A Study On The Implementation Of Rapid Design & Rapid Manufacture Of Metal Functional Exemplars By Combination Of RPM And Precision Casting Process

In order to produce good products by rapid and saving means, it is the key to possess advanced manufacturing technology in today's severely competitive markets. Rapid prototyping technology is just one of high and new technology. However, its applied area is greatly limited because materials used in manufacturing rapid prototypes are almost plastic, wax or other inorganic & non-metal material etc. And we require metal functional exemplars in many areas. So how to convert the rapid prototypes into metal functional exemplars (especially, this kind of important technical equipments like metallic pattern & tooling) will greatly influence the application of the high-new technology. According to the requirement for science & technology and social market, the manufacture of metal functional exemplars by SLA and SLS rapid prototypes used as patterns in precision casting is emphatically studied.The author of the paper has implemented 3D geometry modeling by such 3D geometry modeling software as MDT R5.0 and SOLID WORKS 2000, and also discussed modeling accuracy and model accuracy by exporting STL format files in the two kind of software by PC. Several used-widely rapid-prototyping systems are concluded and the characteristic of rapid prototypes manufactured by them is analyzed. Owing to facing a great deal of problems in the course of manufacturing metal functional exemplars by combining SLA rapid prototypes, SLS rapid prototypes and precision casting process, a great deal of experiments (included inmeasurement of prototypes' residual ash content, measurement of contact angle between prototype and binder, testing of coating thickness on prototypes, testing of gas evolution of mold flour after roasting prototypes in mould) are made. By these technical parameters we can draw a conclusion that there are some special problems when the prototypes made of resin, plastic, or wax can be directly used in making metal functional exemplars through Shaw process or precision investment casting process. For example, as heat expansion coefficient of SLA prototypes from acrylic epoxy resin is usually larger than that of the mould in the course of sintering, mould cracks often occur without some technical measures so that we can't pour liquid metal. As SLS prototypes' rough surface, they should be after-treated (dip liquid resin, solidify, or dip liquid wax, grind the prototypes' surface) before used. When SLS prototypes are used in manufacturing metal functional exemplars through precision casting process, wetting agent should be added in slurry or dope in order to improve wetting condition on prototypes' surface. When sintered, mould should be placed upside down so that thermoplastic prototypes can greatly flow out from mould cavities. This will decrease residual ash' influence on metal functional exemplars. And heat expansion coefficient of some SLS prototypes (for example, modified ABS plastic prototypes, HIPS resin prototypes) is larger than that of investment shell, so shell cracks often occur in the course of sintering without some technical measures so that we can't pour liquid metal. Finally, the author successfully manufactured metal functional exemplars by precision casting process (self-curing slurry mould with phosphate binder or investment casting) with SLA prototypes from acrylic epoxy resin, SLS prototypes from modified ABS plastic and SLS prototypes from wax.