JPH0957617A - Processing prediction control method and processing prediction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make proper prediction of processing even though alteration of a processing speed is made on the way of operation by making intermittent measurement of the processing conditions, calculating a prediction value on the basis of the old measuring value while measurement is not obtained, and performing the control in accordance with the prediction value. SOLUTION: A measurement value immediately before and the one before it are stored in a first register 31 and a second register 32, and from the difference between the two measurement values, a processing speed is calculated by a processing speed calculating means 33. The total amount of processing under the given processing conditions is calculated by a total processing amount calculating part 34. From the processing speed and the total amount of processing, the timing at which the processing conditions are altered is calculated by a changeover prediction time calculation part 35. When the processing conditions are to be altered, a comparison part 36 judges whether the specified value is exceeded by the ratio of the difference between two measurement values obtained by the calculating means 33 to the total amount of processing under the conditions after alteration, and if exceeded, the measuring value is reset and the processing situation is predicted anew.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures the processing status of a work piece at a time interval during processing, and predicts the processing status from the measured values up to that time until the next measurement. A machining prediction control method and a machining prediction device for calculating a control signal based on the predicted value, and a machining prediction control method and a machining method capable of more appropriate prediction even when machining conditions are changed during machining. It relates to a prediction device.

[0002]

2. Description of the Related Art In grinding, in order to improve the machining accuracy, a workpiece being machined may be measured and the machining may be controlled based on the measured machining situation. A typical example of such a processing method is an in-process automatic sizing device, which simultaneously grinds a workpiece and simultaneously measures the dimensional change of the workpiece, and according to the result. It automatically controls operations such as changing machining conditions and stopping machining.

In the processing such as grinding, the processing time, the processing accuracy, and the condition of the processed surface are problems. It is desirable that the processing time is short and good processing accuracy and the processed surface can be obtained. Therefore, usually, at the beginning of processing, the finishing state is not good, but roughing is performed at a high processing speed, and when it approaches the target value to a certain degree, the finishing state is good but the processing speed is low. Further, by performing processing called spark out, which has a better finishing state but a lower processing speed, high processing efficiency, good processing accuracy, and finishing condition are realized. A processing method for changing the processing conditions during such a process is not limited to grinding and is widely used.

Therefore, in the in-process automatic sizing device for grinding, the grinding operation such as rough grinding, fine grinding, spark out, and machining stop is automatically controlled according to the measurement result. However, in the case of grinding the inner surface of a small work piece, it is not possible to insert the stylus of the inner diameter measuring device into the inner surface with the grinding wheel inside. Therefore, for such a workpiece, a grinding wheel and a probe of an inner diameter measuring device are alternately inserted into the inner surface of the workpiece, and the machining is controlled based on the intermittent measurement result. However, in such a control method for automatic sizing, even if the dimension of the workpiece reaches the sizing during the measurement, that is, during the grinding, the sizing signal is not emitted until the next measurement. Since the grinding is continued, an error occurs in the finished size of the work piece.

In order to reduce such an error, various predictive control methods have been conventionally considered, but basically, it is assumed that the next measured value also changes from the change in the immediately preceding measured value. It is a method of predicting. The present invention is directed to a machining prediction control method and a machining situation prediction device that obtain a predicted value of a machining situation in the next machining from such measured values up to then and perform machining according to the predicted value. The machining prediction control method is effective not only when the inner diameter is measured as described above but also when the measurement cannot be continuously performed due to the processing capacity and the like.

