A soft bending pipe is widely used for freezing equipment and shipbuilding. This pipe has some problems such that outside wrinkle, crack, phenomenon of thinning wall. However, the bending machine that can completely solve the problems is not yet. In this study, we have manufactured the self-made mandrel to guarantee both roundness and thickness of the pipe in the bending process for a soft pipe such as a copper pipe. The mandrel consisted of a ball, stick and connection pin. Also, we have manufactured the bending machine that can decrease friction between the pipe and the bending die. The experience was tried to verify the performance of the mandrel and the pushes to the thickness guarantee of the pipe.
A pipe bending process is widely used to manufacture the pipe of various forms and standard in various fields such as the weld pipes of the piping for architecture, refrigeration, air-condition, vehicle, shipbuilding. Because the pipe bending process can manufacture a suitable form by the pipe without producing a mold. The pipe used in a refrigerator or a heat exchanger is soft pipes such as a copper and an aluminum pipe. The soft pipe is need to exchange heat circulating refrigerant and outdoor air. It is one of the key components of a refrigerator. But most of the pipe bending process is used the bending machine consist of a bending roll, a clamp, a slide bar in the manufacture of the bending pipe . this pipe bending process has a residual stress by the plastic deformation of the pipe, so the residual stress is a major cause of the pipe break due to fatigue. Especially, the phenomena likes as a visual wrinkle, spring back, ovalization are often happened during the pipe bending process. However, there is few research on the bending machine which can control precisely the soft pipe during the pipe bending process.