Correction method at time of feed axis reversal

• US 9,588,509 B2
• Filed: 10/26/2011
• Issued: 03/07/2017
• Est. Priority Date: 10/27/2010
• Status: Active Grant

• Current Assignee: Makino Milling Machine Company Limited
• Original Assignee: Makino Milling Machine Company Limited
• Inventors: Kawana, Akira, Mori, Norio, Oda, Mitsunari
• Primary Examiner(s): Lo, Kenneth M
• Assistant Examiner(s): Huntley, Michael J
• Application Number:
  US13/823,797
• Publication Number:
  US 20130173046A1
• Time in Patent Office: 1,959 Days
• Field of Search: 700/186
• US Class Current: 1/1
• CPC Class Codes: G05B 19/182 characterised by the machine tool function, e.g. thread cutting, cam making, tool direction control G05B19/21 - G05B19/40 take precedence
• CPC Class Codes: G05B 19/404 characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia G05B19/19, G05B19/41 take precedence
• CPC Class Codes: G05B 2219/41078 Backlash acceleration compensation when inversing, reversing direction
• CPC Class Codes: G05B 2219/41084 Compensation speed axis with changing, reversing direction, quadrant circle
• CPC Class Codes: G05B 2219/41115 Compensation periodical disturbance, like chatter, non-circular workpiece

Abstract

A stick motion correction method which corrects stick motion which occurs at time of reversal of a feed axis of a numerical control machine tool stores a position command to be commanded to a servo motor from an NC program of a numerical control machine tool for each predetermined control period from a current position command to a later position command, calculates a reversal correction command based on the stored position commands, calculates an advancement time for advancing timing of addition of the reversal correction command to a speed or torque command of the motor from reversal timing of the servo motor, based on information obtained from operation of the motor and adds the reversal correction command to the speed or torque command of the servo motor to precisely correct stick motion at a timing advanced from the reversal timing of the servo motor by an exact time.

Claims

1. A stick motion correction method which corrects stick motion which occurs at the time of reversal of a movement direction of a feed axis of a numerical control machine tool, which stick motion correction method comprising steps of:

storing a plurality of position commands to be commanded to a servo motor of the feed axis in a storage unit from an NC program of said numerical control machine tool for each of a plurality of predetermined control periods from a current position command to a latest position command of said plurality of position commands;

calculating reversal correction commands based on the stored plurality of position commands;

finding in advance a relationship between advancement time values and acceleration values each of which is found from at least three of said plurality of position commands which are stored in said storage unit,

wherein the advancement time values can be used for advancing a timing of addition of said reversal correction command to a speed command or the torque command of said servo motor from the reversal timing of said servo motor;

determining an advancement time using said relationship and corresponding to an acceleration value which is found from at least three of said plurality of position commands which are stored in said storage unit,

at the time of reversal of the movement direction, if the reversal of the movement direction is found from values of the position commands, which are stored in the storage unit, using said relationship, when the feed axis moves actually; and

finding a timing advanced from the reversal timing of said servo motor by exactly said advancement time based on the number of control periods and the columns of the storage unit and adding said reversal correction command at the timing to the speed command or the torque command of said servo motor to correct stick motion.