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Question #: 2336

Question: Hello, I have a Greenbull almost ready to work and I am trying to calibrate the machine, what are the specifics values as steps per units (SPU), ….. to load in planet cnc software to do the best accuracy as possible. My currents values are standar: Steps/unit 200.000, int speed 0.00, Maximun speed 0.00 and Acceleration 15.000 for each axes. Thank for your help.

Current Solution

The greenBull uses roller chain for the X and Y axes. The drive sprockets have 14 teeth and the pitch (from crown to crown, or pin to pin measurement) is 1/4" (0.25 inches). You will need the pitch circumference which is: 14 * .25 = 3.5 inches. We need to find the steps per inch (steps/inch). We now have the inches for one full revolution. Now we need to find the number of steps for one full rotation of the motor. For these sprockets, I find that 16 microsteps is best. Make sure that the drivers for the X and Y axes are set to 1/16 microstepping. The motor have 200 steps per rotation, so the total steps with 1/16 microsteps is 200 * 16 = 3200. So the steps/inch is 3200 step / 3.5 inches = 914.286.

The velocity should be around 400-1000. Test various values for velocity and make sure that no stalling happens. Start with a very low acceleration and determine it's top velocity. When the top velocity is found, reduce the velocity to give you a good factor of safety. Then increase the acceleration until it stall at a low velocity and then reduce the acceleration to give you a good factor of safety for acceleration.

Do the same thing for the z-axis. The lead screw pitch circumference is 0.5 inches (2 turns per inch or 5starts/10tpi).


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