JP2001009639A - Diesinking electric discharge machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately and efficiently perform extremely small quantity work, and to restrain consumption of a machining electrode by sticking a particle layer to a machining object part of a work surface, and peforming diesinking electric discharge machining up to geometry for setting the work surface stuck with the particle layer. SOLUTION: After sticking pasty powder 45 containing conductive powder to a machining surface 39 of a work 23, when bringing a machining electrode 21 near to the machining surface 39 of the work 23 to perform diesinking electric discharge machining, since pasty powder 45 achieves a substitute of machining chips 43 stuck to the machining surface 39 of the work 23, the electric discharge machining is performed in a position of a distance D4 in machining clearance on the lower side by a distance D3 from an upper surface 41 of the work 23. When sticking a particle layer to the machining surface 39 of the work 23 before remachining, discharge is generated at an interpolar distance (the machining clearance) similar to the final finishing machining process, and since extremely small quantity work becomes possible, the other method for sticking the particle layer to the machining surface 39 of the work 23 can also be adopted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sinking electric discharge machining method, and more particularly to a sinking electric discharge machining method capable of easily and efficiently machining a very small amount.

[0002]

2. Description of the Related Art In die sinking electric discharge machining, in order to suppress the consumption of machining electrodes, shorten machining time, and improve machining accuracy, generally, after machining a workpiece under rough machining conditions, medium machining conditions and Processing is advanced so that desired shape dimensions and processing accuracy can be obtained while changing (decreasing) the processing energy in several stages with respect to the finishing processing conditions. This is because, in the sinking discharge machining under the finishing machining conditions, the amount of removal machining per discharge is small, and the finishing machining electrode is easily consumed. In addition, the final finishing process generally has only a processing ability to adjust the surface roughness of the processed surface, and the closer to the final finishing process condition, that is, the lower the processing energy, the more the work and the processing electrode The distance between the electrodes (machining gap) also tends to be small. Normally, these machining steps are automatically performed by being preset in an electric discharge machine. The setting of each processing step includes time management processing for setting the time for performing each step, and processing amount management processing for setting the processing depth or shape to be processed in the step.

In general, after all processing steps have been completed, dimension measurement of a work (workpiece) is performed to confirm processing accuracy. However, in electric discharge machining, machining dust adheres to the machining electrode and the workpiece machining surface during machining, and there is a possibility that a measurement error of about 10 μm to several tens μm may occur if the measurement is performed as it is. Therefore, in order to accurately measure the processing shape or the processing size, it is necessary to clean the processing surface by wiping the processing debris attached to the work processing surface with a rag or the like.

However, in electric discharge machining, a machining gap at which a discharge is possible at a certain voltage (current) occurs when there is almost no machining waste between a machining electrode and a workpiece (between poles) or when machining a workpiece. It tends to be small when no processing chips are attached to the surface, and to be large when the processing chips are dispersed between the poles or when the processing chips are attached to the workpiece. For this reason, after machining, the work surface of the work is cleaned, and the shape or dimensions are measured. When the machining accuracy is excessive or insufficient and rework is required, the machining gap is set at the end of the final finishing machining process. Even if the gap is the same as the machining gap between the electrode and the machining electrode, no electric discharge occurs, and the machining gap needs to be further reduced by about several μm to start the electric discharge.

[0005] As a method for preventing the occurrence of a difference in processing conditions such as a processing gap at the end of the final finishing processing step and at the start of reworking, a minute jump operation is performed at the end of processing to discharge processing chips from the gap. Thus, an electric discharge machining method for measuring a machining shape and a dimension of a work is disclosed in Japanese Patent Application Laid-Open No. Hei 6-79439.

[0006]

However, according to the above-mentioned prior art, the work debris floating between the work and the processing electrode is discharged by a minute jump operation, but the work debris attached to the work surface is completely removed. Therefore, there is a drawback that a measurement error of about 10 μm occurs due to the processing waste, and high measurement accuracy cannot be obtained. Therefore, when a high measurement accuracy of about 10 μm or less is desired, it is necessary to clean the work surface.

[0007] Therefore, several μm using
A problem arises when about m rework is required. That is, even if the machining electrode is moved toward the work to the distance between the work and the machining electrode (machining gap) or the position of the machining electrode in the last electric discharge machining process performed on the work, no electric discharge occurs, Further, the machining electrode may be moved toward the workpiece by a required minute machining amount of about several μm, and the remachining program may end without actually performing the electric discharge machining.

