Adjusting stepper drivers

I have had a couple of ruined prints recently due to dropped steps. These occurred on the Y axis this time but have occurred on the Z axis in the past. I adjust the stepper drivers by trial and error usually while printing a test cube. They are nema 17 motors.
Is there a better way? A more scientific method maybe. I have a clamp on dc ammeter.

What electronics? If it uses a Polulu stepper controller or equivalent, then there should be a pad to measure Vref which you can use to calculate the current. You want to set it to no more than what your stepper motors are rated for to avoid overheating the motors.

Sorry, ramps 1.4 and A4988 drivers. So I set Vref to what voltage?

A Vref of 0.4 V produces a maximum current of 1 A. This is probably a good start, but check you motor specs. I tend to set it lower than this on my printers (Prusa2, Ord Bot Hadron) except for the extruder motor.

brnrd:

NEMA 17 motors can have different torque and electrical specs. You should be able to run at even 1/2 A in most cases. If you don't know the specs, start at 0.3V for Vref and see how if you still have missed steps and make sure the motors aren't getting too hot. You don't need to be running the motors to set the Vref. You don't even need to supply +12V to the electronics. If your controller gets power from the USB, then just plugging it into the computer is enough. This is safer since you don't have to worry about shorting the stepper motor leads while you're making the adjustments.

OK thanks. I will try adjusting them and see if it solves the problem.

brnrd: just to clarify, is Vref on the A 4988 measured at the pin labelled VMOT or VDD ?

Edited 1 time(s). Last edit at 01/27/2014 08:35AM by dave3d.

have a read here [reprap.org]