Wire discharge machining method and wire discharge machining device

Abstract

In step processing in which the plate thickness changes during processing, even if the processing paths of the rough processing step and the end surface finishing step are different, the processing conditions suitable for the plate thickness are automatically changed and set. The wire discharge processing method and wire discharge processing device (100) of the present invention divide the XY plane of the worktable into small areas to form a plurality of divided areas (S101), detect the plate thickness of the workpiece, and store it in association with the divided areas (S102), and then, based on the plate thickness information associated with the divided areas and the plate thickness of the current processing position of the workpiece, it is inferred whether there is a step ahead in the direction of travel of the processing path, and the processing conditions are changed (S103).

Description

Technical Field

[0001] The present invention relates to a wire discharge machining method for performing discharge machining under machining conditions suitable for the plate thickness of a workpiece, and a wire discharge machining device for automatically setting machining conditions suitable for the plate thickness of the workpiece. Background Art

[0002] Wire EDM is an EDM method in which a predetermined machining voltage pulse is repeatedly applied to a machining gap formed between a wire electrode and a workpiece to intermittently generate discharge, and material is removed from the workpiece using the discharge energy to cut the workpiece into a desired machining shape. The wire electrode is stretched between a pair of wire guides.

[0003] In the wire discharge machining method described above, there is a situation where the plate thickness changes during machining of a machining shape (hereinafter referred to as step machining). If the plate thickness changes during machining, the following problems may occur: the amount of material removal increases or decreases, the material removal rate changes, the machining groove width differs at different plate thicknesses and the required machining shape accuracy cannot be obtained; or the wire electrode is prone to wire breakage. Therefore, step machining was previously adopted, that is, the step position of the workpiece was automatically checked, and the electrical machining conditions were appropriately switched to perform discharge machining.

[0004] Patent document 1 discloses an invention related to a wire-cut electrical discharge machining method and a numerically controlled wire-cut electrical discharge machining device. The invention is described as follows: in a rough machining process, a change in plate thickness is detected, and the step position at that time is associated with the plate thickness and stored in advance, and then in an end surface finishing process, when the machining part reaches the area around the step position, the desired machining conditions are changed and set to machining conditions suitable for the plate thickness (technical solution 1).

[0005] Patent document 2 discloses an invention related to a wire discharge machining method and apparatus, which discloses the following steps: in the process of performing the first machining, i.e., rough machining, obtaining step position information through a step position detection element, setting a correction interval in the second and subsequent machining; and when the wire electrode enters the correction interval, gradually tilting the posture of the wire electrode as a correction process (paragraphs 0038 and 0047 thereof).

[0006] [Prior art literature]

[0007] [Patent Document]

[0008] [Patent Document 1] Japanese Patent No. 4294638

[0009] [Patent Document 2] Japanese Patent No. 2885228 Summary of the invention

[0010] [Problems to be solved by the invention]

[0011] When performing EDM, the mainstream method is to first perform rough machining (first cut), pay more attention to material removal rate than shape error or surface roughness, leave a finishing allowance, and then, while changing the offset, perform the same machining path multiple times to adjust the shape accuracy by finishing the surface roughness with end face finishing (after the second cut). However, in recent years, due to the influence of the diversification of products formed by EDM, EDM has also begun to be performed as follows: in end face finishing, only a part of the workpiece is machined by increasing the number of machining times, or when multiple products are taken out from a workpiece, first perform rough machining of the entire multiple products at once, and then perform second cut, third cut, fourth cut (forth cut) on one of the rough-machined products.

[0012] However, in the method of Patent Document 1, the order in which the step difference is detected must be stored together with the position of the step difference detected in the rough machining process, and in the subsequent end face finishing process, the position of the step difference is determined in accordance with the stored order or the reverse order of the stored order to change the machining conditions. Therefore, when the machining path in the rough machining process is different from the machining path in the subsequent end face finishing process, the change of the machining conditions cannot be applied. Therefore, when the machining paths of the rough machining process and the end face finishing process are different, the following change must be made, that is, an auxiliary path is set to make the machining paths consistent.

