EP-4741959-A1 - MACHINE TOOL

EP4741959A1EP 4741959 A1EP4741959 A1EP 4741959A1EP-4741959-A1

Abstract

There is provided a machine tool that can precisely determine a gripping failure. An NC lathe that includes a first spindle including a collet chuck that grips a material of a bar shape, and machines the material gripped by the collet chuck and manufactures a plurality of products having an identical shape by repeatedly executing a machining operation includes determination means for executing determination on a gripping failure of the first spindle based on at least one information of machining timing information and gripping force history information, and current gripping force information, the machining timing information indicating at which timing the machining operation is performed, the gripping force history information being information of a gripping force at a time when the collet chuck grips the material during the machining operations up to the previous machining operation, and the current gripping force information being information of a gripping force at a time when the collet chuck grips the material during a current machining operation.

Inventors

KAGAWA, Yuki
SHIGAMA, KOICHIRO
DENO, MASATOSHI
SAITO, HIROKI

Assignees

Star Micronics Co., Ltd.

Dates

Publication Date: 20260513
Application Date: 20251027

Claims (8)

A machine tool that comprises a spindle including a gripping unit that grips a material of a bar shape, and machines the material gripped by the gripping unit and manufactures a plurality of products having an identical shape by repeatedly executing a machining operation, the machine tool including determination means for executing determination on a gripping failure of the spindle based on at least one information of machining timing information and gripping force history information, and current gripping force information, the machining timing information indicating at which timing the machining operation is performed, the gripping force history information being information of a gripping force at a time when the gripping unit grips the material during the machining operations up to the previous machining operation, and the current gripping force information being information of a gripping force at a time when the gripping unit grips the material during a current machining operation.
the machine tool according to claim 1, wherein the determination means determines that, when the machining timing information is information indicating the first machining operation and when a gripping force of the current gripping force information is outside of a predetermined range, a gripping failure due to a setup mistake is occurring.
The machine tool according to claim 1, wherein the machine tool is connected with a bar feeder in which a plurality of the materials is stored, and that sequentially supplies the stored materials to the spindle, and the determination means determines that, when the machining timing information is information indicating the machining operation immediately after the bar feeder newly supplies the material to the spindle and when the gripping force of the current gripping force information is outside of a predetermined range, a gripping failure due to a material diameter failure of the material supplied by the bar feeder is occurring.
The machine tool according to claim 1, wherein the determination means determines that, when a change amount of the gripping force of the current gripping force information with respect to the gripping force of the gripping force history information exceeds the threshold, the gripping failure is occurring.
The machine tool according to claim 4, wherein the determination means classifies a type of a gripping failure based on whether the gripping force of the current gripping force information with respect to the gripping force of the gripping force history information has increased or decreased when the change amount exceeds the threshold.
The machine tool according to claim 4, further comprising a control apparatus that, when the change amount exceeds the threshold and when the gripping force of the current gripping force information with respect to the gripping force of the gripping force history information increases, executes a removal operation of removing a foreign material caught in the gripping unit.
The machine tool according to claim 1, wherein the determination means classifies a type of the gripping failure based on a combination of whether or not the gripping force of the current gripping force information is outside of a predetermined range and whether or not a change amount of the gripping force of the current gripping force information with respect to the gripping force of the gripping force history information exceeds a threshold.
The machine tool according to claim 1, further comprising: a tool post to which a tool that machines the material is attached and that moves together with the tool; storage means for storing a movement correction value for correcting a designated movement position designated by a machining program; and correction value rewriting means for rewriting the movement correction value stored in the storage means, wherein the correction value rewriting means rewrites the movement correction value stored in the storage means when the determination means determines that the gripping force of the current gripping force information is outside of a predetermined range and a change amount of the gripping force of the current gripping force information with respect to the gripping force of the gripping force history information does not exceed a threshold.

Description

CROSS-REFERENCES The application claims priority of Japanese Patent Application No. 2024-197633 filed on November 12, 2024. The contents of this application are incorporated herein by reference in their entirety. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine tool that machines a material gripped by a spindle. 2. Description of the Related Art There are known machine tools that each machine a bar-shaped material gripped by a spindle (see, for example, Japanese Patent Application Publication No. 2020-97075). The spindle is rotatably supported by a headstock. The spindle is provided with a gripping unit whose state changes between a gripping state for gripping a workpiece and a release state for releasing grip of a material. Furthermore, there has been also proposed a safety monitoring system that determines a gripping failure of a gripping unit by attaching a sensor to the gripping unit (see, for example, Japanese Patent Application Publication No. 2011-121148). SUMMARY OF THE INVENTION However, the safety monitoring system according to Japanese Patent Application Publication No. 2011-121148 performs abnormality determination based on only an output of the sensor attached to the gripping unit, and has a problem that the safety monitoring system can only make uniform determination and has difficulty in precisely determining the gripping failure of the gripping unit. With the above-described problem in view, an object of the present invention is to provide a machine tool that can precisely determine a gripping failure. A machine tool according to the present invention that solves the above problem is a machine tool that includes a spindle including a gripping unit that grips a material of a bar shape, and machines the material gripped by the gripping unit and manufactures a plurality of products having an identical shape by repeatedly executing a machining operation, and includes determination means for executing determination on a gripping failure of the spindle based on at least one information of machining timing information and gripping force history information, and current gripping force information, the machining timing information indicating at which timing the machining operation is performed, the gripping force history information being information of a gripping force at a time when the gripping unit grips the material during the machining operations up to the previous machining operation, and the current gripping force information being information of a gripping force at a time when the gripping unit grips the material during a current machining operation. According to this machine tool, the determination means executes determination on the gripping failure based on at least one information of the machining timing information and the gripping force history information, and the current gripping force information, so that it is possible to precisely determine a gripping failure. Here, this machine tool may execute a plurality of cycles of the machining operation whose one cycle is to manufacture one product. The determination means may classify a type of the gripping failure to determine. Furthermore, the determination means may classify a gripping failure per cause to determine. In this machine tool, the determination means may determine that, when the machining timing information is information indicating the first machining operation and when a gripping force of the current gripping force information is outside of a predetermined range, a gripping failure due to a setup mistake is occurring. According to this machine tool, it is specified that the gripping failure is caused by the setup mistake, so that it is easy to deal with the failure. This machine tool may be connected with a bar feeder in which a plurality of the materials are stored, and that sequentially supplies the stored materials to the spindle, and the determination means may determine that, when the machining timing information is information indicating the machining operation immediately after the bar feeder newly supplies the material to the spindle and when the gripping force of the current gripping force information is outside of a predetermined range, a gripping failure due to a material diameter failure of the material supplied by the bar feeder is occurring. This machine tool specifies that the gripping failure is caused by the material diameter failure, and consequently easily deals with the failure. In this machine tool, the determination means may determine that, when a change amount of the gripping force of the current gripping force information with respect to the gripping force of the gripping force history information exceeds the threshold, the gripping failure is occurring. By so doing, for example, it is possible to determine catch of a small foreign material in the gripping unit as a gripping failure. Furthermore, in this machine tool, the determination means may class