper solution to the extruder.



It seems more people like it and it has become my most popular part in Thingiverse.



But I seem to have a problem leaving things that work alone, and I am testing yet another extruder right now. It is just a bit more compact but it uses nema 17 motors too.

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