I’m still producing threaded pulleys to hone my skills at the lathe.


This is my current setup: Other than Nophead, I don’t use a block of steel with a milled slot to hold the blank pulley. My lathe’s tool holder seems to be not big enough and I don’t have a milling head. Thus, I mounted the pulley on a 5mm thick aluminum plate, using a M6 bolt with some washers, two (jam) nuts and lots of (cutting) oil:


This setup works quite well. I even manage to don’t break the M3 tap bit now…


I still have massive problems getting my MakerBot back into a working condition. After breaking my Printruder when trying to extrude with a .3mm nozzle, I tried to reactivate the original MakerBot MK3 extruder to print replacements for the broken parts.

Unfortunately, the MK3 extruder still don’t work for me. Either the ABS slips or the pinch wheel strips the ABS after a few centimeters of extrusion.

So I decided to give the broken Printruder another try. The main damage is the lower filament guidance hole. It completely broke of. So I tried to replace the printed guidance hole with a short aluminum tube. I also replaced the original timer pulley with the small threaded pulley I created a couple of days ago :


Guess what: The extruder failed again. I used the original .5mm heater section, I just cleaned and rebuilt before. But something must have been extremely wrong with the heater barrel, the nozzle or both. It completely jammed again after a few seconds. But instead of slipping or stripping ABS, I heard some strange noises from the Printruder.

After removing the idler bracket, I saw this:


The ABS was “fold” into the inner of the Printruder!

I’m not sure what force is needed to bend 3mm ABS filament into a tight loop, but this definitely proofed that the threaded pulley was performing way better than the timer pulley, which either slipped or stripped the ABS in case of an extruder jam…

So it was definitely time to find out what’s wrong with the heater section.


After dismantling the heater section, I found some kind of “coal plug” baked into the nozzle. I’m not sure how this plug was created, but I suppose that this was the result of a previous jam and a lot of heat.

The plug didn’t seem to be affected (and softened) by heat, so I needed another way to get it out of the way:


After 4 or 5 hours of soaking the heater parts in acetone, the plug seems to dissolve slowly.


I give it another night…

In the meanwhile, I went back to my lathe and turned a completely new heater barrel from scratch, as described on the RepRap site.


The brass barrel and the nozzle are one piece. I drilled the nozzle with a .5mm drill.


So until the MK3 barrel and nozzle are finished taking an acetone bath, I now have a replacement heater section to (hopefully) re-print the replacement parts for my Printruder and finally to do some more tests with the .3mm nozzles I bought from Makergear.

I reinforced the aluminum tube in the still broken Printruder to avoid further ABS folding in the gearbox.


The first 2m of test extrusion are looking good so far:


Tomorrow, I’ll eventually try printing actual objects with the refurbished Printruder.

I’ll let you know of the results…


  1. Zaggo – Enjoying following your progress. It reads like a good novel – action, anticipation, … – and at the moment I get to play the villain! (by breaking your printruder) :)


  2. I have had the same coking problem.

    Its better to start at 210c and slowly ramp up the tempature, 240 is a widely reported tempature but it seems the termal conductivity for the thermistors vary widely. So if you use 240 as your starting point you might go through a series of jams.

Leave a Reply