9. Tearing.

This is what exactly a mandrel bending machine can do. The mandrel bending is a comparatively precise process using with the mandrel and wiper die, which can produce very few deformations in tubes or pipes. It is capable of bending thin materials to a closer radius than they could normally sustain without breaking or deforming. A flexible, internal mandrel is inserted into the tube shaft at the angle where the tube will be bent. This mandrel prevents the interior from unintended deformation during bending workpieces.  

Figure 1   Mandrel bending diagram

An aluminum-bronze alloy or solid steel insert that supports the pipes or tubes while it is being bent. This common technique keeps the tubes from collapsing, flattening or wrinkling during the bending process. A mandrel also helps to ensure accuracy of the end product by maintaining the shape of the tubes.

Figure 2   Mandrel and dies


Which material pipes need mandrels? A softer metal like copper or brass requires more support during bending than a stronger alloy like stainless steel. Similarly, tubes with a thinner wall is more susceptible to kinking or breakage than one with a thicker wall. Bends with a small radius need the extra support of a mandrel.
Overall, a mandrel is the key to achieving accurate and precise bends. It also extends the life of the toolings, and helps minimize the wear and tear on the bending machine.