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Extruder Screw Barrel and Elements
Extruder Screw Barrel and Elements
The proper selection of extruder screw barrel and element configuration is a critical component of the design. These components have a direct impact on the functional performance of the extruder. These two components also affect the plasticization capacity. There are many different design options, and you may have multiple barrel section and element combinations. Your final selection will likely be governed by availability, flexibility, and economics. This article discusses the basic characteristics of these components.
When determining the exact size of the extruder screw barrel, you should consider the size of the plastic that you plan to process. A large screw barrel will prevent your plastic from overheating, and a smaller barrel will prevent the product from separating. The diameter and length of the extruder screw barrel should be equal to the feed material's inside diameter. The diameter of the plastic screw barrel and the length of the barrel should be roughly proportional to each other.
A long, thin, or angled barrel is best for high-speed plastic extrusion. A longer barrel will reduce the pressure and prevent breakage. Generally, the length of an extruder screw barrel should be at least 70% of its total length. The first part of a vented extruder screw barrel is a standard three-zone screw. The second section is deep, and it will relieve melt pressure. The liquid then moves downstream through the metering and mixing section and through a die.
The screw barrel must have a high heating rate to reach the temperature required for plasticization. The barrel should also be able to meet the heat required for plasticization. The heating time for a small machine is usually less than 30 minutes, while large machines require up to an hour. In order to prevent the plasticizer from overheating, a cylinder cooling channel is arranged with a heat exchanger and a stainless steel water tank. The cooling effect is achieved by controlling the flow of water through a solenoid valve.
The extruder screw barrel must be designed to meet the temperature requirements for plasticization. Depending on the size of the machine, a large-scale machine may need up to a day to achieve this temperature. A small-scale machine may only require a single hour, while a large-scale one can require up to a year. However, a small-scale extruder may be used with several different materials.
The screw barrel of an extruder should be durable. It should be made from durable materials and have a low temperature rating. The screw barrel must have a constant depth. The screws are not interchangeable. If the screws are installed one by one, the barrel will not function properly. When the screws are assembled, it will be easier to replace them as they wear out. They will also allow for the possibility of assembling various combinations of different type of screw configurations.
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