... duct forming machine ZHTF-1500II is used to produce the round rigid air duct for ventilation purpose, diameter from 100-1600mm.Feature1. Special aluminum ... -62 Key words: ZHTF-1500II spiral tubeformer, spiral duct forming machine, ventilationd duct machine, spiral tube former, spiral duct former, ventilationd duct machine, HVAC duct machine, air duct machine. automatic spiral duct former machine