A Database Tool for Managing Customer and Design Information During Product Definition

We developed a new database tool to manage information during the product definition process. This tool is a result of an ongoing research program to coordinate marketing and design engineering efforts in new product developments, and consider the related life cycle issues early in the design process. The database tool facilitates a methodology that integrates customer and design information, and allows reuse of this information during redesign problems. This paper presents the development, implementation, and an example use of the database tool.

Automatic Planning for 5-Axis Sculptured Surface Machining

In modern product design, sculptured surfaces are commonly used for functional and artistic shape design. Design of sculptured surfaces is evolutionary, consisting primarily of incremental changes to existing part surfaces. Manual operation planning for sculptured surface machining is known to be error-prone and inefficient, which requires considerable checking, verification, and rework. Five-axis machining has higher productivity and better machining quality than 3-axis machining. However, the programming for 5-axis machining is more difficult due to the complex simultaneous cutter movements along the machine’s five axes. This paper presents a systematic methodology to generate operation plans for 5-axis sculptured surface machining. A complete operation plan and the error-free cutter path can be automatically generated from the CAD part design. To achieve design for manufacturing of sculptured surface products, the machining unfeasibility information can be fed back to the designer for further design modification. Results of computer implementation and testing examples are also presented.

A Hybrid Approach to Computer-Aided Process Planning for Prismatic Parts

One of the most difficult tasks in automated process planning is the determination of operation sequencing. This paper describes a hybrid approach for identifying the optimal operation sequence of machining prismatic parts on a three-axis milling machining centre. In the proposed methodology, the operation sequencing is carried out in two levels of planning: set-up planning and operation planning. Various constraints on the precedence relationships between features are identified and rules and heuristics are created. Based on the precedence relationships between features, an optimization method is developed to find the optimal plan(s) with minimum number of set-ups in which the conflict between the feature precedence relationships and set-up sequence is avoided. For each set-up, an optimal feature machining sequence with minimum number of tool changes is also determined using a developed algorithm. The proposed system is still under development and the hybrid approach is partially implemented. An example is provided to demonstrate this approach.

CAD and Optimization of Helical Torsion Springs

The convensional procedure of helical torsion spring design is an iterative process because of large number of requirements and relations that are to be attained once at a time. The design parameters are varied at random until the spring design satisfies performance requirements. A CAD of the spring for minimum weight is formulated with and without the variation of the maximum normal stress with the wire diameter. The CAD program solves by employing the method of Lagrange-Multipliers. The optimal parameters, in a closed form are obtained, normalized and plotted. These explicit relations of design variables allow direct evaluation of optimal design objective and hence, an absolute optimum could be achieved. The comparison of optimum results with those previously published, shows a pronounced achievement in the reduction of torsion spring weight.

Compatibility Analysis of Product Design for Recyclability and Reuse

This paper describes a method for evaluating the compatibility of a product design with respect to end-of-life product retirement issues, particularly recyclability. Designers can affect the ease of recycling in two major areas: 1) ease of disassembly, and 2) material selection for compatibility with recycling methods. The proposed method, called “clumping,” involves specification of the level of disassembly and the compatibility analysis of each remaining clump with the design’s post-life intent; i.e., reuse, remanufacturing, recycling, or disposal. The method uses qualitative knowledge to assign a normalized measure of compatibility to each clump. An empirical cost function maps the measure to an estimated cost to reprocess the product. The method is an integral part of our life-cycle design computer tool that effectively guides engineers to an environmentally responsible product design. A refrigerator in-door ice dispenser serves as an illustrative example.

Supporting Creative Mechanical Design

Knowledge-based CAD systems limit designers’ creativity by constraining them to work with the prototypes provided by the systems’ knowledge bases. We investigate knowledge-based CAD systems capable of supporting creative designs in the example domain of elementary mechanisms. We present a technique based on qualitative explanations which allows a designer to extend the knowledge base by demonstrating a structure which implements a function in a creative way. Structure is defined as the geometry of the parts, and function using a general logical language based on qualitative physics. We argue that the technique can accommodate any creative design in the example domain, and we demonstrate the technique using an example of a creative design. The use of qualitative physics as a tool for extensible knowledge-based systems points out a new and promising application area for qualitative physics.

Feature Recognition for Manufacturability Analysis

While automated recognition of features has been attempted for a wide range of applications, no single existing approach possesses the functionality required to perform manufacturability analysis. In this paper, we present a methodology for taking a CAD model of a part and extracting a set of machinable features that contains the complete set of alternative interpretations of the part as collections of MRSEVs (Material Removal Shape Element Volumes, a STEP-based library of machining features). The approach handles a variety of features including those describing holes, pockets, slots, and chamfering and filleting operations. In addition, the approach considers accessibility constraints for these features, has an worst-case algorithmic time complexity quadratic in the number of solid modeling operations, and modifies features recognized to account for available tooling and produce more realistic volumes for manufacturability analysis.

Linking Expert Group Technology With Parametric Design

Expert systems can be integrated with databases and CAD/CAM systems using group technology (GT). By using information in a database, geometric features of parts can be specified by GT codes, and CAD models can be generated automatically using parameterized generic templates. This paper describes a microcomputer-based prototype implementation that merges database, expert, and CAD systems in order to perform GT classification and create CAD models with minimal manual intervention.

Restructuring Applied Thermodynamics: Exploratory Thermodynamics

A graphical method is proposed for removing the “drudge work” of looking up property values and solving the conservation equations and second law in an Applied Thermodynamics course. The vehicle used is VisSim simulation software. The method requires the student to perform the thermodynamic analysis and set up the equations, but the computer finds the property values and solves the equations. This concept allows the student to explore various aspects of the topics covered in such a course, including power and refrigeration cycles, mixtures and psychrometrics, and combustion and equilibrium. Substantial design type problems can be solved easily, as can complicated analyses that are too difficult and time consuming for traditional solution methods.

Use of Finite-Element Stress Analysis in the Design of a Tank-Cannon-Launched Training Projectile

The U.S. Army Armament Research. Development, and Engineering Center (ARDEC) recently expressed a need for a tank-cannon-launched training projectile with reduced penetration capability. The expressed primary design goals for this projectile were to minimize the probability of personnel injury and materiel loss in the event of an accidental impact during a training exercise. In order to meet these design goals, the solid-steel flight body of a current kinetic energy (KE) training projectile, the M865IP, was replaced with a hollow aluminum configuration. Because of the incorporation of aluminum, the structural integrity of the entire projectile during launch was put in question. Thus, a thorough stress analysis of the new design was conducted to alleviate concerns about its structural integrity. Two-dimensional, axisymmetric, quasi-static stress analyses were performed on two new KE training projectile designs. The first analysis indicated that structural failure was possible in the aft portion of the projectile due to compressive loading by the gun gases. Structural failure in this case would be circumferential yielding of the hollow flight body. The aft portion of the round was redesigned, and subsequent stress analysis showed the possibility of structural failure to be resolved. The finite-element modeling approach, the applied boundary conditions, and the results of the stress analyses conducted, based on use of the von Mises failure criterion, will be discussed in detail.