Duct machine:Auto-line III consists of a metal feeding frame, leveling and grooving equipment, hydraulic punching square notch equipment, hydraulic cutter and folder. The electrical control system uses a computer with a closed-loop and feedback system to increase the precision and reliability of the manufacture line. The maximum working speed is 10m/min. The length tolerance is ±0.5mm. The diagonal line tolerance is ±0.8mm. One team will produce 1000m2 of square duct by using this system.