US 4,873,793 A · Numerically controlled machine tool

Abstract

A numerically controlled machine tool for machining a non-circular workpiece according to profile data. The servomotor drive unit of the machine tool includes a frequency voltage converter which outputs a velocity compensation signal proportional to the frequency of position command pulses in the servomotor drive units. A position error signal is modulated by the velocity compensation signal. The numerical controller of the machine tool can measure the position error and phase error, and can compensate for these errors. The numerical controller operates according to ideal profile data and measures the actual position change of a tool slide corresponding to the angle position change of a main spindle. Then, the numerical controller calculates the position error and phase error depending on the actual position change and ideal profile data, and produces execution profile data which are compensated for position error. During machining operation, the numerical controller offsets the rear out position of the execution profile data by the calculated phase error so as to eliminate the phase error.

Claims9

Dependent claims

A numerically controlled machine tool, which has a tool feed axis servomotor, for grinding a non-circular workpiece according to profile data which define a profile generating movement of a tool along the final shape of non-circular workpiece, said numerically controlled machine tool comprising:

a numerical controller for outputting a command position signal according to execution profile data calculated from ideal profile data corresponding to an ideal final shape of said workpiece and compensated for position error due to a follow delay characteristic of said numerically controlled machine tool;
position detecting means for detecting the position of the tool feed axis servomotor, and for outputting a position feedback signal;
a follow error detecting circuit for inputting said command signal position and said position feedback signal, and for detecting a position follow error of said servomotor so as to produce an error signal corresponding to said detected position error;
a velocity compensation signal generating circuit for generating a compensation signal corresponding to a commanded velocity of said servomotor;
an adding circuit for adding said compensation signal to said signal error;
and
an amplifier for driving said servomotor according to the output signal of said adding circuit.

4 more elements

A numerically controlled machine tool for grinding non-circular workpiece by controlling numerically the main spindle rotation and tool feed according to profile data which defines the profile generating movement of a tool along a final shape of said workpiece, said numerically controlled machine tool comprising:

ideal profile data memory means for storing ideal profile data which are calculated from an ideal final shape of said workpiece;
control means for starting profile generating movement of the numerically controlled machine tool according to the ideal profile data;
measuring means for detecting an instantaneous position of a main spindle and a tool slide during the profile generating movement, and for producing measured profile data which indicate actual position change of the tool slide corresponding to angle position changes of the main spindle;
and
phase error calculation means for calculating phase error by comparing the measured profile data and the ideal profile data;
offset means for offsetting ahead a read out position of said profile data by said calculated phase error from a theoretical read out position of said profile data during actual grinding operation.

3 more elements

Dependencies are inferred from the claim text.

Numerically controlled machine tool

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Numerically controlled machine tool

Life of this patent

Abstract

Claims9