JPH06114637A - Shaping discharge machining method - Google Patents

Abstract

PURPOSE:To shorten the time of discharge machining and enhance the total processing efficiency by re-setting the command value in an NC program so that the processing accuracy approaches the target value on the basis of the processing result, and altering the processing conditions. CONSTITUTION:The presumed processing time estimated preceding to the previous processing and the actually taken processing time are read from the recorded data, and for each processing stage, the actual processing time is divided with the presumative processing time to undergo a comparison (S16). As a result, judgement can be passed to which degree the actual processing time lies relative to the processing time value which was presumed prior to the processing. The comparing results for different processing stages are compared, and the feed at the stage where the processing time took the longest for the target is increased (S17). The offset of the NC program is updated on the basis of this altered feed amount (S18), and the next processing is made according to this NC program.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a tool electrode (hereinafter referred to as an electrode).
And an object to be machined are opposed to each other, and the electrode and the object to be machined are moved relative to each other, and a pulsed voltage is applied between both electrodes to machine the object to be machined. The same type of machining is performed based on the NC program in which suitable processing conditions are set based on various parameters to obtain the shape, surface roughness, etc., and the optimum NC program is created each time the same type of processing is repeated. The present invention relates to a die-sinking electric discharge machining method.

[0002]

2. Description of the Related Art Generally, in electrical discharge machining, a machining speed and a machining accuracy greatly vary depending on electrical machining conditions such as an ON / OFF time of a pulse voltage applied, an average machining current value or a servo reference voltage value. Further, differences in machining conditions such as machining allowance, electrode feed amount, machining liquid jet pressure, flow rate, and whether polarity is switched affect the machining result. Further, the mutual relation of these processing conditions affects the processed surface roughness, the processing speed, or the processed shape accuracy. In order to perform the desired processing more appropriately on the work piece, that is, in order to increase the processing speed as much as possible without damaging the material and shape of the electrode and the work piece, generally rough, medium, and finishing are divided into several stages. These various processing conditions are set to appropriate values for processing, and finally the processed surface roughness and shape are approximated.

When the electric machining condition is set to a large value so that a strong discharge energy is generated, the machining amount is high for each discharge, so that the machining accuracy is fast, but the obtained surface roughness is rough. Will be less accurate. On the other hand, when the above electrical machining conditions are set to a small value such that weak discharge energy is generated, the machining rate becomes slower because the amount taken per discharge is small, but the machined surface roughness And shape accuracy are improved. For this reason, the rough machining is performed once, and the whole machining is divided into several stages, and the machining conditions are sequentially set to be smaller, and the machining is performed.

Furthermore, since the required gap is maintained between the electrode and the workpiece, the electrode must be made smaller than the desired machining shape. The value obtained by making the electrode smaller than the processed shape is called the electrode reduction amount or the electrode reduction allowance, but this value is determined in consideration of problems in electrode production. Further, in electric discharge machining, not only the workpiece but also the tool electrode is removed and consumed by the discharge energy as the machining progresses. This degree of wear is affected by various processing conditions. Further, when the same processing is performed a plurality of times, the same electrode is often used repeatedly.

Therefore, the amount of the electrode fed in the machining depth direction or the lateral direction is appropriately set in accordance with the electrode reduction amount and the electrode consumption, which is the dimensional difference between the machining shape size and the electrode formed smaller than that. There must be. In the old days, the operator decides the amount of electrode reduction for the required processing, and based on this electrode reduction amount, surface roughness, processing shape, etc., make a processing plan while considering the processing time, and based on the processing plan. NC to determine the machining conditions of each machining stage and the feed amount and swing amount of each machining stage.
It was designed to be processed by programming. Since this setting requires experience and skill, it requires a worker who has a long working time and is skilled in electrical discharge machining.

On the other hand, in the apparatus disclosed in Japanese Examined Patent Publication No. 60-26648, machining is performed by a combination of electrical machining conditions set by an expert, and the machining conditions at that time are stored and the same is stored. When the types of machining are performed, the stored combinations of the electrical machining conditions are read and set to reduce the work time in the next machining. However, in such an apparatus, when setting the electromachining conditions for the first time, a skilled worker determines the electrode reduction amount while considering the machining accuracy and the machining time, and determines the appropriate amount based on various machining parameters. It is necessary to obtain the electromachining conditions and set the command value of the feed amount of the electrode and the swing width of the electrode. Further, the electromachining conditions set by the skilled worker do not always bring good results in the next machining. In addition to this apparatus, an apparatus for automatically selecting the optimum machining conditions by giving parameters and automatically creating an NC program is disclosed in, for example, JP-A-62-130130 to JP-A-62-130. 130
There is a device disclosed in Japanese Patent No. 131.

