RepRap: Blog

Hmmm.... since the crucial measurement is the position of the extruder head relative to the base, shouldn't we be measuring that value, rather than another piece which has been adjusted to have the same value?

Fewer adjustments == more reliable operation and less user expertise needed.
 

Yes - that will be that case with Mendel. Because that will be changing its heads, the zeroing will happen against each head. But the heads are fixed in Darwin, so this will work just fine.
 

yes, I've been thinking about how you might change heads. Electrically, an RJ-11 or -14 would work nicely except for the fact that they're not qualified for more than a few hundred insertions. They would wipe nicely, but maybe that's why they're qualified for so few insertions.

For the mechanical bits, I think it would be possible to use a latching mechanism. Have a pin and link arrangement like the old-time railroad couplers. The pin gets pushed out of place by the head holder. Have two different movement paths to the head holder -- one to pick/drop the head, and another to engage/disengage the head. Can you picture that? A horizontal motion to insert the link into the slot, then a vertical motion to drop the pin into place. Reversing that would put the hack back into the holder.

Or maybe you've already thought about all that.