FIG. 4 is a diagram showing the configuration of a conventional example in which machining is controlled on the basis of such intermittent measurement results. FIG.
In FIG. 1, reference numeral 100 is a work piece in which a cylindrical hole 101 is processed. 1 is a sizing device for an inner surface grinding machine, 2 is a grindstone for grinding the inner surface of the hole 101 of the workpiece 100, 3 is a grindstone control mechanism for moving the grindstone 2, and 4 is a cutting control mechanism. is there. 11 is a non-processed product 1
00 is a measuring instrument for measuring the inner diameter of the hole 101, and an example of an electric micrometer is shown here. Measuring head 11
Is repeatedly inserted into and retracted from the hole 101 in synchronization with the operation of the grindstone 2. Reference numeral 12 is an amplifier that amplifies the detection signal of the measuring head 11, 13 is an oscillation detection circuit that rectifies the output of the amplifier 12, and 14 is an integral sampling circuit that integrates and samples the output of the oscillation detection circuit 13. And 15 is the integral sampling circuit 1
Reference numeral 4 is an A / D converter for converting the output of 4 into a digital signal, 16 is a detection timer for detecting an oscillation interval from the output of the oscillation detection circuit 13, and 17 is a prediction time of a machining condition change timing. Is a predictive timer, 18 is an interrupt controller that generates an interrupt signal based on a signal from the predictive timer 17, 19 is a CPU that predicts the machining status, and 20 is a timing for changing the machining conditions output from the CPU 19. The signal point control circuit outputs a signal point signal to the cut control mechanism 4. The oscillation interval detection timer 16 generates a signal indicating the period during which the output of the measuring instrument 11 is effective from the output of the oscillation detection circuit 13, and the CPU 19 reads the digital signal output from the A / D converter 15 according to this signal. . The CPU 19 predicts the timing of changing the machining condition according to the output of the A / D converter 15 and the machining condition which is known in advance or obtained from the sizing machine 1, and sets the timer value in the prediction timer 17. When the prediction timer 17 counts the set time, the interrupt controller 18 receives the signal and causes the CPU 19 to generate an interrupt signal, and the CPU 19 outputs to the signal point control circuit 20 a signal indicating that it is time to switch the machining conditions. This is the cut control mechanism 4 from the signal point control circuit 20.
And the processing conditions are changed.

Even if an air micrometer or the like is used instead of a contact type detector such as an electric micrometer, the basic structure is the same. FIG. 5 is a diagram for explaining a change in the machining state when the above-described machining prediction control method is applied to the machining method in which the machining conditions are changed in such a way. As shown in Fig. 5, machining is performed in the order of rough polishing, precision polishing, spark out, and machining stop, and the measured value is preset at precision switching point X, spark out switching point Y, and final dimension (fixed size). When the point becomes Z, the processing conditions are changed. The measurement of the dimension of the processed portion, that is, sampling is performed at a constant cycle. Since at least the surface being measured is not processed during insertion of the stylus, a substantially constant measurement value is obtained. In order to eliminate the influence of noise and the difference due to the contact position of the stylus, the measurement value is integrated by the integration sampling circuit 14 during the sampling period, and the integration value is output as the measurement result. As described above, since processing and measurement are performed alternately, processing is not performed while the measured value is output,
The obtained measured value can be said to be the measured value in the state where the processing just before was completed. The state during processing is predicted from the measurement values obtained by the previous measurements, and this prediction is usually predicted by extrapolation. For example, when the difference between the measured value at a certain sampling point and the measured value at the previous sampling point is obtained, it is predicted that the measured value will change at that rate until the next sampling point. For example, the next sampling point E is predicted from the sampling points C and D in the precision polishing process. In this case, since the processing amount per unit time in the precision polishing process is almost constant, the measurement value at the sampling point E can be predicted with considerably high accuracy. Then, if it is assumed that the predicted measurement value will change to the next constant value, and if it becomes a switching point for changing the machining conditions during that time, the time to that point is proportionally calculated and the time is set in the prediction timer 17. It was

[0008]

However, when the processing conditions are changed, the amount of processing per unit time up to that point changes, so that the next measured value is predicted from the measured value up to that point. The error increases. Until now, the change in the machining amount per unit time due to the change of the machining condition was not so large, and even if the error was large when the machining condition was changed, the sampling was performed twice after the change of the machining condition. It is premised that the error is small, and the method of predicting the next measured value from the immediately preceding two measured values did not cause much problems.

However, in recent years, as the servo technology has improved, the cutting amount in the rough grinding tends to be large in order to shorten the grinding time, and further, the cutting amount in the fine grinding also sparks. It tends to be relatively large with respect to the cut amount at the out. Therefore, the amount of processing per unit time greatly changes with the change of the processing conditions. As described above, the conventional prediction method is based on the premise that the change in the machining amount per unit time due to the change in the machining conditions is small, and when the machining amount per unit time significantly changes with the change in the machining conditions, Since the change in the measured values up to that point is large, there is a problem called overprediction in which it is determined that the machining is proceeding at high speed and the dimension is reached at which the next machining condition is changed. In particular, near the finished size (fixed point), the grinding process is not limited to the polishing and spark-out process as shown in Fig. 5, but also the finishing cutting process, the finishing overcut process, the spark-out process,
In the case of finely dividing into the overfeed process and the like, there has been a problem that a switching signal or a sizing signal is output earlier than the actual processing state due to overprediction.