In this apparatus, data showing the relationship between the electrode reduction amount and the machining time suitable for the machining is obtained based on the data of the material of the electrode and the workpiece, the machining area, the desired finished surface roughness and the machining depth. Several types are calculated from one type and displayed. The operator selects from the displayed data showing the relationship between the electrode reduction amount and the processing time in consideration of problems in electrode production. Then, while setting the number of machining condition switching stages and the combination of machining conditions in each machining stage that are adapted to the selected electrode reduction amount and machining time, the electrode feed amount of each machining stage from the required machining depth and The swing amount is calculated and an NC program is created. As an attempt to eliminate the complexity of the work when such an operator makes a machining plan, JP-A-62-19324 and JP-A-62-62324 are proposed.
-173142, JP-A-62-173144, JP-A-62-7231, JP-A-3-13
Various methods have been proposed, such as Japanese Patent No. 6725, and these devices allow an operator to shorten working time and set appropriate machining conditions and various command values.

[0008]

However, in the electric discharge machining, as described above, the machining conditions, the machining environment, or the conditions possessed by individual machines are intricately and complicatedly intertwined with each other to affect the machining result. The machining conditions and the set command values used do not always bring good results. In that case, it is not easy to change the machining conditions and modify the NC program, and it is an experience and labor-intensive work. Further, even if the desired processing accuracy is obtained under those conditions, there are cases where better processing is possible, and it is possible to increase the processing speed without sacrificing the desired processing accuracy. It may be possible to make settings and create NC programs. The object of the present invention is to solve this problem, to allow the operator to change the machining conditions and modify the NC program more easily than before, to obtain a good machining result each time the machining is repeated, and to reduce the machining accuracy. An object of the present invention is to provide an electric discharge machining method capable of improving machining speed without tightening and further improving overall machining efficiency.

[0009]

In order to solve the above problems, the present invention uses a numerical controller to input a plurality of parameters and expected numerical values of a machining result through an input device. Machining conditions according to each machining stage suitable for the plurality of parameters and the expected machining result are automatically set, and electrical discharge machining is performed using an NC program created based on the set machining conditions. In the electric discharge machining method, the step of recording the machining result obtained by the electric discharge machining in the storage device or the recording medium after the electric discharge machining is finished, the expected machining result and the electric discharge machining A step of evaluating the result of the machining by comparing the result with a step of modifying at least one portion of the NC program based on the evaluation. Changing at least one of the machining conditions used by the electric discharge machining according to the change of the machining conditions and storing a corrected record of the electric discharge machining in a storage device; and the modified NC program. And a step of repeating the above-mentioned NC program every time the electrical discharge machining is performed to create a desired NC program.

[0010]

According to the electric discharge machining method of the present invention, after the electric discharge machining is performed according to the initially set electric machining conditions of each machining stage, the feed amount of the electrode or the swing amplitude of each machining stage, Based on the machining result, the machining condition is changed by resetting the command value in the NC program so that the machining accuracy can be closer to the target value or the machining efficiency can be improved and the machining time can be shortened. Therefore, it becomes possible to finally obtain the set value that has the best machining efficiency and shortens the machining time during the repeated machining.

[0011]

Embodiments of the die-sinking electric discharge machining method according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an example of the basic configuration of an electric discharge machine. First, the outline of the apparatus used in the method of the present invention will be briefly described using this block diagram. E is an electrode and W is a workpiece, which are arranged facing each other with a required gap. A motor MX allows the X-axis direction moving table 1 to reciprocate horizontally in the X-axis direction, and a motor MY allows the Y-axis direction moving table 2 to reciprocate horizontally in the Y-axis direction. Further, the machining head unit 3 can be vertically moved by the motor MZ.

A drive controller 4 drives or stops the motors MX, MY to MZ on the basis of a command signal from the machining controller 5 to move the tables 1 and 2 to the machining head unit 3 to form electrodes E. The workpiece W is relatively moved. Further, the drive control device 4 corrects the error with respect to the movement command by the detection signals of the position detection devices 14 to 16 provided on each axis, and the current position signal is processed by the processing control device 5.
Send to. The processing control device 5 performs arithmetic processing according to a designated system program or NC program and sends a control signal to each device. In addition, information processing from outside is performed. It should be noted that one or a plurality of members such as CPU and ROM, which are the central components of the processing control device 5, may be provided.

