MACHINE TOOL HAVING INSPECTION FUNCTION FOR DETERIORATED STATE OF SPINDLE

• US 20160297043A1
• Filed: 04/12/2016
• Published: 10/13/2016
• Est. Priority Date: 04/13/2015
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: INAGUCHI, Yuuzou
• Granted Patent: US 10,124,457 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B23Q 1/70 Stationary or movable members for carrying working-spindles for attachment of tools or work B23Q1/01 takes precedence; designed to be moved by using particular mechanisms B23Q1/44
• CPC Class Codes: B23Q 17/008 Life management for parts of the machine tool life management B23Q17/0995
• CPC Class Codes: B23Q 3/157 of rotary tools in combination with non-rotary tools B23Q3/15506, B23Q3/15513
• CPC Class Codes: G08B 21/187 Machine fault alarms
• CPC Class Codes: G08B 25/08 using communication transmission lines G08B13/19658, G08B21/0286, G08B25/016 take precedence

Abstract

In order to make it possible to inspect a deteriorated state of a spindle incorporated in a machine tool without disassembling the machine tool, a command for speed V0 is output to the spindle and, when the rotating speed of the spindle reaches V0, power of a spindle motor is interrupted and a timer is started. The spindle continues to rotate with inertia while decelerating. Time T clocked by the timer when the spindle speed decreases to zero is read. When time T is outside a range between the upper and lower limits, the spindle is in the deteriorated state, and an alarm is output. When time T is not greater than the lower limit, the spindle and a bearing of the spindle are deteriorated and friction resistance increases. When time T is larger than the upper limit, oil holding force of grease of the bearing is deteriorated.

Claims

1. A machine tool having an inspection function for a deteriorated state of a spindle, the machine tool including a spindle configured to hold a tool that machines work and rotatably supported by a bearing, a motor configured to drive the spindle, and an encoder configured to measure a rotation angle position of the spindle or the motor,

the machine tool comprising:

speed calculating unit for calculating rotating speed of the spindle or the motor from an output of the encoder;

unit for rotating the spindle or the motor at predetermined speed and thereafter interrupting power of the motor to rotate the spindle with inertia;

clocking unit for measuring, after the power of the motor is interrupted, an inertial rotation time until the rotating speed calculated by the speed calculating unit reaches set target speed;

determining unit for setting the time measured by the clocking unit as a value to be compared with a threshold and determining whether the value is equal to or smaller than a threshold set in advance; and

alarm output unit for outputting an alarm when the determining unit determines that the value is larger than the threshold.

2. The machine tool having an inspection function for a deteriorated state of a spindle according to claim 1, further comprising acceleration calculating unit for calculating acceleration by dividing, by the time clocked by the clocking unit, a difference between the predetermined speed and the set target speed at the time of the interruption of the power of the motor, wherein

the determining unit sets, instead of the time, the acceleration calculated by the acceleration calculating unit as a value to be compared with the threshold, and determines whether the acceleration is equal to or smaller than the threshold set in advance.

3. The machine tool having an inspection function for a deteriorated state of a spindle according to claim 2, further comprising unit for calculating rotation resistance torque from the calculated acceleration and an inertial moment of a rotating body including the spindle, wherein

the determining unit sets, instead of the acceleration, the calculated rotation resistance torque as a value to be compared with the threshold, and determines whether the rotation resistance torque is equal to or smaller than the threshold set in advance.

4. A machine tool having an inspection function for a deteriorated state of a spindle, the machine tool including a spindle configured to hold a tool that machines work and rotatably supported by a bearing, a motor configured to drive the spindle, and an encoder configured to measure a rotation angle position of the spindle or the motor,

the machine tool comprising:

speed calculating unit for calculating rotating speed of the spindle or the motor from an output of the encoder;

unit for rotating the spindle or the motor at predetermined speed and thereafter interrupting power of the motor to rotate the spindle with inertia;

clocking unit for clocking a set predetermined time after the power of the motor is interrupted;

unit for detecting rotating speed calculated by the speed calculating unit when the set predetermined time is clocked by the clocking unit;

unit for calculating a value to be compared with a threshold, on the basis of the predetermined speed at a time when the power of the motor is interrupted, the rotating speed detected when the clocking unit clocks the predetermined time, and the set predetermined time;

determining unit for determining whether the calculated value to be compared with the threshold is equal to or smaller than a threshold set in advance; and

alarm output unit for outputting an alarm when the determining unit determines that the value is larger than the threshold.