[0013] Therefore, in view of the above-mentioned problems, the main purpose of the present invention is to provide a wire discharge machining method and a wire discharge machining device, which can automatically change the machining conditions suitable for the plate thickness in step-difference machining where the plate thickness changes during machining, even if the machining paths of the rough machining process and the end surface finishing process are different, and can more easily obtain excellent machining results. Several specific advantages that can be obtained in the present invention will be described in detail later.

[0014] [Technical means to solve the problem]

[0015] The wire discharge machining method of the present invention includes: a segmentation process, which segments the XY plane of a workstand of a wire discharge machining device into small areas to form a plurality of segmented areas; a storage process, which detects the plate thickness of a workpiece and stores it in association with the segmented areas as plate thickness information; an inference process, which sets a peripheral area including a current machining position of the workpiece as a search range, refers to the plate thickness information associated with the segmented areas within the search range, and infers whether there is a step difference ahead in the travel direction of the machining path based on the plate thickness information associated with the segmented areas and the plate thickness of the current machining position of the workpiece; and a machining condition change process, which sets a peripheral area including the position of the step difference as a machining condition change range, and changes the machining conditions when the current machining position of the workpiece enters the machining condition change range.

[0016] Furthermore, in the wire discharge machining method of the present invention, the storage step is executed in the rough machining step, and the estimation step and the machining condition changing step are executed in the end surface finishing step.

[0017] Furthermore, the present invention is a wire discharge machining device including a numerical control (NC) control device. The features of the present invention are as follows. The NC control device includes: a detection unit that detects the plate thickness of the workpiece in a rough machining process; a storage unit that stores the plate thickness in association with a split area, wherein the split area is formed by dividing the XY plane of the worktable of the wire discharge machining device into small areas; and a processing unit. In the end surface finishing process, the processing unit sets the surrounding area including the current machining position of the workpiece as a search range, and refers to the plate thickness information associated with the split area located in the search range. Based on the plate thickness information associated with the split area and the plate thickness of the current machining position of the workpiece, it is inferred whether there is a step difference in the front of the moving direction of the machining path. Furthermore, the surrounding area including the position of the step difference is set as a machining condition change range, and when the current machining position of the workpiece enters the machining condition change range, control of changing the machining conditions is performed.

[0018] According to the present invention, during rough machining, the XY plane of the worktable of the wire EDM device is divided into a plurality of small areas, and the plate thickness is associated with the divided areas and stored. During end surface finishing, by searching the divided areas around the processing position and referring to the plate thickness information associated with the divided areas, it is determined whether there is a step difference around. Therefore, even if the processing paths of the rough machining process and the end surface finishing process are different, the step difference position can be appropriately determined.

[0019] The characteristics of the wire discharge machining method of the present invention are as follows. The storage process is to store the plate thickness at the time of detection, i.e., the first plate thickness information, and the plate thickness of the previous time, i.e., the second plate thickness information, in association with the divided area. The inference process is to infer whether there is a step difference in the forward direction of the machining path based on the first plate thickness information and the plate thickness of the current machining position of the workpiece when the machining path of the end face finishing process and the machining path of the rough machining process are in the same direction. When the machining path of the end face finishing process and the machining path of the rough machining process are in the opposite direction, it is inferred whether there is a step difference in the forward direction of the machining path based on the second plate thickness information and the plate thickness of the current machining position of the workpiece.

[0020] According to the present invention, the plate thickness at the time of detection and the plate thickness detected last time are stored in association with the segmented area, and the plate thickness to be referred to is switched and changed according to whether the processing paths of the end surface finishing process and the rough processing process are in the same direction or in opposite directions. Therefore, the plate thickness in front of the processing direction can be accurately inferred in the end surface finishing process, so that the accuracy of the estimation of the step position is improved.

[0021] In the wire discharge machining method of the present invention, the storage step is to store the position where the plate thickness of the workpiece is detected in association with the divided area, and the processing condition change step is to set the range centered on the position where the plate thickness of the workpiece is detected as the processing condition change range.

