JPH09183040A - Sizing device, machining system, and machining error detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sizing device whose manufacturing cost can be reduced and which can prevent the failure to notice defective products by abolishing visual inspection through the detection of the stop of work that is a cause of flaws that requires visual inspection. SOLUTION: This sizing device, having a measuring head 13 which outputs measurement signals showing the size of the machined part of a workpiece 100, and having a processing means 20 which processes the measurement signals output by the measuring head 13 and which then outputs a sizing signal for varying machining requirements when the size of the machined part has reached a preset target size, includes a machining error detection means 40 which determines whether or not the amount of variation of the measurement signal per unit time is below a preset threshold and which, when the amount of variation of the measurement signal per unit time is not more than the threshold, outputs a machining error signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures a dimension of a machined portion of a workpiece during machining and outputs a measurement signal called a sizing signal when the dimension reaches a predetermined machining dimension. Size device, a processing abnormality detection device that detects an abnormality occurrence in processing from a measurement signal indicating the size of a processing portion, and a processing system using such a device, particularly because a chuck such as a magnet shoe is used. The present invention relates to a sizing device used in combination with a machine tool in which a work may be temporarily stopped, a machining abnormality detecting device, and a machining system including the machine tool and the sizing device.

[0002]

2. Description of the Related Art It has been practiced to measure the dimensions of a machined portion of a workpiece during machining to improve machining accuracy. For example, if a target dimension is set in advance and a machining stop signal is output when the measured dimension reaches or just before reaching the target dimension, and the machining is stopped, high-precision machining is possible.
A device that measures the dimensions of the processed portion during processing and outputs a signal for controlling the processing operation is called a sizing device.

[0003] For example, in grinding, the degree of surface finish varies depending on the processing amount per unit time, that is, the speed at which the grindstone is moved with respect to the work. Therefore, in the grinding process, high-speed processing is performed up to a dimension larger than the target dimension by a predetermined amount, and thereafter, processing is performed slowly so as to improve the finish, so that high-speed, accurate and good finish is achieved. ing. In practice, it is common to perform processing in the order of a rough polishing step with a high processing speed, a fine polishing step with a low processing speed, and a spark-out step performed to improve the finished state with almost no processing. . In the sizing device, the dimensions of roughing to fine polishing, fine polishing to spark out, and processing stop are set in advance.
It is configured to output a fixed size signal when the set size is reached.

[0004] In grinding, since the processing is performed by bringing a rotating grindstone into contact with a rotating work, generally the outer diameter of the work is important, and a sizing device also measures the outer diameter and outputs a sizing signal. Output. The measuring head that measures the dimensions of the work used in such a sizing device can be basically any type that can measure the outer diameter of the processed part even during processing. Although not shown, a sizing device using a measuring head of a type in which a most commonly used contact comes into contact with a portion to be measured and detects displacement of the contact will be described as an example.

When the outer diameter of a workpiece is measured with a cylindrical rotating body, a probe of a measuring instrument such as a stylus in contact with the outer diameter portion is moved to a position symmetrical with respect to the rotation axis of the rotating body. Measure while setting and rotating the work. The value of the outer diameter was calculated from the sum of the outputs of the two tracings. FIG. 5 is a diagram showing a basic configuration of a conventional processing system using a sizing device.

As shown in FIG. 5, a machine tool (here, a grinding device) 110 grinds a work 100 with a grindstone 111 that rotates at high speed. The control unit 113 controls the processing operation of the grinding device 110. The work 100 is attached to the chuck 112 and rotates. The measuring elements 11 and 12 extending from the measuring head 13 are brought into contact with the outer diameter portion of the workpiece 100 being machined, the displacement thereof is detected by a differential transformer in the measuring head 13, and the displacements of the two measuring elements are added. A value, that is, a measurement signal indicating the outer diameter of the work 100 is output. The signal processing / converting unit 31 converts the measurement signal from the measuring head 13 into a digital signal after analog processing. Based on the digitized measurement signal, the data processing unit 32 determines whether or not a predetermined dimensional value of rough to fine, fine to spark out, or machining stop has been reached. Output the sizing signal when the size is reached.
The control unit 113 performs control such as changing the feed amount of the grindstone 111 based on the sizing signal. Normally, the signal processing / conversion unit 31 and the data processing unit 32 are collectively referred to as a sizing device, but the measurement head 13 may also be referred to as a sizing device. Here, a sizing device including the measuring head 13 is used, but is not limited to this. In the case of gear machining, the measurement signal is not always available, but only intermittently. Therefore, in the case of such processing, it is necessary to have a function of predicting the value of the measurement signal while the measurement signal is not obtained, but since it is not directly related to the present invention, here, a cylindrical shape is not used. The case of grinding the diameter will be described as an example.

