Engineering Design Plastics & Injection Moulding
Plastic injection moulding is a backbone of many designs 
Although plastics may be scoffed at as cheap & nasty, this is usually due to poor deign as well as being poor quality plastic material. It's perfectly feasible to have quality parts produced in (the correct) plastic that adds value to a product, but are yet still economical to produce. Primarily, plastics are so useful because of their mechanical and physical properties, with their ease of tooling for injection moulding giving nearly infinte product shapes, not only enabling good aesthetics, but also ease and efficiency of assembly. Snapfits (or deformation fits) are commonly used in plastic products. Careful design is required to get the balance of force fit correct yet maintain good structural integrity, especially when drop testing. This is where Finite Element Analysis comes in to its own. This is also true for any structural attachment (such as a screw) that a plastic product may undergo.