Abnormality diagnosis device for machine tool, and abnormality diagnosis method

Patent metadata

Field	Value
Publication number	US-10105807-B2
Application number	US-201414761991-A
Country	US
Kind code	B2
Filing date	Mar 5, 2014
Priority date	Mar 7, 2013
Publication date	Oct 23, 2018
Grant date	Oct 23, 2018

Abstract

Provided is an abnormality diagnosis device for a machine tool, and an abnormality diagnosis method, whereby it is possible to diagnose the degree of damage to a spindle system due to a collision. An abnormality diagnosis device (40) for a machine tool (1) has: a displacement sensor (36) for detecting the amount of displacement of a spindle bearing (30); an acceleration sensor (38) for detecting the acceleration of a ram (28); a collision determination unit (46) for determining whether the ram or a spindle (32) has collided with a work piece, on the basis of at least the amount of displacement of the spindle bearing detected by the displacement sensor or the acceleration of the ram detected by the acceleration sensor; and a damage determination unit (50) for determining the degree of damage to the spindle bearing on the basis of at least the amount of displacement of the spindle bearing, the acceleration of the ram, or a frequency characteristic of vibration of the ram due to rotation of the spindle obtained from the acceleration of the ram, when the collision determination unit determines that the ram or the spindle has collided with the work piece.

First claim

The invention claimed is:

1. An abnormality diagnosis device for a machine tool in which a tool for machining a work piece is attached to a spindle, the spindle is supported by a bearing, and the bearing is supported by a ram, and the ram is supported by a saddle, comprising:
a displacement sensor configured to detect an amount of displacement of the bearing;
an acceleration sensor configured to detect an acceleration of the ram;
a first data processor configured to determine whether the ram or the spindle collides with the work piece on the basis of at least the amount of displacement of the bearing detected by the displacement sensor or the acceleration of the ram detected by the acceleration sensor; and
a second data processor configured to determine a degree of damage to the bearing on the basis of a base frequency, a high-harmonic frequency and peak values of the base frequency and the high-harmonic frequency of a vibration of the ram due to a rotation of the spindle obtained from the acceleration of the ram when the first data processor determines that the ram or the spindle collides with the work piece; and
a third data processor configured to estimate an amount of displacement of a tip of the ram,
wherein the second data processor determines that the ram and the saddle are damaged when the amount of displacement of the tip of the ram estimated by the third data processor exceeds an assumed maximum amount of displacement of the tip under the condition that the ram and the saddle are not damaged, and
wherein the assumed maximum amount of displacement is predetermined such that it decreases as an protrusion amount of the ram from the saddle increases.

2. The abnormality diagnosis device for a machine tool according to claim 1 ,
wherein the machine tool includes a moving body which moves in a direction orthogonal to an axial direction of the spindle, and a position detector is configured to detect a position of the moving body, and
wherein the third data processor estimates the amount of displacement of the tip of the ram on the basis of a positional change of the moving body detected by the position detector.

3. An abnormality diagnosis method for a machine tool in which a tool for machining a work piece is attached to a spindle, the spindle is supported by a bearing, and the bearing is supported by a ram, and the ram is supported by a saddle, comprising:
a step of detecting an amount of displacement of the bearing;
a step of detecting an acceleration of the ram;
a step of determining whether the ram or the spindle collides with the work piece on the basis of at least the detected amount of displacement of the bearing or the detected acceleration of the ram;
a step of determining a degree of damage to the bearing, on the basis of a base frequency, a high-harmonic frequency and peak values of the base frequency and the high-harmonic frequency of a vibration of the ram due to a rotation of the spindle obtained from the acceleration of the ram, when it is determined that the ram or the spindle collides with the work piece;
a step of estimating an amount of displacement of a tip of the ram; and
a step of determining that the ram and the saddle are damaged when the amount of displacement of the tip of the ram exceeds an assumed maximum amount of displacement of the tip under the condition that the ram and the saddle are not damaged,
wherein the assumed maximum amount of displacement is predetermined such that it decreases as an protrusion amount of the ram from the saddle increases.

Assignees

• Mitsubishi Heavy Ind Machine Tool Co Ltd

Inventors

• Yamamoto Hideaki
• Iwata Koji

Classifications

• B23Q17/2208

  Detection or prevention of collisions · CPC title

• G05B2219/42328

  Detect bearing, clamp wear · CPC title

• G05B2219/37388

  Acceleration or deceleration, inertial measurement · CPC title

• G05B19/4061

  Avoiding collision or forbidden zones · CPC title

• G05B2219/50186

  Diagnostic of spindle bearing · CPC title