Machining load monitoring system

• US 5,822,212 A
• Filed: 08/12/1997
• Issued: 10/13/1998
• Est. Priority Date: 08/06/1993
• Status: Expired due to Fees

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Onishi, Yasushi, Tanaka, Kunio
• Primary Examiner(s): Gordon, Paul P.
• Application Number:
  US08/911,440
• Time in Patent Office: 427 Days
• Field of Search: 264/184, 264/185, 264/474.16, 264/474.17, 364/178, 364/474.18, 364/474.19, 364/191, 364/192
• US Class Current: 700/174
• CPC Class Codes: G05B 19/4063 Monitoring general control system G05B19/4062 takes precedence
• CPC Class Codes: G05B 2219/50197 Signature analysis, store working conditions, compare with actual

Abstract

A machining load monitoring system to monitor a machining condition by comparing sampled data of a machining load in a trial cutting process and measured data thereof in an actual cutting process with each other precisely with respect to time. An NC command executing unit (1) executes NC commands, and updates a block number and an execution mode in an executed state table (2) when the execution of NC commands of one block is finished. A load monitoring unit (4) compares sampled data, stored in a sampled data table (3), of a machining load in a trial cutting process with measured data thereof in an actual cutting process at given intervals of time. When the block number in the executed state table (2) is updated, sampled data of a new block number are read from the sampled data table (3). The sampled data in the trial cutting process and the measured data in the actual cutting process are compared with each other at predetermined times, and an alarm is issued when the difference between the compared data reaches or exceeds a predetermined level.

Claims

1. A machining load monitoring system for monitoring a machining load on a numerically controlled machine tool, comprising:

an executed state table for storing a block number of one of a plurality of NC commands which is being executed, wherein the NC commands are divided into blocks with corresponding block numbers;

NC command executing means for executing the NC commands and updating the block number of the one NC command stored in said executed state table, as the NC commands are executed;

a sampled data table for storing sampled data of a machining load produced in a trial cutting process, with respect to the blocks of the NC commands; and

load monitoring means for monitoring the block number of the one NC command and a block number of the sampled data, selecting the sampled data having a synchronized block number as the one NC command and changing the sampled data if necessary to synchronize the block numbers of the sampled data and one NC command, comparing the synchronized sampled data with measured data of the machining load in an actual cutting process during execution of the one NC command at predetermined intervals of time, replacing the synchronized sampled data with sampled data of a next block number when a next block number of a next NC command is stored in said executed state table, and issuing an alarm when the difference between the measured data of the machining load in the actual cutting process and the synchronized sampled data reaches or exceeds a predetermined level.

2. A machining load monitoring system according to claim 1, wherein said machining load comprises a load torque of a spindle motor.

3. A machining load monitoring system according to claim 1, wherein said machining load comprises a load torque of a feed axis.

4. A machining load monitoring system according to claim 1, wherein said executed state table stores an execution mode of the one NC command being executed.

5. A machining load monitoring system according to claim 4, wherein said execution mode is either a cutting mode, a fast feed mode, or a non-motion mode.

6. A machining load monitoring system according to claim 1, further comprising an observer for estimating the machining load.

11. A machining load monitoring system according to claim 1, wherein said load monitoring means jumps to the next block number of sampled data in said sampled data table until the block numbers of the sampled data and the one NC command are synchronized if the actual cutting process proceeds faster than the trial cutting process.

12. A machining load monitoring system according to claim 1, wherein said load monitoring means jumps to the next block number of sampled data in said sampled data table until the block numbers of the sampled data and the one NC command are synchronized if the actual cutting process proceeds faster than the trial cutting process, and said load monitoring means maintains the previous sampled data in said sampled data table when the block number of next sampled data is different from the block number of the NC command which is being executed until the next NC command is executed and then the block numbers of the sampled data and the NC command are synchronized if the actual cutting process proceeds slower than the trial cutting process.

7. A machining load monitoring system for monitoring a machining load on a numerically controlled machine tool, comprising:

a sampled data table for storing sampled data of a machining load produced in a trial cutting process;

sampling period generating means responsive to an override signal which indicates a change in an intended cutting speed of the numerically controlled machine tool, for outputting a sampling period signal corresponding to said override signal;

sampled data reading means for reading sampled data from said sampled data table according to said sampling period signal;

sampled data correcting means for correcting the read sampled data based upon said override signal and outputting corrected sampled data; and

load monitoring means for comparing the corrected sampled data with measured data of the machining load in an actual cutting process at predetermined intervals of time, and issuing an alarm when the difference between the measured data of the machining load in the actual cutting process and the corrected sampled data reaches or exceeds a predetermined level.

8. A machining load monitoring system according to claim 7, wherein said machining load comprises a load torque of a spindle motor.

9. A machining load monitoring system according to claim 7, wherein said machining load comprises a load torque of a feed axis.

10. A machining load monitoring system according to claim 7, further comprising an observer for estimating said machining load.

13. A machining load monitoring system for monitoring a machining load on a numerically controlled machine tool, comprising:

an executed state table for storing a block number of one of a plurality of NC commands which is being executed, wherein the NC commands are divided into blocks with corresponding block numbers;

an NC command execution unit for executing the NC commands and updating the block number of the one NC command stored in said executed state table, as the NC commands are executed;

a sampled data table for storing sampled data of a machining load produced in a trial cutting process, with respect to the blocks of the NC commands; and

a sampling period generator responsive to an override signal which indicates a change in an intended cutting speed of the numerically controlled machine tool, to output a sampling period signal corresponding to said override signal;

a sampled data reader to read sampled data from said sampled data table according to said sampling period signal;

a sampled data correction unit to correct the read sampled data based upon said override signal and outputting corrected sampled data; and

a load monitor to monitor the block number of the one NC command and a block number of the corrected sampled data, selecting the corrected sampled data having a synchronized block number as the one NC command and changing the corrected sampled data if necessary to synchronize the block numbers of the corrected sampled data and one NC command, comparing the synchronized corrected sampled data with measured data of the machining load in an actual cutting process during execution of the one NC command at predetermined intervals of time, replacing the synchronized corrected sampled data with corrected sampled data of a next block number when a next block number of a next NC command is stored in said executed state table, and issuing an alarm when the difference between the measured data of the machining load in the actual cutting process and the synchronized corrected sampled data reaches or exceeds a predetermined level.