Introduction to Thermoformed Plastic

Thermoforming is the process of taking a sheet of plastic and heating it into a more pliable form. Then it is placing into a mold in order to shape it into a desired form. The plastic is then trimmed around the form to create a usable plastic product. The plastic film is then heated under high temperatures, enough that it can be stretched into or onto a premade metal mold, on which it can cool into the mold’s shape. This method is different from injection molding or blow molding in that it involves plastic products that are thin and planar rather than a single solid form, like nuts, bolts, and non-hollow parts. Thin-gauge thermoforming is used mostly on lighter plastic products like plastic cups, containers, and lids. Thick-gauge thermoforming can be used to create the plastic parts of cars like the inner car door and dashboard. The most common way of manufacturing thin-gauge products is by feeding a plastic sheet into a set of indexing chains, incorporating pins that pierce the plastic sheet. The sheet is then transported through an oven where it is heated into a forming temperature. Once through the over, the sheet is moved into a form station where a mating mold and pressure box closes in on the sheet. A vacuum is then applied in order to remove any air within the mold while simultaneously pulling the plastic material to the mold, forming the plastic sheet into the shape of the mold. After this, a reverse vacuum forces the formed parts of the plastic off of the mold. The plastic sheet is then moved to a trimming station where the remaining parts of the formed plastic are cut from the rest. The thermoformed plastic trimmed off of the formed parts are collected by a take-up reel or a inline granulator to be recycled. It is common for thermoforming companies to recycle the scrap plastic from their manufacturing process. This is done by compressing them into a granulator where it is ground into plastic flakes. The flakes are either sold or reused in the manufacturing process. There are different kinds of thermoforming molds: wood patterns, machined aluminum molds, cast aluminum molds, and composite molds. Wood patterns are generally used in the first stage of thermoforming. Machined aluminum molds are cut out of a solid block of aluminum, while cast aluminum molds are cast in a foundry. Composite molds are formed from filled resin and are a low-cost alternative to that of machined or cast aluminum molds. Thermoforming is a $10billion industry in the United States, with 25% of it comprised of thick-gauge plastic and 75% comprised of thin-gauge. Many of these companies cater to custom plastic molding.