Tapping control system

A tapping control system for a machine capable of tapping a screw with a tap or cutting with a cutting tool using, as a principal-axis motor, a digital spindle motor controlled by means of a digital control circuit, the system comprising,

• an interpolating circuit for distributing pulses individually to said digital control circuit and the servocircuit to effect linear interpolation in accordance with the pitch value of the screw to be worked,
• a pulse coder responsive to rotation of the digital spindle motor for outputting a feedback signal indicative of a rotational speed of the spindle motor,
• position control means for delivering a speed command to said digital control circuit in accordance with the distributed pulse from the interpolating circuit and the feedback signal outputted from the pulse coder to effect feedback control of the rotational position of said spindle motor;
• and
• switching means for switching the system from an open control position over to a feedback control position;
• said switching means switching to the feedback control position during tapping, said interpolating circuit distributing pulses individually to said digital control circuit and said servo-circuit for linear interpolation in accordance with the pitch value a screw to be worked, wherein said spindle motor and said servomotor are driven in synchronism with each other.

A control system for a multi-function machine tool having a digital spindle motor for tool rotation and a servomotor for tool feed, comprising:

• a digital control circuit, coupled to the digital spindle motor, or controlling the digital spindle motor;
• a servo-circuit, coupled to the servomotor, for controlling the servomotor,
• a control unit, coupled to the digital control circuit and the servo-circuit, for outputting a speed command, the control unit including an interpolating circuit for outputting a linearly interpolated pulse distribution individually to the digital control circuit and to the servo-circuit based on predetermined speed commands for the digital spindle motor and the servomotor fed to the interpolating circuit and correlating to a preselected pitch value,
• a pulse coder, coupled to the digital spindle motor and being responsive to rotation of the digital spindle motor, for outputting a feedback signal indicative of a rotational speed of the spindle motor,
• position control means responsive to the linearly interpolated pulse distribution supplied by the interpolating circuit and the feedback signal supplied by the pulse coder, for outputting a speed command to said digital control circuit based on a difference between the linearly interpolated pulse distribution and the feedback signal,
• speed control means responsive to the speed command outputted from either the control unit or the position control means, and the feedback signal outputted from the pulse code, for outputting a torque command for the digital spindle motor based on a difference between either of the speed commands and the feedback signal, and
• switch means for switching the system from an open control position over to a feedback control position;
• said switching means switching to the feedback control position during tapping, said interpolating circuit distributing pulses individually to said digital control circuit and said servocircuit for linear interpolation in accordance with the pitch value a screw to be worked, wherein said spindle motor and said servomotor are driven in synchronism with each other.