Back to the extruder…

As regular reader of my blog, you already might have noticed that I’m working on several different projects at the same time. Recently these are mainly the heated build platform/raftless printing, a LCD display and last but not least, a .3mm extruder.

After breaking my trusty Printruder during my first .3mm nozzle tests, I had to reprint broken parts for the Printruder, which lead to a heated build surface, which lead to modifying the extruder firmware, which lead to integrating a I2C-LC display… After my recent tests with raftless printing, I eventually came back to the original project: the .3mm nozzle.

Since it was a bad idea last time to use my one-and-only Printruder for the nozzle tests, I started to design a new extruder for this purpose. My first tests with a stepper motor driven extruder weren’t too promising (… the lack of force it was able to push the filament with. Probably a design flaw of mine. I already started redesigning the whole thing, but this is yet another project…), I plan to drive the new extruder with tested and proven mechanics: Printruder motor/gear brackets and MakerBot DC gearmotor with a threaded pulley. For the heater section, I already started to build a PTFE/insulator free design a while ago. After a couple of drawbacks, I finally did a successful first heater test today.

The heater barrel is definitely inspired by nopheads extruder barrel designs:

ExrtruderHead IMG_4697

But there are several differences:

  1. I used brass instead of steel. This might be a disadvantage, since brass has a way higher heat conduction. But I only had brass rods laying around and I’m also not sure if it is more difficult to turn such part from steel. I suppose it mainly depends on the type of steel. So I stick with the metal I am currently used to, after all I’m still a greenhorn when it comes to working with a lathe…
  2. I designed the barrel to hold a heat sink, since the Plastruder doesn’t contain any large aluminum parts I can use for this.
  3. I still use nichrome wire to heat the nozzle.
  4. The barrel has a M6 thread on one end in order to mount a standard MakerBot nozzle on it.


The thin part in the above photos is still 5mm in diameter since I was afraid to rupture the barrel (there’s a 3.5mm bore inside, you know…?).

But that was a real problem during my first heater test: Probably also due to the high heat conduction of the brass material, it was impossible to reach decent nozzle temperatures. Instead, the heat went straight to the heat sink and the upper end of the barrel.

So I disassembled the whole thing again and boldly turned an additional 1mm off the thin part. It’s now 4mm in diameter which means, that the wall thickness is only .25mm.

Here’s an image of the reworked heater section, right before the new temperature test:


Reducing the wall thickness did the trick!

It’s now quite fast and easy to reach ABS extruder target temperature (220°C).

I tested the setup for about 10 to 15 minutes. Here the results:

Target Temperature
(Replicator G)
(Replicator G)
Nozzle outside Top barrel nut Heat sink top Heat sink down
220°C 217°C 180°C 60°C 61°C 69°C
240°C 234°C 193°C 70°C 81°C 88°C


So far so good!

Now I need to print a special retainer plate to attach the heater section to a Printruder and eventually try to extrude some ABS…

It might take a few days since there are all this other projects… And to spice things up, I just printed my first part for a Mendel yesterday :)


Leave a Reply