EXPERIMENTAL AND COMPUTATIONAL ANALYSIS OF VARIOUS DESIGN PARAMETERS OF AUTOMOTIVE COMPONENT USING RAPID PROTOTYPING

Abstract

Manufacturing is one of the most vital wheel cogs for the developing country like India. Government of India is planning to increase the manufacturing capacity of the country and place the India as a manufacturing hub in the world map. India is planning to increase share of the manufacturing industry of the gross domestic product GDP. Prototyping is an important step for the conceptualization of any design and mould making process. Nowadays, several prototyping processes are available. Among all the available prototyping processes, rapid prototyping process takes minimum time to make the prototype model from the 3D CAD model. However, the quality of prototype model produced through rapid prototyping process is inferior over the traditional methods of prototyping. Several reports and published articles are available in the international and national journal & which show that the quality of prototype model produced through the rapid prototyping process is depends upon the printing process parameters. The main focus of this research is to propose the methodology to improve the quality of prototype model developed through the commonly used rapid prototyping technology namely FDM and PolyJet. In this thesis, initially a comparison is being made for FDM and PolyJet technology. Comparative study are carried out on the basis of flatness, cylindricity, roundness, percentage errors in the linear dimension, percentage error in the radial dimension, surface roughness and cost of the prototype model developed via FDM and PolyJet process. For the comparative study of FDM and PolyJet technology, a complex shaped product, radial engine connecting rod was considered. The selected automotive component has cylindrical, linear, radial dimensions and flat surface. vi FDM technology is the most widely used for the printing of prototype parts because of low cost. The quality of printed prototype parts through FDM process depends on the number of process parameters viz., layer thickness, infill pattern, orientation, raster angle, infill density, raster width, number of couture etc. Several studies have been conducted to get an optimum level of process parameters for the FDM process. However, very limited studies are available related to impact of process parameters i.e. infill pattern and infill density on dimensional accuracy, flatness and cylindricity of the fabricated component. In this work, an attempt is being made to investigate the impact of important FDM process parameters i.e. layer thickness, orientation, infill pattern and infill density on flatness, cylindricity, percentage error in the linear dimension, percentage error in the radial domination. Taguchi‟s approach was applied for the selection of optimum level of process parameters. A regression model is also developed for the selected response factors in terms of process parameters. The developed models are good enough to predict the response factors within the experimental domain. For evaluating the goodness of fit of the model, F-test has been applied. Analysis of variance is employed to get the percentage contribution of individual process parameters. A multi Objective optimization „Utility theory‟ is successfully applied to get the best level of process parameters which optimize all the selected response. International tolerance grades for the components fabricated through FDM process are investigated. It was found that tolerance grades of the fabricated samples are consistent. Another focus of this work is to obtain an optimum level of process parameters for the PolyJet process. This study deals with the effect of process parameters viz., vii raster angle, orientation and type of surface finish on dimensional accuracy, flatness and surface roughness of the component fabricated through PolyJet process. Some research works have been reported few studies related to impact of PolyJet process parameters on surface roughness parameter Ra only. However, this work contains all the surface roughness parameters i.e. Ra, Rq and Rz are being considered as response variables. Regression models for the flatness, dimensional accuracy and roughness parameters are also developed. The main outcomes of these models are that they are well within the experimental domain. It is generally noticed that strength of the component fabricated through rapid prototyping is less as compared to the traditional manufacturing process. In this work, a new methodology is presented to improve the tensile strength of the ABS and PLA component fabricated by FDM process. High strength PETG material is used as the reinforcement to improve the unidirectional tensile strength of the material. For validation of the experimental results, a computational model of the unidirectional reinforcement process is also developed. From experimental and computational study, it can be further concluded that due to reinforcement of high strength material, tensile strength of ABS and PLA materials are significantly improved. SEM analysis of the component printed along flat orientation and on-edge orientation is performed to visualize the surface of the fabricated components. Results illustrate that the component printed along flat orientation has less voids and air gaps in comparison to edge orientation. There are some research work have been reported related to elastic deformation behavior of RGD840 material manufactured via PolyJet process. However, no attempt viii is made to investigate the plastic strain in the material. This study also focus on experimental investigation of effect of process parameters on elastic modulus, fracture strength and percentage elongation of the component. Further, calculation of true stress, true strain and plastic strain are also carried out. The value of strength coefficient (K) and strain hardening coefficient (n1) are calculated through graphical method from true stress and plastic strain curve. Numerical simulation is also performed to validate the experimental value of plastic strain. Results revealed that the numerical simulation of plastic strain is a close approximation of the experimental result. Finally, the thesis contains a methodology for improving the clearance between matting parts. In this section, clearance analysis between matting part is calculated, which is based on model developed through archival literature. An assembly joint of automotive components are fabricated through the FDM process. It is observed that the shrinkage phenomena in the solid and hollow parts are different. Shrinkage in the hollow section was more as compared to the solid part.