### First – why?

If you’re keen to upgrade stepper motors because you think it will increase performance, beware.  In a typical flying-mirror gantry arrangement, the Y axis motor needs to physically move the X axis motor, so increased X axis weight will increase inertia. Remember Newton’s second law: Force=Mass x Acceleration (F=ma). If you want increased acceleration, you need to increase Force more than you increase the Mass which is to be moved. So when upgrading the stepper motor, consider whether the increased weight will pay for itself with more than proportional force – otherwise you’ll accidentally decrease top acceleration.

The other thing to consider is why do you want faster movement anyway? The misconception that faster=better is addressed in this blog.

### Stepper motor selection considerations

Adding non-standard stepper motors is a non-trivial exercise. Considerations include:

• The stepper angle. Most off-the-shelf stepper motors such as typical NEMA17 have a step angle of 1.8′ The K40’s default stepper resolution is 0.9′  Are you willing to accept a lower resolution? If so, you will need to change your \$ settings to reflect different travel rates: \$100 and \$101   You should halve the existing steps per mm settings.
• stepper motor wiring (the number of coils, and its internal connections)
• current loading must be within the bounds of MG3 specifications and whatever stepsticks you’re using. If you want to use more power than the minimum of MG3 and its stepsticks, then you’ll need to use external stepper drivers.
• a suitable power supply is needed for the motor voltage and current. Note the K40 PSU is 24V but has current limited to 1A within the K40. You may need an external supply.
• suitable wiring. Many K40’s supply X axis motor with current via a thin ribbon cable. It is inappropriate to supply more current through this tiny cable.