Effect of shrinkage on the design and manufacture of plastic parts in injection molding using CAD/CAM techniques
Department of Mechanical and Industrial Engineering
Master of Science
O'Brien, Keith T.
Injection molding of plastics
Computer aided design software in injection molding has revolutionized injection molding in the design and manufacturing processes. Computer Aided Engineering can be applied to injection molding to increase the process efficiency, reduce part costs, and produce accurate parts in less time. The mold designer has many software programs to choose from to produce satisfactory mold designs from part geometries, and a correct selection can produce profitable results. A study of the need for and the scope of computers in injection molding is performed to evaluate the suitability of a CAE package by considering the value added to the parts using these techniques. The interactive nature of the programs is illustrated with examples and also the ability of the programs to perform simulations of the processes axe studied and the accuracy and reliability of the programs is considered.
Evaluation of part shrinkage is very important to mold parts of required accuracy. The currently used methods in CAD mold design have one major drawback that mold designers experience. The variation in shrinkage coefficients for different resins cannot be compensated for and one cannot predict whether a specific part can be manufactured without warpage. Most CAD simulations cannot accurately predict the variation in shrinkage rates across all dimensions of a specific part. The factors influencing part shrinkage are studied and the variation of shrinkage with molding conditions is illustrated from previous experiments. A comprehensive plan is suggested to perform experiments to enable prediction of part shrinkage more accurately.
njit-etd1991-023 (84 pages ~ 10,513 KB pdf)
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Created April 14, 2004