Approximately 30% of all plastic products in the world are produced by an injection molding process. Within this another 30% are produced using a custom injection molding technology. There are basically six steps involved in the normal injection molding process. The first step is the clamping of the mould, the clamping unit makes for one of the three units of the molding machine. The other two being the injection unit and the mold, once the clamping unit holds on to the mold, the molten plastic is injected into the mold by the injection unit. The plastic is fed in the form of tiny pellets onto a hopper. These are then allowed into a cylinder where they are heated into a molten state and injected into the mold. The steps that follow are referred to as dwelling phase. It basically involves making sure all the cavities in the mold are fully filled. The mold is then allowed to cool with the clamping intact. Finally the mold is opened and the component is ejected out. The biggest advantage of plastic injection molding is the cost factor of the produced parts, especially when you need large number of parts. The disadvantage is the cost of manufacturing the molds; a simple injection mold can cost you $3000 while the bigger complex ones can run into several hundreds of thousands.
Rapid Prototyping: Rapid Prototyping is the process of automated manufacturing of physical components using solid freeform fabrication. They are used in a wide range of applications, everything from medical to fine art. Rapid Prototyping machine works by taking virtual models from software and then converting it into extremely thin, horizontal cross-sections and then goes onto create each of the cross-section in physical space in a cyclic manner until the model is completed. Rapid Prototyping is a WYSIWYG process in which the virtual model bears identical resemblance to the finished physical model. Additional fabrications allows the machine to lay down layers of sheet, liquid or powder material and build up a series of cross-sections These layers are finally automatically fused together to render the final product. The main advantage of rapid prototyping is the ability to create any shape no matter how complex the geometry is. The commonly used data interface between the machine and the software is the STL format. It works by approximating the geometry of a part using triangular facets, smaller the facets higher will be the surface quality. The word “rapid” is used relative top conventional methods which take days to construct a model depending upon its complexity. Rapid prototyping can create the model within a few hours, though it is highly dependent of the type of machines and the size of the model. There have been several new technologies available for rapid prototyping including Fused Deposition Modeling, Selective laser sintering, 3D printing, and Electron Beam Melting. plastic injection molding
