
Possible methods for Rapid Prototyping
In manufacturing, rapid prototyping is seen as a faster means to an end.
What caught my interest the most about rapid prototyping is the somewhat form of art involved in the whole process. Art in the sense that after the designers have given their design concept, with rapid prototyping they get a feel and outlook of what their work would be like even before mass production. It also gives them the opportunity to change anything they are not necessarily pleased with.
Rapid Prototyping essentially is the design(using a Computer Aided Design software) and production of model prototypes, at a faster rate than manufacturing the whole model would naturally take. Prototyping is either done to scale (i.e. in the case of smaller models) or made in a smaller scale to give perspective of what the model would eventually look like. There are various ways of producing these prototypes, but each of theses ways or methods majorly fall under these three categories; Subtractive, Additive and Compressive Processes.
Think of subtractive process as a similar process to that which sculptors go through to create their sculptures. At the start they have a huge mass of material; stone, plaster of Paris, wood, ice and so on. Then using a precise tool, the sculptor removes the unwanted parts of this mass of material, leaving behind the desired sculpture. So also in the subtractive process, unwanted materials are removed from a mass of whatever material is being used, using precise tools attached to a machine which have been given precise coordinates to drill into. This process is either done layer by layer on a stationary block or done on using a precise tool going up and down a spinning block of material. CNC machining is one of the most known form of subtractive processing.
Additive Process is basically the opposite of the subtractive process, in the sense that rather than creating a model from removing materials, it is done by adding materials, as the name implies. But unlike the subtractive process, it does not start with a huge mass of material. In this process the model is created layer by layer by adding more materials as the model increases in height. An example of this is 3D printing. In 3D printing the material is heated into a semi-solid state and passed through a nozzle to create the model layer by layer on a flat surface. Other examples include Selective Laser Sintering(SLS), Stereolithography and so on.
In the Compressive process the material is either heated till it’s malleable and passed through a mould of desired shape or a semi-solid/liquid material is poured into a mould. In both cases, the material is made to take the shape of the mould. A popular example of this is sand casting. In sand casting the mould is made using sand and the liquid material is poured into the mould and left until it solidifies, taking the shape of the sand mould.
Starting from the idea behind the product, the CAD Engineer has to come up with a design concept as earlier said. To choose the right manufacturing process to produce a prototype or the actual model a lot of factors have to be considered. But the most important factors to consider in rapid prototyping are costs and production time.
