1. The whole machine is sheet plate welded structure .To eliminate the internal stress, vibration aging technology is adapted. The machine bears the characteristics of high strength and good rigidity. 2. Double hydraulic oil cylinder is applied for upper transmission ,provided with mechanical limit stopper and synchronous torsion bar, typical of stable and reliable operation, as well as high precision. 3. Electrical control and manual fine-tuning mode are adopted for distance of rear stopper and stroke of gliding block ,and fitted with digital device ,easy and quick in use. 4. Upper die is fitted with deflection compensation device.