外文翻译一种拉丝模的参数化设计系统的知识库

外文原文A knowledge-based parametric design system for drawing diesBor-Tsuen Lin & Chian-Kun Chan & Jung-Ching WangAbstract :The design of drawing dies is a very complex and knowledge-intensive process. This paper describes a knowledge-based parametric design system for drawing dies which requires only a minimum set of parameters to be set before it is able to complete the design of the main components of a die, such as upper dies, lower dies, and blank holders. This minimum set of parameters includes blank sizes, die faces, punch open lines, drawing strokes , and press data. This design system implemented on top of the Pro/E CAD software consists of a drawing die knowledge base, a subcomponent inferencer , a dimension calculator , a subcomponent generator, a system coordinator, and a user interface. We use the design of drawing dies for inner wheel house as a concrete example to show that our system can greatly improve the design quality while reducing the development time and cost.Keywords Knowledge-based systems . Parametric design .Drawing dies . Computer-aided systems . Stamping dies1 IntroductionPress parts are widely used in products of high complexity and precision, such as vehicles, aircraft, and 3C (computer,communication, and consumer electronic) related products.Therefore, the press process has been identified as one of the most important manufacturing processes. Drawing, trimming, and bending dies are used throughout the entire press process for various purposes 1. Designing press dies s a vital step in the development of press processes .Besides the highly complex die structures, interferences among various design parameters make the design task extremely difficult. Therefore, a majority of people still believe that it is art rather than science that plays an important role when designing dies. It takes a long time to gain sufficient experience to become an expert in this field. The highly competitive environment makes it necessary to reduce the time and money spent on designing dies while maintaining high standards for product quality. Therefore, using computer-aided design (CAD) has become one of the most important ways to increase productivity. The views in traditional 2D design systems are difficult to understand. It is very hard (if not impossible) to identify any interference. Moreover, it is difficult to create and modify drawings .These drawbacks of the traditional 2D design systems make them very time-consuming to learn and use. 3D CAD software uses an intuitive and concrete way to present objects to users, which fundamentally avoid those aforementioned problems. Moreover, as a result of the fast development of personal computers, 3D software can be operated on most personal computers, which makes 3DCAD software increasingly popular.Most 3D CAD software offers only simple geometrical modeling function. However, they fail to provide users with sufficient design knowledge, which is of great help in most design tasks. Therefore, the design of automatic, knowledge-based, and intelligent systems has been an active research topic for a long time. Regarding the construction of dedicated system, Nahm and Ishikawa 2 utilized the set-based design approach with the parametric modeling technique to handle the uncertainties that are intrinsic at early stages of the design. Sharma and Gao 3 developed integrated design and manufacturing planning systems to support conceptual redesign and reprovisioning activities. Myung and Han 4 developed an expert system based on a configuration design method. This system allows users to design mechanical products in a 3D environment. Roh andLee 5 proposed a hull structural modeling system for ship design, which was developed using C+ and built on top of 3D CAD software. Lee et al. 6 developed a parametric computer-aided tool design system for cold forging using Auto LISP. In order to make the modeling process more efficient, Kong et al. 7 developed a Windows-native 3Dplastic injection mold design system based on Solid Works using Visual C+. Chu et al. 8 developed a computer aided parametric design system for 3D tire mold production in CATIA using CAA.In the stamping tool design area, Cheok and Nee 9 developed a knowledge-based strip layout design system in AutoCAD. Taking advantage of neural-network and CAD software, Pilani et al. 10 proposed a method for automatically generating an optimal die face design based on die face formability parameters. Ismail et al. 11 developed a feature-based progressive press tool using cheap CAD software. Based on sheet metal operations, Singh and Sekhon 12 developed a punch machine selection expert system, which was built in AutoCAD and used Auto LISP. Tisza 13 developed an expert system for detail process planning of metal forming in AutoCAD. Choi et al. 14 developed a computer-aided design and manufacturing system for irregular-shaped sheet metal products for blanking or piercing and bending operations. Chang et al. 15 established a genetic algorithm to solve the problems of ranking the working steps in progressive dies.Though designing dies is a complex process, technologies used throughout the process are mature, which makes the whole process routine. In order to complete the design process in a scientific approach, this paper introduces a knowledge-based parametric design system for drawing dies, where designers only need to input a minimum set of design parameters, and the system will automatically complete the design of the main components of drawing dies.2 Stamping die design2.1 Configuration of drawing diesA design configuration of a typical drawing die consists of two categories of components. The first category is called “standard components”, which include the wear boards, gas springs, and bolts. These standard components are available in the market with different