Rong Shean Lee

Developing a postprocessor for three types of five-axis machine tools

This paper presents a postprocessor capable of converting cutter location (CL) data to machine control data for three typical five-axis machine tools to establish an interface between computer-aided manufacturing (CAM) systems and numerically controlled (NC) machines. The analytical equations for NC data are obtained using the homogeneous coordinate transformation matrix and inverse kinematics. In addition, the developed postprocessor method is implemented through a trial-cut on a five-axis machine and verified on the coordinate measurement machine. Experimental results confirmed the effectiveness of the proposed postprocessor method which can be used to integrate the various five-axis machine tools employed in manufacturing systems.

Application of numerical simulation for wear analysis of warm forging die

Abstract Warm forging process has better forming precision than hot forging process and has better formability than cold forging. But warm forging die sustains higher temperature and working pressure, the die wear is faster than those of hot forging and cold forging. The purpose of this research is to combine the experimental techniques, wear model and numerical simulation method to predict the wear of warm forging die. The non-isothermal ring compression test was adopted to estimate the friction coefficient in different temperatures and the on-line temperature recording system was setup to correct the heat transfer coefficient of the interface. The wear coefficients in different temperatures were acquired from high temperature wear experiment. Finally, the Archard wear theory and DEFORM, a FEM code, were used to analyze the warm forging of automotive transmission outer-race and predict the die wear condition.

Development of a concurrent mold design system: a knowledge-based approach

Abstract This paper presents research that establishes a systematic methodology and knowledge base for an injection-molding mold design in a concurrent engineering environment. This methodology is, in general, analogous to the methods of design for manufacturing, and is, however, in collaboration with activities of molding product design and mold manufacturing process planning. The practical goal of this research is twofold: to develop a mold-development process that facilitates concurrent engineering-based practice and to develop a knowledge-based design aid for injection-molding mold design that accommodates manufacturability concerns, as well as requirements of products. The research approach includes (i) process modeling and reengineering for concurrent mold design, (ii) identification of functional requirements with a computer-based system, (iii) system framework design, and (iv) system modeling and implementation. The framework supports concurrent engineering based mold design by providing advisory tools that are able to resolve relevant issues at the early stages of mold design. The results of this research will facilitate the rationalization and automation of the mold development process, thus improving the efficiency and quality of, and reducing the cost of, mold development.

A Framework of a Concurrent Process Planning System for Mold Manufacturing.

Abstract This paper presents a research on the development of a computer-based framework that supports concurrent mold manufacturing process planning. The practical goal of this research is three-fold: (1) to develop a systematic and concurrent mold manufacturing process planning model, (2) to develop a computer-based mold manufacturing process planning system based on the concurrent model, and (3) to develop knowledge bases to assist in concurrent type of mold manufacturing process planning that accommodates mold development concerns, as well as the requirements of the products. The approach of this work includes steps of (1) modeling and reengineering concurrent mold manufacturing process planning, (2) analysis of system functional requirements, (3) system framework design, and (4) system modeling and implementation. The results of this research will facilitate the rationalization and automation of the mold development process planning, thus improving the efficiency and quality, and also reducing the cost of molding product and process development.

A Postprocessor Based on the Kinematics Model for General Five-Axis Machine Tools

Abstract This paper presents a novel concept to describe the three types of five-axis machine tools by a generalized kinematic structure. A generic postprocessor capable of converting the cutter location (CL) data to machine control data was developed based on the generalized kinematics model of five-axis machine tools. The machine tools form-shaping function matrix is derived according to the homogeneous coordinate transformation matrix and the kinematic parameters characterizing the configuration of general five-axis machine tools. The analytical equations for NC data are determined by equating the CL data matrix and the form-shaping function matrix. A trial-cut experiment on a typical five-axis machine tool and the verification on the coordinate measurement machine demonstrates the effectiveness of the proposed scheme. The algorithm proposed here can facilitate determination of the postprocessors for various five-axis machine tools more systematically.

