Machine tool control
First Claim
1. A machine tool control system for machining a surface of a workpiece rotating about an axis to a predetermined profile changing in two mutually perpendicular dimensions, comprising a workpiece drive for rotating the workpiece at a speed of at least 3000 RPM, angular position sensing means for producing successive angular position signals representing respective angular positions of the workpiece, a tool for machining the workpiece and movable in a first one of said two mutually perpendicular dimensions towards and away from the workpiece and movable in the second one of said two mutually perpendicular dimensions across the surface of the workpiece, first tool drive means for moving the tool in the first dimension, second tool drive means for moving the tool in the second dimension, second dimension position sensing means for producing a succession of second dimension position signals representing respective positions of tool in the second dimension, digital data processing means having a portion for producing from input digital data fed thereto a succession of digital output signals respectively defining successive positions of the tool in the first dimension, each such digital output signal corresponding to a respective one of the angular position signals and a simultaneously existing one of the second dimension position signals, and the successively defined positions of the tool in the first dimension being the tool positions in said first dimension required for producing the said predetermined profile on the workpiece, output means responsive to the digital output signals for producing tool drive signals, and means feeding the tool drive signals to the first tool drive means for moving the tool correspondingly in said first dimension, the tool drive signals changing discretely in value, and the successive angular position signals occurring at a frequency which is between 20 and 50 times the bandwidth of the tool drive means.
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Accused Products
Abstract
A system for machining a piston blank to a predetermined profile includes means for rotating a blank at a predetermined speed and means for moving a tool axially with reference to the blank. Digital processing means receives input data defining the required profile (or part only of the profile if the profile is symmetrical). In response to this data, to digital information on a channel corresponding to the instantaneous angular position of the blank, and to digital data on another channel corresponding to the instantaneous axial position of the tool, the processor outputs digital data defining the required position of the tool in the direction perpendicular to the surface of the blank in order to produce the required profile. The actuator control processor outputs a corresponding digital signal which, via a digital-to-analog converter, drives a tool actuator so as to position the tool correspondingly. The processor also receives digital tool position feedback signals on a channel and an adaptive control loop senses and compensates for changes in the transfer function between the input of the processor and the tool. Sensors sense dimension distortion and temperature changes, respectively, of the blank and produce corresponding compensating changes in the digial output signals.
28 Citations
23 Claims
- 1. A machine tool control system for machining a surface of a workpiece rotating about an axis to a predetermined profile changing in two mutually perpendicular dimensions, comprising a workpiece drive for rotating the workpiece at a speed of at least 3000 RPM, angular position sensing means for producing successive angular position signals representing respective angular positions of the workpiece, a tool for machining the workpiece and movable in a first one of said two mutually perpendicular dimensions towards and away from the workpiece and movable in the second one of said two mutually perpendicular dimensions across the surface of the workpiece, first tool drive means for moving the tool in the first dimension, second tool drive means for moving the tool in the second dimension, second dimension position sensing means for producing a succession of second dimension position signals representing respective positions of tool in the second dimension, digital data processing means having a portion for producing from input digital data fed thereto a succession of digital output signals respectively defining successive positions of the tool in the first dimension, each such digital output signal corresponding to a respective one of the angular position signals and a simultaneously existing one of the second dimension position signals, and the successively defined positions of the tool in the first dimension being the tool positions in said first dimension required for producing the said predetermined profile on the workpiece, output means responsive to the digital output signals for producing tool drive signals, and means feeding the tool drive signals to the first tool drive means for moving the tool correspondingly in said first dimension, the tool drive signals changing discretely in value, and the successive angular position signals occurring at a frequency which is between 20 and 50 times the bandwidth of the tool drive means.
Specification