How do I use the Spindle Orientation block with gearboxes?
If the motor/gearbox ratio is an integer only exact multiple, (for example, exactly 3/1, 4/1 etc) the encoder may be fitted to either the motor shaft or the spindle side of the gearbox – but please take note of the manual comments regarding pin 12)MOT/ENC SPD RATIO if fitting the encoder to the spindle side of the gearbox.
But if the gearbox ratio is not an integer only exact multiple, (for example, 3.57/1, 2.7/1 etc.) there is a problem. If the encoder is fitted to the motor shaft, the motor shaft will orientate to the same position every time the orientation block is called – this does not equate to the same spindle position every time, and it is not possible to use the marker offset to correct for this (apart from a special case, where the ratio is exactly x.5/1 – where the marker offset can be alternated on and off for alternate stops to correct the error).
The solution is to fit the encoder at the output side of the gearbox – or at least arrange for the marker pulse to be generated by some other mechanism - a proximity switch on the spindle, for example.
The above applies irrespective of the gearbox being a step up or step down type – please also see the manual notes regarding marker masking for reduction gearboxes.