Reference numeral 6 denotes an input device, which is constructed so that a parameter or a predetermined command can be input using not only a switch but also a symbol, a numerical value or the like. A display device 7 receives commands and data from the processing control device 5 and appropriately displays numerical values, figures, graphs, etc. on the screen. There is also a display device 7 having an input function. An external data storage medium 8 can receive data such as an NC program stored in a storage means such as a floppy disk, a machining condition list, a system program, or the like. A temporary storage device 9 stores various preset values, recorded values, and external data obtained during operation, in addition to preset data. An external recording device 10 can store various data as in the temporary storage device 9 and the external data storage medium 8.

Reference numeral 11 denotes a detection circuit which detects the voltage or current between the electrodes, digitizes the signal, and compares it with a predetermined reference signal to send a signal between the electrodes to the machining control device 5. A machining pulse generator 12 controls ON / OFF of a switching transistor (not shown) provided in the machining power supply circuit 13 to determine the ON time / OFF time of the machining voltage pulse supplied between the electrodes. The workpiece W is installed in the machining tank 17, immersed in the electric discharge machining fluid 18, and fresh machining fluid can be circulated and supplied from a machining fluid supply device (not shown) during machining. Reference numeral 19 is a graph showing the processing state of the printer and NC
Can output programs etc. It should be noted that the above shows the basic mode in which the method of the present invention can be carried out, and needless to say, is not limited to the mode of this apparatus.

Before describing the method of the present invention, the relationship between the electrode feed amount, the swing amount, the machining allowance, the surface roughness and the offset will be described. FIG. 2 shows the relationship between the electrodes and the workpiece. In this illustrated example, a state is shown in which the machining is first started, and after the first machining stage is completed, the machining is shifted to the second machining stage. The electrode at the reference position starts machining feed starting from that point. The distance from the electrode reference position to the end of the electrode at the end of the first processing step is the electrode feed amount in the first processing step. The portion from the surface of the workpiece to the end of the electrode located at the end of the first processing step is the stock removal in the first processing step.

The electric discharge machined surface is not uniform but finely uneven. This is defined as the processed surface roughness, and is expressed by the distance between the peaks and valleys of this fine uneven portion. Then, for example, from the portion corresponding to the peak of the processed surface roughness obtained in the first processing stage to the first
The distance to the tip of the electrode after the processing step is the overcut in the first processing step. The distance from the side surface of the electrode at the reference position to the target final finishing surface is the electrode reduction amount,
When the electrode moves in the lateral direction, the amount of swing (or one-side swing amplitude, step amount) of the electrode is generally from the electrode side face at the reference position to the position closest to the side face of the processed part of the workpiece. The offset is the distance from the target shape to the end surface of the electrode, and coincides with the overcut amount during finishing.

FIG. 3 shows the relationship in the machining depth direction, where H is the feed amount, G is the overcut, and R is the machined surface roughness. This figure shows how the machining progresses from the left side. The first machining stage is the first rough machining, and the third machining stage is the final finishing machining. The machining conditions of each machining stage are set respectively, and the NC program has a set of machining condition sequences in which a plurality of types of machining conditions are combined by a code for each machining stage.

Since the machining conditions are set to relatively small values in order from the first machining stage to the third machining stage, the electrode feed amount, overcut, machined surface roughness or offset value becomes smaller respectively. . As described above, the offset value at the final finishing stage is such that the final finished surface roughness is below the final finished surface, so the offset value at the final finishing stage is Matches the overcut amount. Therefore, if the offset value in the first processing stage is X1 and the offset value in the second processing stage is X2, the feed amount H2 in the second processing stage is X1-X2.

FIG. 4 is a view showing the relationship in the side surface direction, and shows how the machining progresses from the upper side. In this case, the swing amplitude (step amount) on the side surface is shown. Here, L is an electrode reduction amount, G is a side surface overcut amount, ε is a swing amount, and R is a side surface processed surface roughness. In this figure, the swinging process is not performed in the first processing stage.

