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# Reply To: Z axis speed ?

New Home Forum Software Development Z axis speed ? Reply To: Z axis speed ?

#20963

Ryan
Keymaster

That line is is correct if your are going to 16th stepping.

The next line is for max speed. you’ll need to change the 8.5 to 16 or 17. And the next line is acceleration you might have to play with the 35.

#define DEFAULT_MAX_FEEDRATE {190, 190, 8.5, 25} // (mm/sec) MPCNC
#define DEFAULT_MAX_ACCELERATION {500,500,35,10000} // X, Y, Z, E maximum

Acceleration is linear so it’s mm/second/second. good visual here, http://prusaprinters.org/calculator/, although it doesn’t help visually with a screw. At top speed in 32nd stepping the screw is going 4535.44*8.5=38,551 steps per second on the z axis alone, that is close to the processor max of about 40,000/sec. you can go all the way down to 1/4 stepping and still be okay. Anything less and it gets a little chunky sounding. What this gets into is max speed of a stepper territory. torque starts to drop off at above 60 rpms. So there are 200 full steps per rev. Just doing the math here, probably best to stay below 200fullsteps/sec = in 32nd stepping that would be 200*32=6400. So 3200(16th steps per sec) is keeping the torque at a max. So 16th steps do not help you torque at max speed you are actually going to be running weaker so you will need to accelerate slower.

At 38,551 steps/sec we are running about 360rpm and that is about 57% of full power.