sizes. The second category is called the “main components”, which include upper dies,lower dies, and blank holders, as shown in Fig. 1. The design of these components totally depends on specific drawing dies and requirements from clients. This paper focuses on the design of the main components.Fig. 1 Structure of main components for a drawing die of inner wheel house2.2 Designing main components for drawing diesThe main components of most drawing dies can be very complex. We detail the design procedures for main components of drawing dies in three steps: initial information,skeleton design, and functional subcomponent design.Initial information: Designers need to gather a minimum set of information of the drawing die, including blank sizes,die faces, punch open lines, drawing strokes, and press data. Blank sizes: blank sizes refer to the dimensions of the blanks. Most of these blanks are rectangular, while the rest are in irregular shapes in order to reduce costs or to make the shaping process more manageable. For most die design tasks, the dimensions of dies are based on the sizes of the blanks. Die faces and punch open lines: as shown in Fig. 2, die faces include product forms, addendums, draw beads ,and binder faces. Product forms are the product shapes after drawing, while addendums , draw beads, and binder faces are used to assist drawing. This paper focuses on the detail structure design of the drawing die, therefore the design of product forms, addendums, draw beads, and binder faces found in a number of papers such as Pilani et al. 10, Chen and Liu 16 and Makinouchi 17, Bigot et al. 18 and is beyond the scope of this paper. Moreover, punch open lines are used to cut die faces into two parts, which serve as the surface forms of upper dies and blank holders. Drawing strokes: drawing strokes are the paths from the point where the upper die meets blank holder, to the lower dead point. Typically, the length of a drawing stroke is the distance between the highest vertex and the lowest vertex of the die face plus 10mm. Press data: press data is the information that includes press machine specifications and data related to press machine and drawing die. Press machine specifications include working strokes of press machines, lower dead point of sliders, heights and dimensions of the bolsters, and positions and dimensions of T-slots and cushion pin holes for the bolsters. Data related to machine and die includes die height, feed level, cushion pin stroke,press center, and die center.Skeleton design: the main responsibility of skeleton design is to identify the main structure of the die, including sizes of upper dies, lower dies, and blank holders, thickness of die faces, avoid structure, layout and thickness of ribs ,positions and sizes of guide, auxiliary structure, and pocket.We use the design of ribs as an example. Below are the design criteria: Distances between adjacent ribs should not exceed 300 mm. Ribs must be placed under each stopper seats and cushion pin seats. Space must be reserved between ribs and safety,cushion pin holes, key slots, and U-slots.The design standards are as follows: The thickness of the surrounding ribs is 40 mm.The thickness of the internal ribs is 30 mm.Fig. 2 Die faces and punch open lines of a drawing die for inner wheel house. a Die face; b Punch open lineFunctional subcomponent design: functional subcomponent design is the process of designing various functional subcomponents that are used to support die drawing. These functional subcomponents include U-slots, key slots, hooks,safety, stopper seat, gauge seat, cushion pin, and wear plane. We use the design for the lower die of cast in type hook, shown in Fig. 3, as an example. Its design criteria are as follows: Fig. 3 Layout of cast in hook in lower die Two hooks are placed in each of the two lateral sides of the die. An additional hook is required when the length of a side exceeds 2,000 mm. The height of a hook (z) is two-thirds of the height of the die (h). The distance (x1, x2 or x3) between the hook and the center of the lateral sides should be either one-third of the width of the lower die (w) or zero. The diameter of the hooks should be determined using the following criteria: while the three lower dies hooks must be able to support at least Wt, where Wt (the total weight of the die) is L (die length) W (die width) H (die height) d (density) 0.3 (porosity ratio) 1.2 (safety factor).The design standards for the hook of cast in type are shown in Fig. 4.Fig. 4 Design standards for the cast in hook3 System structuresThe proposed system completes the die design based on design criteria and related standards. Figure 5 shows the structure of our system, which includes a drawing die knowledge base, a subcomponent inferencer, a dimension calculator, a subcomponent generator, a system coordinator, and a user interface. Each of these tasks will be detailed in the following sections. Fig. 5 System structure3.1 Drawing die knowledge baseIn order to construct dies using standardized 3D approaches,designers need to analyze the die structures and the structures of each of the components and subcomponents. The purpose is to classify the die structures into several categories in a systematic approach, and identify all geometric operations of the modeling processes for each subcomponent. This information will be stored in the systemas templates. Currently, our system has templates for 18 different subcomponents. Moreover, 2D drawings, design parameters, design criteria, design standards, and relationships among various design parameters of each subcomponent are also stored in our system. This information can be used to train junior designers, to query die information, and to develop, modify, and debug programs.3.2 The subcomponent inferencerThe subcomponent inferencer uses formulas that are derived from