# Replace X axis motor with different model

Last week, my X-axis stepper motor died. It was a 42SHD0217-24B model. I ordered the same online, but the vendor made a "mistake" and sent me the 17HS3401S model.

I know these motors use a different voltage, so I adjusted the screw on the stepper driver and managed to get a smooth rotation with the new model. I know that these 2 motors have a rotation of 1.8° per step.

My questions are the following:

• Since they have the same rotation angle per step, I shouldn't have to calibrate the new model, right? (I'll use the original wheel)
• Did the vendor send me a motor with inferior performances?
• Will my performances degrade if I use the new motor? (Lecture on motors appreciated). By that I mean: will my top moving speed be affected? Will the motor miss more steps at high speed?
• can you just try it? print a benchy or something and see how it goes. – dandavis Apr 19 '19 at 18:37
• Yes I will obivously, but I'm looking for a more theoretical explanation, since I want to understand... – JPFrancoia Apr 19 '19 at 18:41
• Not voltage, but amperage (current). Due to the difference in max current, you need to lower Vref of the stepper driver. – 0scar Apr 19 '19 at 21:43

Since they have the same rotation angle per step, I shouldn't have to calibrate the new model, right? (I'll use the original wheel)

Yes, you do not have to change anything, other than the Vref of the stepper driver.

Did the vendor send me a motor with inferior performances?

Yes, the one you received has a lower height, so smaller coils and smaller permanent magnets; basically lower torque.

Will my performances degrade if I use the new motor?

That depends on the loading of the carriage of the X-axis, it could if it is heavy; you now have less torque available to move the carriage. But, this type is frequently found in 3D printer kits and should work.

• The Vref is adjusted by turning the screw of the driver right? (What I did?). I thought I was adjusting the tension because I normally measure the voltage on the driver. But I gues Ur=R.I :) – JPFrancoia Apr 20 '19 at 7:30
• @JPFrancoia Yes you adjust the screw and set the correct Vref according to the stepper driver type to limit current, e.g. for DRV8825 drivers it is Stepper Current Limit = Vref × 2. – 0scar Apr 20 '19 at 21:23