WO1996038261A1

WO1996038261A1 - Abnormal load detecting method

Info

Publication number: WO1996038261A1
Application number: PCT/JP1996/001486
Authority: WO
Inventors: Ryuji Suzuki
Original assignee: Fanuc Ltd
Priority date: 1995-05-31
Filing date: 1996-05-31
Publication date: 1996-12-05
Also published as: JPH08323585A

Abstract

An abnormal load detecting method capable of detecting an abnormal load correspondingly to an operation condition of a machine tool. A load imparted to a driving shaft of a machine tool is detected, and a detected load is compared with an abnormal load detecting level. The abnormal load detecting level is switched in accordance with the operation condition of a machine tool, for example, a manual operation mode and an automatic operation mode, and a quick feed operation and a cutting feed operation of an automatic operation mode.

Description

I i one specification

Abnormal load detection method

Technical field

The present invention relates to a load detection method for a machine tool.

Background technology

In general, in a machine tool having a feed shaft and a spindle, the feed shaft gives machining feed to the work to the tool, and the work or the tool is driven by the spindle to perform cutting or the like. Perform processing.

Conventionally, in such a machine tool, an abnormal load applied to a feed shaft or a spindle has been detected in order to detect a collision between a movable portion and an obstacle. This abnormal load detection is performed by comparing the magnitude of the detected load with the abnormal load detection level.

However, the conventional method of detecting an abnormal load has a problem in that it is not possible to detect an abnormal load according to the operation state of the machine tool. That is, the abnormal load detection level in the conventional abnormal load detection method is fixed to a constant value irrespective of the operation state of the machine tool, and the abnormal load detection level is determined by comparing with the fixed abnormal load detection level. Is being detected. Normally, in machine tools, the load during cutting operation is the largest, and the load during rapid traverse operation or manual feed operation is much smaller than the maximum load during cutting operation. Therefore, the abnormal load detection level used in the conventional abnormal load detection method is set based on the maximum load during the cutting operation. Stipulated.

Fig. 7 schematically shows the relationship between the magnitude of the load during the rapid traverse operation, the cutting feed operation, and the manual operation in the conventional abnormal load detection method, and the abnormal load detection level. The abnormal load detection level L0 is set to a value obtained by adding a margin to that value, based on the maximum load during cutting feed operation.

Fig. 8 shows the relationship between the change in load in each operating state of the machine tool and the abnormal load detection level L0 in the conventional abnormal load detection method. It has been done. In Fig. 8, the abnormal load detection level L0 is based on the maximum load during cutting, so the abnormal load during cutting operation indicated by b in Fig. 8 is the abnormal load cutting detection level L0. Detected when exceeds. However, abnormal loads during fast-forward operation and manual operation indicated by a and c in Fig. 8 are not detected because they do not exceed the abnormal load cutting detection level L O. If a collision between the tool and the jig occurs during rapid traverse operation or manual feed operation, the load level at which the tool or jig is damaged is smaller than the maximum load level during cutting. Then, it is not possible to detect this street collision.

Disclosure of the invention

An object of the present invention is to provide an abnormal load detection method capable of detecting an abnormal load according to the operation state of a machine tool. The abnormal load detection method according to the present invention includes a step of detecting a load applied to a drive shaft of the machine tool during operation of the machine tool and a step of switching an abnormal load detection level according to the operation state of the machine tool. And comparing the detected load with the switched abnormal load detection level to determine whether the detected load exceeds the abnormal load detection level, and determining whether the detected load exceeds the abnormal load detection level. And a step of issuing an abnormal load detection signal when it is determined that the load has been exceeded.

The method of the present invention further includes a step of setting a plurality of abnormal load detection levels for each operating state of the machine tool, and the step of switching the abnormal load detection levels includes a plurality of steps. Includes a step to select an abnormal load detection level from the abnormal load detection levels according to the machine tool operating status.

Machine tools are operated in various operating states, and the magnitude of the load applied to the drive shaft changes according to the operating state. The operation state includes, for example, a manual operation mode and an automatic operation mode, and the automatic operation mode includes a fast-forward operation and a cutting-feed operation. Generally, the load during the cutting feed operation is larger than the load during the rapid feed operation.

The abnormal load detection level is switched according to the manual operation and automatic operation of the machine tool. When the machine tool is automatically operated, it is further switched according to the rapid traverse operation and the cutting feed operation.

The machine tool operates based on the machining program, and the abnormal unloading detection level is switched by a command in the processing program. Rukoto can.