For example, in FIG. 5, there is a switching point to the precision laboratory between the sampling points B and C, and a switching point to the precision laboratory between the sampling points E and F. Since the sampling point D is predicted from the measured values of the sampling points B and C, it is predicted to be P, and has a large error from the actual sampling point D. But P
However, since the spark-out switching point is not reached at P, the measurement is performed at the sampling point D, and the sampling point E and the spark-out switching point Y are measured from the measured values at the sampling points C and D. Is accurately predicted. However, after switching to spark-out in FIG. 5, measurement at the sampling point F is performed, and Q is predicted from the measured value and the measured value at the sampling point E, but Q exceeds the sizing point. Therefore, according to this prediction, the machining is stopped in the middle of the process, and the machining is finished before the target fixed point is reached.

The present invention has been made in view of the above problems, and ensures that accurate machining is always performed even when the predictive control method is applied to a machining method in which machining conditions change midway. The purpose is to

[0012]

In order to achieve the above object, in the machining predictive control method of the present invention, a step of measuring the machining state of the workpiece at a time interval and the following measurement values In a machining prediction control method including a step of predicting a machining situation in machining up to the measurement of, and a step of controlling machining based on a predicted value, when machining conditions are changed, prediction is performed from the immediately preceding two measured values. If the amount of change in the machining status is greater than or equal to a predetermined ratio with respect to the total machining quantity under the machining conditions changed at this time, the predicted value of the machining status and the measured values up to that point are reset. If the amount of change in the machining status predicted from the two measurements immediately before the start of the process is less than or equal to a predetermined ratio with respect to the total machining amount under the machining conditions changed at this time, then leave it as is. Characterized by continuing each process To.

Further, the machining prediction apparatus of the present invention is provided with a first storage means and a second storage means for storing measured values immediately before and before, and measurement values stored in the first and second storage means. Machining speed calculating means for calculating the machining speed from the difference between the machining speed, the total machining amount calculating section for calculating the total machining amount under each machining condition, and the predicted switching time for calculating the timing for changing the machining condition from the machining speed and the total machining amount. In a machining prediction device that includes a calculation unit and performs machining while changing the machining conditions according to the measured values up to then, when changing the machining conditions, two measurements immediately before the modification of the machining conditions calculated by the machining speed calculation means are performed. A comparison unit that determines whether the difference between the values is a predetermined ratio or more with respect to the total machining amount under the changed machining conditions calculated by the machining total amount calculation unit is provided. If the difference between the measured values is less than the specified ratio When it is, the predicted value of the machining situation and the measured value stored in the first and second storage means are reset, and the machining situation is newly predicted according to the measured value after the machining condition is changed. To do.

When the amount of change in the processing situation predicted from the two previous measured values is large relative to the total amount of processing under the changed processing conditions, there is a high possibility that overprediction will occur. Therefore, in such a case, overprediction does not occur by stopping the prediction itself based on the measured values up to that point. If the amount of change in the machining situation predicted from the immediately preceding two measured values is small, overprediction does not occur, so prediction based on the measured values up to that point may be performed.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention is a grinding sizing device having a structure as shown in FIG.
It is characterized by the processing prediction device formed inside. Therefore, here, only the configuration of the processing prediction device formed in the CPU 19 will be described. FIG. 1 is a block diagram showing the functions realized in the CPU 19, and these functions are realized by software.

In FIG. 1, reference numeral 31 is a first register in which the measured value from the A / D converter 15 is input and stored in accordance with the detection timing signal from the oscillation interval detection timer 16 in FIG. Is the first register 3
2 is a second register that captures and stores the measurement value stored in 1 according to the detection timing signal. As a result, the measurement value of the immediately preceding sampling is stored in the first register 31, and the measurement value of the previous sampling is stored in the second register 32. Reference numeral 33 is a processing speed calculation unit that calculates the difference between the measurement values stored in the first register 31 and the second register 32 and calculates the processing amount during the sampling interval. Reference numeral 34 denotes a total machining amount calculation unit which calculates the total amount of machining under the machining conditions from the machining conditions such as switching points and sizing values which are input from the outside by the operator or transmitted from the sizing machine 1. Reference numeral 35 indicates the immediately preceding measured value stored in the first register 31, the machining amount during the sampling interval calculated by the machining speed calculation unit 33, and the machining amount under the machining conditions calculated by the total machining amount calculation unit 34. It is a switching prediction time calculation unit that calculates a switching prediction time for changing the processing condition from the total amount, and the time until the switching prediction time calculated here is set in the prediction timer 17 in FIG. Reference numeral 36 is a comparison unit, which compares the machining amount during the sampling interval calculated by the machining speed calculation unit 33 with the total amount of machining under the machining conditions calculated by the machining total amount calculation unit 34, and performs the machining. It is determined whether the total amount of processing under the condition is sufficiently larger than the amount of processing during the sampling interval.

FIG. 2 is a flow chart showing the prediction operation in the embodiment. The operation of each unit of FIG. 1 will be described below with reference to the flowchart of FIG. In step 201, zero is stored in the register i (not shown) and reset. In step 202, the measured value output from the A / D converter 15 is stored in the first register 31 based on the signal indicating that the measured value from the oscillation interval detection timer 16 is output. In step 203, the total machining amount calculation unit 34 calculates the total amount of machining under the following machining conditions. In step 204, the measurement value output from the A / D converter 15 is stored in the first register 31, and the previous measurement value stored in the first register 31 is stored in the second register 32. In step 205, the processing speed calculation unit 33 calculates the difference between the measurement values stored in the first register 31 and the second register 32, and calculates the processing amount during the sampling interval. In step 206, the comparator 36 determines whether the total machining amount under the machining conditions is sufficiently larger than the machining amount during the sampling interval. Here, when the machining amount calculated during the sampling interval calculated by the machining speed calculation unit 33 is larger than 1/3 of the total amount of the machining amount under the machining condition calculated by the machining total amount calculation unit 34, the overprede Step 2
In step 08, 1 is stored in the register i, and if it is small, it is determined that there is no possibility of overprediction and step 20
At 0, 0 is stored in the register i. In step 209, the time Te until the machining condition is changed next is calculated. In step 210, Te is set in the prediction timer 17.

When Te is longer than the sampling interval, the oscillation interval detection timer 1 is restarted before the prediction timer 17 counts the set time and interrupts.
Since the signal indicating that the measured value is output from 6 is output, the operation from step 204 is repeated, and the value of the register i is updated according to the immediately previous measured value. If Te is shorter than the sampling interval, the prediction timer 17 counts the set time and the interrupt controller 18 interrupts before the operation of step 204 is performed next.

When an interrupt occurs, in step 221,
A switching signal is generated in the signal point control circuit 20. This causes the sizing device to change to the next processing condition. In step 222, it is determined whether the register i is 0.
The value of the register i is stored as 1 when the total amount of processing under the processing conditions from the immediately preceding measured value is sufficiently larger than the processing amount during the sampling interval, and when the value is small, 0 is stored. . Therefore, if the register i is 0, there is no possibility of over-prediction, and therefore step 20
Return to 4. If the register i is 1, there is a possibility of over-prediction, so the routine proceeds to step 223 to clear Te, and the routine proceeds to step 201. This allows
Since the register i is cleared and the measured values are newly stored in the first and second registers, the prediction is not performed until the measurement is performed twice under the changed processing conditions. Therefore, there is no possibility of over-prediction.

Here, a method of calculating Te will be described. Dg is the measured value at the jth sampling
(J), Dg (j-1) is the measured value in the j-1th sampling before that, Dk is the dimension for changing the next processing condition, Tv is the sampling interval, and the last integration in the integration sampling circuit 14 is If the time required for the calculation from the end is Tvc, Te is Tv (Dg (j-1) -D
k) / (Dg (j-1) -Dg (j))-Tvc.

