Sunday, April 05, 2009


Coach Bolt Hack working

I ran up the BfB extruder with the coach bolt drive. Drive is a little inconsistent, but works (12mm/sec or more).

It should be enough to let me build another extruder - i.e. RepStrap itself, with a traditional V1 or V2 extruder.

From Coach Bolt drive

I might try and build a coupler out of polymorph. My solder join is only straightish (a couple of degrees off) because it wasn't held very well while setting. I could also try supergluing a similar reinforcement with the slots - I don't think it will be strong enough on it's own.

I've mounted it on the RepRap
From Coach Bolt drive

And it should be ready to go soon. I tried using the host software to build a 10x10x10 square, but it started moving the Z-axis down, away fron the endstop. I'm not quite sure why yet... I'll try the replicatorG and the g-code to see if it has the same effect.

Very nice idea.

Have you considered JB-weld for the join between the two bolts?

From your first photos I was a little surprised that it was able to turn in the extruder. If you made one again I would consider making a plywood jig to hold the two parts as straight as possible, then working on one side. When it has dried, flip it over and do the other side. Also, it may help to file down the tops of the bolts to take the crown off.
Cut the heads off and file a flat on each shaft. Drill out a coupling nut to fit and drill holes to tap for set(grub) screws. Alternatively drill through so you could pin them together with small bolts or cotter pins. I have my Z axis stepper drilled this way to hold the Z stage. Works fine.
You can fix the incorrect direction thing by switching the coils on the stepper. Hook coil A up where coil B is now, and coil B where coil A is now.

Or switch polarity: switch wire A^1 with A^2 and B^1 with B^2.

That's assuming it's not a firmware issue, of course...
Thanks for the comments.

Coupling nuts look like what I need! I'll try a few connections and post what works
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