Saturday 17 October 2009


Irritatingly, whenever I try to make a new extruder using my existing one, it always breaks down forcing me to have to repair it, even though it is about to be made obsolete. It is as if they know!

The GM3 motor on my extruder started making a noise like a machine gun. On opening it up I found it has stripped a tooth of the final gear.

Since I moved from the 6V version to the 12V version I have been getting pretty good motor life. I do have to lock the clutch and sometimes glue the splined shaft into the last gear, but so far the gearbox has lasted well.

It is just as well my next extruder uses a stepper motor and an all metal drive chain: -

More details soon ...


  1. Maybe the reason for the failure is that HydraRaptor is on a path to eventually create the Higgs boson? Nature won't let that happen.

    (As you probably know, that's been seriously put forth as a possible reason for technical problems at the LHC:

  2. Are you using nema23 sized stepper motor for this design and worm gear?

    I thought the stepper motor from your previous design will be enough:

    Im just curious here ...

    Best regards,

  3. Khiraly,
    It is actually a NEMA17 plus meccano gears.

    Yes the tiny motor and gearbox produce enough torque and are lighter. I do worry about the life of the plastic gearbox though. I will put that version on my Darwin and see how it goes. This one is for HydraRaptor where the weight does not matter.

  4. > It is actually a NEMA17 plus meccano gears.

    So on the stepper motor shaft, there will be something like this?:

    Are you buying it or make with your lathe?


  5. Yes exactly. I bought them but I had to drill out the worm gear to fit the motor shaft.

  6. JSwanljung,
    I don't think anyone has to worry about HydraRaptor creating sub-atomic particles any time soon, but I have had a lot of bad luck on this project.

  7. A worm drive is perfect. Why didn't I think of it. Is NEMA 17 the smallest you could go or are you playing it safe? Mendal has a NEMA 17 directly driving its extruder. I can't wait to read all the details and see it built and running. I'm curious to see exactly how you are planning to adjust the pressure on the filament. From the CAD render it looks like it is just set based on the hight of those two bosses on the retaining plate/bering holder. Keep up the good work; I really enjoy following your progress.

  8. nophead: I just reread you blogposts, and I could not figure out that your gears was functional, or not. Im talking about your last year's october and this year january posts:

    I know, they didnt have perfect involute profile, but was it functional or not? Im wondering about the feasibility of replicating the broken gear of the gearbox.

    Also Im wondering if it possible to make gear with your lathe. (ie. having metal gears, which should last the same, as your current design).

    Just brainstorming here..


  9. MBC,
    Worm gears are good for big reductions in one step and holding position, but they are more lossy than spur gears.

    I think a smaller motor would work but it is hard to find a cheaper hybrid motor than the MakerBot NEMA17 for $15. Permanent magnet motors, AKA tin can, have bushing bearings with several mm of end play, so are no good for a worm gear. NEMA motors have ball bearings with no end play.

    The pressure is applied by M5 wingnuts on long captive bolts. The are long enough to take springs if need be. The bosses are just end stops to prevent the bearing meeting the drive wheel.

    Full details coming soon.

  10. Khiraly,
    I think the spur gears I made would be functional but the teeth on the GM3 motors are tiny. I would not be able to make those. Also they are made from more suitable plastic than ABS, HDPE or Nylon I think.

    Gears can be made on a lathe with a hobbing attachment but the pair were only £7.50.