1.Purpose and Application
Trommel screen is an important equipment for material screening and classification. It is widely used in metallurgy, mining, construction, municipal waste and other industries.

2. Structure and Working principle
The working principle of the trommel screen: the device is supported by four groups of supporting wheels, the power is transmitted to the drum through the transmission member, and the roller rotates passively on the roller to complete the screening operation.
3. Problems in the manufacturing process
It is not difficult to see from the working principle of the trommel screen that ensuring the coaxiality between the two rolling rings and the transmission parts is the most important part in the production of the trommel screen. The low precision of the coaxial manufacturing will result in the reduction of the matching precision of the transmission parts, accelerate the wear rate, shorten the service life, and during the rotation process the drum would oscillate and cause deformation, which makes it difficult to replace the screen plate, and increase the maintenance cost, what’s more, breaking the welded structure, shorten the life of the drum screen at last.
The design of the trommel screen is mostly integral welded structure, especially in the process of manufacturing large welded drums, there is no reliable reference, and welding deformation during the welding process, thus it is very difficult to ensure the coaxiality between the raceway and the raceway, the raceway and the transmission member, and the manufacturing precision is unstable.
 4. Structural improvement
According to the structure and working principle of the trommel screen, the design of improving it is proposed: (1) splitting the large welded structural parts into several small unit members to reduce the production process; (2) Machining the small unit structural parts, and ensuring the manufacturing precision by mechanical processing; (3) assembling the units together with rivets or bolts.
After the splitting, the following measures should be taken to ensure the production accuracy: (1) each member is separately welded and formed; (2) each unit group is subjected to stress-relieving after welding to eliminate welding stress; (3) after stress treatment, each unit is separately send to machine tool processing to ensure that the dimensions and shape tolerances meet the drawing requirements.
5 Conclusion
After the improvement, the trommel screen is divided into several small units, and the large welded structural parts into small unit structural parts, and the structural parts are made less difficult; and the units are assembled and processed together, the structure of the trommel screen is changed by the welded structural parts. The units are assembled together after processing, and the structure of the trommel screen is mechanically processed by the welded structural parts to ensure the production precision and stable quality.