JPH07328896A - Tool breakage detecting method for nc work machine - Google Patents

Abstract

PURPOSE:To eliminate erroneous detection of tool breakage in slit work by discriminating that a tool is broken when a work unit in a no-load condition of a spindle continues by the preset number of times or more. CONSTITUTION:An NC device 20 lowers a spindle IF, and reads a work program 20A a single work unit by a single work unit, and performs work. A CPU 3B measures a load current value by an electric current measuring part 3A in parallel to work operation. When this load current value is smaller than a no-load time reference value stored in a memory 3C, the CPU 3B discriminates that a work unit in no load is detected, and counts the number of detecting times. When a work unit less than a reference value continues, the number of detecting times are added, and when the number of times preset by an input means 3J is attained, the CPU 3B discriminates that a tool 11 is broken, and outputs a warning signal to the NC device 20. The NC device 20 stops work when it detects the warning signal.

Description

Detailed Description of the Invention

[0001]

This invention relates to numerical control (hereinafter referred to as NC
Say. ) This is a method for detecting tool breakage of a processing machine. In particular, the present invention relates to a method for detecting breakage of a tool from a change in load current of a spindle in outer shape processing of a work including slit processing.

[0002]

2. Description of the Related Art Tools such as drills and end mills may be broken during cutting work. A method for detecting tool breakage by the load of a drive device that drives the tool is disclosed in, for example, Japanese Patent Laid-Open No. 61-142053.

Next, the construction of an NC machine with a tool breakage detection function according to the prior art will be described with reference to FIG. Figure 3 shows NC
It is an external view of a processing machine. As shown in FIG. 3, the NC processing machine includes a processing machine 10, an NC device 20, a control unit 30, and an I / O.
It is composed of the device 40.

Next, the structure of the processing machine 10 shown in FIG. 3 will be described. In FIG. 3, 1 is a work and 11 is a tool. Also, 1A
Is a bed, 1B is a table, 1C is a column, 1D is a saddle, 1E is a headstock, and 1F is a spindle.

In FIG. 3, a pair of first rails extending in the X direction are arranged in parallel on the bed 1A. A table 1B on which the work 1 is placed is placed on the first rail.
Are provided so as to be movable in the X direction. A column 1C is provided above the table 1B so as to extend in the Y direction orthogonal to the X direction. A pair of second rails are arranged in parallel on the side surface of the column 1C. A saddle 1D is provided on the second rail so as to be movable in the Y direction.

On the upright surface of the saddle 1D, a pair of third rails are arranged in parallel in the Z direction. A headstock 1E is provided on the third rail so as to be movable in the Z direction. Spindle 1F holding tool 11 on headstock 1E
Is fixed. The tool 11 can be replaced with another tool manually or automatically by an unillustrated automatic tool changing device.
In order to move the table 1B, the saddle 1D, and the headstock 1E in the X, Y, and Z directions, a general drive mechanism combining a motor and a ball screw is used.

The CPU 3B of the control unit 30 is connected to the NC device 20 of the processing machine 10 via the I / O device 40. The current measuring unit 3A and the memory 3C are connected to the CPU 3B. The current measuring unit 3A is connected to the drive device of the spindle 1F and outputs the current value of the spindle of the spindle 1F to the CPU 3B.

FIG. 4 is a partial block diagram of the current measuring section 3A. The current measuring unit 3A shown in FIG. 3 includes a current sensor 31A, an amplifier 32A, and an A / D converter 33A. The current sensor 31A is a drive unit 10F for driving the spindle 1F.
The load current of is converted into a voltage value. The amplifier 32A converts the output voltage of the current sensor 31A into an average value and amplifies it. A
The / D converter 33A outputs the output voltage of the amplifier 32A to the CPU 3
Converted to digital quantity by command from B and the result is CPU
Output to 3B.

Returning to FIG. 3, the load current value of the spindle 1F is a constant value when there is no load, but the load current value slightly increases when the work 1 which is the workpiece is machined. In the configuration of FIG. 3, a value to be added to the no-load current value for experimentally obtaining the reference value is set in advance as the addition value 3D.
In addition, a reference value obtained by adding the above-mentioned added value to the current value when the spindle 1F has no load is written in the memory 3C.

The CPU 3B reads the reference value from the memory 3C and sends it to the comparing and judging means 3E, and at the same time, sends the load current value of the current measuring section 3A to the comparing and judging means 3E. The comparison and determination means 3E compares the reference value with the load current value, and sends the determination result to the CPU 3B. Comparison determination means 3
When the load current value is smaller than the reference value in E, it is determined that the tool 11 is broken, and the CPU 3B causes the alarm means 3F to operate.
Command the alarm display to.