If the dimension under which the machining under the next machining condition is finished and the machining condition is changed to another machining condition is Dl, the total machining amount under the next machining condition is Dk-Dl, and step 206 The determination condition in Dg (j-1) -Dg (j)>
It is represented by (Dg (j-1) -Dl) / 3. Although such a determination condition is used here, this determination condition can be appropriately determined so that overprediction may not occur depending on the processing conditions.

FIG. 3 is a diagram for explaining an example of prediction when changing the processing condition from precision polishing to spark out in this embodiment. As shown in FIG. 3, it is assumed that the measured value predicted immediately before the sampling point E becomes the spark-out switching point. Therefore, at the sampling point E, it is assumed that the measurement value processed for a short time in the spark-out process is output. Since the previous measurement value is the value of the sampling point D, it is predicted that the conventional method will be the sizing point at a sampling interval of about 1/2 after the sampling point E. Therefore, at this point, the processing is stopped, but it is obvious that the target dimension is not the sizing point.
In the present embodiment, in this case, when the processing conditions are changed to spark-out, the above conditions are satisfied, and it is determined that overprediction may occur, so that it is possible to predict when changing the processing conditions to spark-out. Since it is stopped and a new prediction is made based on the measured values of sampling points E and F, no over-prediction occurs.

[0023]

As described above, according to the present invention, the processing state is measured intermittently, and while the processing state cannot be measured, the predicted value is calculated based on the measured values up to that point, and the control is performed according to the predicted value. In this case, even if the processing speed is changed in the middle, more accurate prediction can be performed.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing a prediction operation in the embodiment.

FIG. 3 is a diagram illustrating an operation in the embodiment.

FIG. 4 is a diagram showing a configuration of a sizing processing apparatus that intermittently obtains measured values.

FIG. 5 is a diagram showing an example of conventional control in a sizing processing apparatus that intermittently obtains measured values.

[Explanation of symbols]

 1 ... Sizing apparatus 2 ... Whetstone 11 ... Measuring instrument 12 ... Amplifier 13 ... Oscillation detection circuit 14 ... Integral sampling circuit 15 ... A / D converter 16 ... Oscillation interval detection timer 17 ... Prediction timer 19 ... CPU 31 ... 1st register 32 ... 2nd register 33 ... Machining speed calculation part 34 ... Machining total amount calculation part 35 ... Switching estimated time calculation part 36 ... Comparison part 100 ... Workpiece

Claims (2)

[Claims] 1. A measuring step of measuring a processing state of a work piece at time intervals, a prediction step of predicting a processing state in processing from a measured value up to that time to a next measurement, and a prediction step based on the predicted value. In a machining prediction control method including a control process for controlling machining by changing the machining conditions, when the machining conditions are changed, the amount of change in the machining situation predicted from the immediately preceding two measured values is If the ratio is more than a predetermined percentage of the total machining amount, the predicted value of the machining status and the measured values up to that point are reset, the above steps are started, and the prediction is made from the last two measured values. If the amount of change in the machining status is less than or equal to the predetermined ratio with respect to the total amount of machining under the machining conditions changed at this time, the above-mentioned steps are continued as they are Method. 2. A first memory for storing immediately preceding and previous measured values.
Storage means (31) and second storage means (32), and processing speed calculation means (33) for calculating the processing speed from the difference between the measured values stored in the first and second storage means, Total machining amount calculation unit (3 that calculates the total machining amount under the machining conditions
4) and a switching predicted time calculation unit (35) that calculates the timing of changing the processing conditions from the processing speed and the total processing amount, and performs the processing while changing the processing conditions according to the measured values up to that point. In the predicting device, when changing the processing conditions, the processing speed calculation means (3
Whether the difference between the two measured values immediately before the change of the machining conditions calculated in 3) is a predetermined ratio or more with respect to the total machining amount under the changed machining conditions calculated by the total machining amount calculation unit. A comparison unit (36) for determination is provided, and when the difference between the two measured values immediately before the change of the processing conditions is equal to or more than a predetermined ratio, the predicted value of the processing situation and the first and second storage means. (31, 3
A processing predicting apparatus characterized by resetting the measured value stored in 2) and newly predicting a processing situation according to the measured value after the processing condition is changed.