An experimental and analytical study on the limit drawing ratio of stainless steel 304 foils for microsheet forming

A series of micro-deep drawing experiments were conducted on stainless steel 304 foils with four thicknesses that were heat treated at four different temperatures. Due to heat treatments, a variety of different grain sizes and T/D ratios (the number of grains throughout thickness) were obtained. In this study, the limit drawing rations (LDR) of these foils were obtained; it has also been found that the factors that influence LRD of the foils include, but are not limited to, thickness, grain size, and T/D ratios. Tensile tests were conducted to obtain their mechanical properties that were used for two macroempirical equations to predict the maximum drawing load and LDR. It has been verified that the two equations can be applied to foils that are not thinner than 150 µm for reasonable predictions. However, the size effects are more noticeable and significant for the foils that are less than or equal to 100 µm so that the macroscale empirical equations cannot be applied to them.

Process design based on the deformation mechanism for the non-isothermal forging of Ti–6Al–4V alloy

Abstract Non-isothermal forging has been widely employed in the metalworking industry. Although the die-chilling effect is very significant in the non-isothermal forging process, the process parameters of time and temperature are difficult to measure and control during non-isothermal forging. To cope with this problem, this study employs the thermal-coupled finite element method to examine and to establish the relationship between the process parameters and the deformation behaviour, then deriving useful design rules. The detailed process model based on experimental conditions, and the flow stress model constructed by the localized linear fitting and interpolation method, were used in the finite element analysis. Consequently, the simulation of the non-isothermal forging of Ti–6Al–4V was performed, the predicted results agreeing well with those from experiment. Due to the large temperature gradient, the mode of deformation in non-isothermal forging is different from that in isothermal deformation. Therefore, a deformation mechanism for non-isothermal forging was proposed in this paper to explain the deformation behaviour. Hence, the deformation mechanism governing the metal flow of non-isothermal forging can provide guidelines for forging die design and process design.

Development of a parametric computer-aided die design system for cold forging

Abstract Based on die-design flow charts and data bases collected from the literature, the collected flow chart and data bases of die design, the present paper develops a computer-aided die design system using Auto-Lisp. The design characteristics of the die elements and the die assembly have been expressed in parametric form and programmed. The proposed system has an open architecture, therefore, according to the system structure, die-design engineers can extent the die element design data base and programs. So far, three die-design modules have been finalised, namely: forward extrusion; upsetting; and combined extrusion. With the aid of the proposed system, the functions of die element design, die assembly design, automatic graphics and dimensions generation, redesign, dimension constraint correlations and bill of materials will provide efficiency and convenience of die design.

Tool path generation and error control method for multi-axis NC machining of spatial cam

In this paper, based on the homogeneous coordinate transformation and conjugate surface theory, a tool path generation method is developed for generating spatial cam in order to establish the interface between the design and manufacture of this class of product. The mathematical error (chordal deviation) between the design and manufacture surface has been analysed and used as a basis for selecting the tool path control point. Moreover, the developed tool path generation method is verified through a cutting simulation software with solid model. It is also verified through the trial cut with model materials on a five-axis numerical controlled machine. The results show that the mathematical error of the cam surface can be controlled within given tolerance by the proposed method.

STEP-based product modeling system for remote collaborative reverse engineering

Abstract Production of high-quality products with lower cost and shorter time-to-market is an important challenge in the face of increased global competition, and reverse engineering plays an important role in accelerating product and process development. With the advent of new technologies such as network, multimedia and product data exchange standard STEP (STandard for Exchange of Product model data), there are many advantages to adopt these technologies to enhance the competitiveness of an enterprise. In this paper, a product information recording module for reverse engineering is developed to enhance the performance of product development. A STEP development tool, ST-Developer, and Visual C++ were used to develop this module, which can be used to record key information expeditiously during a collaborative process, and can also be used for further exchange of information, or as the basis for manufacturability evaluation. In this paper, the developed STEP-based information recording system is further integrated with the conventional Computer Supported Cooperative Work methods such as videoconferencing and application-sharing to form a remote collaborative reverse engineering system, which can provides a new strategy for an enterprise to speed up the product development cycle, reducing production cost, as well as sharing knowledge and experience.