Based on the free bending forming principle of spatial tube fittings

the formed tube fittings are divided into stable section and transition section

and the forming process of the two sections are analyzed respectively to obtain the free bending forming process strategy of spatial tube fittings. For the stable section

the mapping relationship between the bottom circle radius and pitch of the space spiral tube and the bending die offset and the clamp torsion speed is analyzed

and the forming process parameters of the space spiral tube are predicted by BP neural network. Through the test

it is found that the maximum relative error between the predicted value of the bending die offset and the numerical simulation test is 1.08%

and the maximum relative error between the predicted value of the clamp torsion speed and the numerical simulation test is 3.4%; For the transition section

the effects of the bending die offset and the loading mode of clamp torsion on the forming of spatial tube fittings are studied by orthogonal design experiment. It is obtained that the loading time of bending die and clamp in the transition section is 0.9 s. Combined with the above analysis

the acquisition strategy of tube free bending process based on primary equivalent approximation and secondary optimization is established

and its feasibility and effectiveness are verified by an example.