Abstract: This paper introduces a numerical control boring (milling) headstock CAD system. The system uses object-oriented thinking to calculate the headstock dynamic parameters and establish a three-dimensional solid graphic library. This system has the characteristics of convenience, high automation, and expandability, which can greatly increase design efficiency and reduce design and production costs. Improve product quality and generate greater economic benefits.
Key words: object-oriented; headstock; parameterized feature modeling; polymorphism; inheritance
Classification number: TP391.72 Document code: A
Article ID: 1001-2265 (2000) 02-0011-03

1 Introduction

Wuhu Heavy Duty Machine Tool Factory's WHZ-02X series CNC boring (milling) bed is a multi-variety, low-volume product, mainly based on the user and market demand for special design and production. In this mode of production, the product is frequently modified. The main drive system is the key component of the boring (milling) bed and is the component with the highest frequency of change. In the past, the design of the main drive system was basically based on manual manual design. It not only had a large workload and a long cycle, and could not meet the needs of market changes. It could not quantitatively analyze the design qualitatively, which greatly limited the improvement of the design level. In order to enhance the market competitiveness, it is particularly important to realize the rapid parallel design of CNC spindle (milling) headstocks. This article uses a comprehensive product modeling system, object-oriented thinking, establish a perfect CAD application environment to meet the market and the user's need for rapid response to product design, to achieve all-related fast-changing product design.

2 overall system frame design

This system calculates the main cutting force and cutting power through the main technical indicators input by the user (maximum stroke, rotation speed, maximum workpiece diameter, etc.), and the rapid design of the machine tool. By querying the 3D machine type spectrum library, the similar design is obtained, which provides a reference for the new design. Using Visual C++, an object-oriented language, to carry out interface design and calculation of dynamic parameters for NC headstock systems, it provides us with the concepts of data abstraction, data hiding and modularization. The system consists of raw data. Input module, cutting force cutting power calculation module, calculation result output module and other major modules, greatly enhance the reliability of the system [1]. A top-down, assembly-oriented full-correlation parallel design idea (DFA) is used to generate a part-drawing [2] from an assembly drawing. From the whole to the local, a parametric graphic library is built. Its essence is the object-oriented idea to establish a three-dimensional solid model of the headstock. The overall framework design of this system is shown in Figure 1. According to the different needs of the user and the market, according to the specific requirements put forward by the demand side, the overall plan optimization design is carried out to realize the overall plan design, dynamic parameter calculation, structural design, assembly interference inspection, component performance analysis and evaluation of the spindle box.

Fig.1 Design of CAD system frame of headstock CAD system for boring (milling) bed

After executing this application, the main process interface is shown in Figure 2. Click on the pull-down menu options in the “calculate cutting force” main menu to pop up the input dialog boxes for car, boring, milling, and drilling forces. Click the OK button, the dialog box disappears, and the calculation result corresponding to the processing method appears on the screen.

Figure 2 main process interface diagram of spindle head CAD system

3 CAD system structure and operation logic of numerical control boring (milling) headstock

3.1 Design of dynamic parameter calculation module <br> This module is to calculate the tangential cutting force, radial cutting force, axial cutting force and cutting power for various processing methods such as car, boring, milling, drilling, and reaming. In the same processing mode, there are many factors affecting cutting force and cutting power. Different material hardness, cutting speed, and tool angle have different influences on the cutting power. Therefore, the calculation formula is also different. It requires more input and output data and the calculation is more complicated. . For this purpose, based on the document/window architecture, a series of new classes are defined by ClassWizard: dialogue classes (Chexueli, Xixueli, Zuanxueli, input of raw parameters and cutting amount for each processing method), and calculation result output class (Chexueresult Xixueresult, Zuanxueresult, in order to facilitate the correspondence and exchange of document and dialog data, define the cutting amount, original parameters and member functions Drawresult(), Serialize() of each processing method in these classes. In order to facilitate the comparison of the calculation results obtained after the input of different cutting amounts and original parameters, multiple document types are used. The object of each calculation result class is defined in the document class so that the document class can access each member data and member function in the calculation result class. Use the member function Serialize() in the document class to call the Serialize() function in different result classes to write data from different processing methods to the persistent storage medium [1], and read the object state from the persistent storage medium later. Reconstruct the object, which can greatly facilitate the management and operation of document data. View class through the GetDocument () function, access to the document pointer to access the document class data, you can call the Drawresult () function in each calculation result class to achieve a variety of processing methods displayed on the screen. The software system framework is shown in Figure 3.

