Tapping control system

• US 4,985,841 A
• Filed: 11/23/1987
• Issued: 01/15/1991
• Est. Priority Date: 03/25/1986
• Status: Expired due to Term

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Iwagaya, Takashi
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/138,842
• Time in Patent Office: 1,149 Days
• Field of Search: 10/129 R, 10/139 R, 364/474.3, 364/474.31, 364/474.33, 408/3, 408/9, 408/10, 408/11, 408/12, 408/13, 408/17, 408/140, 408/142, 409/67, 409/68, 409/69, 409/70
• US Class Current: 700/191
• CPC Class Codes: B23G 1/16 in holes of workpieces by taps B23G1/26, B23G1/32, B23G1/36 take precedence
• CPC Class Codes: G05B 19/186 Generation of screw- or gearlike surfaces
• CPC Class Codes: G05B 2219/41255 Mode switch, select independent or dependent control of axis
• CPC Class Codes: G05B 2219/45216 Tapping
• CPC Class Codes: G05B 2219/50216 Synchronize speed and position of several axis, spindles
• CPC Class Codes: G05B 2219/50226 Synchronize feed and spindle speed in forward and reverse feed
• CPC Class Codes: Y10T 408/165 to control Tool rotation
• CPC Class Codes: Y10T 408/172 Responsive to Tool
• CPC Class Codes: Y10T 408/175 to control relative positioning of Tool and work
• CPC Class Codes: Y10T 408/23 including means to cause Tool to progressively vibrate toward work

Abstract

Disclosed is a tapping control system capable of performing tapping work with high accuracy and reliability in a manner such that rotation of a tap by means of a digital spindle motor (1) is synchronized with axial drive of the tap by means of a servomotor (2).

A digital control circuit (5), used to drive the spindle motor, is supplied with a speed command from position control means (4). The speed command is based on a distributed pulse from an interpolating circuit (3a) for linear interpolation in accordance with the pitch value of a screw to be worked, and a feedback signal indicative of the rotational position of the spindle motor. Also, a servo-circuit (12) for the servomotor is supplied with a distributed pulse from the interpolating circuit. Thus, the two motors are driven synchronously.

According to an aspect of the present invention, the tapping work is performed in a fixed cycle such that forward and reverse rotations of the two motors are repeated to reciprocate the tap.

According to another aspect, switching means (7) is used to intermittently deliver the distributed pulses and the feedback signal, for selective tapping operation.

Claims

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

an interpolating circuit for distributing pulses individually to said digital control circuit and the servo-circuit 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 pulses 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 distributing pulses individually to said digital control circuit and a servo-circuit for a servomotor for axially moving a tool, wherein said spindle motor and said servomotor are driven in synchronism with each other, said spindle motor and said servomotor being forwardly rotatable in a tapping mode for a predetermined amount of tapping work, and said spindle motor and said servomotor being reversely rotatable to retract the tap through a distance less than said predetermined amount of forward rotation, said forward and reverse rotatable motion being repeated alternatingly in a fixed cycle.

2. A tapping control system according to claim 1, wherein said digital spindle motor and said servomotor are driven with a predetermined rotational speed ratio corresponding to said pitch value of said screw.

3. A tapping control system according to claim 2, further comprising:

a tool holder for nontelescopically mounting the tap.

4. A tapping control system according to claim 1 further comprising:

a tool holder for nontelescopically mounting the tap.

5. 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.

6. A tapping control system according to claim 4, wherein said digital spindle motor and said servomotor are driven with a predetermined rotational speed ratio corresponding to said pitch value of said screw.

7. A tapping control system according to claim 6, wherein said switching means is in a switching position corresponding to said open control position at the time of deep cutting, thereby preventing said distributed pulses and said feedback signal from being applied to said position control means.

8. A tapping control system according to claim 5, wherein said digital spindle motor rotates at high speed for deep cutting when the system is switched to the open control mode.

9. A tapping control system according to claim 8, wherein said switching means is in a switching position corresponding to said open control position at the time of deep cutting, thereby preventing said distributed pulses and said feedback signal from being applied to said position control means.

10. A tapping control system according to claim 5, further comprising:

a tool holder for nontelescopically mounting the tap at the time of said tapping work, and the deep cutting tool at the time of deep cutting.

11. A tapping control system according to claim 10, wherein said switching means is in a switching position corresponding to said open control position at the time of deep cutting, thereby preventing said distributed pulses and said feedback signal from being applied to said position control means.

12. A tapping control system according to claim 5, wherein said switching means is in a switching position corresponding to said open control position at the time of deep cutting, thereby preventing said distributed pulses and said feedback signal from being applied to said position control means.

13. A tapping control system according to claim 5, wherein said digital control circuit includes a speed control section, which receives a speed command from either said position control means or a numeric control unit which includes said interpolating circuit, depending on the selected mode, a current control section coupled to said speed control section, and a pulse width modulation control section for delivering a torque command to the spindle motor.

14. A tapping control system according to claim 5, further comprising a numeric control unit which includes the spindle motor interpolating circuit and the servomotor interpolating circuit, and wherein the numeric control unit delivers a speed command to the digital control circuit when the system is switched to the open control mode, and the spindle motor interpolating circuit delivers a pulse distribution to the position control means which then derives a speed command and delivers it to the digital control circuit when the system is switched to the feedback control position.

15. 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.