Corrado Poli

Design knowledge acquisition for DFM methodologies

Design for Manufacturability (DFM) is a philosophy that encourages the communication of manufacturing information at the earliest stages of design in order to design parts and products that can be produced with greater ease and economy. This paper discusses the extensive experience gathered during the development of several DFM models in order to draw some conclusions and express some concerns that should be of interest to all those who develop or use manufacturing models that rely on design knowledge acquisition of knowledge from domain experts and/or industrial sites.

Multimedia tutors for design for manufacturing

Our group at the University of Massachusetts has built design for manufacturing (DFM) computer modules which instruct students on efficient procedures for designing parts for manufacture. The goal is to assist engineering students to gain a deeper understanding of the interaction between features of a part being designed and the corresponding manufacturing requirements of the part in the domains of injection molding and sheet metal stamping. We provide animated sequences of the processes indexed according to the possible designs. The tutors allow students to select a restricted set of parts for manufacture and demonstrate the tooling complexity through both 2D animations and 3D animations. An underlying internal representation of the part being designed provides a non-intrusive critique mechanism to provide feedback to the student.

Design for Injection Molding: a Group-technology-based Approach

The design of parts for economical manufacture by injection molding is an important element in the broader design strategy known as design for manufacturing (DFM). This paper provides an insight into the process of developing a DFM model for injection molding and into the use of such a model in the context of part design. The costs due to the mold making, the costs due to processing and the costs due to material are determined by the features of the part design, and models are presented to demonstrate these dependent relationships. The knowledge for the model databases was gained through extensive interactions with mold makers and molders. An example of the use of the models is also presented and discussed in detail.

Multimedia systems and intelligent tutors for teaching design for manufacturing

Our group has built design for manufacturing computer modules which instruct students on efficient procedures for designing parts for manufacture across the curriculum. The goal is to assist engineering students to gain a deeper understanding of the interaction between features of a part being designed and the corresponding manufacturing requirements of the part in injection molding, sheet metal stamping, and finite element analysis. Animated sequences of the processes are either generated dynamically or indexed according to the possible designs. Students create designs, and the tooling complexity is demonstrated through both 2D and 3D animations. An underlying internal representation of the part being designed provides a nonintrusive critique mechanism to provide feedback to the student.

Design for Stamping: a Group Technology-based Approach:

The design of parts for metal stamping is often accomplished following a rules-of-thumb-based design process. The approach descnbed here, as part of a broader design for manufacturability (DFM) strategy, is based upon detailed models in contrast to rules of thumb and is developed through extensive interactions with toolmakers and stampers. The design for stamping (DFS) system includes consideration of costs due to rooling, costs due to processing, and costs due to material where these costs are functions of the part design, thus enabling qualitative and quantitative assessments at a preliminary concept sketch as well as further developed design stages.

Three-dimensional motion of a large flexible satellite

Utilizing a method for the stability analysis of coupled rigid-elastic systems, the effect of flexible antennas upon the stability of motion of a gravity-gradient satellite is investigated. The satellite is assumed to consist of a compact rigid-body containing four antennas located at right angles to each other, two in the orbit plane and two perpendicular to the orbit plane. The conditions for stability are found to include the well-known rigid-body stability criteria, and, in addition, requirements on the elastic and coupled rigidelastic motion.

Chapter 13 – Selecting Materials and Processes for Special Purpose Parts

When it has been determined that a designed object is to be a special purpose part, the task of engineering conceptual design includes 1. Determining the basic material class (e.g., steel, thermoplastic, aluminum, etc.) “that has the properties to provide the necessary service performance...” and

Chapter 12 – Assembly

This chapter presents a brief introduction to the process of manual assembly. It introduces us to recognize those features of a part, which affect manual assembly time, hence, cost. A set of qualitative guidelines on Design For Assembly (DFA) and a summary of DFA guidelines are provided. It presents a detailed analysis that derived the relations needed to compare the cost of producing a single, more complex injection molded or die cast part with the cost of producing and assembling multiple parts for the same purpose. Since much of the material on assembly in this chapter is based on data and other information extracted primarily from the works in the list references, readers are encouraged to consult these original references, especially the pioneering work of G. Boothroyd for more detailed information and analysis.

Chapter 7 – Die Casting: Total Relative Part Cost

This chapter mainly describes the systematic approach to those features of a die casting that tend to increase the cost to manufacture parts and for estimating the relative tooling costs, processing costs, material costs, and the overall part cost. The system is quite similar to the one for injection molding and highlights those features that significantly increase cost, so that designers can minimize difficult to produce features. In the case of injection molding, tooling cost is a function of die construction cost and die material cost. The processes of injection molding and die casting are somewhat similar. In fact, they are sufficiently similar that the classification system for the determination of relative cycle time developed for injection molding, with only minor modifications, is applicable to die casting.

Chapter 10 – Stamping: Total Relative Part Cost

This chapter explains the methods for evaluating the relative processing cost and the overall relative part cost for stamped parts made on progressive dies. Progressive dies are used for parts unfolded length, Lug, is less than 100mm. The total cost of a stamped part is calculated as tooling cost per part (KJN) plus processing cost (K∼) plus material cost (Km). The chapter also describes the stages of costing like the configuration stage in which the final dimensions and tolerances of the part are not yet established; only tooling cost can be estimated. In this stage, it may be possible to obtain only a lower boundary on the tooling cost. In the parametric design stage, the final dimensions and tolerances are known. The relative processing cost, the relative material cost, and overall relative part cost can be obtained. The chapter concludes by showing that the processing cost of a stamped part represents a very small percentage of the overall part cost as a result of the high–speed presses that are used and that result in very short cycle times. At very high-production volumes, material costs dominate and part design and strip layout design become vital to reduce material consumption. Examples are provided for determining the relative processing cost for the part.