How to solve the problem of PVC centralized feeding?

Published Time:

2022-12-22

Currently, with the increasing proportion of labor management costs and energy consumption costs in the production costs of Chinese enterprises, and the impact of environmental pollution on healthy development, how can we improve the intelligent feeding process of PVC powder raw materials in PVC centralized feeding extrusion production lines?

Currently, with the increasing proportion of labor management costs and energy consumption costs in the production costs of manufacturing enterprises in China, as well as the impact of environmental pollution on healthy development, how can we improve the intelligent feeding process of PVC powder raw materials in the PVC central feeding extrusion production line?

PVC Central Feeding Issues

I. Problems

1. The PVC raw materials in the extruder hopper of the extrusion unit can be transported to the extruders of many enterprises through a spiral structure via a tube chain or long-distance transportation. High-quality and low-quality level switches are set on each extruder hopper. Once a lack of material is detected in the hopper, the conveyor is required to start feeding immediately, which will lead to frequent start/stop of the conveyor, greatly improving the stability of the teaching equipment.

2. In addition, once one of the low-level switches fails, the extruder will not be able to shut down. Once the high-level switch fails, the conveyor will jam due to continuous operation.

In traditional extruders, PVC central feeding generally adopts a quantitative parallel conveying method. The PVC powder in the extrusion hopper changes greatly during consumption. During the discharging process, "punching" and discontinuous discharging (bridging) are prone to occur, which makes the extruder screw easy to twist and break. More importantly, the uneven quantitative feeding of plastic products after extrusion molding has led to serious quality problems of uneven product wall thickness.

II. Technical Points

A programmable controller is used to collect the start and speed signals of each extruder main motor downstream of the entire tube chain, and then perform numerical calculation on the speed signal of each extruder. The required feeding amount for each production line is calculated according to the feeding amount, and then the feeding amount is converted into the speed of the tube chain. The speed of the tube chain is adjusted in real time to control the feeding amount of the extruder. That is to say, when the speed of the downstream extruder main motor suddenly increases or the operating capacity of the extruder increases, the feeding system will immediately detect the change in speed and the increase in feeding capacity, thereby increasing the feeding speed. Conversely, when the speed of the downstream extruder main motor suddenly decreases or the operating capacity of the extruder decreases, the feeding system will correspondingly reduce the feeding speed, and the conveying speed of the tube chain will also decrease accordingly. In addition, the feeding system also reads the current and torque parameters downstream of each extruder. When the extruder exceeds the torque alarm, the PVC central feeding system will automatically close the feed port of the corresponding tube chain conveying tube of the extruder, stop feeding, and not increase the feeding amount of the extruder, thereby reducing the output torque of the extruder and effectively protecting the extruder screw. In addition, when conveying powder over a flexible long distance and multiple machines, a unique redundant pressure relief mechanical design is also adopted to ensure that even if most of the hopper extruders are full of materials, the "scraper" powder pressure generated during the chain operation can be effectively released without leakage in special circumstances.

By real-time collection of key data from all downstream extruders, dynamic uninterrupted operation, and timely adjustment, a series of problems caused by traditional quantitative intermittent feeding can be effectively solved, such as "feeding" and "blocking" of extruder hoppers, easy breakage of extruder screws, unstable extrusion of PVC extruders, and high failure rate of the PVC central feeding system itself.

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