I've upgraded my X and Y stepper motors to the larger ones sold by Ultimachine. Printing appears to be smoother when there are rough spots in the blue tape or the previous print layer . However, I'm a little concerned about the motor temperatures during longer prints. Using a thermocouple on my multimeter, the bottom case of the motors seem to stabilize at 120 F (49 C). Is that too hot? The extruder motor (original part from June 2011) only runs about 90 F (33 C). (All temperatures measured when ambient temperature was 68 F, 20 C).
If 120 F is too hot, any suggestions on how to reduce the temperature? I can think of two that could be quickly done - lubricate the x/y rods and dial down the stepper currents (I think that's what it's called). I have been lubricating the x/y rods with a white lithium grease, but a thinner machine oil may be more appropriate, I don't know. Any thoughts?
Finally, if anyone can suggest a good reference for learning the in's and out's of stepper motors (voltage, current, torque, speed, temperature) I would be eternally grateful. Old dog, new tricks, and all that!