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Peak force test

A project log for MultiBot CNC v2

A low cost 3D printed CNC that can be built with minimal tools yet is capable of great things.

david-tuckerDavid Tucker 12/03/2020 at 02:260 Comments

I was curious to know the max force my cnc could produce so I came up with this test rig. Using the DRV8825 driver at 2 amps (vref 1v, 0.31Nm measured torque) and a 8mm pitch lead screw, I’m measuring a peak force of 12kg. My stepped motor claims a 0.59Nm peak torque, in theory that could yield 23kg of force, however I don’t have drivers that can sustain the current needed to produce that torque.

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After my last test someone asked me about micro stepping. Since I still had the rig setup I ran my tests again at full, 1/4 and 1/16 steps.
At full steps the rig measured 12kg of force but was not running smoothly, the motor tended to overshoot on each step.

At 1/4 step I measured 13kg of force and the steps were much smoother.

At 1/16 step I measured 12kg again.

From these results I would not turn off micro-stepping but I would set them as low as possible to achieve the smoothness you need.

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