There are various kinds of methods to produce pipes and tubes from metals are explained in Mechanicalland. After these production methods to produce tubes and hollow pipes, additional processes must be established to bend the tubes and pipes into desired shapes and angles. It may seem a very basic process but there must be some parameters that must be considered.
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Biggest Problem In Tube Bending Processes
In tube bending processes, the biggest problem is conserving the diameter at the bent section. While bending is applied to a tube stock, there is compression at the inner section and tension at the outer section of the bend radius. Because of these stresses, inner and outer surfaces at the bent section of the tube get flattened out. Because of this flattening, the inner section gets narrow which is not a desirable thing for tube and pipe fittings.
To prevent this flattening, the bend radius of the bending process must be 1.5x of the radius of the tube if the tube is bent without a die. If a die is used to bend the tube, 3.0x of the radius of the bending die must be established.
The thickness of the hollow tube is also a very important parameter. To calculate the effect of thickness, a factor is called the wall factor(WF) is added to the calculations. Wall factor is the division of the diameter of the tube(D) to the thickness of the tube(t). With the increasing thickness, the bending diameter required to prevent flattening increases.
Several Methods of Tube Bending Processes
The mechanisms that are used to bend the metal tubes are quite similar. The first one is the draw bending process.
In the draw bending process, tube stock is clamped around a rotating die via one stationary and one moving clamping unit. When the rotating die rotates, the movable clamping unit moves with it. With this mechanism, the required diameter tube is obtained.
If we take a look at the stretch bending process, straight tube stock is forced to stretch on a bending die by clamping at two ends.
In the compression bending process, tube stock is clamped at the top side of the die, bent by a movable clamp around the die to take the shape of the die.
These are the general aspects of the metal tube bending process and process parameters.
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