Face-hobbing is a productive process to manufacture bevel and hypoid gears. Due to the complexity of face-hobbing, few research works have been conducted on this process. In face-hobbing, the cutting velocity along the cutting edge varies because of the intricate geometry of the cutting system and the machine tool kinematics. Due to the varying cutting velocity and the specific cutting system geometry, working relief and rake angles change along the cutting edge and have large variations at the corner which cause the local tool wear. In this paper, a new method to design cutting blades is proposed by changing the geometry of the rake and relief surfaces to avoid those large variations while the cutting edge is kept unchanged. In the proposed method, the working rake and relief angles are kept constant along the cutting edge by considering the varying cutting velocity and the machine tool kinematics. By applying the proposed method to design the blades, the tool wear characteristics are improved especially at the corner. In addition, in this paper, complete mathematical representations of the cutting system are presented. The working rake and relief angles are measured on the computer-aided design (CAD) model of the proposed and conventional blades and compared with each other. The results show that, unlike the conventional blade, in case of the proposed blade, the working rake and relief angles remain constant along the cutting edge. In addition, in order to validate the better tool wear characteristics of the proposed blade, finite element (FE) machining simulations are conducted on both the proposed and conventional blades. The results show improvements in the tool wear characteristics of the proposed blade in comparison with the conventional one.

With the material processing freedoms of additive manufacturing (AM), the ability to characterize and control material microstructures is essential if part designers are to properly design parts. To integrate material information into Computer-aided design (CAD) systems, geometric features of material microstructure must be recognized and represented, which is the focus of this paper. Linear microstructure features, such as fibers or grain boundaries, can be found computationally from microstructure images using surfacelet based methods, which include the Radon or Radon-like transform followed by a wavelet transform. By finding peaks in the transform results, linear features can be recognized and characterized by length, orientation, and position. The challenge is that often a feature will be imprecisely represented in the transformed parameter space. In this paper, we demonstrate surfacelet-based methods to recognize microstructure features in parts fabricated by AM. We will provide an explicit computational method to recognize and to quantify linear geometric features from an image.

This paper presents a computer-aided design (CAD) module able to analyze different manufacturing configurations of tubes used in mechanical assemblies, such as exhaust system manifolds. It can be included in the knowledge-based expert system category and has been implemented into a CAD platform as a dedicated module able to take into account manufacturing requirements related to tube bending, hydroforming, and cutting. The expert’s knowledge, in terms of set of rules and criteria, has been implemented by means of the automation tools of CATIAV5R10 according to the so-called methodological formal approach. The resulting module is able to join different tubes starting from their geometrical models, obtaining a set of manufacturing alternatives. Each of them is verified with respect to collisions with a bending machine and also in terms of hydroforming process feasibility. Only those solutions that satisfy these checks are accepted as feasible and ranked according to three evaluation criteria related to manufacturing cost and easiness. The system is completely automatic and able to analyze more than 100 different configurations in < 10 min . The feasible solutions are saved as CAD model to allow FEA of hydroforming and other possible CAE activities. Unfeasible solutions are deleted but reported and documented in a log file. The feasible solution rank is given in a table and has been developed according to a multicriteria approach to make optimal solution detection easier. The proposed test case aims to show and discuss these capabilities. By this module, two or more components of the exhaust system manifold can be manufactured in one stroke as a single component, starting from the same pipe and next trimmed to obtain the desired final parts. This capability can be used to reduce scraps and improve cycle time of the manufacturing process.

Setup planning is an intermediate phase of process planning, and automating setup planning constitutes a critical component of computer-aided process planning. The common absence of a clearly defined optimality of setup plans has been a major obstacle to converting automatic setup planning research progress into real advancement in practice. The optimality of a setup plan is a multiple attributes problem associated with uncertainties, and human interaction is vital in clarifying the optimality structure in a dynamic setup planning environment. In this paper, a quantitative setup plan evaluation system driven by multiple-attributes utility analysis coupled with manufacturing error simulation is proposed to serve three purposes: (1) to clarify what is optimality of setup plans, (2) to provide a systematic method of evaluating setup plan alternatives quantitatively, and (3) to incorporate in existing automatic setup planning systems a human interface to fulfill their potential values.