In the case where rework of about 10 μm is required, rework is performed from the viewpoint of electrode consumption and working efficiency described above by returning to the step before the working step based on the final finishing step conditions, that is, returning to the intermediate step. However, since the amount of processing performed in the intermediate process conditions is about several μm, the discharge may not occur even if the processing electrode is fed by the desired processing amount. This causes a problem that the machining time is increased and the consumption of the machining electrode is accelerated. Further, in the case of processing a large number of pieces, the size of the final product changes with time due to the consumption of the processing electrodes, which causes another problem that the dimension control becomes difficult.

Further, conventionally, using time management processing,
Since the skilled worker set the machining gap where electric discharge would occur from experience and intuition, and set the machining time by experience and intuition so that the required micro machining amount could be obtained,
It is difficult to maintain accuracy, and there are individual differences among operators, which makes it difficult to control accuracy. Further, a method of performing re-working under the final finishing condition in which the distance between the dischargeable electrodes (machining gap) is small can be used, but this is not practical because the working electrode is consumed greatly and the processing time is long.

[0010] Such a problem occurs not only in the case of reworking as described above, but also in the case of the first working when a very small amount of working is required. Therefore, an object of the present invention is to solve the above-mentioned problems in the prior art, to perform a fine machining amount with high accuracy and efficiency, and to provide a sinking electric discharge machining method that suppresses machining electrode consumption. is there.

[0011]

DISCLOSURE OF THE INVENTION In view of the above-mentioned object, the present invention provides a method in which a particle layer such as machining dust is previously attached to a clean machining surface of a workpiece in order to create an environment in which stable electric discharge easily occurs from the machining start stage. After that, the die sinking electrical discharge machining is performed. That is, according to the present invention,
(A) a step of attaching a particle layer to a portion to be processed on a work surface; and (b) a step of performing a sink and discharge operation on the work surface to which the particle layer has been attached to a set shape and size. A method is provided.

In one embodiment, the step (a) comprises engraving electric discharge machining for a predetermined time between the work electrode and a work electrode which is set to generate electric discharge, thereby forming a cover on the work surface. This is a step of attaching processing waste to the processing portion. In another embodiment, the step (a) comprises attaching a particle layer to the processed portion of the work surface by covering the processed portion of the work surface with a paste-like powder containing a conductive powder. Step.

Further, according to the present invention, (a) a step of performing a sinking electric discharge machining of a work to a preset machining shape, and (b) a step of removing a work chip attached to a surface of the work, and then performing machining. Measuring the shape and dimension of the work, (c) calculating the shape processing shortage from the set shape and the measurement result of step (b), and (d) processing the work surface. Adhering a particle layer to the portion; and (e) modifying and setting the preset geometric dimensions so that the workpiece is engraved and discharged by the calculated machining insufficient amount.
(F) subjecting the surface of the workpiece to which the particle layer is attached to performing a sinking discharge machining to the shape and dimension set in step (e).

According to the above method, prior to performing the sinking electric discharge machining by the machining amount control machining, for example, the time management machining is performed in the machining gap between the machining electrode and the machining electrode which is determined so that the electric discharge is reliably generated. By performing a sinking electric discharge machining for a predetermined time, that is, by performing a preliminary machining, a particle layer made of machining waste or the like is attached to a machining surface of a work in advance, and a stable electric discharge occurs as in the middle of machining. Create an environment like this. By doing this,
As compared with a state in which the processing surface of the work is clean, the processing gap between the work and the processing electrode can be set to the same condition as during processing. That is, the processing gap between the workpiece and the processing electrode is larger than when the processing surface is clean. Therefore, in the subsequent processing steps, the processing amount management processing can be automatically performed even if the processing amount is very small, and it is possible to easily and highly accurately perform the micro-sinking electric discharge machining with a small processing amount regardless of the skill of the operator. It becomes possible.

Further, if the same conditions as during the machining are made to appear by attaching the machining debris to the machining surface of the work as described above, and then the engraving electric discharge machining is performed under the intermediate machining process conditions, a stable electric discharge is generated. Therefore, it is possible to perform micro-small machining by die-sinking electrical discharge machining under intermediate machining process conditions. Therefore, it is possible to shorten the processing time, suppress the consumption of the processing electrode, and prevent a reduction in the processing efficiency. Further, since the consumption of the processing electrode is suppressed, a change with time of the processing electrode is also suppressed, and a large number of pieces can be processed.

