Short screw designs for the MuCell process.

摘要

A shorter than standard plasticating screw has been developed and tested for the MuCell injection molding process technology, to process a wide variety of materials and applications. The fundamental function of a MuCell screw (reciprocating type), is that in addition to performing the standard functions of a conventional injection molding screw (feeding, melting and metering), it also has to incorporate the additional functions required to properly mix the physical blowing agent with the molten polymer to form a single-phase solution. The single-phase solution, a homogeneous dispersion of blowing agent dissolved into the polymer melt, is the precursor to a microcellular foam structure.; The additional functions needed to create the single-phase solution require that the screw be significantly longer than that of the standard length to diameter ratio screws. Historically, this plastic process technology requires a screw with a flighted length to diameter ratio (L/D) of 28:1. The commercial implementation of such long screw represents its most significant disadvantage. That is a very expensive customized molding machine with a special frame length must be used. The objective of this work was to design and thoroughly test a shorter MuCell screw that can be fitted on a standard size machine platform. This shorter more compact design must be capable of performing at the same level or better than the current commercially proven design.