Dahan's heavy lift cranes including hammerhead tower crane, flattop tower crane and luffing jib tower crane, and building hoists are manufactured using cutting-edge manufacturing technologies and processes covering welding, machining and shot blasting.
Robotic welding can effectively improve safety. 60% welding is completed by robot welding system. The system can automatically adjust welding angle, ensuring high precision and flat and smooth weld joint. It can also adjust current automatically, thus allowing high weld penetration. In addition, robot welding comes with high stability in that robot is emotionless. Gas for welding is a mixture of argon and carbon dioxide. This enables a perfect weld appearance and stability.
Perfect machining process can also enhance safety. The mast section main chords and adapter sleeves will experience end face machining after welding, enlarging contact area with the mast and thereby making the mast more stable. Jib connections are solid forging parts that go through milling, broaching and galvanizing processes, dramatically improving strength and integrality. Mast section connecting plate and ladder step plate feature 45°chamfering process which can greatly increase welding strength.
CNC drilling and milling machines are used to process upper and lower slewing platforms as well as slewing bearing connecting hole and surface, ensuring the compatibility with slewing bearing. CNC boring machine is used to process the location hole of reducer on upper slewing platform. This ensures small gear of reducer can mesh the slewing bearing and the assembly of slewing bearing is more precise.
Shot Blasting and Spraying Process
Large structural parts employ shot blasting process to remove rust before surface spraying treatment. It can effectively remove oxides and welding spatters on the steel surface, eliminate internal stress of work pieces caused in welding and strengthen fatigue resistance and steel surface hardness. Acrylic acid paint specially used for construction machinery is chosen for spraying. After rust removal and spraying, we will enforce strict film thickness test.