The movement in the side surface direction is represented by the swing amount ε. If the offset value of the side face is X, the swing amount ε at each processing stage is LX. The offset value in the side surface direction is calculated with reference to the angle θ when the electrode has a tapered shape. FIG. 5 shows the relationship between each machining stage, machining plan, each machining condition group, and NC program.
This relationship is not particularly limited to this mode, but generally, there is a file of machining conditions regardless of whether they are combined or individual, and whether or not electrical machining conditions or oscillating machining or jet flow exists,
Machining conditions such as the presence / absence of polarity switching are added to the machining condition number in the NC program and stored. These can be displayed on the display device 7 at any time, and the worker can output them to the screen of the display device 7 as needed, and the worker can confirm or correct the contents. still,
Since the details of these settings are the same as those of the conventional one, detailed description of symbols and contents will be omitted.

Next, a method of creating the first NC program will be described with reference to the flowchart of FIG. First, an operator first creates an NC program for machining a desired shape including a machining condition command value, a movement command value, etc. in advance, and stores it in the external data storage medium 8, the external recording device 10 or the temporary storage device 9. Remember. There are various conventional methods for creating this NC program, and the conventional method can be used for the first machining. Here, the following settings are made. The operator selects and inputs the material of the electrode, the processing form, and the processing shape in accordance with the instruction displayed on the display device 7 (S1). Further, the machined bottom area and the desired finished surface roughness are input (S2). Also, the number of electrodes used and the minimum gradient angle θ when the electrodes are tapered
Enter.

Next, the machining control device 5 obtains the maximum average machining current value that can be obtained by obtaining the total volume to be removed by machining. As a result, the maximum possible processing conditions in the first processing stage are recognized. The stored data indicating the applicable electrode reduction amount corresponding to the input parameters is extracted. Then, the processing conditions including the average processing current value IP suitable for the target finished surface roughness value are extracted from the storage device to form a combination of the processing conditions. The machining stage and its condition are sequentially determined from the recognized maximum and minimum average machining current values.

Then, the corresponding machining speed is obtained from the machining speed data recorded in advance from the final machining stage, and the estimated machining time of the final machining stage is found from the surface roughness. By performing this calculation sequentially for each machining step, the estimated machining time of each machining step is calculated, and the total of the estimated machining times of these machining steps becomes the estimated machining time of the entire machining (S3). A plurality of correspondence tables showing the relationship between the workable electrode reduction amount and the working time are displayed on the display device 7 (S
4). Here, basically, the operator may select the electrode that can be manufactured and has the shortest processing time (S5).

Next, the operator inputs the processing depth. The machining control device 5 determines the number of machining steps and the electrical machining conditions corresponding to the desired finished surface roughness specified previously based on the previously selected electrode reduction amount and the inputted machining depth. Is selected from a plurality of processing condition rows and set (S6). Further, the operator inputs a swing shape when performing swing machining, and the machining control device 5 obtains the electrode feed amount H and the electrode swing amplitude ε at each machining stage corresponding to the selected electromachining condition.

Then, the operator selects and sets the shape of the electrode swing according to the displayed menu (S7). Finally, based on the depth feed amount H of the electrode, the electrode oscillation amplitude ε, the combination of electromachining conditions, etc., an NC program is made and recorded. The operator temporarily displays the created NC program and, if necessary, modifies a part of the NC program to obtain a desired NC program (S8). When the preparation for processing is completed, the operator presses a switch such as the input device 6 (not shown) to instruct the start of processing (S9). During machining, the machining control device 5 obtains a machining gap state detection signal from the detection circuit 11 and stepwise on the basis of a preset machining feed amount or machining condition in accordance with the machining state which is sequentially changing. An appropriate command value is sent to the drive control device 4, the machining pulse generator 12, etc. so as to raise or lower the value in order to maintain a good machining state at all times.

The above may be carried out by various conventional methods as described above, but the work of the operator is easy and the working time is shortened without sacrificing the desired processing accuracy. It should be considered as well done. During this electric discharge machining, the machining time actually required for this machining is continuously stored so that each machining step can be graphed. In addition, the behavior of the electrode, the discharge efficiency data, and the like are stored by continuously recording the values in each predetermined sampling period (S10). It should be noted that the discharge efficiency indicates the number of discharge repetitions in a predetermined time, but here, it is expressed using the ideal number of gates and the actual number of gates during a predetermined sampling period.

These in-process data are used as a reference for the next process. Since it is necessary to keep the total number of data constant for easy comparison later, the data recording period or sampling period may be determined by the first estimated processing time and the number of data. The records of those processes are stored in the external recording device 10 or the external recording medium 8. At this time, all the set values such as the material of the electrode used at the same time, the material of the work piece, the number of times of using the electrode, the target surface roughness, the electrical machining conditions, the electrode reduction amount, and the NC program are saved, It is advisable to record it as a symbol or number.

