JPH0530568B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for modifying the shape of a corner portion in wire cut electrical discharge machining.

A wire cut electric discharge machine maintains a predetermined gap between the wire electrode and the workpiece, and applies voltage between the wire electrode and the workpiece to generate a spark discharge between the gaps, and uses the discharge energy to scrape the workpiece. , the workpiece is moved relative to the wire based on machining command data to machine the workpiece into a desired shape, but the workpiece is shaved off by spark discharge generated between the gap between the wire electrode and the workpiece. On the other hand, the cut surface inevitably has an arc shape as shown in FIG. 1A. Therefore, there is no problem in machining the straight parts, but the corner parts become rounded as shown in FIG. 1B, making it impossible to form straight corners. Further, the wire electrode 1 is bent by the pressure of the electric discharge on the surface in the direction of machining progress, and in this bent state bends the recessed portion, resulting in a bulge generally called a corner sag. For this reason, it is extremely difficult to create a recess with straight corners by wire cut electrical discharge machining.

On the other hand, when making punches, dies, and strippers using punching dies, precision dies may be made by grinding the punches and dies, and machining the strippers by wire cutting. The stripper not only prevents the scraps from rising together with the punch, but also is often used to position the punch, so high precision is required.

However, as mentioned above, in wire cutting, the recesses are always rounded, so when processing the stripper with wire cutting, it is very difficult to eliminate the roundness of the recesses and obtain high precision. It was troublesome and difficult. Further, when processing with a wire cut other than the above-mentioned stripper, it is extremely troublesome and difficult to process the corner portions even in the production of items such as gauges that require increased accuracy in straight portions.

Therefore, in order to improve the above-mentioned drawbacks, the present invention makes it possible to easily provide relief shapes in the parts of the recesses that require correction, eliminate the roundness that occurs in the recesses, and improve the precision of straight parts, etc. An object of the present invention is to provide a method for modifying the shape of a wire cut.

Figures 2 and 3 show the principle of the relief shape machining method in a recessed part. In the method shown in Figure 2 A and B, the arc center touches the intersection of two straight lines of the trajectory of the wire electrode in the recessed part, and the center of the arc touches the intersection of the two straight lines. In this method, the wire electrode is rotated so that it is positioned on a line that bisects the angle where the two intersect, and the relief shape is processed.

In addition, the method shown in Fig. 3 A and B involves machining the wire electrode orbit in a recessed portion in an arc relief shape beyond the point where the loci of the straight line portions of the wire electrode intersect and tangent to the loci of the straight line portions. This is a method of providing

In both the methods shown in Fig. 2 and Fig. 3, if the radius of the circular arc in the recess is set large, an uncut portion a is generated as shown in Fig. 3 A, and this uncut portion (cylindrical column) a falls or deforms, causing the wire electrode to The workpiece will shoot and the machining will often stop each time.

Moreover, if it is set to a small value, as shown in FIG. 4, when the angle of the recess is acute, an uncut portion b will be generated.

Therefore, in order to prevent these uncut areas from occurring, if the radius of the relief shape in this recess is made to be approximately the same as the offset value, the above-mentioned uncut areas will not occur and the machining program will be simpler. . Note that the above offset value means that the wire electrode must travel a certain distance (r in Figures 1 and 6) perpendicular to the direction of travel with respect to the path specified by the program. This fixed distance is called an offset value.

FIG. 5 is a main part configuration diagram of a control section of a wire cut electric discharge machine according to an embodiment of the present invention, and FIG.
is an arithmetic unit using a microprocessor, etc.
3 is a tape reader that reads commands from the NC tape 4; 5 is the operation panel, 6 is the memory,
7 is an interface circuit connected to table driving means 8 on which a work is mounted. 9 is a CRT display device, and 10 is a bus.

Therefore, in such a configuration, using the method shown in Fig. 3, we will use Fig. 6 as an example to explain machining of the relief shape in the recess when the radius of the relief shape is made equal to the offset value. An example in which the control section automatically detects recess machining and performs relief shape machining based on a program will be described with reference to a flowchart of the operation processing performed by the arithmetic unit 2 shown in FIG.

