Rapid Prototyping & Manufacturing Technologies - to submit your ...

Rapid Prototyping & Manufacturing TechnologiesIts application is mainly to produce plastics or metal prototypes in small batch byvacuum assisted casting or gravity casting method. The casting materialsnormally used are PU, polyester, epoxy, tin-lead alloy (200 °C), pewter (230 °C)and zinc alloy (400 °C).The batch size is from several pieces to hundreds. Multiple moulds, sometimes,are required depend on the complexity of the parts. In fact, the ease ofproducing multiple moulds is one of the advantages of this technology.However, the process is tedious and required high skill workers attendance.4.2.1 Process DescriptionOne-piece mould approachThis process begins with a master pattern which normally output from RP systemdirectly. It requires to sand and polish the part surface well since the RTV mouldwill reproduce any and all surface defects on the master pattern, and in turn willtransfer them onto the final model. Then, the pattern attached with gatingsystem is mounted in a mould box. Silicone rubber is mixed with specific amountof hardener and poured into the mould box. Degassing in vacuum chamber ispreferred to avoid trapped air caused by mixing and pouring. After solidification,the mould is then spitted into mould halves according to the predeterminedparting lines. Figure 4.1 shows the RTV mould making process of one piecemould approach.Fig. 4.1 Processes of making RTV mould (one-piece mould approach)Page 25IC Professional Training