The above operation and effect are also applicable to the case where the particle layer is adhered to the processing surface by applying the paste-like powder containing the conductive powder to the processing surface of the work. In this case, since it is not necessary to perform preliminary processing by time management processing before performing processing amount management processing, it is possible to further improve work efficiency. For the same reason, in the sinking electrical discharge machining, when it is necessary to rework after measuring the shape and dimensions of the work once completed, the sinking electrical discharge machining method of the present invention is effective.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing a sinking electric discharge machining method according to the present invention. FIG. 2 is a block diagram for explaining the method applied to an NC die-sinking electric discharge machine, and is a configuration diagram of the die-sinking electric discharge machine.

First, with reference to FIG. 2, a general configuration of the NC die-sinking electric discharge machine will be described. The NC die-sinking electric discharge machine 11 includes a moving device 19 including an X-axis feed motor 13, a Y-axis feed motor 15, and a Z-axis feed motor 17 for moving about three axes, X-axis, Y-axis, and Z-axis. , Mobile device 1
9, a machining electrode 21 movable with respect to three axes of X, Y, and Z axes. The work 23 is placed in a processing tank (not shown), and the work 23 is immersed in a processing liquid filled in the processing tank. A servo motor is preferably used as the motor for moving the shaft. The Z-axis feed motor 17 feeds or retracts the machining electrode 21 with respect to the workpiece 23 in the machining progress direction. The X-axis feed motor 13 and the Y-axis feed motor 15 move the machining electrode 21 in two axes orthogonal to each other in a plane perpendicular to the machining direction. Thus, the machining electrode 21 is moved to the workpiece 2 by combining the movements of the X-axis feed motor 13 and the Y-axis feed motor 15.
3 can be made to perform a two-dimensional swinging motion relative to 3,
Further, by combining movements of the X-axis feed motor 13, the Y-axis feed motor 15, and the Z-axis feed motor 17, the machining electrode 21 can be three-dimensionally rocked relative to the work 23.

The processing electrode 21 and the work 23 need only be relatively movable, and the processing tank on which the work 23 is placed may be moved with respect to the processing electrode 21 by the moving device 19. The NC die-sinking electric discharge machine 11 further includes a motor drive control device 25 for controlling the driving of each of the feed motors 13, 15, 17 of the moving device 19, and electric energy (voltage or voltage) between the machining electrode 21 and the work 23. And a processing power supply 27 for applying a current. The NC die sinking electric discharge machine 11 preferably has a contact detection device 29 for detecting contact between the machining electrode 21 and the work 23 in order to cut off electric energy when the machining electrode 21 and the work 23 are short-circuited. Is further provided.

The motor drive controller 25, the machining power supply 27 and the contact detector 29 are further controlled by the numerical controller 31. The numerical control device 31 includes a memory 33 and an input device 35, and stores a processing program in the memory 33 according to a command input by the input device 35, and stores a processing program and a processing step condition stored in the memory 33. Or read. In the memory 33, a plurality of data of processing step conditions according to the material of the work 23 and the processing purpose are set and stored in advance. These data are
For example, they are roughly classified into those for rough machining electrodes and those for finish machining electrodes. The data for each electrode is further divided into a plurality according to the obtained surface roughness and the like.

In the NC die-sinking electric discharge machine 11, if the machining electrode 21 is replaced with a shape measuring means such as a contact type measuring jig 37, the contact type measuring jig 37 is brought into contact with the work 23 to thereby form the work 23. The shape and dimensions can be measured. The contact position between the contact-type measuring jig 37 and the work 23 is detected by the contact detection device 29. Next, one embodiment of the die sinking electric discharge machining method of the present invention in the processing using the NC die sinking electric discharge machine 11 will be described with reference to the flowchart of FIG.

First, through the input device 35 of the NC die-sinking electric discharge machine 11, a machining program relating to a desired machining shape such as machining depth and size reduction of the workpiece 23 and machining process condition data to be used is converted into a numerical control device. 31 and is stored in the memory 33 (step 51). The NC die sinking electric discharge machine 11 performs die sinking electric discharge machining in accordance with the input machining program and machining process conditions (step 5).
3. Step 55).

