Tuning Stepper Motors for CNC

Motor Tuning For Plasma Tables

Tuning a stepper motor for a plasma table may seem like a complicated process, but it really is pretty simple and is done in just a few minutes. Check the end of this article to use the steps calculators. The starting point will be after the motors are installed on the table and running on the correct axis. They must be properly configured in the configurator and have the X motor set to the X axis, Y motor and slave motor set to Y axis and slave axis set to slave to Y axis, and the Z motor set to Z axis. This is decided based on the orientation of the table. When you have the motors installed on the table and are ready to begin the tuning process, you will need to find the diameter of the pinion gear. You can usually find this on the spec sheet, but if needed, just measure it. Then, multiply this number by 3.1416. Write this number down as your distance per revolution. If diameter = 1″ then: Next, divide how many microsteps your stepper motor gets per rotation by your distance per revolution. If your motor is from CandCNC, it will get 2000 microsteps. Doing this will give you your preliminary steps per inch. If you have belt reduction on your table, multiply your steps per inch by the amount of reduction. If, for example, you have 3 to 1 belt reduction:


Now that you have the first calculation for steps per inch, you need to test the BladeRunner for motor control. Make sure you have all the cables connected.
  1. Motors plugged in
  2. Connected to PWM
  3. Connected to 4 port hub
  4. Hub is connected to computer
  5. BladeRunner is connected to computer
  6. BladeRunner is plugged into power.
Load CommandCNC configurator and input the steps per inch that you have obtained in the motor section of your configuration and save and exit. If you are tuning an axis and it’s slave, input the same steps per inch into both. spi Power on the BladeRunner and the motors then load CommandCNC. Hit the “Reset” button. Jog your motors around to make sure they move the right direction based on the DRO. Movement away from x0, y0, and z0 should cause the respective DRO to increase. For the next steps in motor calibration we will be using the MDI screen to enter a motion command and check that the axis moves in the right direction and the proper distance. The MDI is a section to allow you to type in direct g-code commands to make the machine make specific moves. You don’t need to have a deep knowledge of g-code to use it for testing. mdi G-code commands are not case sensitive but be sure to use zero’s and not “O’s” for the numbers.

Make sure your machine is in e-stop before continuing. You will be working with the gantry and can get seriously injured.

On your plasma table, remove the torch and either mount a laser or a sharp pointed tool in its place. Move this to a point that you can mark as a reference point for measuring. Mark the spot as precisely as possible. Back in CommandCNC in the MDI window, type in a distance to send that axis out using g-code. Here is an example: G1 Y30.0 F80 -G1 is a command that means to move in a straight line -Y is the axis we are working on -F is the feedrate we will be using Measure the actual distance traveled with a tape measure from 0 to the point where it stopped and write down the distance to as close a decimal as you can.

Before you make any changes, move the axis back to the start point in the MDI window by using the following code: G00 Y0.000 (or whatever axis you are working on). It will not go back to the same point after you change the steps per inch.

Divide the commanded distance traveled by the actual distance traveled then multiply the answer by the steps per inch. Close out CommandCNC and open the configurator. Input the new steps per inch and repeat the test. Measure again and fine tune the steps per inch until the actual and commanded distances are eyeball equal. Do this on all axes. For the slaved axes, use the same steps per inch for both motors. steps per inch