In order to prevent or reduce the defect of bending pipe and bend pipe fitting to meet the requirements, corresponding countermeasures should be taken to solve the problem in the process of bending pipe. Within the allowable range of product design structure, the bending radius should be designed as large as possible. For several common defects mentioned above, targeted measures should be taken.

1. For pipe fittings with severe flattening on the outside of the arc, the pressing die can be designed into a structural form with an inverse deformation groove when conducting coreless bending to reduce the flattening degree during bending. For the core bend, the wear of the mandrel should be checked in time to ensure that the unilateral gap between the mandrel and the inner wall of the pipe is not more than 0.5mm. At the same time, the advance amount of installing the mandrel should be appropriate.

2, for the pipe arc external bending, should first ensure that the pipe has a good heat treatment state, after excluding the factors of the pipe, check whether the pressure of the pressing die is too large, and adjust the pressure to be appropriate. Check whether the mandrel diameter is too large, the diameter should be repaired, and ensure that the mandrel and the inner wall of the tube have good lubrication, and take appropriate measures to avoid machine shaking.

3. The characteristics of the bending process when the arc is thinned outside the small radius bend are inevitable, but measures should be taken to overcome the excessive thinning. The common effective method is to use the elbow with a booster on the side and a pushing device on the tail. When WORKING, THE PUSHING OR PUSHING MECHANISM PUSHES THE PIPE forward, OFFSETS PART OF the RESISTANCE OF the pipe bending, improves the stress distribution state on the pipe profile, AND moves THE NEUTRAL layer outward, so as to achieve the purpose of reducing the amount of thinning on the outside of the arc. The boosting and pushing speeds are determined according to the actual situation of the bend to match the speed of the bend.

4. For wrinkling inside the arc, corresponding measures should be taken according to the wrinkling position. If the cutting point before wrinkling, the position of the mandrel should be adjusted forward, so that the mandrel is raised appropriately, and the reasonable support of the pipe is reached when the elbow is bent. If the cut point is wrinkled, it should be installed fast, and make its installation position correct, but also adjust the pressure of the pressing module is appropriate pressure; If the inner side of the arc is all wrinkled, in addition to adjusting the pressing die to make the pressure appropriate, but also check the diameter of the new rod, the diameter is too small or serious wear should be replaced with the mandrel.

Therefore, in view of the specific analysis of the reasons of different types of defects, and how to take corresponding measures according to different conditions, such as adjust the position between each mold piece and stress, choose suitable mandrel, good lubrication, add blank mould and boost installation etc, all can reduce to eliminate defects, resulting in better bending pipe fittings. To sum up, in the process of bending pipe fittings, different types and degrees of defects may occur in the bent pipe fittings due to improper technology and operation, etc., especially when the bending radius of pipe fittings is small and the positions and forces between molds are not matched, the possibility of defects is greater.