This paper presents a formability analysis of tailor-welded blanks (TWBs) made of cold rolled steel sheets with varying thicknesses. Steel sheets ranging between 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, and 1.0 mm in thickness were used to produce TWBs of different thickness combinations. The primary objective of this paper is to characterize the effects of thickness ratios on the forming limit diagram (FLD) for a particular type of TWB. The TWBs chosen for the investigation are designed with the weld line located in the center of the specimens perpendicular to the principal strain direction. Nd:YAG laser butt-welding was used to prepare different tailor-made blank specimens for uniaxial tensile tests and Swift tests. The experimental results of the uniaxial tensile test clearly revealed that there were no significant differences between the tensile strengths of TWBs and those of the base metals. After the Swift tests, the formability of TWBs was analyzed in terms of two measures: The forming limit diagram and minimum major strain. The experimental findings indicated that the higher the thickness ratio, the lower the level of the forming limit curve (FLC) and the lower the formability of the TWBs. The findings also show an inverse proportional relationship between thickness ratios and minimum major strains. TWBs with a thickness ratio of close to 1 were found to have a minimum major strain closer to those of base metals. The effects of different thickness ratios on TWBs were further analyzed with a finite element code in a computer-aided engineering package, PAM-STAMP, while the failure criteria of the TWBs in the finite element analysis were addressed by the FLCs which were obtained from the experiments. However, the weld of the TWB in the simulation was simply treated as a thickness step, whereas its heat affected zones were sometimes disregarded, so that the effects of the thickness ratio could be significantly disclosed without the presence of weld zones. The results of the simulation should certainly assist to clarify and explain the effects of different thickness ratios on TWBs .

Flexible fixturing is a necessary aspect of Flexible Manufacturing Systems (FMS) and Computer-Integrated Manufacturing Systems (CIMS). Modular fixtures are most widely used in industry for job and batch production. Computer-Aided Fixture Design (CAFD) has become a research focus in implementing FMS and CIMS. Fixture configuration design is an important issue in the domain of CAFD. A review of the current research in CAFD indicates that a major problem impeding the automated generation of fixture configurations is the lack of studies on fixture structures. This paper investigates fundamental structures of dowel-pin based modular fixtures and fixturing characteristics of commonly used modular fixture elements. A Modular Fixture Element Assembly Relationship Graph (MFEARG) is designed to represent combination relationships between fixture elements. Based on MFEARG, algorithms are developed to search all suitable fixturing unit candidates and mount them into appropriate positions on a baseplate with interference checking. A prototype system for automated design of dowel-pin modular fixture configurations is presented in this paper. Fixture design examples are given at the end of the paper.

Parallel N.C. machines, also referred to as mill-turns, are a new generation of machine tools aimed at increasing machining accuracy and reducing part cycle times. In addition to their capacity to do both milling and turning, these next generation machines tools can perform multiple machining operations simultaneously, involving one or more parts at a time, and can completely finish a part (front and back) in a single setup. Parallel machining raises issues with respect to computer aided process planning which have not been dealt with in the past. In this paper, a prototype CAPP system called PMPS, for parallel machining, is described. First, we briefly highlight the new issues to be dealt with in process planning for parallel machining. Next, the architecture and details of PMPS, a generative CAPP system, is described. Finally, the implementation and results are discussed.

This paper presents a machining accuracy analysis for computer-aided fixture design verification. While discussing the utilization of CNC machine tools and machining centers, machining errors are described in terms of deterministic and random components and analyzed on the bases of their sources, where high machining accuracy and multi-operation under a single setup become major characteristics of manufacturing systems. In machining processes, a resultant dimension may be generated in terms of several relevant dimensions. The dependency of variation among these dimensions is examined and the relationships of locating datum and machining surfaces are analyzed. Variation among linear and angular dimensions are considered. Five basic models of dimension variation relationships are proposed to estimate the machining error, where different formulas of resultant dimension variation are given for different combinations of variation among relevant dimensions. A datum-machining surface relationship graph (DMG) is developed to represent the dependent relationships. A matrix-based reasoning algorithm is designed to search for the shortest path in the DMG. Once the relationship between a specified pair of surfaces is identified, different models of corresponding relationships may be utilized to estimate the possible machining errors which can be used to compare the fixturing accuracy requirement.