initial information and design criteria to identify the quantity, position, and size of each subcomponent. As shown in Fig. 7, the main components of the die consist of 18 subcomponents. Taking the cast in hook in the lower die as an example, four formulas can be derived using the four design criteria described in Sect. 2.2. Therefore, the 18 subcomponents in our system have a total of 138 formulas. A warning message will pop up if the inferencer cannot complete the design using the initial information and related formulas.3.3 The dimension calculatorThis calculator provides shape parameters for each subcomponent .Once the category and size of the subcomponent (design parameters) have been fixed, this calculator is able to get appropriate values for each shape parameter .Taking the cast in hook as an example, there are six categories of design parameters based on the design standards shown in Fig. 4. The 18 subcomponents shown in Fig. 7 have 226 design parameters.3.4 The subcomponent generatorThe subcomponent generator is responsible for generating 3D solid models for each subcomponent based on the quantity, position, and size of the subcomponent, and the geometric operations used in the modeling processes of the subcomponent. Since all parameters of solid models are automatically computed by our system instead of being supplied by users, our system is able to automatically construct 3D solid models. An error message with error code and status will be sent to users by the system coordinator when an error occurs.3.5 The system coordinatorThe job of the system coordinator is to coordinate the different tasks of our system. After users input initial information, the coordinator starts to design each subcomponent based on the design processes of the drawing die.For each subcomponent design, first, the subcomponent inferencer identifies the quantity, position, and size of the subcomponent. Then, all shape parameters of the subcomponent are determined by the dimension calculator and then the subcomponent generator enables the geometric operations of the subcomponent to create the solid model of the subcomponent.3.6 The user interfaceUsers are able to interact with the system using the user interface. The sizes of the blanks, drawing strokes, and press data are input into the system using the user interface.In the meantime, the user interface is also responsible for detecting input errors.4 Procedures for constructing the proposed systemOur system has been implemented on top of the Pro/E CAD system with its “add-on” Pro/Program and Pro/TOOLKIT modules. It constructs parameter-based solid models of drawing dies using initial information, design criteria, and design standards. Figure 6 shows the procedures for constructing our system, which will be discussed in the following sections. Fig. 6 Procedures for constructing our system4.1 Planning die structuresDie structures can be very complex. A complete and systematic plan should be made up front, so that the system is able to construct dies in the same way as the CAD software does, and is able to avoid mistakes when designing system components.When planning die structures, we first collect the structures of all kinds of drawing dies for vehicle sheet metal. Then, we perform analyses on the main components of the die, such as upper dies, lower dies, and blank holders. In the meantime, we also need to identify subcomponents of the main component, such as ribs and functional subcomponents. We then identify the causal relationship for the positions and dimensions of each subcomponent based on their design criteria and standards.In the next step, we determine design procedures (Fig. 7) and structure trees of the solid model (Fig. 8) for the main components of the drawing die. Now, we are able to plan the initial sizes and structures of the main components, and the initial size and position of each subcomponent.Fig. 7 Design procedures for main components of the drawing dies4.2 Constructing plane skeletonOnce planning die structures is completed, we begin to construct the plane skeleton model of the die. In Pro/E, a plane skeleton model should be constructed before designing a parameterized solid model, since the plane skeleton model will be used as a basis for designing the solid model and connecting parameterized formulas. As shown in Fig. 9, the plane skeleton model of the die is completed using the 2D design module of Pro/E. Then, Pro/Es builtin 3D functions, such as extruding and trimming, can complete the design of the local structures for each component and each subcomponent of the dies. Fig. 8 Structure trees of solid models for the main components of the drawing diesFig. 9 Plane skeleton model of drawing diesIn order to meet various design needs, all possible structures of each module are built into the skeleton model.Taking the cast in hook as an example, as shown in Fig. 9,there are six hooks. In the example described in Sect. 5, the subcomponent inferencer determines that four hooks are required. After the system coordinator activates all four hooks, the subcomponent generator will generate the solid model and deactivate the two hooks that are unnecessary.We need to identify the freedom of the die using constraints, since the number of constraints has a direct impact on the design flexibility. Moreover, the number of parameters decreases when more and more constraints are added to the system, which simplifies the programming task. Therefore, it is important to carefully design and apply constraints.Since the dimensions must be positive numbers, we need to consider every possible situation to avoid its zero and negative numbers when designing, especially when there are causal relationships among various parameters.4.3 Setting parametersOnce the plane skeleton model has been constructed, some of the skeleton dimensions are modeled