JP3719305B2 - Wire electric discharge machining method and wire electric discharge machining apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wire electric discharge machining method and a wire electric discharge machining apparatus for machining a workpiece by relatively moving a wire and a workpiece by NC control.
[0002]
[Prior art]
The wire electric discharge machining method is a method in which a voltage is applied between a wire and a workpiece opposed to each other with a gap, and the workpiece is machined by the generated discharge energy. Such a wire electric discharge machining method will be described with reference to FIG. FIG. 5 is a system diagram of a conventional wire electric discharge machine. In the figure, 1 is a workpiece to be machined. 2 is a work mounting base. 3 is a table to which the mounting base 2 is fixed. Reference numerals 4X and 4Y denote motors for moving the table 3 in the X-axis and Y-axis directions, respectively. Reference numeral 5 denotes a wire which is pulled out from the reel 6a in a state where a predetermined tension is applied and wound on the reel 6b. Reference numerals 7a and 7b denote guides for positioning the wire 5. Reference numeral 8 denotes a machining power supply that supplies electric power between the workpiece 1 and the wire 5. Reference numeral 9 denotes an NC device, which includes a calculation unit 9a, a storage unit 9b, and a control unit 9c, and performs various controls for automatically performing machining. Reference numeral 10 denotes a keyboard for inputting necessary commands and numerical values to the NC device 9.
[0003]
Next, a processing procedure of the conventional wire electric discharge machine will be described. FIG. 6 is a front view of the workpiece 1. Reference numeral 11 denotes a product, which is a square whose vertices are indicated by solid lines of A, B, C, and D. When finishing the product 11 by two times of machining, usually, a square abcd indicated by a dotted line slightly larger than the product size is first taken from the workpiece 1 under a machining condition in which the machining speed is more important than the quality of the machined surface and the discharge energy is large. Cut out (hereinafter referred to as first cut). Next, emphasis is placed on the quality of the machined surface rather than the machining speed, and the square abcd is finished into a square ABCD indicated by a solid line under machining conditions with low discharge energy (hereinafter referred to as a second cut).
[0004]
In either case of the first cut or the second cut, incidental information and a shape program necessary for machining are input to the NC device 9 prior to machining. The above-mentioned incidental information items include the processing conditions determined by the diameter and material of the wire 5 and the material and thickness of the workpiece 1 and the surface roughness of the work surface, the diameter of the wire 5 and the direction in which the wire 5 is offset. Designation. When the storage unit 9b is provided with a database for selecting machining conditions, the diameter and material of the wire 5, the material and thickness of the workpiece, and the surface roughness of the machining surface are input to the NC device 9, When an appropriate machining condition is selected by the calculation unit 9a and the database is not stored in the storage unit 9b, the operator inputs the machining condition to the NC device 9 with reference to the machining condition data book. In any of the above cases, each processing condition is assigned a unique processing condition number and arranged. When the processing conditions are determined, the power supply method, the size of the processing gap, the size of the tension to be applied to the wire 5 and the like are determined. In the case of the first cut in FIG. 6, the shape program includes the vertices a, b, c, d, the machining start point S, and the intersection t between the perpendicular line drawn from the machining start point S to the line segment da and the line segment da. The coordinates of the processing end point, the processing order, and the like.
[0005]
At the time of the first cut, the NC device 9 uses the incidental information to determine the sum of the machining gap size determined by the radius of the wire 5 and the machining conditions as an offset amount k, and analyzes the shape program so that the distance from the square abcd is the offset amount k. A route SR-RL-LM-MN-NP-PR indicated by a two-dot chain line in the figure is calculated, and the table 3 is moved in the X-axis and Y-axis directions so that the center of the wire 5 moves on the route at a constant speed. To move the square abcd. Also in the second cut, as in the case of the first cut, a route (not shown) for moving the center of the wire 5 is calculated from the incidental information and the shape program to finish the square ABCD.
[0006]
[Problems to be solved by the invention]
By the way, at the time of processing, the wire 5 bends in a bow shape between the guides 7a and 7b due to the discharge reaction force, and the wire 5 at the portion facing the workpiece 1 deviates from the straight line connecting the guides 7a and 7b. In the case of the first cut, the discharge reaction force is applied almost uniformly to the front semicircular portion in the traveling direction of the wire 5 and the magnitude thereof hardly changes. As a result, the amount of deflection of the wire 5 hardly changes, and almost desired processing can be performed.
[0007]
However, in the case of the second cut, as shown in FIG. 7, since the length of the wire 5 and the product 11 facing each other on the side toward the apex A is opposed to the product 11, that is, the processing amount gradually decreases, The discharge reaction force f shown gradually decreases, and the discharge reaction force gradually increases on the side away from the vertex A. Since the tension of the wire 5 is constant, the amount of deflection of the wire 5 gradually decreases on the side toward the apex A and gradually increases on the side away from the apex A. As a result, even if the center of the wire 5 (actually the guides 7a and 7b) is moved along the path l obtained by the calculation indicated by the one-dot chain line, the machined surface is shown by the solid line in FIG. appear.
