Processing Method for Electrical Discharge Machine

Abstract

A method for generating cavity model applied for machining a part by electrode discharge machine (EDM) using a tool electrode comprising: a. generating a part-before EDM model defining the geometry of a part to be eroded by the EDM machine to obtain a final part; b. generating an electrode model defining the geometry of the electrode applied for eroding the part; c. computing a cavity model defining the geometrical shape of a cavity, which represent the volume of the material to be eroded by the erode based on the part-before EDM model and the electrode model.

Claims

1. A method for generating a cavity model applied for machining a part by electrode discharge machine (EDM) using a tool electrode comprising: a. generating a part-before EDM model defining the geometry of the part, which is to be eroded by the EDM machine to obtain a final part; b. generating an electrode model defining the geometry of the tool electrode applied for eroding the part; and c. determining the cavity model defining the geometrical shape of a cavity, which represent the volume of the material to be eroded by the tool electrode, based on the generated part-before EDM model and the generated electrode model.

2. The method according to claim 1, wherein the part-before EDM model is a computer aided design (CAD) model.

3. The method according to claim 1, wherein the part-before EDM model and the electrode model are input into a Computer-aided design (CAD) tool, in particular, the cavity model is calculated by conducting Boolean calculation between the part-before EDM model and the electrode model.

4. The method according to claim 1, wherein the part-before EDM model defines the geometry of a raw part.

5. The method according to claim 1, wherein the part-before EDM model defines the geometry of an intermediate part, which is obtained by machining the raw part.

6. The method according to claim 5, wherein the raw part is machined by one of the following machining processes to generate the intermediate part: milling, electro-discharge machining, laser machining, cutting, and grinding.

7. The method according to claim 1, wherein the method further comprises: a. generating a first part-before EDM model defining the geometry of the raw part to be eroded by the EDM machine to obtain the intermediate part; b. generating a first electrode model defining the geometry of a first electrode applied for the eroding the raw part; c. computing a first cavity model defining the volume of the material to be removed from the raw part to obtain the intermediate part; d. generating a second part-before EDM model defining the geometry of the intermediate part; e. generating a second electrode model defining the geometry of a second electrode applied for the eroding the intermediate part; f. computing a second cavity model defining the geometry of the material to be removed from the intermediate part by eroding using the second electrode by conducting Boolean operation between the second part-before EDM model and the second electrode model

8. The method according to claim 1, wherein the part-before EDM model is extracted from a Computer-aided manufacturing (CAM) tool.

9. The method according to claim 1, wherein the part-before EDM model is extracted from a mesh file.

10. A method for machining a part by an EDM machine tool comprising: receiving the cavity model generated according to claim 1; determining the machining parameters based on the cavity model; and machining the part using the received cavity model and the determined machining parameters.

11. An electrical discharge machine comprising a machine table on which a part is mounted and a tool holder for holding an electrode applied to machine the part, and a controller configured to receive the cavity model generated by using the method according to claim 1.

12. The electrical discharge machine according to claim 11, wherein the controller is further configured to determine a plurality of machining parameters based on received cavity model.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to describe the manner in which advantages and features of the disclosure can be obtained, in the following a more particular description of the principles briefly described above will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. These drawings depict only exemplary embodiments of the disclosure and are not therefore to be considered limiting of its scope. The principles of the disclosure are described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0023] FIG. 1 illustrates a comparison of the prior art and the present invention;

[0024] FIG. 2a illustrates the prior art;

[0025] FIG. 2b illustrates one example of the invention; and

[0026] FIG. 3 illustrates another example of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] FIG. 1 illustrates a comparison of the model used in the prior art and the present invention. The workpiece model 21 is a model of a final part. This model does not include all the deviations of the geometry due to limited machining accuracy if the part is pre-machined. For example, the corners 211 are modeled as a perfect rectangle. In the reality, such perfect rectangle cannot be achieved if for example the part is pre-machined by milling process, as the diameter of the cutting tool will cause rounding in the corner. If this model is combined with an electrode model 10 to calculate the cavity model, the error in the corner will appear in the cavity model and consequently causes wrong interpretation of the cavity shape and therefore, this will lead to a non-optimized EDM job and the final part cannot be produced efficiently and accurately.

[0028] On the contrary, the part-before-EDM model 23 is derived from the real machining, e.g. from the CAM system, therefore, all the geometry deviations such as the corners 231 due to machining inaccuracy are considered by generating the model. If this model is combined with an electrode model 10 to calculate the cavity model 28, the rounded corner will appear in the cavity model and consequently improve the accuracy of the final part machined by EDM based on the cavity model. It is common to simulate the toolpath and the material removing for the milling process, thus, this information can be input into the process of generating the cavity model directly from the simulation tool of the milling process. A 3-dimensional mesh model of the pre-machined workpiece can be extracted from the CAM system after the milling operation simulation and used as the part before EDM model. The cavity model is computed by combining the electrode model and the part before EDM model. The Boolean operation

[0029] can be conducted to calculate the cavity model based on the part-before EDM model and the electrode model.

[0030] FIGS. 2a and 2b illustrate an example, in which a portion of the electrode shape is engaged in the machining. As shown in FIG. 2b, the left portion of the electrode 10a should not be engaged with the workpiece during EDM machining. If the cavity model is generated only based on the electrode model, the cavity model will include this left portion as shown in FIG. 2a, which does not correspond to the real cavity shape. When the machining parameters are selected based on this inaccurate cavity model, inappropriate machining parameters will be chosen. The computed power setting will be unnecessary high to machine the cavity, which therefore, will increase the electrode wear. This can lead to poor final part accuracy. If several cavities with same shape has to be machined, it is usual that one electrode is used to machine several shapes. However, due to increased electrode wear, the electrode has to be replaced earlier which will increase the number of needed electrodes and therefore, the cost of production will also increase. In further, the machining time will increase due to additional material to be removed by the finishing pass, which was left by the roughing operation due to the electrode wear. As the power setting for the finishing pass is low, the removal of the additional material will increase significantly the machining time. If the part-before-EDM model is used, the generated cavity model as shown in FIG. 2b complies with the real geometrical shape of the cavity, thus the drawbacks can be overcome.

[0031] FIG. 3 shows a further example, in which the final part is achieved by machining a workpiece with two different electrodes. The EDM machining includes two operations. In the first operation, a first electrode is mounted to the machine to erode the raw workpiece to produce an intermediate part. In the second operation, a second electrode is mounted to the machine to erode the intermediate part to obtain the final part. For preparing the first EDM operation, a model of the raw part as a first part-before EDM model 33 and a model of the first electrode 31 are provided and a Boolean operation is conducted to calculate a first cavity model 36. For preparing the second EDM operation, a model of the intermediate part as a second part-before EDM 34 and a model of a second electrode 35 are provided and a Boolean operation is conducted to calculate a second cavity model 37. The second part-before EDM model is an intermediate part model, which is in this embodiment obtained by applying the first part-before EDM model and the first electrode model, in particular by conducting a Boolean calculation there between.