Sarojrani Pattnaik

A review of rapid prototyping integrated investment casting processes

Investment casting is competitive with all other casting processes where the size of the product is within a mutually castable range. Though investment casting is used to produce metal parts of any intricate shapes with excellent surface finish, it suffers from long lead time and high tooling costs, which makes it uneconomical for the production of either single casting, or small and medium production units. These problems could be overcome by the applications of rapid prototyping and rapid tooling technologies for low-volume investment casting production runs. The present article analyzes different classifications of rapid prototyping techniques and it reviews various investigations made on the usability of rapid prototyping- and rapid tooling-integrated investment casting process, with their advantages and limitations. The emerging areas of applications of rapid prototyping like dentistry, jewelry, surgical implants, turbine blades, etc., are accordingly discussed. Further, an elaborate discussion is made on the application of newer technologies for directly developing ceramic shells. This article also emphasizes on various future scopes possible in rapid prototyping-integrated investment casting process.

Parametric optimization of the investment casting process using utility concept and Taguchi method

Investment casting process, also known as lost wax process, is utilized when complex detail, undercuts or non-machinable features and accurate parts are desired. It begins with a wax pattern which is an exact replica of the as cast part. So the properties of the wax patterns are ultimately passed on to the castings. This article highlights the application of utility concept with Taguchi method for the multi-response optimization of wax patterns made by the investment casting process. The wax injection process parameters considered are injection temperature, injection pressure and injection time, whereas the responses are linear shrinkage, surface roughness and penetration, respectively. The experiments are planned as per Taguchi’s L9 orthogonal array. The utility concept converts multi-response optimization problem into single response optimization problem and thereafter Taguchi method is applied. The results indicate that injection pressure is the most significant process parameter influencing the quality characteristic of the wax patterns. The confirmation tests with optimal levels of injection process parameters are carried out to illustrate the efficacy of the proposed method. The results are found to be within the confidence interval. The optimization results revealed that a combination of lower level of injection temperature and injection time along with higher level of injection pressure leads to overall improvement in the quality of the wax patterns. It has also been established that there is some quality loss in terms of surface finish of the wax patterns in multi-response optimization as compared to single response optimization, though an overall improvement in the process is being observed.

Modeling and parametric optimization of investment casting process by uniting desirability function approach and fuzzy logic

Investment casting is accepted worldwide on the basis of the superior quality of the castings being produced in terms of high dimensional accuracy and surface finish. It usually employs disposable wax patterns and the quality of the wax patterns are reflected in the investment cast product. Keeping this in mind, integration of desirability function approach and fuzzy logic for the multi-response optimization of wax patterns made by the investment casting process has been conceptualized in the present study. The aforementioned method overcomes the limitation of the desirability function approach for multi-response optimization problems. The responses, linear shrinkage and surface roughness have been considered for simultaneous optimization. The input parameters considered are injection temperature, injection pressure and die temperature. A fuzzy model has been developed with desirability values of responses as inputs and multi-performance index MPI as output. The optimal levels of the process parameters are determined through the analysis of means of the MPIs. Confirmatory experiments are conducted to verify the optimal settings. The proposed method may be practically employed by the investment casters around the globe to increase the overall efficiency of the process and product.

Optimization of multiple responses in the lost wax process using Taguchi method and grey relational analysis

Investment casting process is one of the most versatile and flexible process which produces near net-shape metal components. The disposable pattern employed in the process is generally made up of wax blend, whose accuracy has a direct effect on the accuracy achievable in the final cast part. This article addresses an approach based on Taguchi method in integration with grey relational analysis for multi-response optimization of wax patterns made by the investment casting process. The experiments are planned using Taguchi’s L18 orthogonal array. The responses considered in this study are linear shrinkage, surface roughness and penetration, respectively. A grey relational grade obtained from grey relational analysis is used to determine the optimal process parameters. The significance of the process parameters on overall quality characteristics of the wax patterns has been evaluated quantitatively by the analysis of variance method. Optimal results have been verified through confirmation experiments, which indicate that the multi-performance characteristics of the wax patterns can be improved effectively through this approach. It was also found that though high injection temperature increases the surface finish of the wax blends, it adversely affects the mechanical properties of the wax blends.

Influence of injection process parameters on dimensional stability of wax patterns made by the lost wax process using Taguchi approach

Investment casting is a manufacturing technique employed to produce near net shape metal components. Wax is the most widely used pattern material. In the present work, the wax blend, to be used in the investment casting process, is prepared by mixing different waxes and starch as filler material to reduce the shrinkage of wax patterns. The effect of the selected injection process parameters on the dimensional stability of the wax patterns made by the investment casting process using silicon rubber mould has been studied and the optimum injection process parameters to reduce the shrinkage of wax patterns have been suggested. The wax injection processing parameters considered for experimentation were injection temperature, injection pressure and injection time. Taguchis L9 orthogonal array was used for designing the experiments. The signal-to-noise and the analysis of variance were used to find the optimum levels and to indicate the impact of the process parameters on shrinkage of wax patterns. The confirmation tests were conducted and the results were found to be within the confidence interval. The analysis of experimental results showed that the injection temperature and injection pressure greatly influenced the dimensional stability of wax patterns.