[0008]
Therefore, in the prior art 1, the processing conditions (for example, processing speed, wire tension, processing fluid pressure, etc.) in the corner portion are changed without changing the route obtained by the calculation. In the prior art 2, the shape accuracy is improved by changing the path in the corner portion with the shape program without changing the processing conditions.
[0009]
However, in any of the above prior arts, it is necessary to collect data by performing actual machining with another workpiece. Usually, it is not possible to find an appropriate processing condition or path in a single test processing, so that the work efficiency is lowered. Furthermore, in order to select an appropriate processing condition or route in a short time, an experienced worker is required.
[0010]
An object of the present invention is to solve the above-mentioned problems in the prior art, improve the work efficiency, and allow a less experienced worker to perform machining with excellent shape accuracy and wire An electrical discharge machining apparatus is provided.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 is applied to each machining condition in a wire electric discharge machining method that calculates a path that is at an offset distance from the finished shape and moves the center of the wire along the path. prepare the corner angle of 30 ° or more 170 ° or less and the corner path correction equation for the a parameter advance, prior to processing, once in the movement direction front side of the corner portion on the basis of the said path correction equation parameters Calculates a correction path that moves away from the machining part side at a first angle set in advance, goes over the corner part, turns and returns to the machining part that follows the corner part at a second angle set in advance. The corner portion moves the center of the wire along the correction path instead of the path.
[0012]
The invention of claim 2 is a wire electric discharge machining apparatus that calculates a path that is an offset distance from the finished shape and moves the center of the wire along the path, and is applied to each machining condition by 30 ° to 170 °. Data storage means storing the following corner angles, corner path correction formulas and parameters, and based on the path correction formulas stored in the data storage means and the parameters, the corner section is moved in front of the moving direction. A correction path that is once separated from the processing portion side by a first angle set in advance, passes the corner portion, and then turns to return to the processing portion that follows the corner portion and returns at a second angle set in advance. The corner section is provided with control means for moving the center of the wire along the correction path instead of the path.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on the illustrated embodiments.
FIG. 1 is a system diagram of a wire electric discharge machine according to an embodiment of the present invention. Components having the same or the same functions as those in FIG. Reference numeral 21 denotes a data storage device. As shown in FIG. 2, a corner angle θ applied to each machining condition, a path correction formula f (X, Y) on the inlet side, and a path correction formula g (X, Y) on the outlet side. And the parameters of the entrance distance p and the exit distance q, the entrance angle α and the exit angle β are registered. Note that the sign of the entrance angle α and the exit angle β is reversed depending on the offset direction.
[0014]
Next, the operation of the present embodiment will be described with reference to FIGS. 3 and 4 in the case of performing the second cut with the processing condition number 1001 in FIG. FIG. 3 is a flowchart showing the control procedure, and FIG. 4 is a plan view of the corner portion, showing the vertex A portion in FIG. 6 in an enlarged manner. Prior to machining, the incidental information and the shape program are input to the NC device 9 (step S10 shown in FIG. 3), and then the corner unit path correction is input to the NC device 9 (step S20). When the route computation start button is turned on (procedure S30), the NC device 9 computes the route SE-EF-FG... At the center of the wire 5 as in the prior art (procedure S40) and stores the result (procedure). S50). The procedure up to step S50 is the same as the conventional one.
[0015]
Next, the necessity of route correction at the corner is confirmed (procedure S60). If necessary, the process of step S70 is performed, and if not, the process is terminated (procedure S200). In step S70, the presence or absence of a corner portion of the path is searched from the machining start point S to the end point. When there is a corner portion, the processing of step S80 is performed, and when there is no corner portion, the processing is terminated (step S200). In step S80, from the machining start point S to the machining end point, an angle θ at which the i-th (i is 1, 2, 3,...) And i + 1-th path intersect at the connection point is calculated, and 30 ≦ θ Whether or not (step S90). If 30 ≦ θ, the process of step S100 is performed, and if θ <30, an alarm is displayed and the operation is terminated (step S110). In step S100, it is determined whether or not θ ≦ 170. If θ ≦ 170, the process in step S120 is performed. If 170 <θ, the correction in the corner portion is not performed, and the process in step 70 is performed. In the case of FIG. 4, first, in step S80, it is calculated that the angle of the first route SE and the second route EF is θ _E = 270 degrees, and the procedure returns to step 70 through steps S90 and S100. That is, the route is not corrected at the connection point E between the route SE and the route EF.