A prototype software system that automatically designs the gating and runner systems, which comprise the feed system, of injection molds is described. The system, called AMDS (Automated Mold Design System), integrates CAE, with iterative redesign and knowledge stored in a features representation of the part. Gating design involves the generation of the best gating configuration represented by number, location, and type of gates, and the determination of the best conditions under which plastic should enter through the gates. Runner design also involves the generation of a runner layout followed by the sizing of the runner segments. The design of both systems is iterative, whereby the design variables are changed, the new design analyzed, evaluated, and redesigned if necessary, until an acceptable design is obtained. The evaluation of the gating design is based on eighteen performance parameters, while the evaluation of the runner system is based on four performance parameters. The system has been tested on three-dimensional parts made up of planar rectangular wall features with holes as add-on features.

This paper addresses the issue of manufacturability measurement for design improvements. With the increasing applications of computer aided engineering, the design engineer must expand the view of design to include ease of manufacturing. Quantitative indicators of manufacturability are the most efficient way of providing manufacturing feedback to the designer. Quantitative measures can be used to indicate redesign targets and rank parts based on ease of manufacturing. A methodology for developing such indicators (manufacturability indices) is presented here, with rotational parts being used as an example. The paper shows how CAD and machining parameters can be utilized to obtain a part’s manufacturing requirements. These requirements are then combined into indices, the use of which is illustrated with examples.

A formal approach for integrating Computer-Aided Design (CAD), Computer-Aided Process Planning (CAPP), and shop floor control for rotational components is presented in this paper. It is assumed that this approach will be implemented within the framework of a three level hierarchical CIM architecture that consists of the following levels in the hierarchy: shop floor, workstation and equipment (Joshi et al., 1991). Our approach to CAPP consists of machining feature identification, definition, classification, representation, and reasoning, provided through a CAD model of a product. Geometric entities are identified from a Drawing Exchange Format (DXF) file. The identified entities form the basis for the construction of primitive manufacturing features. The primitive features are assembled together based upon the precedence among features, into a graph, called a feature graph. However, the primitive features may or may not be manufacturable in terms of depth of cut, tool geometry, surface finish, and material handling required. Hence it is necessary to convert the feature graph into a manufacturing task graph, which consists of specifications of alternative functional tasks that are manufacturable. The task graph may be converted into a hierarchical set of process plans, based on the planning criteria at each level in the control hierachy, to reflect the processing requirements at each level. The shop planning function decomposes the task graph into a set of workstation level plans. Each workstation level plan is aggregated into a set of equipment level process plans by the workstation planning function. The equipment level plan is converted into a unique task sequence by the equipment planning function. This sequence is then executed according to specifications by the equipment level execution function. Provision of alternative routes in process plans provides for flexible means of on-line planning and control.

A computer aided analysis method is described for durability assessment in the early design stages using multibody dynamic analysis, finite element stress analysis, and fatigue life prediction methods. From multibody dynamic analysis of a mechanical system, dynamic loads of a mechanical component were calculated. Finite element stress analysis with substructuring techniques produced accurate stress fields for the component. From the dynamic loads and the stress field of the component, a dynamic stress history at the critical location was produced using the superposition principle. Using Neuber’s rule, a local strain time history was produced from the dynamic stress history. The local strain based fatigue life prediction method was then used to predict “crack initiation” life of the critical component. The predicted fatigue crack initiation life was verified by experimental durability tests. This methodology can be combined with identification of weak links and optimization techniques such that the design optimization for an entire mechanical system based upon durability is possible during the early product development stage.

In recent years, increased attention has been paid to the design of cooling systems in injection molding, as it became clear that cooling affects both productivity and part quality. In order to systematically improve the performance of a cooling system in terms of rapid, uniform, and even cooling, the designer needs a CAE analysis tool. For this, a computer simulation has been developed for three-dimensional mold heat transfer during the cooling stage of an injection molding process. In this simulation, mold heat transfer is considered as cyclic-steady, three-dimensional conduction; heat transfer within the melt region is treated as transient, one-dimensional conduction; heat exchange between the cooling channel surfaces and coolant is treated as steady, as is heat exchange with the ambient air and mold exterior surfaces. Numerical implementation includes the application of a hybrid scheme consisting of a modified three-dimensional, boundary-element method for the mold region and a finite-difference method with a variable mesh for the melt region. These two analyses are iteratively coupled so as to match the temperature and heat flux at the mold-melt interface. Using an example, the usefulness of the simulation developed here in the design of a cooling system for an injection molding process is amply demonstrated.

