Although there are pipe bending multiple methods available, most fall into one of two categories:
Cold bending
Hot bending
Each method has unique benefits and will determine the degree of bending possible and the final shape of the pipe.
COLD BENDING METHODS
Rotary Draw Bending: Pipe or tube is bent using a combination of dies and other various components working in a rotary action. This action draws the pipe or tube forward making the desired bend. Rotary draw bending can also utilize mandrels.
Mandrel Bending: A mandrel is placed inside the tube or pipe that is being bent, especially with thinner wall materials, to prevent defects that can occur in the piece’s bend such as rippling, flattening, or collapse.
Compression Bending: Bending a pipe or tube using a stationary die while a counter die bends the material around the stationary die.
Roll Bending: Used when large radius bends or curves are required, this method passes a piece of pipe or tube through a series of three rollers in a pyramid configuration to achieve the desired curve.
HOT BENDING OR INDUCTION BENDING
Although the bending methods of different heat pipes are slightly different, they are almost a form of induction bending.
This method of heating pipes precisely uses induction heating coils before applying pressure to make the desired bend.
It requires less physical force than the cold bending method and can produce bending of similar or higher quality without the need for filler materials, mandrels, or other additional materials used to avoid deformation.
Although it minimizes the diameter at the bend, induction bending causes some variation in tube thickness.
Normally, the curved inside will be thicker and the curved outside will be thinner. This method is most commonly used for large diameter pipes and long radius curved pipes. However, it is also used for smaller pipe diameters and short radius bends.