The right threaded element is mainly used for the transportation of materials. The shape of the screw groove of the right thread element of the double screw extruder can be rectangular or other shapes. At present, the spiral groove shape is mostly used.
The shape of the left thread element is similar to the shape of the right thread element, except that the spiral direction of the screw groove is opposite.
Since the left thread of the two screw extruder conveys the material in the opposite direction, and the normal thread conveys the material in the extrusion direction, the material builds a high pressure in front of the entrance of the left thread section to overcome the resistance caused by the reverse flow in the left thread. The material is conveyed left through the gap of the reverse thread.
In a double screw extruder, sometimes according to the needs of the extrusion process, different pressure zones should be formed at different positions in the axial direction of the screw or within a relatively short distance (the pressure difference is sometimes as large as several MPa). At this time, left thread elements can be used to achieve this purpose.
For example, add liquid additives or foaming agents at a certain position in the axial direction of the double screw extruder machine. The addition position must be in the low-pressure zone. At this time, a counter-threaded element is set before the addition zone to form a high-pressure seal to prevent liquid additives or foaming agents from flowing in the reverse direction. And a low pressure area is formed behind the reverse thread element to facilitate the addition of additives or foaming agents.
A left threaded element is installed in front of the exhaust port, which can form high pressure before the exhaust area, and suddenly reduce the pressure in the exhaust area to facilitate exhaust. The pressure drop in the left thread of the double screw extrude. The left thread element itself has no forward conveying capacity, and the forward conveying of the material is at the cost of pressure loss.
The pressure drop of the left threaded element is an important factor that must be considered when designing and selecting this element. The left thread element of the double screw extruder is a resistance element. When the pressure increases, a right thread conveying element should be set in front of it to overcome its resistance and convey the material to the die. One pressure peak will appear when one section of left threaded components is added, and two pressure peaks will appear when two sections of left threaded components are added; and so on, multiple left threaded components can be set as needed.
KY CHEMICAL is currently the largest manufacturer of parallel co-rotating double screw extruders in China and Asia, with an annual output of 250-450 units. More than 8,000 extruder systems have been installed worldwide, covering the chemical, plastics, textile, food and pharmaceutical industries. If you have any needs, please feel free to consult.
Tel: +86-25-52706155
E-mail: info@kymach.com
No.59 West Tianyuan Road, Jiangning, Nanjing, Jiangsu Province, China
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