Practical application of efficient and energy-saving extrusion technology in sheet metal production

Extrusion technology has been applied to thermoplastic plastics for over 80 years since 1935. With the rapid development of the chemical industry and the continuous emergence of new thermoplastic materials, extrusion technology has undergone multiple technological iterations. Its products are widely used in daily life, national defense and military industry, aerospace and other fields, with an increasing range of applications and output. With the large-scale rise of the plastic industry, the efficiency of its energy consumption has received more and more attention. High efficiency, energy conservation, large output, and automation are the three major focuses of attention in the plastic extrusion processing industry today, especially in terms of efficiency and energy conservation, which is in line with the national energy-saving and emission reduction policies. This article focuses on the practical application of high-efficiency and energy-saving Is there no way for us to go? Not entirely! The success of high-speed small screws abroad has given us great inspiration: taking a different pathmay help us overcome traditional misconceptions. Firstly, the new screw structure is very helpful for us to improve the existing screw design. Although it cannot achieve the same effect as foreign countries, many principles are well understood, such as the application of spiral feeding sleeves and high-efficiency BM structure screws, which greatly improve the existing screw technology, resulting in a significant increase in production and energy efficiency ratio. Secondly, in the field of single screw, although China may not be able to reach the level of foreign countries in the short term, no customer has forced us to use single screw for production. Their requirements are only high yield, efficiency, and quality standards. We know that for extruders, the more screws are built-in, the better their shear and ash removal effects, and the lower their overall energy consumption. This is extremely beneficial for the processing of certain plastic products. Based on this principle, twin-screw and multi screw extruders have been widely used in sheet metal production lines in recent years. Taking PET sheet processing as an example, using a twin-screw extruder instead of a single screw extruder can achieve excellent performance in raw material adaptability, feeding stability, and material exhaust and dehydration. Especially in feeding stability, it can cover almost all thicknesses of PET bottle sheet and recycled materials, greatly improving the adaptability of the equipment. In addition, due to the superior exhaust dehydration performance of twin screws compared to single screws, the viscosity reduction of PET can be well controlled during the plasticization process, thereby obtaining high-quality sheet products. At present, it is widely believed in the industry that some specifications of PET products (0.2mm-0.8mm) produced by twin-screw crystallization free equipment have reached or exceeded the sheet quality produced by traditional single screw extrusion production lines (with crystallization drying systems). Coupled with its excellent unit energy consumption and raw material applicability, this type of equipment has been widely used. Similarly, in the PVC rolling industry, planetary multi screw extruders have long been widely used, and their comprehensive efficiency is incomparable to traditional single screw and double screw extruders.

5、 Simplify raw material processing system through exhaust system

In the process of plastic processing, moisture and volatile matter have a great impact on the quality of the final product. Generally speaking, the less moisture there is, the more complete the volatiles are detached (de ashed), and the better the quality of the product. To achieve this effect, the raw materials often need to be dried and dehumidified before entering the extruder, but this process consumes a lot of energy. Taking PET as an example, for every ton of PET processed, traditional crystallization dehumidifiers consume 100-150 kWh of electricity, which accounts for a very large proportion of energy consumption. The exhaust technology of the extruder can greatly simplify the raw material processing system and reduce the energy consumption of raw material drying (or dehumidification). Both single screw and multi screw can achieve exhaust. In terms of structural principle, the more built-in screws there are, the better the ash removal and exhaust effect. Twin screw extruder is the most typical type of ash removal extruder, which can achieve multiple ash removal functions in certain special reactive extrusion processes. From an energy-saving perspective, the stronger the exhaust ash removal ability, the lower the requirements for raw material pre-treatment, and thus the more energy-saving.

6、 Replacing multi-step molding with one-step method

Some sheets require multiple steps to be processed using traditional techniques, such as multi formulation granulation and raw material treatment (such as drying and dehumidification) before extrusion. After extrusion, multiple processes such as multi-layer lamination, gluing, and printing are also required, resulting in high process costs. If the process steps can be simplified and a one-step molding method can be used locally, it can significantly reduce production costs and increase product competitiveness. In the field of sheet materials, the use of twin-screw production for PET sheets, the integration of PET sheet forming and vacuum forming, PVC table edge forming, and adhesive coating are typical cases that have achieved good economic and energy-saving effects.

At present, in China, the traditional sheet metal market has become saturated, profit margins have been decreasing year by year, and business risks are increasing. With the continuous increase in domestic labor costs, it has become a difficult problem that every industry must face, and it is particularly important in the plastic sheet industry. More than 95% of the heating and driving of sheet metal machinery rely on electricity, and there is a joking saying in the industry that "affordable equipment cannot afford electricity". They are typical power consumers, and increasing production and reducing unit energy consumption have a positive significance in improving product competitiveness, which is the goal we are striving to "squeeze out people".