[0016]
Next, the angle θ _F at the connection point F between the second route EF and the third route FG is calculated, and θ _F = 90 degrees, so the process of step S120 is performed. That is, a position that is separated from the point F on the path EF by the distance p registered in the data storage device 21 and the offset amount k is set as the correction start point I, and the coordinates X _I , Y _{I of the} correction start point _I and the XY coordinate system. The inclination γ of the path EF is substituted into the inlet side correction formula f (X, Y) registered in the data storage device 21 to determine f (X, Y) (step S130). Further, a position that is separated from the point q on the path FG by the distance q registered in the data storage device 21 and the offset amount k is set as the correction end point K (step S140), and the coordinates X _K and Y _{K of the} correction end point K are The inclination δ of the path FG in the XY coordinate system is substituted into the exit side correction equation g (X, Y) registered in the data storage device 21 to determine g (X, Y) (step S150). Next, an intersection point Q between the inlet side correction equation f (X, Y) and the outlet side correction equation g (X, Y) is obtained (step S160). When the intersection point Q exists, the route EF− stored in step S50 is obtained. After replacing FG with the correction route EI-IQ-QK-KG (procedure S170), the processing of procedure S70 is performed. If the intersection point Q does not exist, that is, if the inlet side correction equation f (X, Y) and the outlet side correction equation g (X, Y) are parallel, the process of step S110 is performed. Thereafter, the corner correction path is calculated in the same manner, and the path stored in step S50 is replaced with the correction path.
[0017]
At the time of machining, the NC device 9 moves the table 3 in the X-axis and Y-axis directions so that the center of the wire moves along the memorized path. Therefore, the corner portion passes through the correction path and machining with excellent shape accuracy. Can do.
[0018]
In the above embodiment, since the path through which the wire 5 passes is calculated in advance prior to machining, for example, even when the angle θ of the corner portion is less than 30 degrees or there is no intersection Q, the machining is not interrupted. Processing with excellent accuracy can be performed.
[0019]
In the above description, the case where all the routes are straight lines has been described. However, when one of the routes is a straight line and the other is a curved line, the angle at which the tangent line of the curve at the connection point intersects the straight line may be obtained. . Further, the functional equation for calculating the correction paths on the inlet side and the outlet side is not limited to the linear equation, and may be an n-order equation or other functional equations, and the angle θ is not limited to the range of 30 ≦ θ ≦ 170, It may be further expanded. If θ <30 in step S90, the process of step S70 may be performed instead of displaying an alarm (step S110). Similarly, when there is no intersection in step S160, the process of step S70 may be performed instead of displaying an alarm (step S110). Furthermore, correction control may be selected on a program, or the data table may be stored in the storage unit 9b of the NC device 9 without providing the data storage device 21. Further, the correction path of the corner portion to be processed may be calculated while processing.
[0020]
【The invention's effect】
As described above, according to the present invention, the corner portion is separated from the processing portion side by a first angle once preset in front of the corner portion in the moving direction, passes the corner portion, and then turns to turn the corner portion. Since the machining portion subsequent to is processed by returning to the second angle set in advance, it is possible to reliably prevent the corner portion from being drooped .
[Brief description of the drawings]
FIG. 1 is a system diagram of a wire electric discharge machine according to an embodiment of the present invention.
FIG. 2 is a diagram showing data stored in a data storage device.
FIG. 3 is a flowchart showing a control procedure.
FIG. 4 is a plan view of a corner portion.
FIG. 5 is a system diagram of a conventional wire electric discharge machine.
FIG. 6 is a front view of a workpiece.
FIG. 7 is a diagram showing the magnitude of the discharge reaction force at the corner and the processing result.
[Explanation of symbols]
5 Wire 21 Data storage device

Claims (2)

In the wire electric discharge machining method of calculating a path at a distance of an offset amount with respect to the finished shape and moving the center of the wire along the path,
The path correction equation of the corner angle and the corner portion below 170 ° 30 ° or more to apply for each processing condition and the parameters in advance to prepare,
Prior to machining, based on the path correction formula and the parameters, the corner portion is moved away from the machining portion side at a first angle once set in front of the moving direction, and after turning the corner portion, it is turned. Calculating a correction path for processing by returning at a second angle set in advance to the processing portion following the corner portion;
The wire electric discharge machining method, wherein the corner portion moves the center of the wire along the correction path instead of the path. In a wire electric discharge machining apparatus that calculates a path at a distance of an offset amount with respect to the finished shape and moves the center of the wire along the path,
Data storage means storing a corner angle of 30 ° or more and 170 ° or less applied for each processing condition, a path correction formula and parameters of the corner portion;
After separating from the processing portion side at a first angle once set in advance in the moving direction of the corner portion based on the path correction formula and the parameters stored in the data storage means, and after exceeding the corner portion A control path that turns and calculates a correction path to be processed by returning to the machining section following the corner section at a preset second angle, and the corner section moves the center of the wire along the correction path instead of the path. When,
A wire electric discharge machining apparatus characterized by comprising:

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