FIG. 6 is a diagram showing changes in the measurement signal due to processing. The sizing device monitors the measurement signal and detects when the size S1 for switching from the rough grinding to the fine grinding, the size S2 for switching from the fine grinding to the spark out, and the size S3 for stopping the processing are respectively detected, and such a size is set. When it is detected, the processing conditions such as changing the feed amount of the grindstone 111 are changed. The processing is carried out in the order of rough polishing, precision polishing, and spark out, and the value of the measurement signal changes accordingly as shown in the figure. The amount of feed of the grindstone 111 is large during the rough grinding, so the change in the value of the measurement signal is large, and during the fine grinding, the grindstone 11 is large.
Since the feed amount of 1 is reduced, the change in the value of the measurement signal becomes small, and the feed amount of the grindstone 111 becomes almost zero at the time of spark-out, so the value of the measurement signal hardly changes.

[0008]

In a grinder, a lathe, etc., a work is generally held mechanically on a rotary shaft, but a chuck called a magnet shoe type which is easy to work with is widely used. Used. This magnet shoe chuck is intended for works that can be attracted by a magnet such as iron. An electromagnet is provided on the rotary shaft of the device, and the work is set and then the electromagnet is activated to fix the work to the rotary shaft. It is a thing.

In a grinding machine using such a magnet shoe type chuck, the rotation of the work may be stopped due to the magnetized state of the chuck during processing of the work. If it is stopped as it is, the sizing signal is not output, so that it is possible to detect that an abnormality has occurred in processing due to time management in the grinding device, and to take appropriate action. However, the workpiece once stopped may start rotating again, and the machining may be terminated as it is. In such a case, a groove is formed at the portion where the grindstone was in contact when stopped. If the groove is deep or a temporary stop of the work occurs near the end of the machining, even if the machining is completed, a flaw of several μm as shown in FIG. 7 is generated. It is not easy to find such scratches by automatic measurement after processing, and it is difficult to find them without visual inspection. Therefore, all processed workpieces are visually inspected. However, it is difficult to visually inspect all,
Not only does the cost increase, but defective products are shipped due to oversight.

The present invention has been made in view of the above problems, and predicts the occurrence of minute scratches, which have hitherto relied on visual inspection, at the processing stage to predict the occurrence of scratches. An object of the present invention is to realize a sizing device, a processing abnormality detecting device, and a processing system having such a device.

[0011]

In order to solve the above-mentioned problems, the sizing apparatus of the present invention is such that, in the case of normal processing, the change in the measurement signal per unit time accompanying the processing is substantially constant. Focusing attention, when the change of the measurement signal per unit time is less than or equal to a predetermined threshold value, it is determined that an abnormality has occurred in machining.

That is, the sizing apparatus of the present invention processes the measurement signal output from the measurement head and the measurement head that outputs the measurement signal indicating the dimension of the processed portion of the workpiece, and sets the dimension of the processed portion in advance. In a sizing device equipped with a processing means for outputting a sizing signal for changing the processing condition when the target dimension is reached, the change amount of the measurement signal per unit time is below a predetermined threshold value. It is characterized by further including a machining abnormality detecting means for determining whether there is a machining abnormality and outputting a machining abnormality signal when the amount of change in the measurement signal per unit time is equal to or less than a threshold value.

The machining abnormality detecting means comprises a threshold value storing means for storing a threshold value, and a judging means for comparing the threshold value stored in the threshold value storing means with the change amount of the measurement signal per unit time. It is desirable that the threshold value storage means be able to store a plurality of threshold values corresponding to a plurality of processing conditions, and the determination means compares the threshold value corresponding to the processing conditions with the amount of change of the measurement signal per unit time. Further, it is desirable that the threshold value stored in the threshold value storage means (42) can be set from the outside, and for that purpose, a threshold value input means for inputting the threshold value from the outside is provided.

When the temporary stop of the work which is the cause of the scratch occurs, the measurement signal does not change. Therefore, when the change of the measurement signal per unit time becomes much smaller than the normal value, the work is temporarily stopped. Can be determined to have occurred. In the present invention, the machining abnormality detection means determines whether the change of the measurement signal per unit time is less than or equal to a predetermined threshold value, and when the variation is less than or equal to the threshold value, a machining abnormality signal is generated. You can know. Even if the work is temporarily stopped, the scratch is not always generated, but it is also possible to perform a detailed visual inspection on the work in which the processing abnormality signal is generated, and the productivity is much improved.

