Thermoforming is an industrial process in which sheet plastic of any thickness is heated to increase its flexibility, then is conformed to a mold before cooling into its new permanent shape.  The plastic is not melted, as in injection molding, but rather the plastic is forced to fit the shape with vacuum suction.  A common example is the stiff plastic packaging that many toys and tools come in.  The molded plastic is rigid, and yet it is shaped to perfectly encapsulate the product.  Although the process may to apply to any sheet plastic, typically the thickness is great enough that it cannot be easily bent when cut to the size of a book, and the impression cannot be easily compressed or deformed.

Some other common applications include the outside of medicine capsules, disposable plastic cups, lids of nearly any variety, and even objects as large as garbage cans.  Some very thick objects are made using thermoforming rather than injection molding, even though the product might be the result of either.  Examples of these include the interior of car doors and plastic palates, which are used in stead of wooden palates in warehouses.  Increasingly more objects are being produced as a result of advancing thermoplastic technology, simply because the material is never melted, and therefore there is no degradation in its chemical makeup.

thermoplastics and plastic thermoforming have many advantages, one of the largest is that the plastic is never melted.  Between partial heating and vacuum molding, less energy is used than in melting and repeated melting of the waste.  There is little risk of the parts sticking together because of a melting mishap.  Thermoplastics are not as sticky when hot.  One disadvantage is large volumes of dry waste, the result of cutting and trimming.  These leftovers can be shredded and returned to the thermoplastic facility.  Since the plastic sheets are generated in a separate factory, it is easy to outsource this material, avoiding additional machinery that might otherwise need to be purchased.  This is excellent for the small factory, although large factories often produce their own sheeting, both to reduce costs and to meet their own unique specifications.