It is a plastic injection machine on the whole blank. This structure can easily ensure high manufacturing accuracy and assembly accuracy, and can also simplify assembly work, facilitate the installation, assembly, and disassembly of the heating and cooling system, and the heat is relatively evenly distributed along the axial direction. Naturally, this kind of barrel requires higher processing and manufacturing conditions.
It means that a barrel is composed of several barrel sections. Plastic injection machine combination barrels for experimental extruders and vented extruders. The former is to facilitate changing the length of the barrel to adapt to screws with different aspect ratios, and the latter is to set up an exhaust section. In a certain sense, combined barrels are conducive to local material collection and processing, which is beneficial to small and medium-sized factories. But in fact, the combined barrel requires very high processing accuracy. The barrel sections of the combined barrel are often connected with flange bolts. This destroys the uniformity of barrel heating and increases heat loss. Setting up and maintaining the heating and cooling system is also inconvenient.
To not only meet the material requirements of the barrel but also save valuable materials, many barrels have an alloy steel bushing inside the base body of ordinary carbon steel or cast steel. The bushing can be removed and replaced after wear. The bushing and barrel must cooperate well to ensure the heat conduction on the entire barrel wall is unaffected. There should be no relative movement between the barrel and the bushing, and they must be easily removed. This requires choosing the appropriate fit accuracy of moulding plastic machine.
IKV Plastic Injection Machine barrel
A longitudinal groove is provided on the inner wall of the feeding section of the barrel:
To improve the solid conveying rate of moulding plastic machine, according to the solid conveying theory, one method is to increase the friction coefficient of the barrel surface, and another method is to increase the area of the cross-section perpendicular to the screw axis that the material at the feeding port passes through. Setting up a longitudinal groove on the inner wall of the feeding section of the barrel and making a section of the inner wall of the barrel close to the feeding port of the feeding section into a tapered shape are the embodiments of these two methods.
According to relevant information, the specific structure of opening a longitudinal groove or processing a taper at the feeding section of the barrel is as follows:
Under normal circumstances, the length of the taper can be (3-5) D (D is the inner diameter of the barrel). When processing powder materials, the taper can be lengthened to (6-10) D. The size of the taper depends on the diameter of the material particles and the diameter of the screw. As the screw diameter increases, the taper decreases (and the length of the feeding section increases accordingly).
Longitudinal grooves can only be opened in the section of the barrel before the material is still solid or begins to melt. The groove is about (3-5) D long and has a taper.
The number of grooves is related to the screw diameter. According to IKV, it is equivalent to about one-tenth of the screw diameter (cm). Too many grooves will cause the material to flow back and reduce the conveying capacity. The shape of the groove can be rectangular, triangular, or other shapes. The width and depth of the groove, which is rectangular in cross-section, are related to the diameter of the screw.
Forced cooling of the barrel in the feeding section:
To increase the solid transport capacity of moulding plastic machine, there is another method. It is to cool the barrel of the feeding section. The purpose is to keep the temperature of the transported material below the softening point or melting point, avoid the appearance of melt film, and maintain the solid friction properties of the material. After adopting the above method, the transportation efficiency increased from 0.3 to 0.6. Moreover, the extrusion volume is less sensitive to changes in die pressure.
However, this system also has the following shortcomings: strong cooling will cause significant energy loss; due to the extremely high pressure that may be generated at the end of the barrel feeding section (some as high as 800-1500 kg/cm2), there may be damage to the grooves. The thin-walled barrel is dangerous; screw wear is greater.
Shape and location of the feeding port:
The shape of the feeding port and its location on the barrel has a great impact on the feeding performance of the plastic injection machine. The feeding port should allow materials to be freely and efficiently added to the barrel without bridging. When designing, it should also be considered whether the feeding port is suitable for setting up a feeding device, whether it is conducive to cleaning, and whether it is convenient to set up a cooling system in this section. The shape of the feeding port (viewed from above) is round, square, or rectangular. Generally, rectangular ones are used, with the long side parallel to the axis of the barrel, and the length is about 1.5-2 times the diameter of the screw. Daoben is a professional manufacturer of plastic injection machine.