Final Rapid Prototyping

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  1 A SYNOPSIS ON A COMPARATIVE STUDY OF VARIOUS TECHNIQUES FOR IMPROVING SURFACE FINISH OF FDM PATTERNS For M. Tech. In Mechanical Engg. Supervisor: Researcher: Parlad Kumar Tejpal Singh Assistant Professor Roll No. 11293039 Department of Mech. Engg. DEPARTMENT OF MECHANICAL ENGINEERING PUNJABI UNIVERSITY, PATIALA 2014  2 INTRODUCTION The term rapid prototyping   (RP) refers to a class of technologies that can automatically construct physical models from Computer-Aided Design (CAD) data. It is also called as Desktop manufacturing. With the development of technologies, rapid prototyping has become more  popular. RP focuses on small quantities and complex geometries, and its application on investment casting gives designers the freedom to rapidly modify and redesign a  product without a significant increase of the total time and cost. It also reduces the time and labour. Methodology of Rapid Prototyping Rapid Prototyping Technologies Prototyping technologies Base materials Selective laser sintering polycarbonate, nylon.  3 Fused deposition modelling ABS, Polycarbonate. Stereo lithography Photosensitive resin. 3D printing Starch, ceramic powder. Laminated object manufacturing Paper, plastic, cellulose. Fused Deposition Modeling (FDM)  Fused Deposition Modeling (FDM) was developed by Stratasys in Eden Prairie, Minnesota. In this process, a plastic or wax material is extruded through a nozzle that traces the part's cross sectional geometry layer by layer. The build material is usually supplied in filament form, but some setups utilize plastic pellets fed from a hopper instead.    In FDM process, a gantry robot-controlled extruder head moves in two  principal directions over a table, which can be raised and lowered as needed.    A thermoplastic filament is extruded through the small orifice of a heated die.    The initial layer is placed on a foam foundation by extruding the filament at a constant rate while the extruder head follows a predetermined path.    When the first layer is completed, the table is lowered so that subsequent layers can be superimposed    In some parts, the filament is required to support the slice where no material exists beneath to support it.    The solution is to extrude a support material separately from the modelling material. The use of such support structures allows all of the layers to be supported by the material directly beneath them.    The support material is produced with a less dense filament spacing on a layer, so it is weaker than the model material and can be broken off easily after the  part is completed.    The layers in an FDM model are determined by the extrusion-die diameter, which typically ranges from 0.050 to 0.12mm. This thickness represents the  best achievable in the vertical direction.  4 Review of Literature Kumar, P. et al. investigated structure for formulating a hybrid investment casting  process for industrial uses. For this purpose many controls and effects regarding to  process have been discussed to achieve the optimum mechanical and metallurgical  properties. The authors discussed the various steps of the FDM process. In addition to this post processing of the process and factors related to properties were also illustrated. It was concluded that this hybrid process can be used for various industrial and biomedical applications. Rao, A.S. et al. (2012) found experimentally the post processing techniques to improve the surface finish of Fused deposition modelling parts. The Authors used the chemicals through Design of Experiments and Annova technique with different concentrations to find out the parameters regarding the surface finish. For this a specimen was dipped in Acetone and methylethylketone chemicals to obtain optimum results. It was concluded that in methylethylketone the initial parameters have negligible effects as compare to Acetone. Kumar, P. et al. (2012) discussed a review for the application of fused deposition modelling for rapid investment casting. The authors presented information about the using of FDM in investment casting and also collect and illustrate the data available about the FDM materials, their properties, factors related to process, accuracy to  produce prototypes .For this difference between the investment casting and Rapid investment have also been described. It was found that the material with high strength and having low diffusion temperature are suitable for making IC patterns. Khan, F.K. et al. (2006) investigated the effect of support structure thickness and slice layer on the model regarding its surface roughness made by FDM technique. On both sides of the model measurement of roughness was done perpendicular to the direction of build layer. The authors concluded that the part of the model which is adjacent to the top layer of the support has smoother structure than to the surface without support. Bakar et al., 2010 found the effect of three process parameters such as layer thickness, contour width and internal raster by using FDM technique. Experiment was conducted on model that posses a number of geometrical shapes and sizes such as holes, cubes, cylinders which are easily machined on plastic parts. It may be concluded that the
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