In this study, Taguchi method is used to investigate the effect of critical process parameters of investment casting on dimensional variations of thin walled, complex geometrical stainless steel component. A set of experiments have been conducted to calculate shrinkages which is a measure of dimensional variation. The process parameters considered here are number of ceramic coats, pouring time, pouring temperature, and casting cooling rate. The signal-to-noise ratio and analysis of variance are used to study the influence of these parameters on shrinkage. Optimized condition for reduced shrinkage deviation can be obtained by selecting lower number of ceramic coats, faster and laminar metal pouring, lower superheated metal temperature, and faster cooling rate. Analysis of variance reports that the number of ceramic coats is the most significant parameter with more than 80% contribution whereas other parameters are insignificant. Investigation results also indicate that constraint dimension (width) has 25%-27% higher dimensional variability than non-constraint dimensions (height) for the selected component.
Variation in final casting dimensions is a major challenge in the investment casting industry. Additional correction operations such as die tool reworking as well as coining operations affect foundry productivity significantly. In this paper influence of basic parameters such as wax material, mould material, number of ceramic coats and feed location on the dimensional accuracy of stainless-steel casting has been investigated. Two levels of each factor were chosen for experimental study. Taguchi approach has been used to design the experiment and to identify the optimal condition of each parameter for reduced dimensional deviation. Analysis of variance has been carried out to determine the contribution of each process parameter. The result reports that selected parameters have significant effect on the dimensional variability of investment casting. Mould material is the dominant parameter with the largest contribution followed by number of ceramic coats and wax material whereas feed location is having negligible contribution.
The investment casting industry falls under the highly technological but extremely labor-intensive industry. The increasing need of the complexity, close dimensional accuracy and high reliability of the castings at the most competitive cost has become basic necessity for sustaining growth in the global market place. The purpose of this paper is to study the present manual processes in the Indian investment casting industry and to identify the opportunities to automate them and evaluate its impact on the product quality, productivity and yield which are essential performance parameters for investment casting industry. The approach adopted is to identify and study all the manual processes in the foundry, rejection analysis of a foundry using Pareto analysis followed by cause-effect analysis for defects arising from the manual activities using Ishikawa diagram. Reasoning of shell shop selection for automation and limitation of existing manual layout has been discussed. Process automation using robotics in shell shop uses robot for repetitive dipping, coating and drying cycles on each mould resulted in reducing rejection from 11.2 % to 3.5 %, cycle time reduction from 4-5 days to 2-3 days, improvement in yield from 29 % to 38 % and productivity from 27 % to 32%. Absence of programmer's skills to coat complex geometries to achieve better results is the constraint of the shell automation technique. Higher capital cost restricts the use of robot in wax assembly, foundry shop and post casting operations.
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