Losing Steps
I had an issue where the motors would lose a couple of steps when homing from the extreme of both axis. Couldn't figure it out at first, but I believe I have found the culprit. I know it is explained that the steppers are tuned before they leave to a Vref of 0.34 however, both of mine were set to 0.24 & 0.27 (I did get mine from US stock, not sure if that makes a difference). Since I have already put in an auxiliary 24V power supply and hooked up common ground I am not hindered by the 1A restriction, I bumped them up a little. The motors are running coolish (X is running slightly warm to the touch, but not hot. Y is cold to the touch) and the lost step issue seems to be resolved. Can someone tell me the specs of the K40 stepper motors so I don't have to pull one out to inspect? Are they standard 1.7A motors? I seem to remember Paul stating somewhere they were very low amperage, but I could be wrong. I would just like to tune them properly.
The standard motors are a tad smaller than the NEMA17s they run on max 350mA each.
So you could potentially replace them for better spec NEMA17s. Remember everything on the K40 is squeezed out for cost (lenses, mirrors, gantry, controller, PSU, motors etc.)