The spiral duct forming machine is used to produce the round rigid air duct for ventilation purpose, diameter from 80 ... The spiral duct forming machine ZHTF-1500I is used to produce the round rigid air duct for ventilation purpose, ... duct forming machine, ventilationd duct machine, spiral tube former, spiral duct former, ventilationd duct machine, HVAC duct machine, air duct machine. Spiral duct ...