Error identification method of machine tool

Patent metadata

Field	Value
Publication number	US-9910422-B2
Application number	US-201615011997-A
Country	US
Kind code	B2
Filing date	Feb 1, 2016
Priority date	Feb 23, 2015
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

An error identification method of a machine tool includes an initial position measurement step of indexing a main spindle head rotation axis to an initial angle to measure an initial position of a measured jig, a table reference angle calculation step of calculating a reference angle of the table, a reference position measurement step of indexing the table rotation axis to the reference angle and indexing the main spindle head rotation axis to the initial angle, a relative position measurement step of respectively indexing the table rotation axis and the main spindle head rotation axis to a plurality of predetermined angles, an arc approximation step of approximating the plurality of measured position values into an arc, and an error calculation step of calculating an error of a center position of the rotation axis, a tilt error of the rotation axis, or a tilt error of the translational axis.

First claim

What is claimed is:

1. An error identification method for identifying a geometric error of axes in a machine tool including a table configured to hold a workpiece, one or more main spindle head configured to mount a tool, three or more axes of translational axes, one or more axis of a table rotation axis configured to perform a rotational motion on the table, and one or more axis of a main spindle head rotation axis configured to perform a rotational motion on the main spindle head, the error identification method comprising;
a mounting step of mounting one of a measured jig and a position measurement sensor to one of the main spindle head and the table, or mounting another of the measured jig and the position measurement sensor to another of the main spindle head and the table, an initial position measurement step of indexing the main spindle head rotation axis to an initial angle to measure an initial position of the measured jig using the position measurement sensor;
a table reference angle calculation step of calculating a reference angle from an angle of the table rotation axis in the initial position measurement step;
a reference position measurement step of indexing the table rotation axis to the reference angle and indexes the main spindle head rotation axis to the initial angle to measure a reference position of the measured jig by the position measurement sensor;
a relative position measurement step of indexing the table rotation axis to a plurality of predetermined angles based on the reference angle of the table rotation axis and indexing the main spindle head rotation axis to a plurality of predetermined angles to measure each position of the measured jig by the position measurement sensor;
an arc approximation step of approximating the plurality of measured position values measured at the relative position measurement step into an arc; and
an error calculation step of calculating an error of a center position of the rotation axis, a tilt error of the rotation axis, or a tilt error of the translational axis from the arc approximated in the arc approximation step.

2. The error identification method of the machine tool according to claim 1 , wherein
in the relative position measurement step, when combinations of the plurality of predetermined angles of the table rotation axis and the plurality of predetermined angles of the main spindle head rotation axis include a combination of the reference angle of the table rotation axis and the initial angle of the main spindle head rotation axis, the reference position measurement step is skipped, and
in the relative position measurement step, the table rotation axis is indexed to the reference angle, and the measured position value which is measured by indexing the main spindle head rotation axis to the initial angle is defined as a measured value at the reference position.

3. The error identification method of the machine tool according to claim 1 , wherein
in the arc approximation step, a difference value between a command position of the measured jig and a measured position value of the measured jig is calculated using a predetermined angle of each of the rotation axes in the relative position measurement step, the command position being performed by coordinates transformation of the measured value at the reference position, and
a plurality of the difference values are approximated into an arc.

4. The error identification method of the machine tool according to claim 2 , wherein
in the arc approximation step, a difference value between a command position of the measured jig and a measured position value of the measured jig is calculated using a predetermined angle of each of the rotation axes in the relative position measurement step, the command position being performed by coordinates transformation of the measured value at the reference position, and
a plurality of the difference values are approximated into an arc.

Assignees

• Okuma Machinery Works Ltd

Inventors

• Matsushita Tetsuya

Classifications

• G05B2219/49193

  Orthogonality of axis, deviation from 90-degree correction · CPC title

• G05B19/404 Primary

  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 title