Steve,

What happens if you lose step, because of some disturbance in your system ?

Agreed. You ARE doomed.

One of the reasons why I had laid emphasis on the proper selection and application of steppers in my posting.

We had this test rig for plotting the performance curve of an automotive power steering servo valve - it had to be torqued in both CW and CCW upto 7 Deg angle precisely for that. The original implementation was with a DC drive + encoder feedback. Actually the torque worked out to 20NM max. Had this converted to a stepper drive without feedback and 2 rigs are running the last 3 years, testing about 200 valves per day. The third machine is on its way. Not that the conversion was a cakewalk but that is history now.

Incidentally all (?) printers use steppers for paper feed and cartridge traverse . I suppose there is no feedback - or do they have feedback ? Someone out there who is an expert on printers ?

Raghu