Monday, April 13, 2009


Get your stepper to put splines on its own shaft

The new pinch-wheel extruder needs to be able to grip the plastic filament that it is extruding to drive it down into the melt chamber. A splined stepper shaft does that nicely, but splined steppers are both rare and expensive.

Here's how to get your stepper to spline its own shaft...

The only special equipment needed is a Dremmel or similar minidrill. The rest is stuff like bits of wood, cable ties, and an old door hinge...

See here for full instructions. The top picture shows the results.

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Nice technique. Does it drive the filament well?
I'll try that tomorrow and report...
Very nice Adrian!

Given the success that nophead had with worm gears, I wonder what would happen if you also rotated the stepper 90 degrees in the g-clamp and cut a shallow groove perpendicular to the regular spline grooves. That would give the shaft more than just a flat edge contact with the plastic. (However, it may just make it easier to strip the plastic.)
Great stuff, Adrian! You might want to look into buying one of Dremel's diamond cutting wheels. They are remarkably inexpensive and a lot more robust for working hard metals than the usual abrasive cutting disks.

I am really rather surprised at you, though. That wooden lashup looks like something I'd do. Why didn't you just print the parts? :-D

Another way to make a worm wheel would be to make a groove in the splines. Nophead found the 3 mm groove was good, as he posted in "All Torque and No Traction" at:

Ideally some kind of abrasive rod or hacksaw cord could be found with a 3 mm diameter. Otherwise you could employ the edge of a used grinding wheel. I remember that after I used the edge of a grinder wheel for a long time, the edge got rounded. At some point the radius must of been 1.5 millimeters.
> Why didn't you just print the parts?

Because people just getting started might not have a RepRap :-)
LOL! So true! :-D
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