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Use of grey relational analysis found to be convenientand easiest method to estimate the significance of theseprocess variables for multiple quality factors having differenttargeted objectives. In this study, it has been found that melttemperature and injection speed have almost equal influence,but more than that of injection temperature and pressure inachieving desired part shrinkage and higher part weight.These experiments using DMLS molds have shown that allprocess variables except injection pressure contributedsignificantly on shrinkage and weight at their highest (third)level. The optimized variables are compared with the range ofvariables suggested in processing data sheet of said polymer.Figure 5 DMLS mold surface after producing 5,000 Nylon 66 moldingsTable VII Significance of molding parametersInjection moldingAverage grey relational gradeby process parameters level(experimental layoutshown in Table II)Significanceof moldingparametersparameters Level 1 Level 2 Level 3 Max-MinInjection pressure 0.5700 0.6217 0.6367 0.0667Melt temperature 0.5611 0.4271 0.6607 0.2336Injection speed 0.4877 0.6182 0.7225 0.2348Injection time 0.5794 0.5720 0.6770 0.1050This has indicated that the optimized variables are either nearor slightly more than the corresponding upper limits.The surface characterization of DMLS mold even afterproducing 5,000 moldings did not show any visible damages,in spite of their low hardness, scratch and wear resistanceproperties. This study confirms the potential application ofDMLS molds for producing few thousands of moldings ofindustrial quality, provided the process variables areoptimized for specific mold geometry. The mold lifehowever still poses a challenge for further improvement toenable them batch production molds. Authors are currentlyworking towards hard coating of TiN, CrN by CVD and alsoplasma ion implantation on DMLS molds surface to enhancemold life, and preliminary experiments have shown promisingimprovements.ReferencesDeng, J. (1989), “Introduction to grey system”, Journal ofGrey System, Vol. 1 No. 1, pp. 1-24.Dolinsek, S. (2005), “Wear characteristics of laser sinteredmolding tools”, Wear, Vol. 259, pp. 1241-7.GE Plasticsw (2008), “Injection molding mini guide”,available at: http://kbam.geampod.com/KBAM/Reflection/Assets/8654.pdf (accessed March 14, 2008)Karunakaran, K.P., Akula, S. and Pushpa, V. (2004), “Hybridlayered manufacturing: direct rapid metal tool makingprocess”, IMECH Eng. 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