Hm, never even thought that that might be a factor. Yes, it uses relays. I'm not sure how much belt travel will be off because of that, but given that it would be a constant it would likely already be accounted for a an offset to 'center of part' which is where I try to hit the parts to make sure they don't spin like mad.

That sounds reasonable, where you may have more luck with something more accurate is if you had to run the blower for a shorter time, or maybe pulse it to lower the wind speed (I'm not sure if that's possible).

The relay pulses are about 50 msec, that's mostly limited to ensure there is enough air to rapidly hit multiple bins in a short time, as well as to be able to 'pick out' a part from two adjacent parts on the belt without hitting the other two. That took a while to get right!