Nurdle extruder – Generations

The same friend who has been bringing me the HDPE nurdles recently brought me a new and improved extruder head that he had made in his spare time at his work. As you can see, its a tad more professional looking than my own home made extruder heads.

Each generation of the nurdle extruder thus far. The newest is on the right already rapped in polyimide tape.

Its made from a solid section of aluminium that has been drilled out. At one end is a opening in which a smaller slug of aluminium sits in. This slug makes up the die and can be swapped out for different sizes. Its secured in place by two bolts that are screwed in from the sides.

The new extruder. The bars on teh right are inserted and act as the die. The furthest one on the right is a blank ready to be drilled. Just above the ruler is a solid bar ready to be cut to make further die slugs.

Having changeable dies is fantastic as it will allow me to play around with different shape filaments. I could perhaps cut a slit to make a flat sheet, a circle to produce a hollow tube or many small holes to make a multi thread twisted rope. But thats for another day.

At the moment I’m still having trouble getting the auger to turn at a constant speed. Belt slip has been the biggest problem leading to many stops and starts.

Test extrusions.

I’m finding that the amount of force required to turn the auger gets excessively large after running for a short while until the point that the belts will slip. I tried to solve this by reducing the length of the auger that was in the feed pipe and by reducing the number of nurdles in the feed bin. Neither seemed to help.

Removing the feed pipe exposed the problem.

The top of the extruder where the feed barrel connects.

Its a little hard to make out, but your looking at the top of the extruder head where the feed barrel that has the auger in it sits above. When I lifted off the feed barrel it became clear that it had become much too hot and the nurdles were passing their Tg. I had designed against this in my own extruder with the bell shaped end mating with a PTFE wrapped feed barrel. I will need to do something similar for this extruder as well.

About Richard

I am a Materials Engineering working in the field of Magnetic Materials in Melbourne, Australia. This blog covers my personal interest in all things CNC.
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2 Responses to Nurdle extruder – Generations

  1. rob_melb says:

    Any chance of seeing the extruder at work as I have an interest in building one for the Melbourne “Connected Communities Hacker Space” CCHS use, since there seems to be no local source of PLA or ABS filament to my knowledge. I would further like to see the ability to develop the use of different materials for rep-rapping. The target size would be for 2.9mm dia filament. Plus this may enable shorter cycle time on local projects.
    Ref – (new site soon)
    Regards Rob B

    • Richard says:

      Hi Rob

      Although I’m confident that the drill bit extruder idea is sound in principle, the extruder I have needs a bit more work.

      Once its at the point of producing a constant diameter filament that is automatically spooled I will be sure to take plenty of video. I would be more than happy to bring it along to a Hackerspace meeting as well seeing as I’m relatively local.

      A 2.9mm filament diameter shouldn’t be a problem, it would just require some testing with different die sizes. As for extruding PLA or ABS, it should be a breeze compared to extruding HDPE due to its lower Tg. However you may still need a source of nurdle feed stock even if you are planing to use recycled plastics. A filament made from 100% recycled plastics might not be of high enough quality to print with, but more test is needed to say for sure.

      Anyway, I plan on getting right back into the 3d printing/extruding scene as soon as my last exam is over tomorrow.

      Regard, Richard.

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