The barrel and screw form the extrusion system of the Injection Moulding Machine. Like the screw, the barrel is also operated under high pressure, high temperature, severe wear and certain corrosive conditions. During the extrusion process, the barrel also has the effect of transferring heat to the material or transferring heat away from the material. A heating and cooling system is also installed on the barrel to install the head. In addition, the feed port is to be opened on the barrel. The geometry of the feed port and the choice of its position have a great influence on the feeding performance. The smoothness of the inner surface of the barrel and the opening of the inner wall of the feeding section have a great influence on the extrusion process. The above factors must be considered when designing or selecting the barrel.
First, the barrel structure
In terms of the overall structure of the cartridge, there is an integral cartridge and a combined cartridge.
(1), the overall barrel
It is processed on the whole billet. This structure is easy to ensure high manufacturing precision and assembly precision. It can also simplify the assembly work of the Plastic injection machine, facilitate the installation and assembly and disassembly of the heating and cooling system, and the heat distribution along the axial direction is relatively uniform. Naturally, the barrel requires high requirements. Processing and manufacturing conditions.
(two), combined barrel
It means that a cylinder is combined by several barrel segments. Experimental extruders and vented extruders use a combination of cartridges. The former is to facilitate the change of the length of the barrel to adapt to the screw without the aspect ratio, the latter is to set the exhaust section
Second, the material and strength calculation of the barrel
(1), barrel material
Just like a screw, in order to meet the working requirements of the barrel, it must be made of high-quality materials with high temperature resistance, wear resistance, corrosion resistance and high strength. These materials should also have good machinability and heat treatment properties. In addition to 45 gauge steel, 40Cr, 38CrMoAL, the cylinder can also be made of cast steel and ductile iron.
(B), the decision of the wall thickness of the barrel
1, the decision of the wall thickness of the barrel
The barrel is rarely scrapped due to insufficient strength, mainly due to corrosion and wear. The decision of the wall thickness of the barrel, in addition to considering the strength, is more considering the processability and thermal inertia of the barrel structure. The wall thickness determined by the latter two factors is often greater than the value calculated by the strength condition.