Publish Time: 2022-10-17 Origin: Site
This article introduces the features of the center feeding system of a twin-screw extruder in terms of quantitative feeding and mixing hopper material level control as follows.
The following is a list of contents
Twin-screw extruder equipment installation height reduction, easy maintenance
The strict control of dosing
Real-time control of material level by means of weighing and metering of the mixing hopper
Some solutions install most of the equipment such as the dosing feeder and mixing hopper at a high place, 6-13m above the ground, while the self-designed solution sets the dosing feeder at 2-3m above the ground and the mixing hopper at 5m. Therefore, the self-designed solution is better and is conducive to equipment maintenance. The reasonable design not only meets the process requirements of the system but also greatly reduces the engineering manufacturing and production operating costs.
The control of the hopper level and the characteristics of the dosing feeder determine that the hopper is fed in a batch mode. Therefore, each batch feeding of the mixing hopper will cause significant fluctuation in the material level. For continuous and stable feeding of the system, reliable automatic control of the hopper level is necessary.
The twin-screw extruder is designed for strict control of dosing. Once the material enters the screw, it is forced forward. When conveying tough materials or overfeeding, the material has no room to retreat and is prone to overload stopping accidents. When the material is not enough, the discharge is not stable. Therefore, the feeding of the twin-screw extruder needs to be equipped with an additional quantitative feeding device. So that according to the nature of the material, the size of the extrusion volume, strictly controls the feeding volume. This is also the key to the design of the feeding system scheme for twin-screw extruders in large BOPP film production lines, and the twin-screw extruder must be dosed quantitatively. Our system is designed with a loss-in-weight metering feeder to quantitatively feed the twin-screw extruder with an accuracy of 3-5‰. Moreover, the automatic control of the system synchronizes the feeding of the loss-in-weight feeder with the screw speed of the twin-screw extruder to ensure precise feeding at each instant.
The mixing hopper is weighed and dosed to provide real-time control of the material level, with normal and abnormal states converted according to the line breaking signal. When the material reaches a high level, the total amount of material supplied to the mixing hopper decreases by 5%; similarly, when the material reaches a low level, the total amount of material supplied to the mixing hopper increases by 5%. Keep the hopper level fluctuating in this range. In addition, set high and low material levels for alarm. Note that the loss-in-weight metering feeder should not change its setting parameters frequently and drastically, because after the parameters are changed, the feeder automatically corrects to a stable state, which requires a process of about 10 to 40s.
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