Modeling of plasticization during injection molding has been a complex issue. particularly for the solid conveying zone. This can be further complicated by break-up of the solid-bed due to the reciprocation motion experienced in injection molding. The break-up of the solid-bed can introduce molding quality problems such as inhomogeneities in parts. A transparent barrel system has been set up for injection molding to observe the solid-bed break-up mechanism and the conditions that influence this process. This paper summarizes some solid-bed break-up results relevant to injection molding. These results may be useful to the modeling community for experimental verification of their simulations, and to the molding community for setting up molding conditions to prevent the occurrence of solid-bed break-up. (C) 2004 Society of Plastics Engineers.