[0015]

FIG. 1 is a block diagram showing the overall configuration of a processing system according to an embodiment of the present invention. In FIG. 1, reference numeral 100 is a workpiece, 110 is a grinding device,
111 is a grindstone, 112 is a magnetoshoe chuck, 113 is a controller, 11 and 12 are probes, 13 is a measuring head, and 20 is a signal from the measuring head to generate a sizing signal. Reference numeral 40 denotes a processing unit and 40 denotes a processing abnormality occurrence detection unit. The processing unit 20 includes a signal processing / conversion unit 31 that converts the measurement signal from the measurement head 13 into an analog signal and then converts the signal into a digital signal, and a predetermined rough measurement based on the digitized measurement signal. It comprises a precision processing unit, a data processing unit 32 which determines whether or not the dimension value of sparking out from the precision processing unit or processing stop has been reached, and outputs a sizing signal when such dimension is reached.

As is apparent from comparison with FIG. 5, the present embodiment differs from the conventional example in that a machining abnormality occurrence detecting section 40 for detecting the occurrence of machining abnormality from the change of the measurement signal is newly provided. The machining abnormality occurrence detection unit 40 includes a threshold value storage unit 42 that stores a threshold value, and a determination unit 4 that compares the amount of change of the threshold value stored in the threshold value storage unit 42 and the measurement signal per unit time.
1 and a threshold value input section 43 for inputting a threshold value from the outside. The threshold storage unit 42 can store a plurality of thresholds, and a plurality of thresholds according to processing conditions are externally set and stored via the threshold input unit 43. The determination unit 41 reads out the threshold value corresponding to the processing condition from the threshold value storage unit 42 and compares it with the change amount of the measurement signal per unit time. The machining abnormality occurrence detection unit 40 is actually realized by a computer system. Since the data processing unit 32 of the processing unit 20 is also realized by a computer system, the data processing unit 32 can be shared with the computer system and realized as a sizing device having a function of detecting the occurrence of a machining abnormality. Further, it is also possible to realize the processing abnormality occurrence detecting unit 40 as a processing abnormality occurrence detecting device by adding a digitized measurement signal from the existing sizing apparatus to the existing sizing apparatus. Is.

FIG. 2 is a diagram showing the hardware configuration of the measuring head 13, the processing section 20, and the processing abnormality occurrence detecting section 40. Here, the data processing unit 32 and the machining abnormality occurrence detection unit 40 are realized by a common computer system. However, regarding the functional part of the data processing unit 32,
Since it is the same as the conventional sizing device, it will be omitted from the description.

In FIG. 2, reference numerals 11 and 12 are probes, 14 and 15 are first and second differential transformers 14 and 15 provided on the measuring head, and 16 and 17 are differential transformers 14. , The first and second rectifier circuits that rectify the outputs of 15 to output a DC component, 25 is an adder circuit that adds detection signals of the first and second rectifier circuits, and 26 is a master measurement value of zero. The reference numeral 28 denotes an auto-zero circuit for subtracting the correction value so that the reference numeral 28 denotes an A / D converter for converting the output of the auto-zero circuit 26 into a digital signal. Reference numbers 51 to 58
Is a part constituting a computer system, and a CPU
51, ROM 52, RAM 53, I / O port 54, display interface 55, input key interface,
It is composed of a display device 57 and an input keyboard 58.

In the RAM 53, the threshold storage unit 42 shown in FIG.
Is provided with a threshold value register corresponding to, and the respective threshold values at the time of fine polishing, at the time of rough polishing, and at the time of spark out are stored. Further, such a set of threshold values is stored for a plurality of types of works. These thresholds are input by the operator using the input keyboard 58 while looking at the display device 57.

FIG. 3 is a diagram showing a change in the value of the measurement signal due to processing in this embodiment. The change in the value of the measurement signal is basically the same as in FIG. The threshold value for determining that the work has stopped is 50 μm / 500 ms during the rough grinding, 10 μm / 200 ms during the fine grinding, and the stop of the work is not detected during the spark out. Therefore, it is determined that the work has stopped when the value of the measurement signal does not change by 50 μm during 500 ms during the rough-polishing.
If the value of the measurement signal does not change by 10 μm within 0 ms, it is determined that the work has stopped. Here, the reason why the sampling interval in the rough polishing is longer than that in the fine polishing is that the processing speed is high and the error is large. However, this is merely an example, and various settings can be made according to the processing conditions.

FIG. 4 is a flow chart showing the work stop determination processing in this embodiment. The work stop determination process will be described with reference to FIG. In step 501, the processing mode at that time is detected. Information about the processing mode is obtained from the sizing device. In step 502, the processing mode is determined.
Proceeding to step 3, the threshold value at the time of rough polishing is read out and stored in the register, and if it is refined processing, it proceeds to step 504 and the threshold value at the time of precise polishing is read out and stored in the register. If spark out, it proceeds to step 505. . At the time of sparking out, since the work stop judgment is not performed, until the next work is processed,
Wait without performing work stop determination processing.