[0022] Furthermore, in the wire discharge machining method of the present invention, the machining condition changing step changes the machining condition in stages relative to a target value to be changed when changing the machining condition.

[0023] According to the present invention, the range centered on the position where the thickness of the workpiece is detected is set as the range for changing the machining conditions. Therefore, even if the machining path deviates in each machining step, the step position can be reliably determined and the machining conditions can be changed.

[0024] Furthermore, according to the present invention, when the set processing conditions are changed, the processing conditions are changed in stages relative to the target value to be changed, so that the processing conditions are not changed drastically at the step position. Therefore, the influence of the inevitable small error caused by the step position being determined by the region on the processing result can be reduced.

[0025] [Effects of the Invention]

[0026] The wire discharge machining method and the wire discharge machining device of the present invention can automatically change the set machining conditions at the step position even when the machining paths of the rough machining process and the end surface finishing process are different. Therefore, a wire discharge machining method and a wire discharge machining device that can more easily obtain excellent machining results can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram showing a wire electrical discharge machining device 100 according to an embodiment of the present invention.

[0028] Figure 2 It is a schematic diagram showing an enlarged view of the processing area and the periphery of the wire electrical discharge machining device 100 according to the above embodiment.

[0029] Figure 3 This is a schematic diagram for explaining the segmentation process of the embodiment. Figure 1 .

[0030] Figure 4 This is a schematic diagram for explaining the segmentation process of the embodiment. Figure 2 .

[0031] Figure 5 This is a flowchart showing the process from storing plate thickness information to changing machining conditions in the wire discharge machining method of the present invention.

[0032] Figure 6 This is a flowchart showing a process of storing plate thickness information and the like for each divided region in one cutting process in the wire discharge machining method of the present invention.

[0033] Figure 7 This is a schematic diagram showing a state of storage of region division data during one cutting process in the wire discharge machining method of the present invention.

[0034] Figure 8 This is a flowchart showing a step of estimating a step position during machining after secondary cutting in the wire discharge machining method of the present invention.

[0035] Fig. 9 It is a schematic diagram showing a method of searching and determining a step position during secondary cutting processing according to the present invention.

[0036] Fig.10 It is a schematic diagram showing a method of searching and determining a step position during secondary cutting according to the present invention (when the offset directions are the same).

[0037] Fig.11 It is a schematic diagram showing a method of searching and determining a step position during secondary cutting according to the present invention (when the offset direction is different).

[0038] Fig.12 This is a flowchart showing a process of changing processing conditions during secondary cutting processing according to the present invention.

[0039] Fig.13 It is a schematic diagram showing a method of changing processing conditions during secondary cutting processing according to the present invention.

[0040] Fig.14 It is a schematic diagram showing the details of the method of changing the processing conditions during the secondary cutting process of the present invention.

[0041] Fig.15 It is a block diagram showing the configuration of the NC control device 5 of the wire electrical discharge machining device 100 according to the present invention.

[0042] Fig.16 Schematic diagram showing details of a method for changing processing conditions during secondary cutting processing of the present invention Figure 2 .

[0043] [Explanation of Symbols]

[0044] 1: Workbench

[0045] 2: Wire electrode

[0046] 3, 4: Wireframe

[0047] 5: NC control device

[0048] 51: Input

[0049] 52: Storage

[0050] 53: Processing Department

[0051] 54: Display unit

[0052] 55: Inspection Department

[0053] 100: Wire EDM device

[0054] K1: Processing path for one cutting

[0055] K2: Processing path after secondary cutting

[0056] W: Workpiece DETAILED DESCRIPTION

[0057] Figure 1 Schematic diagram showing a wire electrical discharge machining device 100 according to an embodiment of the present invention. Figure 2 It is a schematic diagram which enlarges the processing area and the periphery of the wire electrical discharge machining device 100 according to the present embodiment. Figure 5 This is a flowchart showing the process from storing plate thickness information to changing machining conditions in the wire discharge machining method of the present invention.