When the electric discharge machining is completed as described above (S11), in order to further shorten the machining time without impairing the machining accuracy in the next machining, the N used in this machining is used.
Try to modify the C program easily. Usually, in the electric discharge machining, a slight deviation occurs in the desired product at this point. Also, there may be a setting method that requires less processing time. Therefore, after that, the NC program is changed so that the result of this machining can be used more efficiently without reducing the next machining accuracy.

A method of updating the NC program of the present invention will be described with reference to FIGS. 6 to 9. First, the worker measures the finished surface roughness of the side surface and the bottom surface as a processing result (S1).
3). This may be directly measured by an operator or may be automatically measured by providing a measuring device such as a laser, but here, it is assumed that the operator measures. This measurement result is sent to the external recording device 1 via the input device 6.
Record it at 0 etc.

Next, the dimensional difference between the intended processed shape and the actual processed shape with respect to the lateral direction and the depth direction of the processed shape is measured and recorded as in the case of the surface roughness. This data can also be automatically measured and recorded using a measuring device such as a laser, but it will be described as being performed by an operator. Similarly, the electrode wear length is recorded. This electrode wear length is the relationship between the wear rate α and the electrode wear length l, the working depth d, and the number of times of use a: 1 = α · d
-Represented by a. The data of the electrode consumption length is used when correcting the feed amount or the swing amount of the electrode when the same electrode is repeatedly used.

First, the first method will be described. This method calculates a more preferable electrode feed amount on the bottom surface (processing depth direction), side surface (feed amount in the side surface direction) or offset value from past processing data depending on the processing time. Note that the following points are used here for the reduction of the processing time and the improvement of the surface roughness. Even if the electrical processing conditions are properly set, the surface roughness will be left unremoved if the electrode feed amount is inappropriately set. Further, in the electric discharge machining, the machining speed becomes slower toward the finishing machining stage, so that if the machining allowance in the finishing machining stage is large, the entire machining time becomes long. Therefore, in this method, the machining time is mainly short-circuited, the feed amount is corrected, and all the values to be changed are automatically changed in accordance with the correction. The processing control device 5 compares the required surface roughness allowance Rr with the actually measured surface roughness Ra (S15). If the actual surface roughness Ra is less than or equal to the allowable value Rr (YES), it is determined that there is no problem in terms of surface roughness. The permissible value Rr is defined by Rr = Rp · (1 + Rk [%]) μmRmax (1). However, Rp is a target surface roughness, and Rk
Is a value shown as a ratio to Rp.

For example, the target surface roughness Rp is 10 μm,
When the value recognized in the product is within 10% of the target surface roughness, the allowable value Rr is 11 μm. Therefore, in this case, if the actually obtained surface roughness Ra is 11 μm or less, the processed surface roughness is good. When the measured value Ra is worse than the allowable value Rr (NG), the remaining amount must be reduced in order to improve the surface roughness.
Therefore, the next processing may be performed by slightly increasing the feed amount in the machining depth direction or the feed amount in the side surface direction (hereinafter, simply referred to as the feed amount). The offset is changed on the NC program. Note that the relationship between the stock removal, the feed amount, the offset, etc. is as described above, and therefore the description thereof is omitted here.

Then, the estimated machining time Tp estimated prior to the previous machining and the machining time Ta actually required
Is read from the recorded data, and the actual machining time Ta is divided by the estimated machining time Tp for each machining step and compared (S1).
6). As a result, it is determined how much the actual processing time was with respect to the processing time predicted before the processing. Then, the comparison results of the respective processing steps are compared with each other, and the feed amount is increased in the processing step in which the processing time is the longest with respect to the target (S17). It should be noted that on the NC program, the offsets of all the previous stages are changed. In the example of FIG. 10A, the feed amount, for example, the processing time Ta3 in the third processing stage
If the achievement rate of 1 is highest, the feed amount in this processing stage is increased. Increasing the feed rate generally results in increasing stock removal. Here, the machining allowance value is increased by 10 μm with respect to the bottom surface reference value, but this increase amount is taken into consideration so as not to always perform over-machining. By doing so, it is possible to solve the shortage of the machining feed amount and bring it close to the desired surface roughness. As described above, changing the feed amount in the third machining stage requires changing the offset in the first and second machining stages on the NC program.

