Application status and development prospects of domestic extrusion equipment

In addition to the increase in the output of the main engine, the auxiliary engine capacity has also reached a very high level.

The comparison data shows that the domestic output of the single extruder of the domestic extruder is less than 60% of the foreign advanced level, and the production speed of the auxiliary engine is less than 50% of the advanced level of the foreign countries. Although the price of domestic equipment is only one-fifth to one-tenth of that of imported equipment, due to the large gap between the single-machine production speed of domestic plastic machinery and foreign countries, the consumption of unit-weight products in production energy consumption and staff salaries has increased significantly. Therefore, in many occasions, domestic equipment does not have an advantage in cost performance.

(2) Gaps in molding accuracy

With the rapid increase in the variety and quantity of plastic products, people are increasingly demanding the geometric accuracy and intrinsic performance uniformity of extruded products. The main way to improve the precision of extruded products is to overcome various fluctuations in the extrusion process through machinery, processes and advanced control measures. To achieve precision extrusion molding, on the one hand can meet some of the strict requirements on the geometric size and shape and molding process conditions of the molding requirements of the product, but also the basis for high-speed extrusion molding.
Japan's Itochu TEXMAC Co-Extrusion Double-lumen Catheter The medical catheter production equipment consists of three extruders, which are molded with two lumen catheters and an outer sheath tube, and the inner lumen catheter is molded and sheathed with an outer sheath. Compounding is done once in a set of molds. In order to ensure the stability of the duct geometry, the three extruders are equipped with a melt gear pump, while the tractor is driven by a servo motor. The in-line tester monitors the geometry of the catheter at any time to provide the necessary data for the closed-loop control system. The device can produce various shapes of medical catheters by changing the mold.

US PEI (Precision Extrusion Inc.) precision extruders for the production of medical catheters, the use of special design and manufacturing technology, and statistical process control (SPC) technology, making the extruder temperature deviation can be controlled at ± 1 °C, the pipe wall thickness deviation can be controlled within 2%. In contrast, the domestically-manufactured extrusion equipment usually has a temperature control accuracy of 5°C to 10°C, and the wall thickness deviation of the pipe is more than 10%, which cannot meet the requirements for producing high-precision products such as medical catheters and optical fibers. Such high-precision extrusion equipment currently relies mainly on imports.

(3) Gaps in production efficiency

Domestic extrusion equipment is limited by the design and processing level, and there is still a big gap between production efficiency and foreign products. Table 3 shows the data of the single-screw extruder's specific output. The specific output is the increment of the extrusion output per 1 r/min of the screw speed. This parameter reflects the plasticizing and conveying capacity of the extruder plasticizing system.

Table 4 shows the specific energy consumed by foreign extrusion equipment to process different polymers, and the specific energy directly reflects the high energy consumption of the processing process. The specific energy of domestic equipment is generally higher than the value in the table, mainly because the single output of domestic equipment is too low. Low output of single machines will not only increase energy consumption, but also increase labor costs, which will increase production costs of products.

(4) Gaps in the level of measurement and control

The level of plastic processing equipment depends largely on the level of measurement and control. The control system of foreign advanced plastics machinery generally adopts a programmable system with PC, PLG, PCC as the core, and adopts fuzzy control, statistical process control (SPC) and remote monitoring based on network on some high-precision production equipment. , fault diagnosis and control systems.

Advanced online measurement systems based on infrared, laser, ultrasonic, electromagnetic induction, and high-energy ray measurement principles provide the necessary conditions for the precise control of plastics processing. In terms of advanced measurement systems, China basically relies on imports.

(C) Development Prospects of Extrusion Equipment

Extrusion equipment is moving in the direction of high speed, precision, efficiency, and green.

High speed

The main way to increase the output of the extruder is to use an efficient plasticizing system and increase the screw speed. The screw speed of foreign parallel twin-screw extruders has reached 1500r/min, and the screw speed of single-screw extruders has also increased. As the speed of extrusion molding is mainly dictated by the speed of the production of the extrusion molding auxiliary machine, the speed of the extrusion molding auxiliary machine should be maximized, including the fiber cooling setting system, the high-speed tractor, and the high-speed cutting machine. In order to achieve high-speed extrusion molding, high-speed extrusion molding molds should also be developed, and online measurement and closed-loop control systems should be adopted.

Refinement

In the traditional concept, extrusion molding is an efficient and low value-added plastic processing method, but the development and application of precision extrusion molding technology will change this state, see Table 5. The formation of precision products can bring high added value, and can even play a role of gold. In the case of medical plastic catheters, the prices of precision products such as dialysis tubes, artificial blood vessels, and stents for interventional use are generally hundreds of times higher than the value of their raw materials, and some are more than 10,000 times higher.

Precision extrusion equipment is a prerequisite for the production of precision extrusion products. The development of precision extrusion equipment will bring tremendous business opportunities and substantial profits to plastic machinery manufacturers. At present, the value of precision extrusion equipment is more than 5 to 10 times the price of general extrusion equipment. China's precision extrusion equipment is still in its infancy and has a lot of room for development.

Efficient

The main technical way to improve efficiency is to increase the extrusion speed without increasing the specific extrusion energy, and also to increase the degree of automation of equipment to reduce labor costs. Krauss Maffei Germany successfully developed a vacuum sizing system for automatically changing the diameter of the pipe, which can complete the conversion of the diameter of the pipe in a few minutes. The system and the corresponding extruder head reduction system can be used to reduce the replacement of the extruder. Specifications waste raw materials and save time and power consumption.

Green

Greenization mainly includes the following ways:

Low energy extrusion technology, such as the development of low temperature, low pressure extrusion technology;

Non-toxic materials technology, such as the use of non-lead PVG thermal stabilizers, halogen-free flame-retardant materials, etc., it is necessary to develop the extrusion molding equipment and process technology;

Degradable plastic products processing equipment and technology;

Wood plastic extrusion molding technology. (Text / Wu Daming)