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Injection molding machine parts - double alloy barrel analys

Article source:未知 Clicks: Pubdate:2017-11-05
Cylinder, also known as the barrel, is an important part of injection molding machine parts, which together with the screw to complete the plastic conveying, plasticizing and injection processes, but also other devices (heaters, cooling devices, hoppers, metering Device, etc.).

Cylinder generally made of the overall structure. There is a certain clearance between the inner hole of the barrel and the screw, and the heating and cooling device is externally installed. The barrel is installed on the injection seat, that is, the hopper seat, and the front end is connected with the nozzle.

1, feeding barrel in the form of feeding mouth. As the majority of injection molding machine using gravity feeding and forced feeding form, feeding port cross-sectional shape must ensure that feeding capacity. In order to increase the delivery capacity, the feeding port should try to increase the screw material area and the screw and barrel contact area. The cross-sectional shape of the feed opening can be symmetrical or offset. Symmetric feeding port is small, easy to manufacture, delivery capacity is low, bias feed port suitable for high-speed screw feed, have better transport capacity, but the manufacturing difficulties. When using the spiral forced feeding device, the shape of the feeding port should be symmetrical and circular in plan view, while the gravity feed should be biased.
2, barrel wall thickness. Barrel wall thickness to ensure that the cylinder withstand the melt and gas pressure sufficient strength. At the same time also have a certain thermal inertia, in order to maintain the temperature stability. Cylinder wall is too thin, although the heating up fast, light weight, save material, but vulnerable to changes in the ambient temperature, poor process temperature stability. Cylinder wall too much not only bulky structure, and slow heating, thermal inertia, Temperature regulation process is easy to produce more serious hysteresis, is not conducive to adjustment. General diameter and diameter ratio of 2-2.5.
3, barrel and screw radial gap.This gap that is the difference between barrel bore and screw diameter, known as the radial gap.If the gap is too large, the material plasticization quality and plasticization ability to reduce the time of injection If the gap is too small, it will bring great difficulty to the machining and assembly of the barrel and the screw.
4, Barrel heating and cooling Barrels are widely used resistance heating ribbon heater, cast aluminum heaters, ceramic heaters, etc., because the resistance heater is small, easy to manufacture and maintain.

In order to meet the processing temperature distribution requirements, the need to barrel heating segment control.Generally divided into 3-5 sections, each section of about 3-5 screw diameter.Temperature control precision is generally not more than 5 degrees on the heat-sensitive materials The best not more than 2 degrees. In the compression section, should be equipped with a larger heating power of the heater material plasticization process, the smaller the heat of shear, under normal circumstances, the barrel is not set up a separate cooling device, thanks to natural cooling . In order to maintain a good feeding and conveying role, to prevent the heat transfer barrel to the transmission part, set in the feed inlet cooling water jacket cooling heat.  

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