AN INTERACTIVE CADCAE SYSTEM FOR MOLD DESIGN



AN INTERACTIVE CAD/CAE SYSTEM FOR MOLD DESIGN | |

|Ivan Matin, Miodrag Hadzistevic, Janko Hodolic, Djordje Vukelic |

|Department for Production Engineering, Faculty of Technical Sciences, Trg Dostiteja Obradovica 6, Novi Sad, Serbia |

|matini@uns.ac.rs, miodrags@uns.ac.rs, hodolic@uns.ac.rs, vukelic@uns.ac.rs |

Abstract: In injection molding, the design of the molds is of critical importance for the product quality and efficient processing. This paper describes a knowledge-based parametric design system for mold design, which requires only a minimum set of injection molding parameters to be established before being able to complete the design of the main components of a mold. This CAD/CAE system contains of Pro/E and special developed modules for calculation, selection, modification and design. Developed CAD/CAE system can greatly improve the design quality while reducing the development time and cost.

Key words: CAD/CAE system, injection molding, mold design

1. INTRODUCTION

The highly competitive environment makes it necessary to reduce the time and money spent on mold design while maintaining high standards for product quality. Therefore, using computer-aided systems has become one of the most important manners to increase productivity. Most CAD software offers only simple geometrical modeling function. However, they fail to provide users with the 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 a dedicated system, Deng et al. [1] developed an expert mold design system based on the configuration design method. This system allows users to design a mold in the CAD/CAE environment. Kong et al. [6] developed a Windows-native plastic injection mold design system based on the Solid Works using Visual C++. Lou et al. [7] utilized the set-based design approach with the parametric modeling technique to handle the uncertainties that are intrinsic at early stages of the mold design. In the stamping tool design area, authors [8, 9] developed a knowledge-based strip layout integrated design system in Pro/E. An interactive mold design systems were developed for dividing the mold design into four major steps, as well as for parting surface design, core and cavity design, runner system design, and mold base design [2,7]. It also provided the ability to control and manage projects, and assist designers in completing projects correctly. Systems have been constructed using the experience and knowledge of a product design and mold manufacturers. The researchers first determine the parting line for the plastic part, followed by the calculation of the number of cavities required. The cavity layout is created based on the input information of the layout pattern and the orientation of each cavity. The mold base is loaded automatically to accommodate the layout. Alternatively, Low and Lee [8,9,10] proposed a methodology of standardizing the cavity layout design system for plastic injection mold such that only standard cavity layouts are used. When only standard layouts are used, their layout configurations can be easily stored in a database for fast retrieval later in the mold design stage. Other mold design system was developed by Ma [11], offering collaborative design systems, a standard mold base, and a decision-making system to improve the concurrent mold design efficiency in CAD software. Constructing standard components is an efficient manner to shorten the mold design cycle in the mold development. The advantages of using standard components include the ability to ensure the consistency of mold development and the reduction of manufacturing costs and time. The most important purpose of an interactive CAD/CAE environment’s standard mold base is to assist designers in managing and using standard components correctly and efficiently. A mold base controls components via a three-level classification by class, type, and order number. Using the standard components library, designers browse for the components they need and save valuable time lost in searches. The standard components library includes three techniques for constructing models: general type, program type, and family table type [14]. General type components are typically complicated and invariant. Users need only to specify the component needed, and are not required to specify any dimensions, such as slide groups. Program type components have similar shapes but different features, such as date-code inserts. Family table type components, such as ejector pins, have variable dimensions. There are two ways to find components in the mold base by class and type, or by directly linking to the window containing the desired components.

2. KNOWLEDGE-BASED APPROACH

A knowledge-based approach broadly means to build up a system, usually called a knowledge-based system (KBS), for solving complex decision problems in a specific domain. A KBS, normally in the form of an intelligent computer program, uses knowledge and inference procedures to solve problems that are difficult enough to require significant human expertise for their solution. The typical structure of a knowledge-based system is shown in Fig. 1. [11, 14]

[pic]

Fig. 1. The typical structure of a knowledge-based system

The developed interactive CAD/CAE system is based on a typical structure of a knowledge-based system. It comprises of the knowledge base, containing encoded expertise from the expert. The inference engine on the other hand provides strategies for processing the encoded knowledge in order to reach KB solutions. The KB system also provides a user interface for the KB system/user interaction. Links to a traditional database provide the KB system with the opportunity to import and use data in the inference or reasoning process. Knowledge is represented by a set of primitive components. Such primitive component is called a knowledge object, and it consists of a functional features and associated data. Mold design represents a generic sequence of activities, and each activity is represented by a mold function. A function defines effects on associated data, and it is represented by various forms, such as mathematical formula, decision tables, constraints and logical formula. Data types include simple data types, such as numerals and their aggregation, and also complicated data types, such as geometry and other objects.

