Concurrent design of die structure for the hottest

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Concurrent design of automobile panel die structure

Abstract: This paper analyzes the whole process of concurrent design, introduces how the new CAD software technically supports concurrent design, and establishes a concurrent design process model of panel drawing die structure

1 preface

automobile panel dies have the characteristics of high precision, complex shape, large structural size and high requirements for coordination. In the actual design process, the design task of a complex panel is often completed by a design combination. The traditional mold design adopts the "serial" sequential design method, which leads to the isolation of each design link. In addition, the limitations of two-dimensional drawing expression and the low efficiency of manual design make it difficult for designers in the design team to exchange information accurately and timely, and they can not find defects in mold design in time. Sometimes, it will cause rework, prolong the cycle of mold design, and affect the design quality. However, general general mechanical CAD software, including molds, mostly adopts the bottom-up design process, that is, the detailed geometric structure design of the parts constituting the conceptual design model is carried out first, and then the assembly relationship between the parts is determined. It is difficult or impossible to solve the overall problems such as assembly coordination and function assurance directly related to the structure. Therefore, it also affects the quality and efficiency of structural design. In this case, people began to study the new CAD software of top-down concurrent design process, so as to provide designers with product assembly level design support, and fully ensure the parallel collaborative work ability between designers. The so-called concurrent design is that multidisciplinary designers coordinate the exchange of information and design products in parallel, so as to greatly shorten the time required by the traditional serial design and improve product quality and enterprise competitiveness. As an important part of concurrent engineering, concurrent design has become a research hotspot in the field of design

2 realization of concurrent design process

2.1 analysis of concurrent design process

the concurrent design process of automobile panel die structure is divided into conceptual design, layout design and detailed design stages

2.1.1 conceptual design stage

through the analysis of the design requirements, the functional model of the panel die is established, and the design constraints on the die layout and structure are generated. The results of the conceptual design are represented by the panel mold function model diagram, as shown in Figure 1

the meaning of the mold function model diagram is: the mold function structure tree is obtained through the decomposition of the mold function, and the function unit of the root of the tree represents the total function of the mold; Each functional unit can be further decomposed into the next level sub functional unit structure until the structure of each functional unit is finally decomposed into features or parts. Among the sibling unit nodes belonging to the same functional unit at the same level, the local functional unit network is formed through the functional feature nodes; All nodes in the function structure tree and related function feature nodes constitute the final global function structure network of the product. Through the network diagram, the relevant functional units are connected with each other

2.1.2 layout design institute

after establishing the functional model of the automobile panel die, through the comparison relationship of "function - action principle - structure", establish the overall layout of the die, and determine the key action surface and the relationship between the main parts/components. The result of layout design is the overall assembly drawing of panel die

the assembly sequence of the panel mold is to assemble the parts into sub assemblies (i.e. components) first, and then participate in the assembly of the overall mold. The assembly model of the mold can also be represented by tree structure in the sense of topology, as shown in Figure 2

2. 1.3 detailed design stage

according to the overall assembly drawing of the panel mold, divide the design task to each member of the design group, and complete the detailed design of several mold parts/components at the same time to obtain a complete mold part drawing. The die structure of large automobile panel is complex, with hundreds of parts, and the workload of detailed design is huge, so the work of concurrent design is mainly reflected in the detailed design stage. In this phased design process, design activities are carried out from top to bottom. In terms of each stage of the whole design process of the panel die structure, the functional model, the final assembly, and the parts/components all have a gradual refinement process from coarse to fine, from simple to complex, and from general to accurate. The work of each stage is not completed at one time, but needs to be modified repeatedly. Because the design information can be exchanged accurately and timely, and there is a good work coordination mechanism, the modification workload required for the application of concurrent design method is significantly reduced, and the design quality is significantly improved. The whole process of panel die concurrent design is shown in Figure 3

2.2 software technical support

mold designers divide labor and cooperate in the design process, and achieve high quality and efficiency of mold design by exchanging design information. Pro/enginee software provides technical support for concurrent design of automobile panel die structure

2.2.1 three dimensional parametric design

three dimensional design directly looks at the whole process of design, and whether the designed mold structure is reasonable at a glance; Through the three-dimensional model, designers can accurately understand the design intention of others; The three-dimensional design can determine the spatial position of die parts/components and carry out interference inspection, so as to meet the requirements of high coordination of panel parts; With a three-dimensional model, we can analyze and shape all kinds of parts

