Plastic bending usually involves changing the shape of sheet plastic or incorporating angles into rigid plastic tubing for specific applications. Bending usually requires heating the plastic until it is pliable, then producing the number of bends necessary. This can be done manually or by an automated plastic bending machine. Plastic materials commonly used in the bending process include those manufactured from acrylic, polyvinyl carbon, or styrene.
Both small and large manufacturers use electric line or strip heaters for plastic sheet bending. The heater contains a specially designed heating element that runs along a straight line for the desired length. The heat produced by the element may be anywhere from 500 to 900 degrees Fahrenheit (260 to 482 degrees Celsius). Most heaters have a regulator that allows the machinist to adjust the heat intensity based on the thickness of the plastic. The line heater generally lies in a thermally protected channel at a depth lower than the table holding the plastic sheeting.
Depending on the type of plastic products a manufacturer produces, heating line elements might be adjustable on certain machines, situated in a channel anywhere within the plane of the plastic sheet. With the elements turned on, the plastic heats along the line created by the element. After reaching the desired temperature, the plastic becomes pliable enough to accept a bend. In this state of deformation, workers usually place the plastic sheet in a holding area that maintains the bend until the plastic cools. While some plastic bending machines merely heat the plastic, others heat, bend, and cool the product.
Plastic tube bending also usually involves heat, but the process might occur in a manufacturing factory, on a construction job site, or in a personal workshop as part of a do-it-yourself project. Manufacturers generally have large automated machines that process a number of pipes at one time. The machine heats the tubing at the appropriate place, applies the proper degree of bend, and cools the finished product.
While on the job, a plumber might require tubing with more than one specific bend. Tubing might be required to bend around a spa or to conform to other spatial requirements, but many professionals prefer the durability of rigid polyvinyl carbon tubing as opposed to flexible tubing. Achieving the proper shape, however, often requires heating the entire length of tube. Once heated, the plastic becomes spongy and can be bent as it is installed.
Hobbyists might use a mandrel or a combination of heat and a mandrel for plastic bending tubes. Mandrel bending involves inserting something into the tube, which ensures the internal integrity of the pipe during bending. Common materials used for mandrel bending include metallic flexible tubes or sand. Once the plastic tubing is bent, the mandrel is removed. Heated sand may be used in a thermal type of mandrel bending process, the heat making the plastic pliable and the sand maintaining the tubing shape.