The coal mine machinery based on the three-dimensional feature modeling of the top-down reducer Tan Jiacai (Hunan Engineering College, Hunan Xiangtan 411101) designed the concept, gave a top-down assembly design system development program, built the product layout, provided a The assembly-oriented design environment, through the hierarchical assembly model and parametric modeling technology, generates other zeros and components from the key parts of the product, and supports the product from concept design to detailed design, with Pio/ENGINEER software as the platform. The reducer product has been put into practical use for the object.
(3) x ((DFA.DFM)el provides the conditions. Can %lis repair n parts e also A only modify the painted Li*u / file: can be used to bookmark1 1 foreword in the current majority In the CAD system, the product design mainly adopts the bottom-up design process of bottom-up, that is, designing the part drawing and then assembling it. Although it has powerful part solid modeling function and part assembly function, the assembly coordination, The overall problem of function guarantee and so on can only be mastered by the operator. After assembly, if the design result is not satisfactory, it is necessary to re-design, add, delete, change and other cumbersome work of each part, and the modification is difficult and the efficiency is low. The actual design process of a product is a complex creative process, which can be divided into functional design, conceptual design, detailed design and design analysis. It is also called the “Top-down” design process. Starting from the overall and overall design, and then detailed design of each part under the constraints of the overall design. This article applies top-down technology, with PRO/E as the platform, to achieve the reduction
2 Support top-down CAD technology to support top-down CAD technology, starting with the conceptual design stage, functional decomposition should be performed, that is, the total function is decomposed into a series of first-level sub-functions by design calculation, and each sub-function is determined. Functional parameters, followed by structural design, that is, according to the overall function and the requirements of each sub-function, the overall structure (assembly) is designed and the positional relationship, connection relationship and cooperation relationship between each sub-component (sub-assembly) are determined.
Positional relationships, connection relationships, mating relationships, and other parameters are determined by geometric constraints or parameter constraints, and the like. Its theoretical model is as shown.
Supporting top-down CAD technology has the following advantages: it conforms to the product design process and the designer's thinking process.
When designing a product, the initial consideration is the function that the product should implement. Finally, the geometry of these functions is considered. Therefore, the design process of the product is a gradual process from abstraction to concrete.
It is convenient to realize the synergy of multiple subsystems and realize parallel design. In the initial stage of product design, that is, the concept design stage, important information such as the main functions, key constraints, and coordination relationships of the product are determined. When the task is assigned, these key constraints are also assigned to the subsystems. Subsystems work well together to avoid conflicts. The key constraints of the period are passed to the subsequent design stage, so that in the subsequent design, the feasibility evaluation can be carried out according to the constraints of the previous design, thus achieving assembly-oriented design (DFA) and manufacturing-oriented design (DFM).
3 Reducer's top-down design 3.1Pio/E-supported top-down design technology design, by defining the design intent of the top layer and passing information from the top layer of the product structure to a valid sub-assembly or part . Top-down design has the following main design concepts in working mode: determining design intent, planning, creating product structure, product 3D space planning, sharing design information through product structure level, and component design in assembly. Top-down design technology is the best way to control and control Pro/ENGtNEER software-related design tools when designing products.
When assembling a part, the designer can first plan the constraints of the part assembly, and define the relationship and constraints between each assembly part to help the designer not have to add a new one each time when assembling the part. The constraints are taken into account when the parts are used, because the parts can be assembled automatically using the Layout file. If you want to model the three-dimensional features of the top-down reducer, Tan Jia will automatically add the changed place to the assembly file.
The three-dimensional spatial planning of the assembly can be used to describe the space requirements of the components, important installation locations or movements, and to share design information between subsystems and as a means of control between these subsystems. Designing the overall layout only makes the design clearer, strengthens the communication of design data between components, supports the sharing and transfer of design data between components, and easily confirms, controls, and observes the design globally, so that the communication of design data is unimpeded. The designed product is more flexible.
Part design and editing in the assembly environment: In the process of product assembly, according to the shape and size of the designed zeros, parts and standard parts, use the constraints between the parts to create new parts or carry out the original parts. modify.
3.2 The top-down design of the reducer The basic structure of the reducer consists of sub-assemblies such as transmission parts (gears, couplings), shafting components (input shaft system and output shaft system), cabinets and accessories. The main process of top-down design: analysis, determination of the transmission plan, design of key parts. Key parts are important parts that affect product performance and product structure. In the reducer products, the shaft can be selected as the key part, because the shaft is the assembly basic part of the bearing, coupling, positioning sleeve, gear, seal and other parts. It has an assembly relationship with a plurality of zeros and components, and at the same time is an important part of the most complicated force, which needs to be designed and checked for strength, and must be controlled, so it is identified as a key component.
The assembly design process with the important part design process as the main line is established, and the main shapes and dimensions of other main transmission parts and components are designed in parallel. Mainly include: analysis and calculation of the main dimensions and shape of gears, bearings, couplings, etc.
Depending on the spatial position and connection between the shaft, gears, rolling bearings and the housing, the Pro/E Layout can be used to construct the product layout (including the calculation results for the shaft, rolling bearings and gears). As shown in the figure, a secondary cylindrical gear reducer and layout diagram, wherein the main reference is: the first stage gear meshing center line 1, the second stage gear meshing center line 2, the axis 11, the axis 12 and the axis 13, mainly The size constraints are: the center distance between the axis and the axis; the distance between the end faces of the two gears of the second section, the distance of the gear end face from the inner wall of the box; the distance between the outer wall of the box and the coupling, the pinion and the large gear The difference in tooth width, the distance between the end face of the bearing and the inner wall of the casing, and the outer elongation of the shaft, etc., are determined according to the structural design of the product and the calculation of the main parts.
According to the product layout diagram, the main zeros and parts are transferred and assembled. These zeros and components mainly refer to shafts, gears, bearings and simple cabinets, and their mutual positional relationship is determined according to the layout drawing.
Analyze the positioning relationship of the shafting parts, modify the local dimensions of the shaft and gear in the assembly environment, such as forming various assembled holes, shoulders, etc., and use the assembly constraint relationship to generate new positioning parts, such as bushings.
Assemble other zeros, components, such as oil marks, bolts, perspectives, etc., and produce appropriate features on the cabinet.
Add other features of the cabinet.
4 The advantage of the top-down design method is obvious. It provides an assembly design environment for the design community. The whole design process starts from the top layer and controls the overall design goals and performance status of the product from the beginning. As a detailed design, component design relies on conceptual design, functional design and preliminary design at the beginning of product development.
The product layout-based assembly design pattern described in this paper ensures that the design of each member of the design community is effectively controlled from the beginning of the product design to the final product assembly, thus reducing duplication in the design process. The product development cycle has been shortened and practical applications have been made in the product design of the reducer.

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