Object-oriented NC programming technology of the h

2022-08-19
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With the development of automobile industry and the continuous updating of automobile body modeling, a large number of molds for inner and outer body coverings, reinforcing plates, connecting plates and other metal stamping parts should also be updated. Automobile cover molds are important process equipment for the production of automobile body. Their main characteristics are large size, complex working surface and generally free-form surface, High dimensional accuracy and surface roughness are required. Therefore, higher requirements are put forward for the manufacturing quality and cycle of automobile molds. NC programming is one of the important links in mold manufacturing, which plays an important role in mold quality and cycle length

commercial cad/cae/cam integrated software represented by UG, pro/engineer, CATIA, etc. provides a series of technical support for the automotive industry from design to manufacturing and related processes, but it is still a general cad/cam software fundamentally. At that time, according to the decision-making procedures of listed companies, it is a practical problem for enterprises to combine their powerful functions with their own characteristics, integrate their own experience and professional knowledge, and make them integrated and intelligent, so as to improve the efficiency of design and manufacturing. Using ug/api, grip, vc++ and other tools, this paper uses object-oriented technology to develop the NC programming of auto panel dies, and develops a NC programming system suitable for auto panel dies

second, the traditional NC programming method and its shortcomings

the characteristics of automobile panel dies determine the complexity of NC programming. Generally speaking, the processing of a set of molds requires dozens of NC programs to complete. The traditional programming method (as shown in Figure 1) is a process programming. Every NC programming operation must go through this process, even if sometimes only one parameter is modified. Therefore, the process of setting parameters is cumbersome. In addition, it takes a certain amount of time to generate the tool path by computer, which generally accounts for more than 30% of the programming time, which also affects the programming efficiency and the quality of the program

Figure 1 flow chart of traditional NC programming method

III. BMW in NC programming takes the above measures to apply object-oriented technology

1 Object oriented parameter definition

in the programming system described in this paper, the concept of class and object is introduced into parameter definition. There is a hierarchical relationship between various types or objects, and each layer has the characteristics of inheritance from top to bottom. You can derive a class through class inheritance. In the derived class, you can not only add new members, but also modify its base class through function overrides to make it easier to use. As shown in Figure 2, common parameters and features of auto panel dies are defined in auto panel die class A. Drawing die Class B1 is derived from a, which inherits all the parameters and features of class A. at the same time, the common parameters and features of drawing die are defined in Class B1, which is derived downward in the same way

Figure 2 classification of auto panel dies

2 Basic form of parameter definition

class deep drawing die: public auto panel die

{

private:

ls_parameters par;//parameters

bool getqicheparameters();//copy parent parameters

bool setqicheparameters();//modify parent parameters

...

public:

virtual bool setlssamplers mode();//define the processing template

virtual bool setlsparameters() ;//Set the parameter

...

}

3. Object generation

(1) object generally, an instance is an object. In NC programming, an operation to generate an NC program is an object

(2) a job can be a processing procedure, a part or a part, such as the lower die and the upper die, and even the NC programming process of a set of dies

in a job, according to the attribute characteristics of the job, a user-defined class is derived from its corresponding class resources, and the section shortening parameters and characteristics that define this job are modified through the human-computer interface. Therefore, this user-defined class has determined most of the parameters to complete this job. Then several objects are generated from this class to complete the final parameter setting

4. Automatic setting of associated parameters

in NC programming, many parameters are interrelated, that is, when one or several parameters are determined, other associated parameters are also determined. In order to reduce the number of manually set parameters, the mathematical relationship is used to describe this association in the NC system

5. Automatic batch processing generates CLSF

CLSF as the tool path source file. Transfer one or more jobs with set parameters to CLSF generator, generate and save CLSF and related information in batch. This part of the work program is completed automatically, which can realize unmanned operation. Most of the running time is arranged after work, which is very helpful to improve efficiency

Figure 3 program block diagram

6 Automatic batch generation of post-processing

post processing is the process of generating NC programs using CLSF tool path source files. CLSF files are sorted, combined, and transferred to the post processor. NC programs and related information are generated and saved in batches

IV. advantages

1 With the inheritance of parameters and the program calculation of associated parameters, the number of manually set parameters can be put into use only after passing strict tests, which further reduces the programming operation and reduces accidental human errors

2. The automatic batch generation of the program greatly improves the programming efficiency

3. It can realize assembly line operation. The subsequent sequence can obtain the previous sequence information through inheritance, and then pass it to the next sequence after operation and processing

4. It can be integrated with CAPP system

v. processing examples

taking the surface processing of the upper die of the drawing die of the automobile cowl panel beam (as shown in Figure 4) as an example, this paper introduces the basic process of automatic NC programming. It can be seen from Figure 4 that the cowl panel beam is a product with large size and complex profile. In the actual programming, 11 boundary parameters are used to divide the profile into 11 machining parts. The parameters of these 11 machining parts are exactly the same except for the boundary parameters and the related parameters of the boundary parameters. The basic process is described below

1. parameter definition

☆ a user class is derived from the upper die class of the deep drawing die

☆ define the profile data, product benchmark, product material thickness, processing template and other information in the user class

☆ generate 11 objects circularly in the user class and add boundary parameters, so that each object corresponds to a processing part

☆ user defined parameters are completed, and the associated parameters are automatically generated by the program. The parameters such as row spacing, cutting direction, cutting mode and cutting speed are

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