In the abnormal load detection method of the present invention, the abnormal load detection level is switched according to the operating state of the machine tool, thereby detecting the abnormal load according to the actual operating state. This makes it possible to detect an abnormal load in an operating state where the maximum load is small.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an explanatory diagram showing the configuration of a machine tool and its control system for implementing the abnormal load detection method of the present invention,

FIG. 2 is a flowchart showing an abnormal load detection process according to the present invention.

FIG. 3 is a graph showing the relationship between the operating state of the machine tool and the abnormal load detection level in the present invention.

FIG. 4 is a graph showing abnormal load detection during rapid traverse operation according to the present invention.

FIG. 5 is a graph showing abnormal load detection during cutting feed operation according to the present invention.

FIG. 6 is a graph showing abnormal load detection during manual feeding operation according to the present invention.

Fig. 7 is a graph showing the relationship between the magnitude of the load and the abnormal load detection level in the conventional abnormal load detection method.

Figure 8 is a graph showing the relationship between the load change and the abnormal load detection level in each operating state of the machine tool in the conventional abnormal load detection method.

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 1, a drive motor 2 is connected to a drive shaft 1a of a machine tool 1 that operates in various operation states. The control device 4 outputs a current command value I c of the drive motor 2 to the drive circuit 3 based on the added program and the feedback signal from the drive motor 2. The drive circuit 3 drives the drive motor 2 based on the command value Ic.

The load detecting means 5 detects a load applied to the drive motor 2. The load detecting means 3 monitors, for example, a drive current command value Ic output from the control device 4 to the drive circuit 3 or a drive current I actually supplied to the drive coil of the drive motor 2. Then, the load applied to the drive shaft 1a is obtained using the current command value Ic or the drive current I, the torque constant of the drive motor 2, and the motor acceleration. In order to obtain the load of the drive motor 2, various methods other than the above-described methods, for example, a method of estimating the load applied to the drive motor 2 by a disturbance estimation observer are known. Is omitted.

The load detected by the load detecting means 5 is compared with the abnormal load detection level by the comparing means 6. The comparing means 6 includes a comparing circuit for comparing the load value detected by the load detecting means 5 with the abnormal load detection level, and the comparing circuit includes an abnormal load detecting level as a threshold value for detecting an abnormal load. Is set, and the abnormal load detection level is switched according to the actual operation state of the machine tool 1.

Hereinafter, the abnormal load detection processing according to the present invention will be described with reference to the flowchart of FIG. First, it is determined whether the machine tool is operated in the automatic operation mode or the manual operation mode (step S1). When the machine tool is operated in the manual operation mode, an abnormal load detection level for the manual feed is set as a comparison level in the comparison means (step S2), and the comparison level is set. The load value detected by the load detecting means is compared with the threshold value.

If it is determined in step S1 that the machine tool is operated in the automatic operation mode, the process proceeds to step S3, in which the rapid traverse operation or the cutting feed operation is performed. Is determined.

If it is determined in step S3 that the machine tool performs the rapid traverse operation, an abnormal load detection level for the rapid traverse operation is selected as a comparison level for detecting an abnormal load (step S3). Step S4), the comparison level is set as a threshold value, and the load value detected by the load detection means is compared.

If it is determined in step S3 that the machine tool does not perform the cutting feed operation, the abnormal load detection level for the cutting feed operation is selected as the comparison level for detecting the abnormal load (step S3). In step S5), the comparison level is compared with a load value detected by the load detection means as a threshold value.

For the abnormal load detection level, a plurality of different abnormal load detection levels for various operation states of the machine tool are set and stored in a storage means in advance, and the abnormal load detection level is determined according to the judgment result of each judgment processing. Then, the abnormal load detection level corresponding to the operation state of the machine tool 1 is read from the storage means and set as a threshold value of the comparison means. Alternatively, the value of the potentiometer for inputting the threshold value to the comparing means may be switched according to the determination result of each determination process. Further, a plurality of comparison means are prepared in which each abnormal load detection level is set as a threshold value, and the comparison means corresponding to the operation state is selected according to the judgment result of each judgment processing. It can be configured to switch.

If it is determined that the load value detected by the load detecting means does not exceed the abnormal load detection level corresponding to the operation state of the machine tool, the operation of the machine tool is continued. If it is determined that the load value detected by the load detection means exceeds the abnormal load detection level corresponding to the operation state of the machine tool, it is determined that an abnormal load has occurred and the abnormal load detection signal is output. Emit. In this case, an alarm is issued

— Notify the occurrence of an abnormal load in the evening, and perform processing such as stopping the operation of the machine tool.

