So if I wanted to go to GT2 belts & pulleys on my Makergear Prusa what would you recommend for sizes? Adafruit started carrying them and the prices look pretty good (and I need to order some other parts anyhow…)
The more teeth the lower the positioning resolution, so the general wisdom is the fewest teeth possible is better. However, you want to have a big enough pulley that there are sufficient teeth meshing at all times to prevent jumping. The generally accepted minimum for GT2 belts seems to be 14 teeth, so the 20 tooth pulley is probably a better choice.
You can check out the difference in resolution with this (very handy) page if you’d like: http://calculator.josefprusa.cz/#MotorStuffSPMB
Thanks @Stephen_Baird !
Not only do you gain better positioning with a smaller diameter you also gain torque.
I should clarify, the generally accepted minimum number of teeth in contact with the belt at all times is 6 and the smallest pulley that will give you that level of contact is one with 14 teeth, so the 20 tooth pulley gets you that minimum and will give you more accuracy than the 36 tooth pulley.
Stephen Baird, aren’t belt tension and angle of wrap more relevant to belt slipping? An academic question, really. The smallest GT2 pulley that fits on the 5 mm shaft will grip just fine, if tight enough to eliminate lash. That’s what I have on my MG Prusa.
I’m not super well versed in the engineering behind pulley choice, but it seems like angle of wrap and “minimum number of teeth in contact with the belt” are just two different ways of expressing the same physical reality. One, angle of wrap probably, is just the correct way to describe it while the other is a layman’s understanding of what’s going on.
With the 20 tooth pulley it is a one to one conversion in steps/mm from T2.5 belts with 16 tooth pulley or T5 with 8 tooth. I don’t think it can be much smaller than 20 with 5mm ID.
I have 20 teeth gt2 pulleys on my laser cut printrbot. Best upgrade ever.
What GT2 pitch are we talking about anyways?
The two standard pitches for HTD / RPP / GT / GT2 / GT3 (which all share a compatible tooth profile) are 8mm and 14mm.