NC based on this changed feed amount
The program offset is updated (S18), and this NC
The following processing is performed by the program (S9). As a result, in the next processing, processing with better surface roughness can be expected. On the other hand, when the actual surface roughness Ra is equal to or less than the allowable value Rr (OK), it means that at least the finished state is not bad (S15). However, there is a sufficient possibility that this surface roughness Ra can be obtained in a shorter processing time.

Therefore, the actual processing time Ta at each processing stage
Is checked to see if it is taking too long for the target machining time Tp, and the total machining time is shortened by reducing the feed amount in the machining step which takes time. Here, the allowable time Tr is designated, and the quality of the processing time is judged by comparing the actual processing time Ta with the allowable time Tr for each processing stage (S19). Tr = Tp · (1 + Tk [%]) min …………………… (2) where Tp is the target machining time and Tk is a value shown as a ratio to the target machining time Tp. is there.

For example, if the target machining time is 38 minutes and the delay is up to 25%, the allowable time Tr is 47 minutes and 30 seconds. If the actual machining time Ta exceeds the target machining time Tp beyond the allowable range, the estimated machining time Tp estimated prior to the previous machining and the actually machining time Ta are recorded data. The actual machining time Ta is divided by the estimated machining time Tp and compared for each machining condition. Then, it is determined how much the actual processing time was with respect to the processing time predicted before the processing. As a result, the comparison results of the respective processing steps are compared with each other to reduce the feed amount in the processing step that requires the least processing time for the target (S20). At this time, as described above, the offset is reduced in the NC program.

In the example of FIG. 10B, for example, when the achievement rate of the machining time Ta3 in the third machining stage is the lowest, the feed amount in this machining stage is reduced. Increasing the feeding amount also increases the stock removal,
Here, the machining allowance value is reduced by 10 μm with respect to the bottom surface reference value, but this reduced value is always taken into consideration according to each set electrical processing condition. Therefore, if the feed amount of the machining stage having the best comparison result cannot be changed, the feed amount of the machining stage having the best comparison result is changed next. By this work, the NC program is updated (S18), and this NC program is used in the next machining (S9). By using this NC program, the machining time can be shortened to the extent that the machining accuracy is not lost in the next machining.

When the machining time is within the estimated machining time at each machining stage, it is judged that the command value of the substantially optimum machining condition in the machining is obtained, and the update of the NC program is completed. Yes (S22). This NC
By using the program, it is possible to perform machining with a shorter machining time while obtaining the expected surface roughness in subsequent machining. When updating the NC program by the second method, the NC method is further updated by the second method.
Attempt to update the program (S21).

Next, the second method will be described. This method is to correct the NC program by finding the cause by the erasing method based on the past processing information when the processing accuracy and processing time targets are not achieved. This method is based on the following points. As described in the first method, that is, when the surface roughness is poor, even if the electrical machining conditions are proper, if the feed amount is not proper, the surface at the previous machining stage remains and can be left unremoved. Further, if there is a large stock removal in the finishing step, the processing time becomes long. In this method, the cause is clarified by examining each processing stage, so the feed amount is corrected on the surface roughness improving side and the offset is corrected on the processing time reducing side.

First, the required allowable surface roughness Rr is compared with the actually obtained surface roughness Rb measured in this processing (S23). If the actual surface roughness Rb is equal to or less than the allowable value Rr, it is determined that there is no problem in terms of surface roughness. This comparison is the same as the method at S1 of comparing the surface roughness by the first method. When the actual surface roughness Rb is worse than the allowable value Rr (NG), it is determined that the machining feed amount is insufficient and there is a leftover portion.

In this case, first, the record data of the past processing is searched, and it is determined whether the surface roughness has been better than the allowable value (S24). If the surface roughness has not been better than the allowable value in the past machining (NO), search the past data further to see if this is the first time to correct the surface roughness. (S2
5). This is because it is necessary to set the first correction point to the first processing stage in order to make corrections in order from the rough processing stage.
If the surface roughness is bad and the NC program has been updated in the past (YES), as a result, it is determined whether or not the surface roughness of this machining is better than that of the previous machining. The surface roughness Rb and the surface roughness Rc of this processing are compared to obtain (S26). This comparison is the surface roughness R of the previous processing
The evaluation value Rr 'is calculated using a, and the surface roughness R of this machining is calculated.
If c is within the evaluation value Rr ′, it is considered that the surface roughness of processing is improved. Rr ′ = Rb · (1−Rk ′ [%]) μmRmax (3) However, Rk ′ is a designated ratio.