When machining the inside of the corner ABC shown in Fig. 6, the wire electrode moves to the right of the path specified by the basic program, that is, the machining surface, by an offset value r, and the wire electrode moves from point P to point Q.
It moves linearly to a point, forms an arc QR→ with a radius of offset value r at the corner, and then moves linearly from point R to point S. First, A
Assume that one block command M ₁ (x ₁ , y ₁ ) is given at a point, and the next block command is M ₂ (x ₂ , y ₂ ). That is, x ₁ on the X axis from the position of point A,
A command M ₁ is given to linearly process up to the position y ₁ on the Y axis, and the next command M ₂ is similarly given to the position x ₂ on the X axis, Y
The command is to continue machining in a straight line up to y ₂ on the axis. Therefore, it is determined whether the machined surface to be machined by these commands M ₁ and M ₂ is a corner of a concave part or a corner of a convex part, and if it is a concave part, the above-mentioned relief shape is formed. , command M ₁ (x ₁ ,
Corner B formed by y ₁ ) and command M ₂ (x ₂ , y ₂ )
At the point, an offset vector e→ ₁ for the command M ₁ (x ₁ , y ₁ ) and an offset vector e→ ₂ for the command M ₂ (x ₂ , y ₂ ) are determined. As shown in Fig. 8, ΔABB' and ΔBQB'' are similar, so the X-axis and Y-axis components of the offset vector e→ ₁ are +y ₁ · r/√ ₁ ² + ₁ ² and −x ₁ , respectively.・r/√ ₁ ² + ₁ ^2. In other words, the offset vector e→ ₁ is as follows: e→ ₁ = (+y ₁・r/√ ₁ ² + ₁ ² , −x ₁・r /√ ₁ ² + ₁ ² ) ...(1) Similarly, the offset vector e→ ₂ is as follows: e→ ₂ = (+y ₂・r/√ ₂ ² + ₂ ² , −x ₂・r /√ ₂ ² + ₂ ² ) … …(2).

Next, it is determined whether this corner portion is a convex portion or a concave portion. This is the direction of the cross product of the offset vectors e→ ₁ and e→ ₂ obtained as described above (cross product operation e→
The sign of the value obtained by performing ₁ x e→ ₂ ) and the offset are determined depending on whether the command path is on the right or left side. In other words, the cross product of offset vectors e→ ₁ and e→ ₂ is (1),
From equation (2), e→ ₁ ×e→ ₂ = (y ₁・r/√ ₁ ² + ₁ ² ) × (−x ₂・r/√ ₂ ² + ₂ ² ) −(−X ₁・r/ √ ₁ ² + ₁ ² ) × (y ₂・r/√ ₂ ² + ₂ ² ) = r ²・(−y ₁・x ₂ +x ₁・y ₂ ) /√ ₁ ² + ₁ ²・√ ₂ ² + ₂ ² ), and the judgment is made depending on whether this value is positive or negative and whether the offset is on the right or left side of the path, and the following combination is a recess.

If the cross product e→ ₁ ×e→ ₂ is positive, the offset is on the left side. If it is negative, it is on the right side... (3) For example, in Figure 6, if machining is performed in the order of A → B → C, the cross product e→ ₁ ×e→ ₂ = |e ₁ |・|e ₂ |sin(2π−θ) =−r ² sinθ, and the cross product e→ ₁ ×e→ ₂ has a negative sign, and the offset is on the right side of the path, so the concave part It's a corner.

Also, if we reversely process C→B→A,
The _{offset is on the left side of the path, and its cross product is e→ 1 × e → 2 =} | e ₁ ｜・｜e ₂ ｜sinθ = r ² sinθ, which is positive. Therefore, in this case as well, the corner portion is a recess. Also, as shown in Figure 9, A→B
When machining →C, the offset is on the right side, and the cross product is positive as e→ ₁ ×e→ ₂ = |e ₁ |・|e ₂ |sinθ = r ² sinθ, which is obtained from equation (3). It's not a recess. In other words, it is a convex portion, and normal processing is performed without processing the relief shape of the corner.