Vibration Characteristics of a Cracked Cantilever Beam under Free Vibration

The objective of this paper is to perform free vibration analysis of a cracked cantilever and to analyze the relation between the modal natural frequency with crack depth, modal natural frequency with crack location. Also the relation among the crack depth, crack location and natural frequency has been analyzed. Only single cracks at different depths and at different locations are evaluated. And the analysis reveals a relationship between crack depth and modal natural frequency. As we know when a structure suffers from damage its dynamic property can change and it was observed that cracks caused a stiffness reduction with an inherent reduction in modal natural frequencies. Consequently it leads to the change in the dynamic response of the beam. The analysis was performed using ALGOR software. Modal natural frequency was found to be decreasing with increases in crack depth. And the same was found to be increasing with increases in crack location from the fixed end.

Supply chain integration in relation to manufacturing industries

Manufacturers have been exploring innovative strategies to achieve and sustain their competitive advantages by facing a new era of intensive global competition. Such a strategy is Supply Chain Management (SCM), which has gained a tremendous amount of attention from both researchers and practitioners since the last decade. Supply chain management (SCM) has been considered as the most popular operations strategy for improving organizational competitiveness in the twenty-first century. It has attracted a lot of attention recently due to its role involving all of the activities in industrial organizations ranging from raw material procurement to final product delivery to customers. Well-designed supply chain systems can substantially improve efficiency and product quality, and eventually enhance customer satisfaction and profitability. In this paper, a manufacturing engineering perspective on supply chain integration is presented. Research issues discussed include product and process design for supply chain, design valuation of manufacturing supply chain, agent-based techniques for supply chain integration, intelligent information sharing across supply chain, and development of standards for product, process, and production data exchange to facilitate electronic commerce. The objective is to provide guidelines and references for manufacturing engineers and researchers that are interested in supply chain integration.

A novel method of increasing ceramic shell permeability and optimizing casting shrinkage and tensile strength of the investment cast parts

This study explores about enhancing the permeability of the ceramic shells used in the investment casting process using cheaply available sawdust particles. An increase in shell’s permeability augments the cooling rate of the casting which enhances its mechanical properties. It was found that the inclusion of sawdust particles into the ceramic slurries exhibited positive impact on the shell’s permeability. It is a well-known fact that electromagnetic stirring process increases the mechanical properties of the castings, but its effect on casting shrinkage has never been realized. Thus, this study further throws light on the impact of electromagnetic stirring in reducing the shrinkage and improving the tensile strength of the casting. In a nutshell, it was found that the final product quality of the investment cast part improved by the combinational treatments adopted in this research work.

A prediction model for the lost wax process through fuzzy-based artificial neural network

The application of investment casting process is rapidly increasing, specifically for near net shape manufacturing of complex and small engineering components. The process begins with making of wax patterns, thereafter employing a precision mould, dewaxing, pouring molten alloy and knocking the shell, followed by minor finishing operations. This study is about predicting the quality of responses of the wax patterns namely linear shrinkage and surface roughness using fuzzy-based artificial neural network. The process parameters considered are injection temperature, injection pressure and holding time, and experiments have been performed as per Taguchi’s L18 orthogonal array. As optimum parameter levels were different for both the responses, fuzzy logic reasoning has been used to combine all the objectives and transform the experimental results into single performance index known as multi-response performance index. Later, modelling of the process has been done using artificial neural network with experimental process parameters as inputs and multi-response performance index as output obtained from fuzzy modelling. Further, experiments have been conducted at random combination of parameter levels to validate the developed model, and it has been found that the actual results agreed well with that of the predicted value on the basis of mean absolute percentage error and correlation plots.

Optimization of the Investment Casting Process Using Genetic Algorithm

This paper presents a study in which an attempt has been made to improve the quality characteristic (surface finish) of the wax patterns used in the investment casting process. The wax blend consists of paraffin wax (20 %), carnauba wax (10 %), microcrystalline wax (20 %), polyethylene wax (10 %) and teraphenolic resin (40 %), which provided an improved pattern wax composition. The process parameters considered are injection temperature, holding time and die temperature. The injection process parameters are optimized by genetic algorithm. Further, verification test have been conducted at the obtained optimal setting of process parameters to prove the effectiveness of the method. Finally, a good agreement between the actual and the predicted results of surface roughness of the wax patterns has been found.