In this die-sinking electrical discharge machining, as usual, rough machining is first performed by using rough machining electrodes under rough machining process conditions divided into several stages, and then by using finish machining electrodes. Processing is sequentially performed under finishing processing step conditions divided into several stages. As the stage approaches from the rough machining process condition to the final finish machining process condition, the machining energy, that is, the current of the machining pulse applied between the machining electrode 21 and the work 23 is reduced, and approaches the final finish machining process condition. As the removal processing capacity decreases, the surface roughness of the finish processing surface decreases.

After the completion of the working under the final finishing working process conditions, the shape dimension (for example, the dimension such as the working depth) of the work 23 is measured by the shape measuring means using the contact type measuring jig 37 or the like (step). 57). At this time, especially when it is necessary to perform accurate measurement, it is necessary to clean the processing chips attached to the processing surface of the work 23 using a rag or the like.

In step 59, if the difference between the initially input set shape and the shape and dimension obtained by the processing is within the allowable range, the work 23 passes and the processing ends. Generally, the allowable range of the dimension is about ± 10 μm of the set dimension. If excessive processing, such as the depth of the processed hole is too large, is performed beyond the allowable range, for example, in the case of the depth, rework such as polishing of the work surface is performed, and the depth of the hole is reduced. Within the allowable range (step 61). If the machining shape is less than the allowable range as compared with the initially input set shape and the machining is insufficient, re-machining is further performed by sinking electric discharge machining.

Here, when high precision processing is required for the workpiece 23, for example, when the workpiece 23 is related to the manufacture of a semiconductor product, a small processing amount of about 5 μm or less is required. There is. However, as described above, if the processing dust attached to the processing surface of the work 23 is removed, electric discharge does not easily occur, and a processing gap that enables discharge between the processing electrode 21 and the work 23 is formed in the final finishing processing step. The discharge becomes smaller than at the end, and the discharge becomes unstable (discharge does not occur stably even under the same conditions). Therefore, when the electric discharge machining is performed in the machining process before the final finishing condition, that is, in the process condition of the intermediate machining process, even if the machining electrode position in the final finishing machining process or the interelectrode distance between the workpiece 23 and the machining electrode 21 is reached. Discharge does not occur, and the machining electrode 21 is sent toward the work 23 by the necessary machining amount without causing discharge,
This intermediate process is completed without electric discharge machining, or the electric discharge is unstable.
Is removed and the processing accuracy is significantly impaired.

Therefore, in one embodiment of the die sinking electrical discharge machining method according to the present invention, prior to reworking the shortage by machining amount management machining, preliminary machining by time management machining is performed (step 63). Here, the preliminary machining is a time management machining in which a machining gap is set between the machining electrode 21 and the workpiece 23 where electric discharge occurs reliably and a machining time is set.
This means that electric discharge machining is performed for a predetermined time, for example, about 1 to 2 minutes. As the processing step conditions at this time, final finishing processing step conditions, that is, processing step conditions that hardly have a workpiece material removing ability in the processing step for adjusting the surface roughness of the processing surface, or surface roughness below the desired processing amount It is preferable to use a finishing electrode under a processing step condition that provides a finished surface having a certain degree. This is because under these conditions, the work material removal ability is very small and there is little possibility of removing the work surface material beyond the required processing amount.

Preferably, following the above-mentioned pre-machining, further back to the same machining process conditions as the intermediate machining process conditions at the beginning of the rework to be carried out, the time-managed machining is repeated for a predetermined time in the same manner as described above. Processing is performed (step 65). In this way, by performing the pre-machining retroactively to the first machining process condition for the re-machining, the discharge can be performed more stably.

After performing the above-described preliminary machining, the machining shape is corrected and set in consideration of the insufficient amount of micro machining (step 67), and re-machining is performed in the same procedure as usual (step 69). After the rework, the shape measurement is performed again, and the above procedure is repeated until the shape is passed. As another embodiment of the present invention, instead of the preliminary processing in step 63, the processed portion of the work surface may be covered with a paste-like powder containing a conductive powder (step 63 '). In this case, as the conductive powder, a carbon-based substance such as graphite, a metal such as chromium, a semimetal such as silicon, or the like is used. Making the powder into a paste ensures that the powder does not float in the working fluid and adheres to the surface of the work 23.

