Andrew May wrote:
On 08/02/2012 17:09, Andrew May wrote:
On 08/02/2012 17:02, Brian Gaff wrote:
How does this carriage know its relative position, and I suspect if the
drive is slipping its somewhere in that drive and thus the slippage is
misaligning the sensor.

Brian


As far as I can see the initial reference position is found by moving
the carriage to the back where there is possibly some sensor, optical or
otherwise. Then step back a known number of steps to achieve the
reference position. This all works fine. It is when it tries to move
back to this position after focussing that it fails to get there and the
problems ensue.

Andrew
Perhaps I should add, if I haven't mentioned it before that this is a
screw drive not a belt drive. So no belt to slip.
is it a twin screw?

I've seen nasty problems with a laser cutter when one belt on one side
slipped a cog and the whole thing went out of square - putting a BIG
strain on the whole mechanism.