Next, the operation of FIG. 3 will be described. In Figure 3,
The tool 11 is held by the spindle 1F and rotated.
After this, the NC device 2 is instructed by the machining program 20A.
0 is operated to move the table 1B and the headstock 1E in the X direction or the Y direction to position the tool 11 at the machining position. At this time, the CPU 3B determines from the input signal of the I / O device 40 that the spindle 1F is rotating and is not processing, reads the no-load current value from the current measuring unit 3A,
The addition value 3D is added to the no-load current value and the result is stored in the memory 3C as a reference value. Then, the spindle 1F is lowered.

Next, the current value of the spindle 1F being processed is compared with the reference value. If the current value is smaller than the reference value,
Immediately determine that the tool has broken.

FIG. 5 is a flowchart showing the above operation. In step 201 of FIG. 5, the spindle 1F is rotated. In step 202, the no-load current value of the spindle 1F is read by the current measuring unit 3A. In step 203, the addition value 3D is added to the no-load current value and stored in the memory 3C as a reference value.

At step 204, the spindle 1F descends to start machining. In step 205, the load current value of the spindle 1F is measured by the current measuring unit 3A. In step 206, the comparison determination means 3E compares the measured value of the load current with the reference value. In step 206, if the measured value is greater than the reference value, the process proceeds to step 207, and if the measured value is less than the reference value, the process proceeds to step 208.

In step 207, it is determined whether all the processing has been completed. If the processing has not been completed in step 207, the next processing unit is processed.
Return to the previous stage of 5. When the processing is finished in step 207, a series of operations is finished.

At step 208, the CPU 3B gives an instruction to stop machining. In step 209, the CPU 3B commands the alarm means 3F to display an alarm, and ends the series of operations.

[0017]

FIG. 3 shows a printed circuit board processing machine as an example of the NC processing machine. The work 1 of FIG. 6A has a printed circuit board to be processed arranged on a plane, and the printed circuit board 1 of FIG. 6A may have the slit 1A processed.

FIG. 6A shows the slit 1A shown in FIG.
It shows a state in which the end mill 11 is used for machining. In FIG. 6A, the tool 11 is rotating clockwise and the slit 1
The first cutting surface 1B of A has a good finish, but the second cutting surface 1C of the slit 1A is a rough surface as compared with the first cutting surface 1B.

In order to solve the problem shown in FIG. 6A, after the tool 11 has moved to the left as shown in FIG. 6C, the same trajectory is returned as shown in FIG. By such a returning operation, the cutting surface 1B and the cutting surface 1C have the same finish. The returning operation of FIG. 6D has an effect of removing the chips remaining in the slit 1A.

In the returning operation of FIG. 6D, the load current value of the spindle 1F becomes equal to the no-load current value. Therefore,
The tool breakage method having the configuration of FIG. 3 has a problem that it is determined as a tool breakage even though the tool 11 is not broken.

According to the present invention, the tool for slit machining is determined by determining that the tool has broken when the number of machining units for which the spindle load current value is smaller than the reference current value is continuous a plurality of times. An object of the present invention is to provide a tool breakage detection method for an NC processing machine that eliminates false detection of breakage.

[0022]

In order to achieve this object, the present invention provides a current measuring unit 3A for detecting a load current value of a spindle 1F for driving a tool 11, and a spindle 1F.
The CPU 3B reads the reference current value for each machining unit of the spindle 1F and compares the load current value with the reference current value. The memory 3C stores a reference current value determined from the no-load current of F. If the load current value is smaller than the reference current value and the number of processing units determined to be smaller than the reference current value continues a plurality of times, it is determined that the tool has broken.

[0023]

In the present invention, the NC device 20 positions the spindle 1F in the X or Y direction in accordance with the machining program 20A. Next, the CPU 3B measures the no-load current value by the current measuring unit 3A, adds the addition value 3D, and stores it in the memory 3C as a reference value. Next, NC
The apparatus 20 lowers the spindle 1F, reads the machining program 20A one machining unit at a time, and performs machining.

In parallel with the processing operation, the CPU 3B measures the load current value by the current measuring unit 3A. When the load current value is smaller than the reference value stored in the memory 3C, CP
U3B determines that a processing unit with no load is detected, and counts the number of detections. When a processing unit whose load current value is larger than the reference value is detected, the count value 3H of the counting circuit 3G is initialized to zero. When the processing unit below the reference value continues, the number of times of detection is added, and when the number of times set by the input means 3J is reached, the CPU 3B determines that the tool 11 has broken, and the NC device 2
An alarm signal is output to 0. When the NC device 20 detects the alarm signal, the machining is stopped.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the construction of an NC processing machine according to the present invention will be described with reference to the embodiment of FIG. The control unit 31 in FIG. 1 has a counting circuit 3G, a counting value 3H, a counting value 3J, and an input unit, and the other components are the same as those in FIG. That is, in FIG. 1, the counting circuit 3G, the count value 3H, and the input means 3J are added to the control unit 30 of FIG.