5. A machine tool having an inspection function for a deteriorated state of a spindle, the machine tool including a spindle configured to hold a tool that machines work and rotatably supported by a bearing, a motor configured to drive the spindle, and an encoder configured to measure a rotation angle position of the spindle or the motor,

the machine tool comprising:

speed calculating unit for calculating rotating speed of the spindle or the motor from an output of the encoder;

unit for rotating the spindle or the motor at predetermined speed and thereafter interrupting power of the motor to rotate the spindle with inertia;

comparative-value calculating unit for calculating a value to be compared with a threshold, from a measured value of the encoder during inertial rotation of the spindle;

determining unit for determining whether the value calculated by the comparative-value calculating unit is equal to or smaller than a threshold set in advance; and

alarm output unit for outputting an alarm when the determining unit determines that the value is larger than the threshold.

6. The machine tool having an inspection function for a deteriorated state of a spindle according to claim 4, wherein the value to be compared with the threshold is acceleration or rotation resistance torque during spindle deceleration.

7. The machine tool having an inspection function for a deteriorated state of a spindle according to claim 1, wherein a value to be compared with a threshold for a plurality of temperatures near the spindle is calculated and stored in advance as reference data or a function calculated from the data is stored, a correction amount is calculated on the basis of the reference data or the function, and the value to be compared with the threshold is corrected or the threshold is corrected.

8. The machine tool having an inspection function for a deteriorated state of a spindle according to claim 1, further comprising unit for storing an execution enabling condition for the inspection function for the deteriorated state of the spindle in storing unit in advance and, when an inspection command for the deteriorated state of the spindle is given, determining whether the stored execution enabling condition is satisfied, and determining possibility of execution of the inspection of the deteriorated state of the spindle.

9. The machine tool having an inspection function for a deteriorated state of a spindle according to claim 8, further comprising storing unit for storing an operation history of the spindle, wherein

the execution enabling condition is whether the operation history stored in the storing unit satisfies an operation history determined in advance.

10. The machine tool having an inspection function for a deteriorated state of a spindle according to claim 8, further comprising storing unit for storing date and time when an inspection for the deteriorated state of the spindle is executed, wherein

the execution enabling condition is whether an elapsed time from the last inspection date and time stored in the storing unit exceeds a threshold set in advance.

11. The machine tool having an inspection function for a deteriorated state of a spindle according to claim 8, further comprising a temperature sensor configured to measure at least one of temperature of the spindle motor, bearing temperature of the spindle, and temperature near the bearing of the spindle, wherein

the execution enabling condition is whether the temperature detected by the temperature sensor is within a set threshold range.

12. The machine tool having an inspection function for a deteriorated state of a spindle according to claim 1, wherein

the machine tool is a machine tool including a tool replacing device, and

the machine tool executes the inspection function for the deteriorated state of the spindle during tool replacement in a period after the tool is detached from the spindle and before a next tool is attached.

13. A machine tool having an inspection function for a deteriorated state of a spindle, the machine tool including a spindle configured to hold a tool that machines work and rotatably supported by a bearing, a motor configured to drive the spindle, and an encoder configured to measure a rotation angle position of the spindle or the motor,

the machine tool comprising:

speed calculating unit for calculating rotating speed of the spindle or the motor from an output of the encoder;

unit for rotating the spindle or the motor at predetermined speed and thereafter interrupting power of the motor to rotate the spindle with inertia;

acceleration calculating unit for calculating acceleration of deceleration on the basis of an output of the encoder read at every predetermined cycle during the inertial rotation of the spindle;

position/acceleration storing unit for storing, at the every predetermined cycle, the rotation angle position read from the encoder and the acceleration calculated by the acceleration calculating unit; and

unit for determining whether acceleration equal to or larger than a predetermined threshold occurs in every same rotation angle amount, wherein

the machine tool outputs an alarm when it is determined that acceleration equal to or larger than the predetermined threshold occurs in the every same rotation angle amount.