A New Methodology for Recognition of Milling Features from STEP File

In recent years, various researchers have come up with different ways and means to integrate CAD and CAM. Automatic feature recognition (AFR) from a CAD solid model for down stream applications like process planning and NC program, greatly contribute to the level of integration. When generating G&M codes from CAD DXF file, it leads to the loss of geometric information and the user is to edit and fills the details of the lost data. STEP is an international standard for geometric and non geometric data transfer between CAD, CAE and CAM and it replaces the IGES and DXF. For that reason this paper proposes an automatic feature recognition methodology to develop a feature recognition system using STEP file. The proposed methodology is developed for 3D prismatic parts that are modeled any CAD software having STEP output file format. A JAVA program is used to implement the geometric data extraction algorithm, which has been developed for extracting the geometric information from the STEP file. A feature recognition algorithm is used to recognize the different features of the part such as slot, pocket etc based on geometric reasoning approach by taking B-rep data base as input. The authors present an example to demonstrate the application of the proposed methodology

A Hybrid Differential Evolution Approach for Simultaneous SchedulingProblems in a Flexible Manufacturing Environment

Scheduling of machines and transportation devices like Automated Guided Vehicles (AGVs) in a Flexible Manufacturing System(FMS) is a typical N-P hard problem. Even though several algorithms were employed to solve this combinatorial optimization problem, most of the work concentrated on solving the problems of machines and material handling independently. In this paper the authors have attempted to schedule both the machines and AGVs simultaneously, with makespan minimization as objective, for which Differential Evolution (DE) is applied. Operations based coding is employed to represent the solution vector, which is further modified to suit the DE application. The authors have proposed two new strategies of DE in this paper which better suits the problem. We have developed a separate heuristic for assigning the vehicles and this is integrated with the traditional DE approach. The hybridized approach is tested on a number of benchmark problems whose results outperformed those available in the literature

The Impact of Powers-of-Two Based Schedule on the Minimization of Inventory Costs in a Multi Product Manufacturing Environment

This paper discusses about the scheduling problem of a multi product manufacturing industry. Often there has been a problem of applying optimization algorithms to solve the makespan minimization criterion of a job shop due to its inherent NP-hard nature. It is therefore unrealistic to try obtaining a solution through a commercial solver in polynomial time. In this context, we propose a computationally effective heuristic, which is based on the powers-of-two policy in inventory, for solving the minimum makespan problem of job shop scheduling. The research discussed in the current paper is a real time scheduling problem faced by a large scale and complex turbine manufacturing job shop. It is worth noting that by integrating the material requirements planning (MRP) with the feasible schedule obtained, this policy also proves to be useful in minimizing the inventory costs

Experimental Studies of Resin Systems for Ablative Thermal Protection System

The present work was initiated to finalise resin for the development of thermal protection system (TPS) for the external surface of a polymeric composite rocket motor case made up of Carbon roving and Epoxy resin. The temperature on the outer surface of the composite case increases due to kinetic heating caused by aerodynamic drag and vehicle velocity. These rocket motor casings are functionally required only in the ascent phase of missile trajectory till motor action time and stage separation. Due to which the experienced heat flux is relatively less, and the temperature on the external composite case is in order of 250 °C - 300 °C depending on missile configuration and trajectory, unlike extreme thermal conditions on ablative nozzle liners exposed to rocket motor exhaust. The maximum allowable temperature in the present study for the Carbon-Epoxy case is 100 °C due to degradation in mechanical properties. The thermal protection system on the external surface will function as a heat-insulating layer based on the working mechanism of ablation. The resin of the thermal protection layer has a substantial impact on the manufacturing process and curing aspects, especially compatibility with the pre-cured carbon epoxy case layer. The generation of test results for thermal stability, cure characteristics and Tg for Epoxy resin has also been included in present studies as an additional objective that provides significant inputs for process development. The test results for Epoxy resin is also used as a basis for the finalisation of resin for the thermal protection layer for processing aspects apart from its basic thermal stability characteristics. The ablative thermal protection working mechanism is based on the ablation phenomenon. In the case of ablation, resin plays a vital role due to pyrolysis and other thermal characteristics. In the present experimental studies, the Phenolic resin and Silicone resin are considered as candidate resin materials for ablative thermal protection system based on available literature and in house experience. The main objective of the present studies is to evaluate thermal stability, char yield after final decomposition through DSC and TGA techniques for both resins as these are fundamental characteristics needed for the present specific application. The test results for specific grades (formulation) of phenolic and Silicone resins are generated and compared. In the present work, the experimental studies to evaluate glass transition temperature (Tg), thermal stability, and cure characteristics for Epoxy resin is also carried through DSC. The test results of specific grade Epoxy resin provides a basis to assess thermal margins for resins selected for ablative thermal protection system and inputs for process development and design requirements. The scope of the present studies is aimed to finalise the resin system for external thermal protection of composite rocket motor case based on thermal characteristics test results and other compatibility aspects with the structural layer