2.2.2 assembly design environment

assembly design environment is the core part of new CAD software that is different from general CAD software. The overall designer can fully consider the overall performance of the die and improve the overall design quality and efficiency by designing the panel die in the assembly environment; The lower designers can work at the same time after forming rough design requirements at the upper level to shorten the design time; Parts/components become an organic whole through assembly relationship constraints, which is easy to ensure the consistency and integrity of the design, and supports the parallel and collaborative work of the design team. The assembly design environment provides the design function of "virtual parts". The so-called virtual part refers to that the parts/components are only represented by a name or a coordinate system, regardless of geometry. Through the assembly of virtual parts, the functional structure and assembly structure of panel die can be determined. Virtual parts can be designed and modified in the assembly environment, and they can be turned into "real parts" by generating geometric entities. Many polyurea engineering technicians, constructors and supervisors of any part lack formal polyurea technical training to design, modify, assemble and delete

2.2.3 design task processing

the decomposition of design tasks and the processing of related subtask relationships are the key problems of concurrent design. This decomposition and processing should be based on the principle that the design tasks should be executed in parallel as far as possible, and be successful as soon as possible, so as to improve the quality of the mold and shorten the development cycle. In the assembly environment, the overall designer of the panel mold determines how many tasks of each sub assembly and parts need to be completed by other designers after the decomposition of the final assembly ligand by grasping the perfection of the parts/components design. The design perfection of parts/components in the final assembly is subject to accurately reflecting the function and assembly relationship of the mold and accurately transmitting information to the lower level designers. The assembly can be decomposed into components and parts for detailed design at any time, and can be reassembled at any time to return to the assembly environment for design, and various inspection and analysis can be carried out

2.2.4 unified product data model

when designing the panel mold, the parts/components can exist in the assembly or alone, which provides great convenience for the implementation of concurrent design. Parts/components in the assembly should be designed with features that require high assembly and coordination. When they exist alone, they should be designed in detail. The two aspects of design can be carried out alternately. Because there is a unified product data model, it can ensure the consistency and synchronization of the design of parts/components in the two states. In addition, the modification of mold design is an essential, cumbersome and error prone link in the process of mold development. The unified product data model, full parameterization and full correlation of the software make it easy to modify the mold in the design stage. One modification in the design can be extended to the whole design, and all design drawings and product data can be automatically changed at the same time, avoiding inconsistencies caused by human negligence

2.3 concurrent design process model

2.3.1 concept of dynamic model

the concurrent design process of automobile panel die structure is a dynamic process, and the concurrent design process model is the dynamic model of the design system. With the dynamic model, each designer can put forward relevant modification suggestions according to their current state in the design process, and achieve the optimization of the overall concurrent design by coordinating and exchanging information and eliminating conflicts. The dynamic model has not only the hierarchical relationship between upper and lower levels, but also the parallel relationship of the same level. Parallel relationship is very important to describe the process of concurrent design, but the role of hierarchical relationship can not be ignored. Because the whole dynamic model is a network model, the solution of the hierarchical relationship of this unit directly affects the design of adjacent parallel units

2.3.2 design evaluation coordination mechanism

the complexity of automobile panel dies may lead to conflicts in aspects such as compatibility, geometric dimension connection, specification type, power design and work sequence in concurrent design. In the assembly environment, we evaluate and modify the function, structure and other technical indicators of the whole automobile panel mold, so as to eliminate conflicts and ensure the integrity and coordination of the mold. Although the quality of each part design directly affects the performance of the whole die, it is relatively insignificant to evaluate a single part in the process of concurrent design. In the process of concurrent design of automobile panel die structure, the communication of design information, the evaluation of design quality, the control of design process, the coordination between designers and other issues are the most important. The above problems can be solved through the following mechanisms:

① the overall designer carries out the General Assembly Design of the panel mold, then disassembles the parts/components and assigns them to the lower level designers at all levels for detailed design at the same time

② when the lower level designers carry out the detailed design, if they find that the design intention is unclear or a part needs to be modified, they can send an inquiry or modification application to the upper level designers

③ after necessary calculation, evaluation and coordination, the upper designers issue the design intent description or agree to the modification instruction; Because of the multi-level structure of the panel die, if the upper designer has no right to deal with the problems involved in the lower design, the problem can be submitted to the higher designer or even the overall designer

④ the lower level designers continue the detailed design according to the design instructions or modification instructions issued by the upper level

⑤ the upper designers and overall designers assemble the parts/components after the detailed design of the lower layer, and carry out technical verification in terms of function, structure and so on. When they are satisfied, they will end the whole design, otherwise they will disassemble the parts/components for modification

in the process of design discussion, the designer can't see the overall effect of design and modification in time, and check its correctness, so as to make the design of each part coordinate synchronously and go hand in hand. This mechanism solves the problems of parallelism and hierarchy in the structural design of automobile panel dies, which is beneficial to the designers

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