1 An overview on research work in Leoben in the fields of rapid heat cycle molding, surface topography and visual appearance of injection molded parts Gerald R. Berger and Walter Friesenbichler, Department of Polymer Engineering and Science, Chair of Injection Moulding of Polymers, Montanuniversitaet Leoben, Leoben, Austria Gernot A. Pacher and Dieter P. Gruber Polymer Competence Center Leoben GmbH (PCCL), Leoben, Austria Abstract Different aspects on surface quality of injection molded parts have been researched in Leoben in the last 10 years. This paper will give a short overview on our research work, considering rapid heat cycle molding, surface topography and visual appearance of polymer part surfaces with special focus on weld lines, sink marks, and gloss differences, respectively. Rapid Heat Cycle Molding In the recent years the requirements on surface quality and good aesthetics of plastic products increased continuously while in contrast products got always lighter, smaller and also thinner. When the conventional injection molding cannot meet those high requirements, rapid heat cycle molding (RHCM), also known as dynamic mold temperature control (DMTC) or variotherm(al) processing, is used. In the rapid heat cycle first the mold surface is heated up to a high temperature (typically close to or above TG or TS) in order to improve melt flowability, replication of micro structured surfaces and the quality of high appearance surfaces, e.g. Piano- Black TV front shells, respectively. During injection phase the high temperature is maintained. After filling and packing the cooling phase starts. Cooling ends with the demolding of the part and the next cycle begins. The cooling may be done conventionally or actively by higher pressure, lower fluid temperatures, and pulsed [14], respectively. The whole mold, a mold insert, or only the cavity surface may be heated up. The heating energy source can be inside or outside the mold: Hot steam [1], hot gas [2], heat generation by induction [3-6] or high frequency proximity effects [7], absorption of infrared light [8-11,26- 27] or laser light [12], conformal temperature control by a hot and a cold liquid [13] or pulsed cooling [14], electrical heating cartridges [15], contact of the mold insert to a very hot aluminum block [16], and Joule’ heating of coated mold inserts [17-18] are known. A very common approach of RHCM is to use water as heating and cooling fluid. Commercial systems consist of separate water- circuits for heating and cooling, which are alternatively pumped through the mold cooling- channels [19]. This principle was adapted by the so-called BFMold ® technology [20,21] where the heating/cooling channels are replaced by a ball-filled slot near the cavity surface flooded through with hot and cold water sequentially. Thus this configuration enables both, good and uniform heat transfer by significantly increased contact surface and support of the cavity plate against mechanical load from the injection pressure (Fig. 1). Several studies have shown the use of RHCM improves the surface quality of injection-molded parts [22-28] however; part warpage may increase due to asymmetric cooling conditions, as for parts with high appearance quality surfaces only one side of the