Method of operating a stepper motor in a dental tool machine

A method of operating a stepper motor for use in a dental tool machine for removing material from a dental blank, the method comprising:

• a step of adapting without use of any rotary encoder-based regulation torque reserves of the stepper motor at operating points to net load moments (M_net) about the rotational axis of the stepper motor respectively, wherein the adapting step comprises:
• a first step (S1) of predicting, through simulation, the net load moments (M_net) beforehand;
• a second step (S2) of predicting, through simulation, the supply current (I_tr) to be supplied to the stepper motor for setting up the torque reserves that correspond to the predicted net load moments (M_net) respectively;
• and further comprising:
• a step (S3) of operating the stepper motor based on the predicted supply current (I_tr), wherein the net load moments (M_net) corresponds to a superposition of the load moments (M_df, M_mf) respectively due to drive forces arising through a drive train of the stepper motor and the machining forces arising through the material removal from the dental blank which are respectively predicted in the first predicting step based on a drive train simulation (S_dt) and a material removal simulation (S_mr) of the dynamic acceleration/deceleration along a drive train trajectory corresponding to the movement of the dental tool, and the dental tool trajectory.