can anybody tell me what subject in Mechanical engineering deals with the making of External cases for electronic gadgets? I know I need to use CAD/CAM but I am asking this question because I want to know about the materials - How to determine what to use, where and why. Suppose I want to design an IP 67 casing for an electronic gadget, How would I go about it, where do I start?
the two main methods of making hard cases for electronic gadgets are 1) injection molding and 2) blow-molding, vacuum forming or sheet molding (these have similarities as described below).
Injection molding is the squirting of molten plastic into a cavity in a metal mold, which is then opened up to remove the finished part. It is used when the part has to have a lot of fine details accurately included in it, which is easily done by appropriately machining the mold cavities. The housings for digital cameras and cell phones are made this way.
Blow-molding is done by pumping air into the center of a glob of molten plastic that is inside a mold cavity. The glob inflates and adopts the shape of the cavity. The mold is then split open to remove the finished part. Inexpensive plastic and glass bottles are made this way.
Vacuum-forming is done by heating up a thin sheet of plastic until it is soft and then draping it over a form. Small holes in the form are connected to a vacuum source, which then sucks the soft sheet into close contact with the form so the plastic sheet assumes the shape of the form.
Sheet molding is similar but may use air pressure on one side of the sheet instead of vacuum on the other side to push the soft plastic into contact with the form.
Sheet molding, blow molding and vacuum-forming are used to make inexpensive carrying cases for small electrical appliances, the side pieces of brief cases, and hard-sided luggage. Grades of plastic sheet are available with reinforcing fiber in them which significantly increases the strength of the finished part.