Help with new pinions

[frankwilliams]

I just received my 7.2 upgrade and while checking of the list of parts I noticed that my pinions are 25T not 30T. All the posts I have read say they should be 30T. Which is correct? My machine in a PRT Alpha 4'x8'. Any help would be greatly appreciated.

[richards]

Frank,

I received 30T pinions when I upgraded. Why not give Shopbot a call. If they've shipped the wrong parts by mistake, they'll make everything right. (I received the wrong stepper drivers with my upgrade, but they had the right ones to me in just a few days.)

[frankwilliams]

I called shopbot this morning and they gave me some different unit values for the 25T's. I suppose there are trade-offs on either side, 25T has better resolution and a little less holding power than the 30T's. I'm sure I'll be happy. Just out of curiosity, what are the right drivers for that upgrade?

Thanks Frank

[richards]

The stepper drivers look identical; however, the 'correct' drivers use a 5X multiplier and the 'wrong' drivers used a 4X multiplier. As far as I understand, the 5X drivers are flashed especially for Shopbot.

If you have 25T pinions and 4X drivers, you will have higher resolution and higher torque but you will have slightly less top speed. (I don't think that top speed would be an issue. Normally, I cut at 50% or less of top speed to get the quality of cut that I need. Going faster causes messy cuts.)