There are three forms of drum in structure

(1) integral cylinder
Processing method - in the overall material processing out.
Advantages - easy to ensure high manufacturing accuracy and assembly accuracy, can simplify the assembly work, the cylinder heat evenly, more applications.
Disadvantages - because the length of the barrel is large, the processing requirements are higher, and the requirements of the processing equipment are also very strict. The inside surface of the cylinder is difficult to repair after wear.
(2) combination of materials
Processing method - the cylinder is divided into several sections of processing, and then each section is connected with flange or other forms.
Advantages - simple processing, easy to change the length-diameter ratio, more used to change the screw length-diameter ratio.
Disadvantages - high requirements for machining accuracy, because of many sections, it is difficult to ensure the coaxiality of each section, flange connection destroyed the cylinder heating uniformity, increase the heat loss, heating and cooling system is difficult to set up and maintenance
(3) bimetal barrel
Processing method -- Insert or cast a layer of alloy steel material inside the matrix of general carbon steel or cast steel. It can not only meet the material requirements of the cylinder, but also save precious metal materials.
Bushing cylinder: The cylinder is equipped with a replaceable alloy steel bushing. Save precious metal, bushing replaceable, improve the service life of the cylinder. But its design, manufacture and assembly are complicated.
(2) Casting cylinder: centrifugally cast a layer of alloy about 2mm thick on the inner wall of the cylinder, and then obtain the required diameter of the cylinder by grinding method. The alloy layer is well combined with the matrix of the barrel, and the combination along the axial length of the barrel is uniform, neither the tendency of spalling, nor cracking, and sliding performance, high wear resistance, long service life.