In step 506, steps 503 and 50 are performed.
The value of the measurement signal is read and stored at the sampling interval read in 4. The reading of the value of the measurement signal is also sampled to generate a sizing signal, which does not necessarily match the sampling interval read in steps 503 and 504. Normally, sampling for generating a sizing signal is performed more frequently, so some of them are ignored to match the sampling intervals. In step 507, sampling is performed similarly and the measured value is stored.

In step 508, the difference from the measured value at the previous sampling is calculated, and in step 509 it is determined whether it is smaller than the threshold value read in steps 503 and 504. If it is smaller, it is determined that the work is stopped, so the routine proceeds to step 510 to notify that an abnormality has occurred. If it is larger than the threshold value, it is normal. Therefore, it is detected in step 511 whether or not the machining mode is changed. If it is not, the process returns to step 507, and if it is changed, the process returns to step 502.

As is clear from the above processing, when the machining mode is changed, the amount of change in the value of the measurement signal will also be different, so the previously stored measurement value is ignored and newly stored. Judgment starts from the value. Also, in the above process, it is determined for each sampling whether there is a change in the processing mode, but this may increase the time from the change in the processing mode until the next sampling. When there is a change, interrupt processing may be performed.

As described above, in this embodiment, it is possible to determine whether the work is stopped. In addition, this work stoppage determination process can be realized only by adding a program to the computer provided in the original sizing device, and since it is not necessary to add hardware, it can be realized at a very low cost.

[0026]

As described above, according to the present invention,
Since the work stoppage, which is the cause of scratches that require visual inspection, is detected, it is possible to eliminate or greatly simplify visual inspection, which not only reduces manufacturing costs, but also may overlook defective products. Is reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a processing system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a hardware configuration of a measurement signal processing portion in the embodiment.

FIG. 3 is a diagram showing a change in the value of a measurement signal due to processing in the example.

FIG. 4 is a flowchart showing a work stop determination process in the present embodiment.

FIG. 5 is a diagram showing a configuration of a processing system using a conventional sizing device.

FIG. 6 is a diagram showing a change in the value of a measurement signal due to processing in a conventional example.

FIG. 7 is a diagram showing an example of a scratch caused by stopping rotation of a work.

[Explanation of symbols]

 11, 12 ... Sensor 13 ... Measuring head 18,19 ... Auto zero circuit 20 ... Processing unit 31 ... Signal processing / converting unit 32 ... Data processing unit 40 ... Processing abnormality detection unit 41 ... Determination unit 42 ... Threshold storage unit 43 ... Threshold Input unit 100 ... Workpiece (workpiece) 110 ... Machine tool (grinding device) 111 ... Grinding stone 112 ... Chuck 113 ... Control unit

Claims (6)

[Claims] 1. A measurement head (13) for outputting a measurement signal indicating a dimension of a machined portion of a workpiece (100), and a measurement signal output by the measurement head (13) are processed to determine a dimension of the machined portion. A sizing device comprising a processing means (20) for outputting a sizing signal for changing a processing condition when a preset target dimension is reached, wherein a change amount of the measurement signal per unit time is preset. A constant size characterized by comprising a machining abnormality detecting means (40) for judging whether or not it is below a predetermined threshold and outputting a machining abnormal signal when the amount of change in the measurement signal per unit time is below the threshold. apparatus. 2. The processing abnormality detecting means (40) is a threshold value storing means (42) for storing the threshold value, a threshold value stored in the threshold value storing means (42), and an amount of change per unit time of the measurement signal. The sizing device according to claim 1, further comprising a determining means (41) for comparing 3. The threshold value storage means (42) stores a plurality of threshold values corresponding to a plurality of processing conditions, and the determination means (41) stores a threshold value corresponding to the processing conditions and the measurement signal per unit time. The sizing device according to claim 2, which compares the change amounts of 4. The sizing apparatus according to claim 2, further comprising threshold input means (43) for inputting a threshold stored in the threshold storage means (42) from the outside. 5. A machine tool (110) for machining a workpiece (100), and the workpiece (1) being machined by the machine tool (110).
00) which outputs a measurement signal indicating the size of the processed part and the measurement signal output by the measurement head (13), and the size of the processed part reaches a preset target size. A processing system comprising a processing means (20) for outputting a sizing signal for changing processing conditions at times, and determining whether the amount of change of the measurement signal per unit time is less than or equal to a predetermined threshold value. The machining system is provided with a machining abnormality detecting means (40) that outputs a machining abnormality signal when the amount of change in the measurement signal per unit time is equal to or less than the threshold value. 6. A machining abnormality detection device for detecting abnormality occurrence in machining from a measurement signal indicating a dimension of a machined part of a workpiece (100) being machined, the unit time of the measurement signal during normal machining. Threshold value storage means (42) for storing the lower limit of the change amount per hit as a threshold value, and judgment means (4) for comparing the threshold value stored in the threshold value storage means (42) with the change amount per unit time of the measurement signal.
1) A processing abnormality detection device comprising: