This looks odd:units = scale.get_units(), 10;
PWM doesn't control the force consistently I'm afraid.You need to measure the current through the motor, that is linearly related to the torque of the motor.You can then use a PID loop to set the torque by adjusting the PWM in a feedback loop.However if the motor is stalled (stationary), then the relationship between PWM and force will be moreconsistent. It will change as the motor warms up though.
can you give some details about your motor driver module?
My motor driver is from Cytron Technologies. MD13S. Rare right?
Is there a tutorial? cause i can't seem to find any related to it.