Subtractive techniques, prototyping

There are three main ways to create a rapid prototype. Formative techniques use machines to make raw materials into the desired shape. Subtractive processes start with a large solid, then remove material to make the shape desired. Additive processes rely on layering material over and over until the part or product reaches its final position and shape. 

Control (CNC) machines. An additional technique is the formative method where material is reshaped rather than added or subtracted. However, material forming is more a manufacturing production technique rather than a prototyping method. For example, sheet forming and blow molding considered in Chapter 10 are forming... 

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