[0058] The wire discharge machining device 100 of the embodiment of the present invention includes: a pair of wire threading frames 3 and 4; a wire electrode 2 stretched between the wire threading frames 3 and 4; a worktable 1 placed in parallel with the XY plane, which is a reference plane when machining the surface of the workpiece W; and an NC control device 5. The wire discharge machining device 100 moves the wire threading frames 3 and 4 relative to the workpiece W on the XY plane, repeatedly applies a predetermined machining voltage pulse to the machining gap formed between the wire electrode 2 and the workpiece W to intermittently generate discharge, removes material from the workpiece W using the discharge energy, and cuts the workpiece W into a desired machining shape.

[0059] The wire discharge machining device 100 is divided into a plurality of machining steps such as a rough machining step and a finishing step to cut the workpiece W. The rough machining step of first roughly machining the workpiece W into a desired machining shape is called primary cutting, and the end surface finishing step of machining the machining surface of the roughly formed machining hole is called secondary cutting, tertiary cutting, and quaternary cutting according to the machining step order.

[0060] The wire discharge machining device 100 of the present invention divides the XY plane of the worktable 1 into small areas during the primary cutting process, and stores the plate thickness information for each divided area (S101: dividing process, storing process). Then, in the processing process after the secondary cutting process, the plate thickness information of each divided area stored during the primary cutting process is used to retrieve and infer the step position of the workpiece W (S102: inferring process), and control of changing the processing conditions is performed (S103: processing condition changing process).

[0061] Fig.15 It is a block diagram showing the configuration of the NC control device 5 of the wire electrical discharge machining device 100 according to the present invention.

[0062] The NC control device 5 is a device that numerically controls the operation of the entire wire electrical discharge machining device 100 , and includes an input unit 51 , a storage unit 52 , a processing unit 53 , a display unit 54 , and a detection unit 55 .

[0063] The input unit 51 is an input device such as a keyboard or a touch panel provided to overlap the display surface of the display unit. The display unit 54 includes a display device such as a liquid crystal display, and is used to display a setting screen and the like.

[0064] The storage unit 52 stores programs for performing various processes and various setting values.

[0065] The detection unit 55 detects the machining feed speed (F value), the number of discharges, the machining voltage, and the like in real time while the in-line electrical discharge machining device 100 is being driven.

[0066] The processing unit 53 includes a driving unit 531 and a digital control unit 532 .

[0067] The digital control unit 532 converts a machining program including a trajectory of a machining shape and machining conditions into a command signal for operating devices such as a machining power supply device, a motor control device, and a machining fluid supply device of the wire electrical discharge machining device 100 .

[0068] Furthermore, the digital control unit 532 executes a segmentation process, a plate thickness information calculation process, a storage process, a step position estimation process, and a processing condition change process described later, and performs processing for automatically detecting the step position and changing the processing conditions.

[0069] The driving unit 531 actually drives each device according to a command from the digital control unit 532 .

[0070] Next, regarding the step (S101) of storing the plate thickness information and the like for each divided area during a single cutting process, Figure 6 The flowchart is described below.

[0071] First, after the power is turned on, the NC control device 5 divides the XY plane, which is a reference plane during processing, into equal parts to set divided areas M[i][j] before starting a single cutting process ( S201 : dividing step).

[0072] When a cutting process is started (S202), the NC control device 5 acquires the position of the wire electrode 2 on the processing path K1 at each sampling time (sampling time) Δt (hereinafter, the position of the wire electrode 2 on the processing path is referred to as the processing position). In addition, the plate thickness information is calculated using the processing transmission speed (F value), the number of discharges, the processing voltage, etc. detected by the detection unit 55 (S203: plate thickness information calculation step).

[0073] The NC control device 5 searches for the segmented area M[i][j] within which the current processing position is located, and determines whether the segmented area data D[i][j] described later has been stored in the searched segmented area M[i][j]. When the segmented area data D[i][j] is stored, the calculated plate thickness information is not rewritten, but only the x-coordinate and y-coordinate of the current processing position are rewritten. When the plate thickness information is not stored in the segmented area data D[i][j], the first plate thickness information, the second plate thickness information, the x-coordinate and y-coordinate of the current processing position, the offset direction, and the index value are stored (S204: storage process).

[0074] S203 and S204 are repeatedly performed at each sampling time Δt until one cutting process is completed.

[0075] Figure 3 and Figure 4It is a schematic diagram showing the splitting process of this embodiment.

[0076] Specifically, for the splitting process of S201, as Figure 3 , Figure 4 shown, it is a process of equally dividing the XY plane with a preset splitting width to set a plurality of splitting regions M[i][j]. For example, the splitting width is set to 0.5 mm, and it is equally divided into small regions of 0.5 mm square with 2000×2000. The splitting region M[i][j] is divided into L parts in the x-axis direction and J parts in the y-axis direction. For convenience, in this specification, each splitting region is denoted as M[i][j] (0≦i<L, 0≦j<J, where i and j are integers greater than or equal to 0).

[0077] Specifically, the plate thickness information calculation process of S203 is a process of calculating the plate thickness of the workpiece W on the machining path K1 during one cutting process. The plate thickness of the workpiece W can be obtained by substituting the correction coefficient, the detected machining feed rate (F value), the number of discharges, and the machining voltage into a specified calculation formula. The correction coefficient is determined respectively according to the wire diameter used and the material of the workpiece.

[0078] The storage process of S204 is a process of storing data (splitting region data D[i][j]) for each of the splitting regions M[i][j] on the machining path K1 during one cutting process. Specifically, the splitting region data D[i][j] refers to the current plate thickness information, i.e., the first plate thickness information now_thick, the previous plate thickness information, i.e., the second plate thickness information pre_thick, the serial number of the data record, i.e., the index value index, the x coordinate value x_pos of the position where the plate thickness is detected, the y coordinate value y_pos of the position where the plate thickness is detected, and the offset direction information offset indicating which side of the machining surface of the machining path K1 is located in the traveling direction with respect to the workpiece W, and is stored in association with the splitting region M[i][j]. Here, the so-called second plate thickness information refers to such information that the first plate thickness information now_thick stored in the splitting region data D[i][j] with the previous index value is stored.

[0079] For example, consider the following situation: the x coordinate of the current processing position is 100.24 mm, the y coordinate is 200.54 mm, the current plate thickness is 40 mm, the index value is the first plate thickness information stored in the previous segmented area data D[i][j] is 30 mm, the offset direction is "right of the direction of travel", and it is stored as the tenth segmented area data D, and as the segmented area M[i][j], the segmentation width is set to 1.0 mm, and it is divided into 2000×2000 small areas of 1.0 mm square. At this time, the segmented area data D

[100]

[200] as the segmented area M

[100]

[200] is stored as follows: x coordinate value x_pos=100.24 mm, y coordinate value y_pos=200.54 mm, first plate thickness information now_thick=40 mm, second plate thickness information pre_thick=30 mm, offset direction information offset="right of the direction of travel", and index value index=10.

[0080] Here, in a cutting process, the plate thickness information cannot be detected in the segmented area M[i][j] that is not on the processing path K1, so the data stored in the segmented area data D[i][j] does not exist. At this time, the index value cannot be rewritten, so the index value is 0.

[0081] Figure 7 It is a schematic diagram showing a state of storage of region division data during one cutting process in the wire discharge machining method of the present invention.

[0082] According to the Figure 6 Flow chart of Figure 7 As shown, the following state is presented: the segmented area data D[i][j] ( Figure 7 Among them, the segmentation area M represented by the slash is the area storing the segmentation area data D), and the segmentation area data D[i][j] is not stored in the segmentation area M[i][j] that does not exist on the processing path K1 of a single cut (for example, the index value is 0).

[0083] Figure 8 This is a flowchart showing a step of estimating a step position during machining after secondary cutting in the wire discharge machining method of the present invention. Fig. 9 It is a schematic diagram showing a method of searching and determining a step position during secondary cutting processing according to the present invention.

[0084] Here, the step position estimation process (S102) during the secondary cutting process is described. The secondary cutting process, the tertiary cutting process, the quaternary cutting process, and the subsequent processing processes are also the same process, so in the following description, the secondary cutting process is cited as an example for description.

[0085] When the secondary cutting process starts, the NC control device 5 obtains the current processing position P_now for each sampling time Δt, and sets the search range H1 from the current processing position P_now. Fig. 9 As shown, the divided area M[q][r] including the current processing position P_now, and the eight divided areas around the divided area M[q][r], namely, M[q-1][j-1], M[q-1][r], M[q-1][r+1], M[q][r-1], M[q][r+1], M[q+1][r-1], M[q+1][r], and M[q+1][r+1] are set as retrieval objects (where q and r are integers greater than 1).

[0086] Next, it is searched whether there is a divided area M storing divided area data D within the search range H1 (S301). Fig. 9 In the example shown, it is shown that the divided area data D exists in the divided area M[q-1][r+1] and the divided area M[q][r+1]. Fig. 9 Among them, the divided region M indicated by the oblique lines is a region storing the divided region data D. When there is no divided region M storing the divided region data D, the processing conditions are not changed (S311).

[0087] Next, determine whether the offset direction in the current processing (processing of the second cutting) is the same as the offset direction in the first cutting (S302). When the offset direction in the current processing is the same as the offset direction in the first cutting, select the segmented area M with the largest index value among the multiple segmented areas retrieved (S303), and store the selected segmented area M as the reference segmented area MT. Then, the first plate thickness information stored in the segmented area data of the reference segmented area MT is stored as the reference plate thickness information change_thick (S305). On the other hand, when the offset direction in the current processing is different from the offset direction in the first cutting, select the segmented area M with the smallest index value among the multiple segmented areas retrieved (S304), and store the selected segmented area M as the reference segmented area MT. Next, the second plate thickness information stored in the segmented area data of the reference segmented area MT is stored as the reference plate thickness information change_thick (S306).

[0088] Fig.10 and Fig.11 Schematic diagram showing the method for searching and determining the step position during secondary cutting processing of the present invention. Fig.10 and Fig.11In FIG. 1 , for the sake of convenience, the index values ​​(9, 10, ...) of the segmented area data D are recorded in the segmented area M, and the portion with a plate thickness of 60 mm is hatched with dots. The portion without hatching with dots is the portion with a plate thickness of 30 mm. In addition, for the sake of convenience, the plate thickness values ​​are set to 60 mm and 30 mm, but in fact there is no limitation and it can be any value.

[0089] The following is a description of the reason for changing the selection method of the segmentation area M according to the difference in the offset direction. The offset direction in the wire EDM device is information indicating whether the machining path K1 is located on the right or left side of the machining surface of the workpiece W in the moving direction. The information related to the offset direction can determine whether the moving direction of the wire EDM device is the same direction or opposite direction in the first cutting and the second cutting. If the offset direction is the same, then the moving direction is the same in the first cutting and the second cutting ( Fig.10 ), if the offset direction is opposite, then the travel direction is opposite in the first cutting and the second cutting ( Fig.11 ).

[0090] When a plurality of divided regions M having divided region data D exist within the search range H1, it becomes a question of which divided region M's divided region data D to refer to.

[0091] When the first cut and the second cut have the same travel direction ( Fig.10 ), whether there is a change in plate thickness (step difference) in the front of the secondary cutting direction becomes a problem, so the ( Fig.10 In the case of index=12, the segmented region M is set as the reference segmented region MT (S303). And the first plate thickness information now_thick stored in the segmented region data D of the reference segmented region MT is set as the reference plate thickness information (S305). Fig.10 In the case of the same direction of travel in the first cutting and the second cutting, the segment area M[q-1][r] with an index value of 12 is set as the reference segment area MT, and the first plate thickness information now_thick is set as the reference plate thickness information with reference to the segment area data D[q-1][r] (S305). The reason for this is that the value of the plate thickness that is expected to change in the front in the direction of travel of the second cutting is the value of the first plate thickness information now_thick.

[0092] On the other hand, when the primary cutting and the secondary cutting are in opposite directions ( Fig.11 ), the one with the smallest index value ( Fig.11In the case of index=10, the segmented region M is set as the reference segmented region MT (S304). And the second plate thickness information pre_thick stored in the segmented region data D of the reference segmented region MT is set as the reference plate thickness information (S306). Fig.11 In the case of , the travel directions are opposite in the first cutting and the second cutting, so the segment area M[q+1][r] with an index value of 10 is set as the reference segment area MT, the segment area data D[q+1][r] is referenced, and the second plate thickness information pre_thick is set as the reference plate thickness information. The reason for this is that the value of the plate thickness that is expected to change in the front in the travel direction of the second cutting is the value of the second plate thickness information pre_thick.

[0093] Next, the NC control device 5 determines whether the current plate thickness is different from the reference plate thickness information (S307). If they are different, it is determined that there is a step difference in the front direction of the secondary cutting, and the process is transferred to the processing condition change process (S308). If the current plate thickness is the same as the reference plate thickness information, it is determined that there is no step difference in the front direction of the secondary cutting, and the processing conditions are not changed (S309), but the process returns to the beginning, and S301 to S309 are repeatedly executed for the next processing position P_now that has been moved at each sampling time Δt.

[0094] Fig.12 is a flow chart showing a process of changing processing conditions during secondary cutting processing of the present invention. Fig.13 It is a schematic diagram showing a method of changing processing conditions during secondary cutting processing according to the present invention. Fig.14 It is a schematic diagram showing the details of the method of changing the processing conditions during the secondary cutting process of the present invention.

[0095] Here, the processing condition changing step (S103) of actually changing the processing conditions using the divided region data D of the reference divided region MT will be described.

[0096] First, the processing condition change range H2 is set (S401). Specifically, the x-coordinate value x_pos and the y-coordinate value y_pos of the position where the plate thickness is detected in a single cutting process are read from the segmented area data D of the reference segmented area MT, and the processing condition change range H2 is set with the position where the plate thickness is detected as the center. Here, a rectangular range with a range in the x-axis direction of x_pos±x-direction processing condition change range H2x and a range in the y-axis direction of y_pos±y-direction processing condition change range H2y is set as the processing condition change range H2 ( Fig.14 ).

[0097] Next, it is determined whether the current processing position P_now is within the processing condition change range H2 (S402). When the processing position P_now is outside the processing condition change range H2, monitoring is performed until the processing position P_now enters the processing condition change range H2.

[0098] When the processing position P_now enters the processing condition change range H2, as long as the processing position P_now does not cross the condition switching standby interval U1 from the boundary of the processing condition change range H2 to enter the inside, the processing condition will not be changed (S402). Once the processing position P_now crosses the condition switching standby interval U1 from the boundary of the processing condition change range H2 to the inside (S403), the pre-stored condition switching number N2 and condition switching interval U2 are read (S404), and the processing conditions are changed in stages with the condition switching number N2 and condition switching interval U2 while processing (S405). Then, when the NC control device 5 receives the command to end the secondary cutting process, the processing is ended.

[0099] Fig.16 Schematic diagram showing details of a method for changing processing conditions during secondary cutting processing of the present invention Figure 2 .

[0100] This method is a specific method of changing the machining conditions in stages with the condition switching number N2 and the condition switching interval U2. First, the NC control device 5 refers to the reference plate thickness information selected in S307 or S308, reads the machining conditions suitable for the plate thickness of the reference plate thickness information from the database, sets the machining conditions as the final target value, and changes the machining conditions in stages at each switching interval U2 to set the conditions for the wire discharge machining device 100. If the machining conditions are set while gradually changing them in stages, the machining conditions read from the database will eventually be set in the wire discharge machining device 100.