In this way, the command M ₁ (x ₁ y ₁ ) and the command M ₂
When the machined surface formed by (x ₂ y ₂ ) is determined to be a recess, the wire electrode first moves linearly from point P to point Q with an offset value r, and at point Q, If the offset is on the right side of the path, counterclockwise (GO3); if the offset is on the left side, clockwise (GO2)
I do. In this case, since it is on the right side, it is rotated counterclockwise around an arc whose radius is the offset value r to process the relief shape. Next, move linearly from point R to point S. In this way, a relief shape in the recess is formed.

Therefore, the above relief shape processing may be stored in the memory 6, and it may be automatically determined for each corner whether or not it is a recess, and if it is a recess, the above relief shape processing may be performed.

However, if the control unit of the wire cut automatically detects concave machining from the basic program and processes the relief machining shape in this way, if it determines that it is a concave part, the relief machining will be performed on all the recesses. It is good to be able to select whether or not to perform relief shape processing when there is no need to create a relief shape or when relief shape processing should not be performed.

To do this, in Figure 5, you can create an NC tape so that the processing described above is performed at all corners where relief shape machining is required, and in the program of NC tape 4. A selection index indicating whether or not to perform the above-mentioned relief shape processing may be provided for each corner (concave portion), and the selection index may be selected depending on the workpiece to be machined.

Also, after inputting and memorizing all the basic programs from NC tape 4, use the editing function to
While displaying the basic program on the CRT display device, a method may be adopted in which a command is corrected from the operation panel 5 to perform the above-mentioned relief shape processing where relief shape processing is required.

As described above, the present invention enables relief shape machining to be performed on recesses in wire cut electric discharge machining, so that it is easy to round the recesses in processes such as stripper machining that require increased precision in straight parts. It is something that can be processed and maintain straight lines.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the rounding of a concave corner in wire cut electric discharge machining, Figures 2 and 3 are diagrams of the principle of relief shape machining, and Figure 4 is
FIG. 5 is a diagram illustrating a problem when the radius of relief shape machining is made small, and FIG.
A diagram of the principle of relief shape processing performed by an embodiment of the present invention,
Figure 7 is a flowchart of relief shape machining, Figure 8
The figure is an explanatory diagram of the offset vector, and Figure 9 is
It is an explanatory view when a corner is a convex part. 1...Wire electrode, 2...Arithmetic unit, 3...
... Tape reader, 4 ... NC tape, 5 ... Operation panel, 6 ... Memory, 7 ... Interface circuit, 8 ... Table driving means, 9 ... CRT display device, 10 ... Bus, W ...... Work, r...Offset value, _e1 , _e2 ...Offset vector.

Claims (1)

[Claims] 1. In the wire cut electric discharge machining method, if the intersection of machining paths by two blocks commanded by the basic program is the intersection of recess machining, the offset value of the wire electrode with respect to the machining path is calculated around the intersection. A wire cut shape modification method that adds a machining path of a wire electrode movement locus of a circular arc with a radius to the above-mentioned intersection. 2. Store the above basic program in the storage unit in the control device of the wire-cut electric discharge machine, then put the control device into a program editing state, select the recess into which the relief shape is to be inserted, and insert the relief shape block. A method for modifying the shape of a wire cut according to claim 1. 3. A patent claim in which the above-mentioned base program is a basic program having a block for machining a relief shape having a selection index at the intersection point of machining the concave portion, and by selecting the above-mentioned index, machining the relief shape in the selected concave portion is performed. The method for modifying the shape of a wire cut according to item 1. 4. The control device of the wire cut electric discharge machine calculates the offset vector of each machining path at the intersection of the machining paths of the two blocks commanded by the above basic program, and calculates the direction of the cross product of the two offset vectors and the offset vector. 2. The method for modifying the shape of a wire cut according to claim 1, wherein machining of a recess is determined based on the direction, and if the machining of a recess is determined, the wire electric discharge machine is controlled to automatically machine a relief shape at the intersection.