The determination of the operating state of the machine tool performed in step S1 or step S3 includes a symbol indicating the operating state in a machining program for controlling the machine tool. Describe the level value of the abnormal load detection level for the operating state, and read it by reading the symbol and level value.o

When a symbol indicating the operating state is described in the machining program, a plurality of abnormal load detections preset in the storage From among the levels, the abnormal load detection level corresponding to the symbol read from the load program is read, and the read level value is set in the comparison means. When describing the value of the abnormal load detection level in the program, set the level value read from the program as the threshold value for detecting the abnormal load.

The relationship between the operating state of the machine tool and the abnormal load detection level in the abnormal load detection method of the present invention will be described with reference to FIG.

Fig. 3 shows the operation in the manual operation mode and the rapid feed and cutting feed operation in the automatic operation mode. The abnormal load detection level L3 is set for manual feed operation, the abnormal load detection level L2 is set for rapid traverse operation, and the abnormal load detection level L1 is set for cutting feed operation. The load on the machine tool is indicated by the solid line. Each abnormal load detection level is set in the order of 3 <L2 <L1.

During normal operation of the machine tool, the load applied to the drive shaft of the machine tool is less than the abnormal load detection level L2 during rapid traverse operation, and the abnormal load detection level L1 during cutting feed operation. The following is the abnormal load detection level L3 at the time of manual operation, and the abnormal load is detected at each abnormal load detection level in each operation state.

Figure 4 shows abnormal load detection during rapid traverse operation. The abnormal load detection level is set to L2 for fast-forward operation. In Fig. 4, the comparison means changes the load level to the abnormal load detection level. Compare with L2 to determine whether the load level has exceeded the abnormal load detection level L2. If an abnormal load occurs as indicated by the one-point line a during fast-forward operation, an abnormal load detection signal is output.

Figure 5 shows abnormal load detection during cutting feed operation. During the cutting feed operation, the abnormal load detection level is set to L1. The comparing means compares the load level with the abnormal load detection level L1, and determines whether the load level has exceeded the abnormal load detection level L1. If an abnormal load occurs as indicated by the dashed line b during cutting feed, an abnormal load detection signal is output.

Figure 6 shows abnormal load detection during manual feed operation. The abnormal load detection level is set to L3 for manual feed operation. In FIG. 6, the comparing means compares the load level with the abnormal load detection level L3, and determines whether the load level has exceeded the abnormal load detection level L3. If an abnormal load occurs as shown by the one-dot chain line c during manual feed operation, an abnormal load detection signal is output.

During rapid traverse positioning, it is possible to detect a collision due to interference between the tool and the jig, thereby stopping machining and preventing defective machining. In addition, in the use state of the manual feed, it is possible to detect a collision or the like that occurs during the middle setup or a work mistake, thereby improving work safety. You. By setting the abnormal load detection level according to various operating conditions of the machine tool As a result, productivity, reliability, workability and safety can be improved.

Claims

The scope of the claims

1. A method for detecting an abnormal load applied to the drive shaft of a machine tool operating in various operating states,

(a) detecting a load applied to the drive shaft during operation of the machine tool;

(b) a step of switching the abnormal load detection level according to the operation state of the machine tool;

(c) comparing the load detected in step (a) with the abnormal load detection level switched in step (b), and determining whether the detected load exceeds the abnormal load detection level. Steps to determine

(d) a step of generating an abnormal load detection signal when it is determined in step (c) that the detected load exceeds the abnormal load detection level. Method.

2. (e) The method further comprises a step of setting a plurality of abnormal load detection levels for each operation state of the machine tool, wherein the step (b) is performed in the step (e). An abnormal load detection method including a step of selecting an abnormal load detection level according to the operating state of a machine tool from among a plurality of set abnormal load detection levels.

3. The abnormal load detection method according to claim 1, wherein the step (b) includes a step of switching the abnormal load detection level according to manual operation and automatic operation of the machine tool. How to get out.

4. The abnormal load detection method according to claim 1, wherein the step (b) includes a step of switching the abnormal load detection level according to a rapid traverse operation and a cutting feed operation.

5. The machine tool operates on the basis of an applied program, and the step (b) includes a step of switching the abnormal load-off detection level according to a command in the processing program. The abnormal load detection method according to any one of claims 1, 2, 3, and 4.

6. The abnormal load detection method according to claim 1, wherein the drive shaft of the machine tool includes a feed shaft and a main shaft.