When the surface roughness Rb of the current machining is better than the surface roughness Rb of the previous machining (OK), the offset of the machining stage changed when the NC program was updated last time is further increased. By doing so, the processing shortage is resolved (S27). This is the offset changed on the NC program when the NC program was last updated (S28). The machined surface roughness Rc is the previous machined surface roughness Rb
If it is worse (NO), it can be seen that the surface roughness did not improve at the machining stage when the feed amount was changed when the offset of the NC program was last updated, so the next change It is checked whether or not there are processing conditions at the processing stage (S29).

If there is another machining condition that can be changed next (YES), the offset is once returned to the previous value and the feed amount at that machining stage is increased (S).
30). This completes the update of the NC program this time (S30), and the next processing is performed (S9). If there is no machining condition of another machining stage that can be changed next (N
In (O), the offset is temporarily returned to the previous value, and a machining stage is added as shown in FIG. 5C according to a predetermined average machining current under the final finishing machining conditions of the existing machining stage (S31). ).

In S25, if the NC program was not updated in the past to improve the surface roughness due to the poor surface roughness (NO), the feed amount in the first machining stage is first set. If the feed rate cannot be changed due to the relationship between the feed rate and the electrode reduction value, the average machining current value is lowered by one step in the electrical machining conditions such as on time and off time to weaken the electric discharge machining energy. (S3
2). The first machining stage is the first rough machining stage, and it is intended to prevent over-machining in the initial machining by increasing the machining feed amount at this stage or decreasing the average machining current value. is there. This makes this NC
After updating the program (S28), the next processing is performed (S9).

If the surface roughness was good in the past at S24, that is, if the actual surface roughness was less than the allowable value, it is possible that the surface roughness was deteriorated by updating the NC program last time. There is. Therefore, N of the machining stage changed last time
The offset of the C program is returned to the value before the change (S33). Here, the reason for changing the offset instead of the feed amount will be briefly described. In the case of the feed amount, only that machining step will be changed, but in the case of offset, the machining steps above that machining step will also be changed in order.By focusing on the offset, the cause is clarified and effective. Can be modified to.
Therefore, at least the offset of the processing stage cannot be changed any more (S34). Therefore, it is checked whether or not there is a processing condition at another stage (S3).
5).

If a machining condition of another stage exists (YES), the offset of the machining stage one step higher than the machining condition of the machining stage which has reached the update limit is reduced (S3).
6). Incidentally, the reason why the processing steps below are not changed is that the processing steps below this have already been changed. This completes the update of the NC program this time (S28), and the next processing is performed (S9). If the processing conditions of the upper stage do not exist (NO), it is determined that the surface roughness and the processing time are compatible with each other in all the processing conditions of the processing stages (S37).

By the way, when the NC program is processed next time, the surface roughness may not be deteriorated or the processing time may be too long. Here, whether the result is more stable or not is obtained. To make sure that
Once again, perform machining with the NC program and NC
Try to update the program. On the other hand, when it is determined that the change of the offset has already reached the limit in all the machining steps that can achieve both the surface roughness and the machining time when machining is performed by the NC program after the last machining is completed, It is determined that the update of the NC program is completed (S
38). When machining is performed using the NC program determined in this way, after the electric discharge machining shown in the flowchart of FIG. 6, it is confirmed whether the update of the NC program is completed (S12), and the update of the NC program is completed. If it is determined that the NC program has not been updated, the update of the NC program is tried again (S14) even if it is determined in S39 that the offset change limit has been reached.

On the other hand, in S23, when the surface roughness of the previous processing is within the allowable value and it is judged to be good (O
In K), it is first checked whether or not the NC program has been updated in order to see whether or not the machining time can be further shortened despite the good surface roughness in the past (S39). In other words, this is because the lower machining step is corrected here, so that in the first case, the machining step to be corrected first must be one machining step higher than the final machining step. As a result, if the NC program has been updated (YES), the offset of the machining stage changed last time is reduced to further shorten the machining time (S41). Then, along with the change in the offset, the machining allowance, the feed amount or the swing amount are updated (S42), and the next machining is performed (S9). If the NC program has not been updated (NO), the offset in the machining step that is one step higher than the final machining step is reduced (S4).
1). Note that the offset in the final processing stage impairs the shape accuracy, so it is not changed. The NC program is updated according to this change (S42).

