Numerical control device

• US 9,753,449 B2
• Filed: 04/08/2013
• Issued: 09/05/2017
• Est. Priority Date: 04/08/2013
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Sato, Tomonori, Takeyama, Toru, Nishiwaki, Kenji
• Primary Examiner(s): Patel, Ramesh
• Application Number:
  US14/769,317
• Publication Number:
  US 20150378347A1
• Time in Patent Office: 1,611 Days
• CPC Class Codes: G05B 19/402 characterised by control arrangements for positioning, e.g. centring a tool relative to a hole in the workpiece, additional detection means to correct position G05B19/19 takes precedence
• CPC Class Codes: G05B 19/4063 Monitoring general control system G05B19/4062 takes precedence
• CPC Class Codes: G05B 2219/23431 Change program on detection of deviations
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

A numerical control device includes: a control unit controlling movement of shafts of a machine tool by a position command according to a machining program and acquiring position information on the shafts; a monitoring point determination unit determining a monitoring point in the machining program and a monitoring shaft according to the type of an instruction or an instruction related to travel described in the machining program; and a monitoring unit monitoring whether error or deviation based on the position information at the monitoring point of the monitoring shaft exceeds a predetermined threshold, wherein the control unit controls movement of the shafts based on the monitoring result of the monitoring unit, and the numerical control device further comprises an analysis unit presenting whether the cause of the error or deviation is a mechanical factor or a control factor based on the monitoring result and outputting the analysis result.

Claims

1. A numerical control device comprising:

a control unit that controls a movement of a plurality of shafts of a machine tool by a position command according to a machining program and acquires position information on the shafts;

a monitoring point determination unit that determines a monitoring point, which is to be monitored, in the machining program and a monitoring shaft that is the shaft to be monitored, in accordance with a type of an instruction or an instruction related to a travel described in the machining program; and

a monitoring unit that monitors whether an error or a deviation based on the position information at the monitoring point of the monitoring shaft exceeds a predetermined threshold, wherein the control unit controls a movement of the shafts on a basis of a monitoring result of the monitoring unit, and

the numerical control device further comprises an analysis unit that presents whether a cause of the error or the deviation is a mechanical factor or a control factor on a basis of the monitoring result and that outputs an analysis result of the factor to an output unit.

2. The numerical control device according to claim 1, wherein the monitoring unit uses, as the position information at the monitoring point, a machine position of the shaft measured by a sensor installed in the machine tool and a motor position measured by a position detector installed in a motor that drives the shaft.

3. The numerical control device according to claim 1, wherein the monitoring point includes an end point or a start point of a pair of positioning travels that cause at least one of the shafts to travel in directions opposite to each other.

4. The numerical control device according to claim 1, wherein the monitoring point includes a point to stop for a predetermined time after a positioning travel or a cutting feed travel.

5. The numerical control device according to claim 1, wherein the monitoring point includes a quadrant projection point.

6. The numerical control device according to claim 1, wherein the monitoring point includes a point where it is determined that a cutting resistance is large or a change of a cutting resistance is large on a basis of a travel instruction described in the machining program.

7. The numerical control device according to claim 6, wherein

the point where it is determined that a cutting resistance is large or a change of a cutting resistance is large includes any of or a combination of:

(1) a first cutting feed travel;

(2) a last cutting feed travel;

(3) an entrance of a hole, a hole bottom, an exit of a hole;

(4) an end of a groove; and

(5) a corner portion of a pocket,

in a machining cycle.

8. The numerical control device according to claim 1, wherein the monitoring point includes a quadrant projection point or a point where it is determined that a cutting resistance is large or a change of a cutting resistance is large and where it is assumed that a speed command or an acceleration command is small.

9. The numerical control device according to claim 8, wherein the point where it is assumed that a speed command or an acceleration command is small is a point where a command channel is tangent-continuous or a direction change of a tangent is small, where a feed speed command is constant, and where a sign of speed of at least one of the shafts is reversed.

10. The numerical control device according to claim 1, wherein the monitoring point includes a point where a change of any of mass, a moment of inertia, and a speed reduction ratio of the machine tool is large.

11. The numerical control device according to claim 10, wherein

the point where a change of any of mass, a moment of inertia, and a speed reduction ratio of the machine tool is large includes any of or a combination of:

(1) immediately after a workpiece, a tool, or a jig is replaced;

(2) a point where servo control is started after replacement of a workpiece, a tool, or a jig; and

(3) a first travel after replacement of a workpiece, a tool, or a jig.

12. The numerical control device according to claim 1, wherein the monitoring point includes a machining cycle for finishing, a point where accuracy is designated, or a machining cycle for finishing and a point where accuracy is designated.

13. The numerical control device according to claim 1, wherein the monitoring point includes a point immediately after a configuration of the shaft to be controlled is changed or a first travel after the change.

14. The numerical control device according to claim 1, wherein the monitoring point includes a first travel after a control mode related to position control or speed control is changed.

15. The numerical control device according to claim 2, wherein the monitoring point includes a travel instruction to stop a travel if a sensor signal output from the sensor or a load of the motor becomes a predetermined value or falls within a predetermined range.

16. The numerical control device according to claim 1, wherein the monitoring point determination unit changes the monitoring shaft according to a type of a travel command described in the machining program.

17. The numerical control device according to claim 1, wherein when a plurality of same machining cycles are included in the machining program, the monitoring point includes a first machining, a last machining, or both the first machining and the last machining of the same machining cycles.

18. The numerical control device according to claim 1, wherein when the monitoring point is continuous over a plurality of travels of a same type, the monitoring unit performs monitoring only in a first travel, a last travel, or both the first travel and the last travel of the travels.

19. The numerical control device according to claim 1, further comprising a storage unit that records therein the position information at the monitoring point of the monitoring shaft as log data.

20. The numerical control device according to claim 19, wherein the log data includes load data on the monitoring shaft.

21. The numerical control device according to claim 1, further comprising an input unit by which an operator corrects the monitoring point and the monitoring shaft that are determined by the monitoring point determination unit and are output by the output unit, wherein

the monitoring unit performs monitoring at the corrected monitoring point of the corrected monitoring shaft.