Rashpal S. Ahluwalia

Feature-based noncutting tool path selection

Abstract This paper describes feature-based noncutting tool path selection using integer programming (IP). The IP approach provides an optimum tool travel sequence while avoiding multidispatch of tools. The paper also describes the tool dispatching sequence, tool visiting sequence, and IP constraints for manufacturing features. The noncutting tool path is compared with the cutting tool path to select the shortest possible total tool path.

Feature modification in incremental feature generation

Abstract Feature interaction is a common problem in feature generation methods such as incremental feature generation, automatic feature extraction, feature-based design and manual feature definition. Research on feature interaction involves analysing the interaction relationship, decomposing the interacted features into atomic or single features, and defining their relationship, human interpretation being required. The paper presents an approach to handling the feature interaction problem in incremental feature generation. As a protrusion or depression feature is defined, the interaction between the features is analysed. The relationship is then defined and the interacting existing feature is redefined according to the interaction cases. The approach involves feature existence analysis and modification procedures. The existence analysis classifies the existing features into three groups; features remaining without interaction, features to be removed, and features remaining after being partially removed. It further classifies the last group into only the face set being removed, only the boundary edge path being removed, and the face set including the boundary edge path being removed. The three interaction cases in the last group require modification procedures. The modification procedures are (a) decide whether the remaining part of an existing feature is valid for a feature definition, (b) update it as a new feature, and (c) define the features relationship. The above procedures are performed through tracing the Boolean operations and convexity of an intersection edge loop generated during design evolution.

FORCOD: A coding and classification system for formed parts

Abstract Part coding and classification systems are required to apply the group technology philosophy. Thus far, most coding and classification systems are for metal removal processes. This paper proposes a coding and classification scheme for the metal forming process. Coding details based on part geometry, tolerance level, surface finish, material, heat treatment, and defect level are defined. As an example, based on the proposed coding scheme, a multi-objective cluster analysis problem is formulated and solved for bosses and connecting rods, which are typical examples of forged parts.

Feature generation in concurrent engineering environment

The three basic approaches to obtain features, namely feature based design (FBD), automatic feature extraction (FEX), and manual feature identification (FID), are inappropriate for the concurrent engineering (CE) environment. This paper presents an approach which generates shape features as the part design evolves. The proposed feature generation procedure is based on using temporal geometry data, The evolving part geometry is defined by constructive solid geometry (CSG) and boundary representation (B-rep). The feature generation procedure is performed at each Boolean operation. It requires two steps, new feature generation and modification of existing features, The feature generation procedure continues until the design activity is finished. For new feature generation, an intersection edge loop (I-loop) and classified boundary components (B-comp) obtained from boundary evaluation procedure are used to determine depression or protrusion (D/P). Face adjacency of the D/P is matched with templates to generate domain specific semantics. Such an approach enables several down stream activities to be considered during design evolution.

NC tool path generation for 5-axis machining of free formed surfaces

This paper presents a ‘tool axis vector’ approach for machining sculptured surfaces. Such an approach is well suited for highly twisted, rolled, or bent surfaces. The tool paths are generated for a 5-axis milling machine. The proposed approach is based on tilt angle, cutting direction, and a vector normal to the cutting surface. Gouging is avoided by checking the interference between the cutting tool and the part surface. The algorithm also finds maximum path intervals that generate maximum admissible cusp height within the specified tolerance limits. Such an approach minimizes the tool path and machining time. The paper presents an example to illustrate the details of the algorithm.

A distributed approach to job scheduling in a flexible manufacturing system

Abstract Several Flexible Manufacturing Systems (FMS) have been developed in recent years and it is likely that many more will be developed in the future. This paper presents a distributed approach to job scheduling in an FMS. Because of the characteristics of an FMS, the proposed model assumes that each machine tool (node) in an FMS is equipped with a general purpose computer capable of controlling the node and communicating with the other nodes in the system. At first the system is assumed to be operating normally and a linear programming model is formulated to solve the job scheduling problem. When the system malfunctions, the job rescheduling is based on a non-linear programming model. A strategy matrix is utilized and maintained at each node to monitor the system. All scheduling decisions are made in a distributed manner by each node in the network. Such an approach frees up the main processor for other task and is well suited for a large and complex manufacturing system. A simple hypothetical FMS is utilized to illustrate the formulation and the utilization of the proposed model.

A Software Tool for Reliability Estimation

Over the years, several tools have been developed to estimate the reliability of hardware and software components. Typically, such tools are either for hardware or software. This paper presents the Software Tool for Reliability Estimation (STORE), which can be used for systems containing hardware and/or software components. For software components, exponential, Weibull, gamma, power, geometric, and inverse-linear models were implemented. Goodness of fit statistics are provided for each model. The user can select the most appropriate model for a given system configuration and failure data. The STORE program can analyze series, parallel, and complex systems. Tieset and cutset algorithm is utilized to determine the reliability of a complex system. The paper presents several examples to demonstrate the software tool.

The Combinatorial Multi-Mode Resource Constrained Multi-Project Scheduling Problem

This paper presents the formulation and solution of the Combinatorial Multi-Mode Resource Constrained Multi-Project Scheduling Problem. The focus of the proposed method is not on finding a single optimal solution, instead on presenting multiple feasible solutions, with cost and duration information to the project manager. The motivation for developing such an approach is due in part to practical situations where the definition of optimal changes on a regular basis. The proposed approach empowers the project manager to determine what is optimal, on a given day, under the current constraints, such as, change of priorities, lack of skilled worker. The proposed method utilizes a simulation approach to determine feasible solutions, under the current constraints. Resources can be non-consumable, consumable, or doubly constrained. The paper also presents a real-life case study dealing with scheduling of ship repair activities.

Database for dismantling of obsolete vessels

This paper describes a database tool for Dismantling of Obsolete Vessels (DOVE). DOVE 1.0 consists of three databases: a) The Obsolete Vessels Database (OVD), b) The Metals and Alloys Database (MAD), and c) The Cutting Technology Database (CTD). The OVD provides information on ship name, type, year built, number, status, light displacement, length, beam, changes made, dead weight, number of propellers, propulsion type, and vessel location. The MAD provides information on several metals and alloys and the CTD has information on cutting technologies, decontamination technologies, and waste processing methodologies. DOVE 1.0 runs on an IBM compatible personal computer and was implemented in Visual Basic 6.0 using Microsoft Access as the database.

Comparison of ship dismantling processes in India and the U.S.

This paper compares ship-dismantling processes in India and the U.S. The information for India was collected during an informal visit to the ship dismantling sites in Alang, India. The information for the U.S. was obtained from the MARAD report. For a 10,000-ton passenger ship, the Indian contractor makes a profit of about 24% compared to a loss of about 15% in the U.S. The loss in the US is primarily due to high labor costs, compliance to safety and health regulations and lack of market for used components and scrap metal.