3. GENERAL STRUCTURE OF AN INTERACTIVE CAD/CAE SYSTEM FOR A MOLD DESIGN

Generally, plastic injection molding design includes a plastic part design, a mold design, and an injection molding process design, all of which contribute to the quality of the molded product as well as the production efficiency. The developed program system makes possible to perform: 3D modeling of the parts, analysis of part designs, numerical simulation of injection molding, and mold design with calculation [3,4]. By the realization of the proposed integrated system, this problem could be solved. The main part of the system consists of a knowledge base. The knowledge base is organized by knowledge objects, and practically managed by a commercial database system. A knowledge engine accesses to the knowledge base, and invokes appropriate applications. General structure of a developed interactive CAD/CAE system for a mold design is presented in Fig. 2. [4,13]

[pic]

Fig.2. General structure of an interactive CAD/CAE system for a mold design

System consists of four foundation modules. These are:

• CAD/I module for the solid modeling of the part,

• CAE/I module for the numerical simulation of the injection molding process,

• CAE/II module for the calculation of parameters of the injection molding and mold design,

• CAD/II module for the final mold modeling (Core and Cavity design and the design of all residual mold components).

CAD/I module is the first module in an interactive CAD/CAE system for a mold design. This module is used for generating the CAD model of the plastic products. The result of this module is a solid model of a plastic part with all necessary geometrical specifications. CAE/I module is utilized for the numerical simulation of the plastic injection molding. Using Pro/Plastic Advisor, a user can optimize the injection molding parameters and optimize the part geometry and a plastic material. CAE/II module has been developed to solve the problem of a mold thermal, rheological and mechanical calculations and the mold selection. The next section shows the details of the general structure of the CAD/II module.

1. Structure of the CAD/II module

CAD/II module is used for the final CAD modeling of the mold (core and cavity design). This module uses additional software tools for the automation, creating a core and a cavity from the CAD model, including the shrinkage factor of plastic materials and the automation splitting mold volumes of the stationary and movable plates. The product information standard in a CAD/CAE system has different types which deal with the geometry representation, the feature representation and the integrated representation. The integrated representation can incorporate some kinds of non-geometry information, such as expert experience and knowledge, into product modeling, resulting in an efficient manner to realize the intelligence and the automation of a product design and a mold design.

Additional capability of the CAD/II module are software tools that:

• Apply a shrinkage that corresponds to the designed plastic part, geometry, and molding conditions, which have been computed in the CAE/I and CAE/II module for the automation of core and cavity design;

• Make a conceptual CAD model for non-standard plates and mold components;

• Design core and cavity inserts, sand cores, sliders, lifters, and other components that define a shape of a molded part;

• Populate a mold assembly with standard components such as standard D-M-E mold base, and CAD modeling ejector pins, screws, and other components creating the corresponding clearance holes;

• Create runners and waterlines, whose dimensions have been calculated in the CAE/II module;

• Check the interference of components during the mold opening, and check the draft surfaces.

After applying the dimensions and selecting the mold components, the CAD/II module generates a 3D model of the fixed and movable plates. Geometry mold specifications, which are calculated in the CAE/II module, are automatically integrated into the CAD/II module; as a result, the CAD/II outcomes are an assembly of mold plates. Features and specifications of the CAD/II module are as follows: specialized 2D GUI enables the instant customization of a mold base and components; automatic assembly of components – ‘pick and place’; necessary clearance holes, threads, counter bores, etc. are automatically added to plates; part-level features are already fully dimensioned; custom components can be created, saved and reused; mold base consists of „D-M-E“ mold components. The structure of the CAD/II module is presented in the Fig.3.

[pic]

Fig.3. Structure of the CAD/II module

Mold base assemblies and components with automatic functions, such as the on-the-fly customization component, sizing, placement, trimming, and clearance cut and thread creation, are provided for the following: Complete Mold Base Assemblies, Plates, Leader and Return Pin Assemblies, Locating Rings and Sprue Bushing, Screws and Washers, Automatic Drawing, and BOM Creation. The drawings of the mold assembly and plates, completed with hole charts, are created automatically. Mold opening simulation, completed with the slider and ejector simulation is created automatically.

4. CONCLUSION

Completing the mold design stage in the shortest possible time is the goal of every mold designer. Design automation substantially increases the overall efficiency of the design process, reducing the occurrence of the design flaws as well as the time-to-market reduction. An interactive CAD/CAE system proves to be a confident software tool for the plastic industry for the injection molding dental parts whose material is an integral part of the plastic material database. All modules of the CAD/CAE system are 3D solid-based, feature oriented, and parametric. Plastic flow simulation product is in the CAE/I and allows engineers to determine the injection molding parameters. CAD/II module also enables engineers to capture their own unique design and best practices directly within the database components. The module for the calculation of the mold specification and the parameters of injection molding (CAE/II) improves the design efficiency, reduces the mold design errors, and provides the full information needed for the mold selection. The future work of this research can focus on two issues. The first one is to analyze the market to define which plastic parts used in dental laboratories are in deficit and to determine the commercial for the injection molding in the Serbian industry. The second one are research possibilities for the full application of an interactive CAD/CAE system for the mold design for plastic parts, which is used in the dentistry.

REFERENCES

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ACKNOWLEDGMENTS

Results of the investigation presented in this paper are a part of the research realized in the framework of the project “Research and Development of Modeling Methods and Approaches in the Manufacturing of Dental Recoveries with the Application of Modern Technologies and Computer Aided Systems“– TR-035020, financed by the Ministry of Education and Science of the Republic of Serbia.

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