Research on generative computer-aided process planning (CAPP) for turned parts using combined fundamental and heuristic principles is presented. The rationale for the process planning approach is that many preconditions of machining processes can be expressed as a small number of domain principles. The domain is defined by processes and the part description as features for simple turned parts. The motivation is to detect faulty designs early on in the design process. Preliminary designs defined by features are first evaluated using manufacturability rules in a rule-based expert system, developed in LISP. Manufacturability rules are based on feature properties such as accessibility, stability, and critical material thickness. The rules were acquired from design and manufacturing personnel from industry through interviews. Parts that satisfy the manufacturability checks are used to generate all feasible process plans. A search algorithm selects the “best” process plan from the feasible set. Process plans are generated and subsequently optimized using two distinct sets of feasibility and optimality criteria which may be either fundamental or heuristic in nature. The presently incorporated criteria successfully restrict the set of plans to a small number without missing any apparently feasible process plans. Manufacturability evaluation, feasible process plans, and optimal process plans for actual industrial parts have been obtained and compared.

This paper deals with computer aided measurements by a “stylus” of doubly contoured surfaces. The main result consists in the proposal of suitable algorithms, to be implemented on a personal computer, to efficiently correct the measurement errors involved by the geometry of the stylus.

This paper presents a methodology for the simultaneous product and process design of components manufactured in small and medium lot-sizes. A key aspect of this methodology is to ensure that such components are manufacturable for the lowest possible cost in specially designed manufacturing facilities such as manufacturing cells. A computer-based design environment is proposed to cooperatively assist product designers in performing this task. The design environment is based on the model-based reasoning concept. Explicit product and manufacturing facility models are presented to support the reasoning process. These models are based on a combination of feature-based, geometric and process performance models. The reasoning mechanism is based on the Multiple Cooperative Knowledge Sources (MCKS) paradigm with explicit separation of domain and control knowledge. Domain knowledge sources deal with the product and process refinement activities while control knowledge sources deal with managing the concurrency between these two activities. The framework of the design environment is described in detail and justifications are provided for the modeling and reasoning mechanisms chosen. Preliminary results obtained from an implementation of the design environment for the simultaneous product and process design of Bearing Cages are presented. The paper concludes by summarizing the main contributions of this research and presents directions for future research work.

A computer code is developed as a part of an ongoing project on computer aided process modelling of forging operation, to simulate heat transfer in a die-billet system. The code developed on a stage-by-stage technique is based on an Alternating Direction Implicit scheme. The experimentally validated code is used to study the effect of process specifics such as preheat die temperature, machine ascent time, rate of deformation, and dwell time on the thermal characteristics in a batch coining operation where deformation is restricted to surface level only.

This paper deals briefly with the concept of form measurement and brings out the different criteria for form evaluation of engineering surfaces. A new criterion based on the minimum average deviation has been suggested. The geometrical forms, namely straight line, circle, plane, and cylinder, are analyzed. Simple numerical examples are included in this paper to illustrate the different methods.

This paper presents a methodology for analyzing the heat-transfer process during the injection molding of plastics as an aid to mold design. A numerical scheme using the Boundary Element Method (BEM) with “zonal” approach has been developed to solve the quasi-steady temperature field and its normal derivative over the entire surface of the mold plates including the cavity wall as well as parting surface. In order to obtain a solution for the temperature field, a cycle-averaged heat-transfer coefficient is introduced from a transient heat-conduction analysis and applied as the boundary condition at the cavity surface. The numerical predictions as compared with the experimental data have shown that the cycle-averaged solution used in this study gives a reasonable representation of the transient temperature variation over the cavity surface. Based on the numerical predictions, the mold designer will be able to design a proper cooling-system for a mold to achieve better part quality and high productivity through more uniform cooling and shorter cycle time, respectively.