Many buyers will consider this question, so do you need a mandrel?Let's first understand the mandrel, what is the mandrel? Figure 1 is a collection of pipe bending machine molds. It can be seen that in addition to wheel molds, guide molds, clamping molds, and mandrels (red) are also included.

Figure 1: Mandrel

Its main function is to support the inner wall of the pipe when bending with the pipe bending machine to prevent deformation and other problems. In order to use the machine normally, a core rod (green) will be equipped. The rod is sent to the position where the head is bent.
There are many kinds of mandrels, such as cylindrical mandrel, universal one-way, double, three and four ball head mandrel, directional single, bowl type ball mandrel, caterpillar mandrel, multi-ball head mandrel, etc. Generally, a single-ball or multi-ball mandrel can be used. So what's the difference between using a mandrel and not using a mandrel? Make a comparison below. Figure 2 is a comparison of pipe fittings without mandrel and mandrel.

Figure 2  Influence of the mandrel 

It can be seen that if the mandrel is not used, the inner wall will collapse when the pipe is bent, which will affect the appearance. Therefore, it is recommended to use a mandrel for products that have requirements on appearance.

So do all exterior parts need mandrels? Not really! If the wall thickness of the pipe fitting is thicker and the structure is not easily deformed, it is not easy to deform. At this time, the use of the mandrel will not only have no substantial effect, but also cause the pipe fitting to break due to the transition restriction. Therefore, for uncertain situations, it is recommended to communicate with the machine manufacturer to see if it is necessary.

The above is the analysis of the mandrel. If your product is an appearance part (such as tables and chairs) and the pipe wall is thin, we recommend using a mandrel, or your product needs to be reprocessed to meet the assembly requirements. If only ordinary parts do not have much requirements for appearance, or the wall thickness of pipe fittings is moderate, consider not using mandrels.