The hook part of the tensioner die hook 3 and the shoulder of the table on the 2nd movement mode 21 are close to each other, and the 2nd movement mode 2 moves by moving the 1st movement mode 2 and demoulding. Since the hook 3 moves to the end of the restriction block 13 and loses the support of the restriction block 13, the steel wire tensioner hook 3 opens under the elastic force of the torsion spring 31, causing the hook part of the hook 3 to leave the shoulder of the table on the second motion mode 21 and the hook part of the hook 3 leaves the shoulder of the table on the second motion mode 21. Leaving the one motion mode 2 and the second motion mode 21, the second motion mode 21 continues to move, causing the one motion mode 2 to remain stationary, thereby extracting the mandrel 5 from the workpiece for secondary demoulding.0018 The above recited is only an embodiment of the utility model, and common knowledge of the specific construction and features known in the scheme is not much noted here. For a person skilled in the art, several deformations and improvements can be made without departing from the structure of the utility model, and these should also be regarded as the scope of protection of the utility model.