Hello,

I have an application that involves two short (10 feet), and parallel (2 feet apart) indexing conveyors that are mechanically linked through shafts and at either end.  Each conveyor is made from matching timing belts and timing pulleys. The conveyor is used to transport sections of stainless steel tube that sit in profiles that are attached to the timing belts. The conveyor is driven by a servo drive and servo motor with a gearbox (ratio to be determined).  I need to index the conveyor a distance that matches the profile pitch, then stop and wait for another index trigger from another piece of machinery.   The indexing is always in the same direction so the profiles on the belt will “recirculate”.  Lets assume that I have ten indexes in one full rotation of the conveyor, will I get accumulating positional errors if I perform my index solely on the encoder count from the servo motor, or should I use a registration sensor?  When I spec a gearbox, is the ratio an exact ratio? ie could a nominal 3:1 gearbox be in reality a 3.0000001:1?

Thanks
Martin