Development of Computer Assisted Tool Design for Material Forming Processes

Current practice in designing tooling components for semisolid processing requires extensive commitments of human resources. Even when utilizing currently available Computer Aided Design (CAD) systems, tool design remains a complex task requiring large amount of design knowledge. Considerations such as part material, tool material, characteristics of die filling, flow behavior of semisolid slurries must be carefully thought by the tool designer to reach an acceptable tooling solution. This paper proposes the framework for computer assisted tool design by integrating tool design domain knowledge into CAD system to help tool designers. Introduction Semisolid processing requires a low viscosity of the semisolid material to fill up the die cavity completely, and a high solid fraction to prevent various defects from internal porosity. Die designs based on the conventional pressure die casting can not be used, instead it requires modification to it [1,2]. Changes required after initial fabrication of tools can lead to significant cost increases, therefore, the need to “design it right the first time” is critical. Tool delivery times are also lengthy and tooling changes delay production schedules. This paper presents the methodology to merge conventional CAD concepts with knowledge of semisolid tooling and part design, setup, and production information. Various databases, including material property, part geometry, and equipment parameters are integrated into CAD system and are utilized by the separate tool design module to provide necessary information during decision making for tool design process. The system will considerably reduce the tool design cycle time through the combination of the domain knowledge of tooling design and CAD system capabilities. Also it will assist the human designer by automating and/or simplifying routine calculations and table-lookup for technical data. System Objectives The proposed tool design system analyzes the current practices of the human designer and simulates the activities in a computer program. The integrated design system is comprised of the following subsections. • Development of the semisolid tooling design process: Understanding and documentation of the tool design steps is required. It will show each subtasks and the sequential relations among them. • Development of subtasks involved in the design process: The subtasks in the tool design process flow identify the input/output data. A problem-solving strategy for each subtask will be developed. Detailed flow path and information needs will be identified. Solid State Phenomena Vols. 116-117 (2006) pp 669-672 online at http://www.scientific.net © (2006) Trans Tech Publications, Switzerland Online available since 2006/Oct/15 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 130.203.133.34-14/04/08,11:17:16) • Development of the design database structure and its relations: The development of a common data structure for storing tool design information allows communications within different sections of the database. The various databases will likely have different structures to handle data efficiently, however interrelations among various databases must be maintained. Temporary storage capabilities for retrieved and/or calculated data must be addressed. The information management system should be globally transparent to the user. • Streamlining of current design practices: The proposed tooling design system will streamline the current design practice. Engineering calculations and other selection methods automated will shortened the design cycle and make the design practice closer to the Just-In-Time manufacturing environments. • Development of user interface for the system: The design of common user interface throughout the system that is modeled after the existing protocols will ensure user-friendliness. Also the design of the screen sequences for data input will guide the user of the system through the design process and ensure no design steps have been overlooked. Knowledge Engineering To complete tool design, a tool designer must utilize information relative to material properties, press capabilities, specific knowledge of the semisolid process and tooling characteristics. Material and press information is readily available from suppliers, however, tooling knowledge is primarily resident in the engineer and is dependent on individual expertise. The collection and organization of this necessary data were collected using Knowledge Engineering technique. There are three types of knowledge engineering methods; interviewing, verbal protocol, and observational studies [3]. Several interviews were conducted with tool designers. The data collection and its analysis provided an overall picture of the semisolid tool design process and areas for improvements and possible automation with the help of computer software. Once the expert knowledge is gathered, the next step is identifying and defining the abstract structure of the problem, and dividing into subtasks. Each subtask is designed in modular fashion and arranged in an appropriate position according to the control structure. Integration Architecture The integration method is such that the database resides external to the CAD system and is managed by a database management system. When tool design knowledge is needed, the computer-assisted Tool Design System sends a signal to the database management system of the Tool Design Database, which in turn fetches data and supplies it to the Tool Designer. When the Tool Design System needs geometric information of the part, the system asks the CAD system’s geometry database and uses it (Fig. 1). Fig. 1 Schematic Diagram of Integration Architecture CAD System computer-assisted Tool Design System Tool Designer Tool Design Database information flow direction 670 Semi-Solid Processing of Alloys and Composites