Software Questions

Does the software support the following:
A different stepper motor? (i.e. one that has say 1.8 degree steps instead of 0.9)
ASE(standard) Pitch threads instead of metric ones. Just to say that you get 1.27 rotations per mm(1/4" rod at 20 threads per inch) instead of 1.25 rotations per mm(M8 rod at 1.25 pitch)

I'd suggest that you look at 3/8-24 instead of 1/4-20 if you're going to substitute American studding for metric. The thread pitch is much closer to the metric standard and 1/4-20 tends to sag a bit at the lengths required by Darwin.

Yes, the host software supports 200 step/rev motors. This has been done and is known to work, possibly with some mild loss of precision. Eric M's system (which right now is about as close to extruding a minimug without actually doing so as it is possible to be!) uses such steppers, for example.

There are also preferences to deal with calibration of motion distances:

XAxisScale(steps/mm)=11.4855
YAxisScale(steps/mm)=11.4855
ZAxisScale(steps/mm)=320

so yes, theoretically you could use a close non-metric equivalent for the studding and the software will handle it. I don't know of anyone having done this yet who is using the RepRap host software and a Darwin-like robot, so I think you'd be somewhat "on your own" experimenting in that regard. But it "should" work :-)

Using the beefier studding Forrest recommends sounds good to me, if you decide you have to go non-metric. I think you will have to modify some (many?) of the RP-ed parts if you do that within a Darwin-like robot design.

At this point (pre-Darwin v1.0), IMO, staying metric is more helpful to the project as a whole. A US-specific non-metric Darwin variant is a worthwhile idea to cut costs for US residents ... *after* the basic worldwide-replicable Darwin v1.0 is released. Until then, such a variant is likely to divert scarce brainpower and troubleshooting resources away from the primary task. But that's just my opinion.

Jonathan

Thank you for the answers.

The beefier rods are correct, and actually a 5/16 rod and is 0.0625mm narrower then a 8mm shaft, so that would be the correct way to go with it. If it were to be done that way. I am of course, not suggesting anyone follow my lead though.

None of this would be posted until I acctually have a good working model. Before that though, I still have to get the stepper motors, all the electronic parts, build them, test them... yada yada, yada yada. Kinda in the same boat as the rest of you.

And yes, a SAE conversion would take some brain power away. However, there are far more wholesale changes to this project to reduce costs and still keep in the spirit of what is going on that I/myself will at least have a look into them.

Thanks guys...