As described above, each time the machining is repeated, the feed amount or the offset value is changed with reference to the machining result and the machining data, so that the desired surface roughness can be obtained and the machining time can be improved. It is possible to create an NC program that can further reduce Therefore, each time the machining is repeated, the machining time can be further shortened without impairing the machining accuracy.

By the way, here, the offset value is updated according to the roughness of the machined surface. However, for example, shape accuracy data has already been obtained. It is highly possible that this dimensional difference is due to a wrong overcut. By comparing the obtained shape accuracy processing result data with the allowable shape data value to correct the overcut amount in sequence, it is possible to perform processing with higher shape accuracy. Further, the same operation as the NC program update as described above can be performed.

Here, the electrical processing conditions are not updated except for a part. There are many uncertainties in electromachining conditions and there is a risk of damaging the machining shape especially in the final finishing stage.Avoid changing electromachining conditions aggressively to shorten machining time. However, as a third method, a routine for updating the electrical processing conditions can be added. In particular, as described above, the data on the discharge efficiency and the behavior of the electrode during the electric discharge machining are obtained at every predetermined sampling and sequentially recorded. Such data may be an effect of electrical processing conditions, among others.

For example, when the discharge efficiency is lower than the allowable range, the average machining current value and the applied voltage may be set incorrectly, or the combination thereof may be bad. It is possible to change the processing conditions and improve the discharge efficiency. Alternatively, in the behavior of the electrode, when the change rate of movement is far from the normal range, there is a possibility that the setting of the servo speed is incorrect. Therefore, by checking whether the data of the behavior of the electrode is within the normal range, it is possible to sequentially set the servo speed to an appropriate direction each time the machining is performed, so that more stable machining can be performed.

[0053]

As described above, according to the electric discharge machining method of the present invention, the following excellent operational effects can be exhibited. Since the machining conditions are automatically set based on the machining parameters, the NC program is created, and the created NC program can be updated relatively easily and appropriately, the machining is repeated. For each time, it is possible to easily obtain an NC program that can perform machining with a shorter machining time without impairing the machining accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic configuration of an electric discharge machine for carrying out the method of the present invention.

FIG. 2 is a diagram showing a relationship between electrodes and a workpiece.

FIG. 3 is a diagram showing a relationship between a processing stage and a processing depth direction.

FIG. 4 is a graph showing a relationship between a processing stage and a lateral direction.

FIG. 5 is a diagram showing a relationship among each machining stage, a machining plan, a machining condition group, and an NC program.

FIG. 6 is a flow chart for explaining the method of the present invention.

FIG. 7 is a flowchart for explaining a first updating method.

FIG. 8 is a flowchart illustrating a second updating method.

FIG. 9 is a flowchart illustrating a second updating method.

FIG. 10 is a graph showing a machining allowance value with respect to a processing standard of a bottom surface.

[Explanation of symbols]

 4 Drive Control Circuit 5 Machining Control Device 9 External Storage Device 10 Temporary Storage Device 11 Detection Circuit 12 Machining Pulse Generator 13 Machining Power Circuit 17 Machining Tank 18 EDM Liquid E Electrode W Workpiece

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshio Ishizu 78 Nagaya, Sakai-machi, Sakai-gun, Fukui Prefecture Sodick Fukui Factory Co., Ltd. (72) Inventor Noritake Mitsuya 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (3)

[Claims] 1. A machining step suitable for the plurality of parameters and the expected machining result by inputting a plurality of parameters and numerical values of an expected machining result through an input device using a numerical controller. In the electric discharge machining method in which the electric discharge machining method is automatically set, and the electric discharge machining is performed by using the NC program created based on the set machining condition. Recording the result in a storage device or a recording medium; evaluating the result of the machining by comparing the expected result of the machining with the result of the electric discharge machining; and the NC based on the evaluation. A step of modifying at least one part of the program, and a step of modifying the NC program together with the modification of the machining conditions used by the electrical discharge machining. A step of correcting at least one position and storing a corrected record of the electric discharge machining in a storage device; a step of performing electric discharge machining again using the corrected NC program; and a step of correcting the NC program every time electric discharge machining is performed. And a step of repeatedly performing the above steps to create a desired NC program. 2. The die-sinking electric discharge machining method according to claim 1, wherein the desired NC program is created by using the data relating to the corrected recordings of the past NC program of a plurality of times obtained by repeating the above-mentioned steps. 3. The die-sinking electric discharge machining method according to claim 1, wherein the compared machining results are the finished surface roughness of the workpiece and the machining time.