26-02-2013, 03:09 PM
Combined Grey Relational Analysis and methods for optimization of process parameters in cylindrical grinding
Combined Grey Relational Analysis and methods.doc (Size: 238.5 KB / Downloads: 127)
Abstract
Optimization of grinding processes remains as one of the most challenging problems because of its high complexity and non-linearity. Optimization of process parameters is done to have great control over quality, productivity and cost aspects of the process. This paper deals with the analysis of process parameters such as speed, feed and infeed as the influencing factors on surface finish developed and roundness error produced based on Grey relational method and Taguchi’s design of experiments. Based on the factors selected and levels taken, L9 orthogonal array is selected for our work. The results obtained by Grey relational method is compared with that of the optimal condition obtained by using Taguchi’s tools
Keywords: - Taguchi method, Grey relational analysis, ANOVA, grinding.
INTRODUCTION
Grinding process is dissimilar to other machining processes such as turning and milling, as the multipoint cutting edges of the grinding wheel don’t have uniformity and act differently on the work piece at each grinding. These complexities and difficulties of illustrating the grinding process also raise obstacles to the optimization of the grinding process and to the verification of the interrelationship between grinding parameters and outcomes of the process. The effects of the control factors on the quality characteristics of cylindrical grinding are analyzed using Taguchi’s tool to determine the optimum control factor.
THE TAGUCHI METHOD
The Taguchi method is a powerful tool in quality optimization for manufacturing processes. Taguchi method makes use of a special design of orthogonal array (OA) to examine the quality characteristics through a minimal number of experiments. The experimental results based on the OA are then transformed into S/N ratios to evaluate the performance characteristics.
GREY RELATIONAL ANALYAIS
The Grey system Theory initiated by Deng is mainly utilized to study uncertainties in system models, analyze relations between systems, establish models and make forecasts and decisions. The meaning of “grey” can be expressed as characteristic between black and white. The GRA is an important method in grey system theory. Data pre-processing in this analysis is the process of transferring of original sequence to a comparable sequence. For this the experimental results are normalized in the range between zero and one. Following the pre-processing, a grey relational coefficient γ is calculated to express the relationship between the actual normalized experimental results. The grey relational coefficient γ can be expressed as,
ξ = constant (0.5)
EXPERIMENT SETUP
The experimental set-up for the external cylindrical grinding used in this study is shown in figure. The work piece is held between head stock and tailstock centers. A disc type grinding wheel performs the grinding action with its peripheral surface. Both traverse and plunge grinding can be carried out in this machine as show in
A: rotation of grinding wheel
B: work table rotation
C: reciprocation of worktable
D: in feed
Plain centre type cylindrical grinder
The grinding wheel used for the experiment is A80J5V10X. The work piece material used for our experiment was EN-24 steel, which is high tensile steel suitable for pump shafts and turbine rotors in general. The composition of EN-24 material is given in the table below.