The counting circuit 3G shown in FIG.
The result of is counted. When the load current value is smaller than the reference value stored in the memory 3C, the CPU 3B counts the number of detections in the counting circuit 3G. When a processing unit whose load current value is larger than the reference value is detected, the count value of the counting circuit 3G is initialized to zero.

The input means 3J inputs the detected value into the count value 3H. Normally, "2" is input as the count value. Depending on the processing frequency, the count value or "3" is input. CP
U3B compares the detected value of the counting circuit 3G with the counted value 3H,
When the detected value and the counted value match, an alarm signal is output to the NC device.

Next, the operation of FIG. 1 will be described with reference to the flowchart of FIG. In step 101 of FIG. 2, the tool 11 is held and rotated on the spindle 1F. NC device 20
Positions the tool 11 at the processing position according to the command of the processing program 20A. In step 102, CPU3B
Determines from the input signal of the I / O device 40 that the spindle 1F is rotating and that machining is not in progress, and measures the no-load current value from the current measuring unit 3A. In step 103, the addition value 3D is added to the no-load current value and stored in the memory 3C as a reference value. Then, the spindle 1F is lowered.

At step 104, the CPU 3B initializes the count value of the counting circuit 3G to "0". Step 105
Then, one line of the machining program 20A is read. Step 1
At 06, it is determined whether the processing is completed. In step 107, the NC device 20 starts processing the work 1. At this time, the CPU 3B determines from the input signal of the I / O device 40 that processing is being performed, reads the load current value from the current measuring unit 3A, and writes it in the memory 3C.

Then, the comparison / determination means 3E compares the reference value with the load current value, and when the load current value is smaller than the reference value, adds the number of detections of the counting circuit 3G. This determination is performed for each machining unit, and when a machining unit whose load current value is larger than the reference value is detected, the detected value is initialized to zero.

In step 108, the number of detections by the counting circuit 3G and the count value 3H are compared. If the number of detections does not match the count value 3H in step 108, step 109
Proceed to. In step 109, it is determined whether or not the detection value is updated by this processing. If not updated, the process proceeds to step 110.

In step 110, the load current of the spindle 1F is measured. In step 111, the measured value of the load current is compared with the reference value of the memory 3C, and if the measured value is equal to or more than the reference value, the process proceeds to step 112. It should be noted that the process also proceeds to step 112 when the detection count is updated in step 109.

At step 112, it is judged whether one processing unit is completed. If not finished in step 112, the process returns to the previous stage of step 108. When the measured value is smaller than the reference value in step 111, the process proceeds to step 113. In step 113, "1" is added to the number of detections of the counting circuit 3G, and the process returns to the previous stage of step 108. When the process ends in step 112, the process returns to the stage before step 105.

When the number of detections and the count value 3H coincide with each other in step 108, the CPU 3A determines that the tool 11 has been broken, outputs an alarm signal to the NC device 20, and step 114
Proceed to. At step 114, the NC device 20 gives an instruction to stop the machining, and at step 115, an alarm is displayed.

In this embodiment, the table 1B is described as being controlled to move in the X direction, but the present invention is not limited to this, and the column 1C may be moved in the X direction. Good.

[0036]

As described above, according to the present invention, it is determined that the tool is broken when the machining unit with the spindle unloaded is continuous for a preset number of times or more. Even during machining, it is not erroneously detected as a tool breakage.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an NC processing machine according to the present invention.

FIG. 2 is a flowchart showing the operation of FIG.

FIG. 3 is a configuration diagram of an NC processing machine with a tool breakage detection function according to a conventional technique.

FIG. 4 is a partial configuration diagram of a current measuring unit 3A.

5 is a flowchart showing the operation of FIG. 1. FIG.

FIG. 6 is a change diagram of a processing state of the work 1.

[Explanation of symbols]

 1 Work 1A Bed 1B Table 1C Column 1D Saddle 1E Headstock 1F Spindle 3A Current measurement part 3B CPU 3C Memory 3D Addition value 3E Comparison judgment means 3F Alarm means 3G Counting circuit 3H Count value 3J Input means 10 Processing machine 11 C 20 Tools 20 Numerical control) device 31 control unit 40 I / O device

Claims (1)

[Claims] 1. A current measuring unit (3A) for detecting a load current value of a spindle (1F) for driving a tool (11), and a memory for storing a reference current value determined from a no-load current of the spindle (1F). (3C), the CPU (3B) reads the reference current value for each machining unit of the spindle (1F) and compares the load current value with the reference current value, and the load current value is the reference current. A tool breakage detection method for an NC processing machine, characterized in that it is judged that the tool (11) has broken when the number of machining units judged to be smaller than the value continues a plurality of times.