In this case, immediately after the paste-like powder is adhered to the surface of the work 23, the electric discharge machining can be performed under the intermediate machining process conditions, the time required for the preliminary machining can be reduced, and the reworking operation can be performed. Efficiency is improved. FIG. 3 is a diagram for explaining a die-sinking electric discharge machining method when the preliminary machining is performed.

As shown in FIG. 3A, the work 23
When the processing surface 39 is cleaned,
The processing electrode 21 at a position below the upper surface 41 by a distance D1.
Is located, and the discharge is enabled only when the machining gap between the machining surface 39 of the workpiece 23 and the machining electrode 21 is the distance D2. When the preliminary machining is performed in the machining gap, machining chips 43 are generated, and electric discharge easily occurs. Then, the gap voltage between the work 23 and the machining electrode 21 decreases, so that the machining gap is increased to maintain the gap voltage at a predetermined value (because the gap voltage increases almost in proportion to the machining gap). From)), as shown in FIG.
The processing electrode 21 has a distance Δ upward from the processing surface 39 of the work 23 (from the upper surface 41 of the work 23 to a position at a distance D3).
It moves by G and the machining gap is in the state of the distance D4. In the die sinking electrical discharge machining method of the present invention, preliminary machining (step 6)
After this state is reached by 3), rework (step 69) for the insufficient machining amount is performed.

For example, the processing electrode 21 is positioned at a distance D1 from the position of the processing electrode 21 shown in FIG. 3B to the upper surface 41 of the work 23 shown in FIG.
When the machining electrode 21 is advanced by performing the sinking electric discharge machining to the same position as the machining electrode 21 shown in FIG. 3A, the machining surface 39 is lowered downward by the distance ΔG, that is, the electric discharge machining is performed by the distance ΔG. .

Therefore, conventionally, the machining electrode 21 is not shown in FIG.
The discharge did not occur even when the electrode was lowered to the machining electrode position shown in (a), and the machining program was terminated. However, by performing the preliminary machining (step 63), if the electrode was lowered to the same machining electrode position, the distance ΔG was reduced. Processing will be performed. Thus, a very small amount processing becomes possible. FIG. 4 is a diagram for explaining the die sinking electric discharge machining method of the present invention when a particle layer is adhered to the work processing surface by applying paste-like powder to the work processing surface.

As shown in FIG. 4 (a), after a paste-like powder 45 containing a conductive powder is adhered to a processing surface 39 of a work 23, a machining electrode 21 is formed in order to perform a sinking electric discharge machining.
Is brought close to the processing surface 39 of the work 23, the paste-like powder 45 takes the place of the processing waste 43 attached to the processing surface 39 of the work 23, and thus, as in the case after the preliminary processing described above, FIG. As shown in (2), since the machining gap can be discharged at the position of the distance D4 below the upper surface 41 of the work 23 by the distance D3, the same effect as that of the preliminary machining can be obtained.

Prior to rework, the work surface 3 of the work 23
When a particle layer is adhered to 9, a discharge occurs at the same gap distance (machining gap) as in the final finishing machining step, and a minute amount of machining can be performed.
Other methods for attaching the particle layer to the processing surface 39 of the work 23 are also possible. In any of the above-described embodiments, stable electric discharge is performed from the first processing step condition of the reworking, so that it is possible to perform high-accuracy micro-amount processing. In addition, since the electric discharge machining can be performed under the intermediate machining process conditions, the time required for the rework is reduced, and the consumption of the finish machining electrode is suppressed.

As described above, as shown in FIG.
The embodiment of the present invention has been described by taking, as an example, a case where further rework is required when performing a sculpture electric discharge machining on, but the present invention is not limited to application to rework. . That is, it is also suitable for a case where a very small amount of processing (not re-processing) is required for the work 23. As described above, in a state where the processing surface of the work 23 is clean and no processing chips or the like are attached, a processing gap where discharge is possible is close and the discharge becomes unstable. Therefore,
For example, when the workpiece 23 is required to be machined in a very small amount of about 10 μm or less, if the electrical discharge machining is first performed under the intermediate machining process condition having a high work material removal capability, the workpiece 23 is abnormally discharged to a depth of 10 μm or more. In some cases, a part to be processed may be formed, and no discharge may occur even when the processing electrode 21 approaches the workpiece 23 by a required processing amount. For this reason, conventionally, it was necessary to perform the processing from the beginning under the final finishing processing step conditions (for example, processing step conditions in which a finished surface having a fine surface roughness such as a surface roughness of 5 μm or less is obtained). . Further, when a smaller amount of machining is desired, it is impossible to perform the sinking electric discharge machining using the machining amount management machining.