Figure 3 Frame diagram of the calculation of dynamic parameters

3.2 The establishment of three-dimensional solid graphic library of spindle head
3.2.1 Marking Uniqueness, Classification: The name of the component is unique, and the classification of sub-assemblies in the headstock assembly.
The headstock is used to contact the motion source (motor) and the executive organ (spindle) of the machine. Its function is: 1 Pass the certain power from the movement source to the executive organ. 2 to ensure that the implementation of the organ a certain speed and a certain range of speed. 3 According to the needs, the start, stop, reversal and braking of the movement can be conveniently performed. According to the numerical control boring (milling) bed TK6410 spindle head function requirements, assembly relations and design constraints, the spindle box is divided into the following major components: spindle type (I axis, executive organ in the spindle box), transmission mechanism type (II, III Axis, to ensure that the implementation of the organ a certain speed and a certain range of speed, the transmission is a two-stage transmission: from the motor output shaft → connecting shaft → II shaft → III axis → II axis → I axis, so as to achieve the milling axis Required speed; from the motor output shaft → connecting shaft → II axis → I axis, so as to achieve the required speed of the 镗 axis), motor output shaft type (connecting shaft is connected with the motor output shaft through the gear shaft sleeve, used to transmit the motor power to Speed ​​change mechanism), cylinder type (piston in the cylinder assembly moves the shift forks on the II and III axes, and the shift fork moves the double slip external gear on the II axis to move axially away from the gear on the III axis. The inner gear on the right end is meshed with the inner gear, which realizes the transmission output from the motor output shaft → connecting shaft → II shaft → I axis) and the box type (the arrangement of the axes in the box is related to the shape of the box, and the box is inside Each component supports and seals And subjected to various load) sub-assembly and the like. Under the constraint of the overall assembly relationship, these sub-assemblies are concurrently designed in parallel, and each functional unit can be further decomposed into the next sub-functional unit structure. The speed change mechanism is divided into II and III axis components, and the II and III axis component subassemblies are further subdivided into shafts, bearings, and transmission components on the shaft until the structure of each functional unit is finally realized as a known shape feature or Parts unit [3].
3.2.2 Polymorphism, Inheritance—The diversity of the assembly constraints among the interchangeability of sub-assemblies and interchangeable sub-assemblies in parts and general assemblies.
In the part, the parent-child inheritance relationship between the base feature and the auxiliary feature. In the assembly, from top to bottom, the inheritance parameters inherited from the assembly-constraint relationship in the upper-level assembly, such as the parent-child succession relationship from the total assembly → sub-assembly → sub-assembly, such as the positioning surface The dimensional parameters of the mating surface, supporting surface, and reference surface and the processing requirements will become the design constraints of the next-level assembly. There are two kinds of parameters in the design process: 1 Inheritance parameters The parameters inherited from the previous layer, the design department of this layer must not only meet, but also have no right to directly modify. If the two holes of the shift fork are respectively matched with the II and III axes, the pitch parameters and the aperture parameters of the two holes on the shift fork are shown in FIG. 4 . 2 Generated parameters Derived from the inherited parameters, or according to the current design needs, as shown in Figure 4 fork total length, total width dimensions, when the inherited parameters have changed, the associated parameters to be adjusted. When the distance between the two holes on the fork and the aperture change, the total length and total width of the fork change correspondingly.

Fig. 4 inheritance diagram of shift fork size parameter

In object-oriented programming, polymorphism refers to the ability of the same message to be interpreted as a different meaning after it is received by different objects. It is closely related to the inheritance of classes. An object can accept several messages of different forms and contents. Messages of the same form can be sent to different objects. Different objects can have different explanations for messages of the same form and thus respond differently. In the spindle box, the structural constraints are better than the messages. The same sub-assembly can adopt different or same structural constraints, and can be assembled with different sub-assemblies into different assemblies. If the II axis subassembly uses the same structural constraints (gear drive) and I, III axis, and the connecting axis are assembled into different assemblies, different structural constraints (end face alignment) and the cylinder assembly are assembled into the assembly. The classification, polymorphism, and structural constraint diversity of each subassembly in the headstock are shown in Fig. 5.

Figure 5 Diversity, polymorphism, and structural constraints of various subassemblies in the headstock

4 Conclusion

In this paper, Visual C++ is used to calculate the dynamic parameters of the spindle box. The assembly-oriented full-correlation parallel design (DFA) is used to establish a three-dimensional solid model of the spindle box. Its essence is to use object-oriented concepts such as object-oriented class, inheritance, polymorphism, and dynamic binding to establish a headstock CAD system, which greatly enhances the system's scalability and stability, enabling this system to be used for future CAD. / CAM/CAE integration lays the foundation.

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