[0101] As described above, the wire discharge machining method of the present invention infers the step position in the end face finishing process based on the plate thickness information of each divided area detected and stored in the first cutting to determine the step position. Therefore, even if the processing path K1 of the first cutting is different from the processing path K2 after the second cutting, the step position can be reliably determined after the second cutting, and the set processing conditions can be automatically changed. In addition, the wire discharge machining method of the embodiment has the following advantages: the step position can be detected even when the processing direction of the second cutting is different from the processing direction of the first cutting. The wire discharge machining method of the present invention does not have to be implemented in the same form as the embodiment, but can be implemented by making appropriate modifications as in the examples listed above.

[0102] [Industrial Applicability]

[0103] The present invention can be effectively used for precision machining of molds or metal parts having step differences. The wire discharge machining method of the present invention provides a machining method that has excellent machining shape accuracy of such molds or metal parts and improves operability.

Claims

1. A wire discharge machining method, characterized in that: include: A segmentation process, in which the XY plane of the worktable of the wire discharge machining device is equally divided into small areas in the x-axis direction and the y-axis direction with a pre-set segmentation width to form a plurality of segmented areas; a storage process, in which the plate thickness of the workpiece is detected and stored in association with the segmented areas as plate thickness information; an inference process, in which a peripheral area including the current processing position of the workpiece is set as a search range, and the plate thickness information associated with the segmented areas located within the search range is referred to, and based on the plate thickness information associated with the segmented areas and the plate thickness of the current processing position of the workpiece, whether there is a step difference ahead in the travel direction of the processing path; and a processing condition changing step of setting a peripheral area including the position of the step difference as a processing condition changing range, and changing the processing conditions when the current processing position of the workpiece enters the processing condition changing range.

2. The wire discharge machining method according to claim 1, characterized in that: The storing step is executed in the rough machining step, and the estimating step and the machining condition changing step are executed in the end surface finishing step.

3. The wire discharge machining method according to claim 2, characterized in that: The storage step is to store the plate thickness at the time of detection, i.e., the first plate thickness information, and the plate thickness at the previous time, i.e., the second plate thickness information, in association with the divided areas. The inference process is to infer whether there is a step difference ahead in the moving direction of the processing path based on the first plate thickness information and the plate thickness of the current processing position of the workpiece when the processing path of the end surface finishing process and the processing path of the rough processing process are in the same direction. When the machining path of the end face finishing process is in opposite directions to the machining path of the rough machining process, it is inferred whether there is a step difference ahead in the moving direction of the machining path based on the second plate thickness information and the plate thickness of the current machining position of the workpiece.

4. The wire discharge machining method according to claim 1, characterized in that: The storing step is to store the position where the plate thickness of the workpiece is detected in association with the divided area. The processing condition changing step is to set a range centered on a position where the plate thickness of the workpiece is detected as the processing condition changing range.

5. The wire discharge machining method according to claim 1, characterized in that: The processing condition changing step changes the processing condition in stages relative to a target value to be changed when changing the processing condition.

6. The wire discharge machining method according to claim 1, characterized in that: The machining condition changing step changes the machining conditions when the current machining position of the workpiece crosses a condition switching standby section provided inside the boundary of the machining condition change range.

7. A wire discharge machining device, comprising a numerical control device, wherein the wire discharge machining device is characterized in that: The numerical control device comprises: The detection section detects the plate thickness of the workpiece during the rough machining process; a storage unit that associates the plate thickness with a divided area and stores it as plate thickness information, wherein the divided area is obtained by equally dividing an XY plane of a table of the wire electrical discharge machining device into small areas in an x-axis direction and a y-axis direction by a predetermined dividing width; and Processing Department; In the end face finishing process, the processing unit sets the surrounding area including the current processing position of the workpiece as a search range, refers to the plate thickness information associated with the divided area located within the search range, and infers whether there is a step difference in front of the travel direction of the processing path based on the plate thickness information associated with the divided area and the plate thickness of the current processing position of the workpiece, and sets the surrounding area including the position of the step difference as a processing condition change range. When the current processing position of the workpiece enters the processing condition change range, control of changing the processing conditions is performed.

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