Even in the case where the work 23 needs to be processed in a very small amount (not in the rework), the above-mentioned preliminary processing and application of the paste-like powder 45 are performed on the work 23. As a result, a state in which the processing dust 43 floats between the workpiece 23 and the processing electrode 21 as in the middle of the processing step and a state in which the particle layer is attached to the processing surface 39 of the workpiece 23 are created, and the processing gap can be increased. Become like Therefore, it becomes possible to start electric discharge machining from machining under the conditions of the intermediate machining process, thereby increasing machining efficiency and suppressing consumption of machining electrodes. In addition, since it becomes possible to use the processing amount management processing, it is possible to easily perform the small amount processing.

In addition, if a Die-sinker EDM machine is designed to perform pre-machining automatically, it is possible to easily and precisely perform a small amount of machining without relying on the experience and intuition of a skilled person. It becomes possible.

[0039]

As described above, according to the present invention, by applying a particle layer to a clean processing surface of a work by preliminary processing or application of a paste-like powder, it is possible to reduce the likelihood of electric discharge machining. Since the same state as the state where machining chips are floating between the workpiece and the machining electrode or the state where the particle layer (machining scrap layer) adheres to the machining surface of the workpiece is created, and then the engraving discharge machining is performed, As a result, stable electric discharge can be performed in the same appropriate machining gap, and machining amount management machining can be used even for micro-small machining. Therefore, it is possible to easily and highly accurately perform the micro-sinking electric discharge machining without relying on the experience and intuition of a skilled person.

Further, since it is possible to perform machining under intermediate machining process conditions even with a small machining amount, the overall machining time is shortened, machining efficiency is increased, the consumption of machining electrodes is suppressed, and multiple machining is performed. In this case, it is also possible to reduce the temporal change of the dimensions.

[Brief description of the drawings]

FIG. 1 is a flow chart showing a sinking electrical discharge machining method according to the present invention.

FIG. 2 is a block diagram showing a configuration of a die-sinking electric discharge machine for explaining the die-sinking electric discharge machining method of the present invention applied to an NC electric discharge machine.

FIG. 3 is a diagram for explaining a sinking electric discharge machining when a preliminary machining is performed.

FIG. 4 is a diagram for explaining a sinking electric discharge machining when a paste-like powder is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... NC die sink electric discharge machine 21 ... Processing electrode 23 ... Work 39 ... Machining surface 43 ... Processing waste 45 ... Paste powder

Claims (4)

[Claims] 1. A step of: (a) attaching a particle layer to a portion to be processed on a surface of a work; and (b) a step of subjecting the surface of the work to which the particle layer has been adhered to a sinking discharge machining to a set shape and size. Diesinking electrical discharge machining method characterized by including: 2. The method according to claim 1, wherein the step (a) comprises: performing an engraving electric discharge machining for a predetermined time between the workpiece and a machining electrode in which electric discharge is caused to occur, so that machining dust is formed on a portion to be processed on the surface of the workpiece. 2. The method according to claim 1, further comprising the step of: 3. The step (a) is a step of attaching a particle layer to the processed portion of the work surface by covering the processed portion of the work surface with a paste-like powder containing a conductive powder. Item 8. The sinking electrical discharge machining method according to Item 1. 4. A step of: (a) subjecting a workpiece to a sinking electrical discharge machining to a predetermined shape and dimension; and (b) a shape and dimension of the workpiece that has been processed after removing machining debris attached to the surface of the workpiece. (C) calculating an insufficient shape processing amount from the set shape dimensions and the measurement result of step (b); and (d) attaching a particle layer to a portion to be processed on the work surface. (E) correcting and setting the preset geometric dimensions so that the workpiece is subjected to the shape-sinking electric discharge machining by an amount corresponding to the calculated machining insufficient quantity; and (f) adhering the particle layer. And a step of subjecting the work surface to a sinking electrical discharge machining to the shape and dimension set in step (e).