The introduction in Fiat Auto of large injection molded body panels, such as the Fiat Uno Turbo rear doors, has created the need to better understand the technology and the correlations between defects after molding and painting and the possible causes. To evaluate the influence of a large amount of variables, both formulation and injection molding parameters, statistically designed experiments offer the possibility to do this with a limited number of trials. This particular study utilises a three level, five variable design. The variables are: formulation molecular weight both of the polyester resin and the low profile additive, process parameters mold temperature, injection speed and holding pressure time. All other conditions were kept constant. The following properties of the molded parts were evaluated: mechanical properties, flexural strength modulus, elongation and impact strength, surface quality waveiness, blistering and cracking. This statistical design of five variables at three levels takes twenty-nine experiments meaning nine different formulations. A surface analyser is used to evaluate the surface quality. To evaluate the blister porosity incidence the molded parts were painted on the paint-line of the Fiat Tipo rear door. The result of this study is a list of correlations between defects and possible causes, and a remedy (with suggestion both on formulation and molding parameters) to optimize the quality of DMC injection moulded parts is given. The presentation will give a brief description of the Fiat Tipo rear door injection molding process deisgn solutions, production cycle, molding conditions, after molding operations, bonding and painting phase. The Fiat Tipo rear door is the first large series (over two thousand parts/day) injection molded part utilising a fully automated production line.
A cause/defect study of injection molded DMC parts
Eine Ursache/Defekt-Untersuchung von spritzgegossenen DMC-Teilen
1989
6 Seiten, 6 Bilder, 4 Tabellen
Conference paper
English
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