?Extrusion is both an efficient, continuous, low-cost, adapt to wide processing molding method, but it is also a low-precision, low-value-added molding processing plastic packaging methods. Development of precision extrusion technology and equipment to meet a variety of precision molding products processing requirements, the extrusion molding into a high-precision, high value-added processing method is the current polymer processing technology research hot spots.
Developers need sophisticated extrusion technology
Precision extrusion through the extrusion process is a precise control of elements, to achieve high-precision products, geometry and material of high uniformity of morphology molding process. Precise extrusion molding main features are: the extrusion process parameters small fluctuations, extrusion equipment is very stable working state, the molded article geometric accuracy than the conventional extrusion molding method increased by 50% or more. Development of precision extrusion technology urgency mainly in the following aspects.
(1) High-precision molding needs: to fiber optics, medical tubing, audiovisual film base, photographic film base, transparencies, represented by a series of high-precision products, increasing market demand. Geometric accuracy of such products often than ordinary products increased by 50% or more, ordinary extrusion equipment for these sophisticated products is powerless, but must use the sophisticated equipment and technology to complete extrusion molding.
(2) special material molding process requirements: For some hazardous packaging company and toxic materials processing require precise extrusion equipment. Such as red phosphorus-containing polymer composite extrusion, you need to strictly control the extrusion process, because the red phosphorus is very easy to burn, the extrusion process control is not good, with great danger. Some plastics will break down at high temperatures the machine is corrosive, harmful low molecular weight volatiles. Such as polytetrafluoroethylene (PTFE) and ethylene – tetrafluoroethylene copolymer (ETFE) will decompose at a temperature of the hydrogen fluoride gas, the gas to have a strong corrosive extrusion equipment, the human liver is very injury, the gas will lead to degradation of PTFE and ETPE chain reaction, and must be strictly limited. clear plastic box In the military field, an extruder can be used for the processing of explosives, the danger of self-evident, in addition to rational design of plasticizing system and precision machining, the strict control of the extrusion process is the most critical element of safety. In the above-mentioned types of hazardous and high-temperature decomposition polymer extrusion processing, precision extruder can play an irreplaceable role.
(3) reactive extrusion molding requirements: In addition to the plastic box modern plastics extruder plastic package function, but also has the function of chemical reactor, the material in the extruder can complete bulk polymerization, chemical grafting, bond between the copolymer obtained, coupling / cross-linking, controllable degradation, functional and functional group modification, preparation of polymer alloy, nano / polymer composites, etc. Reactive extrusion process requires strict control of the reaction temperature, pressure, residence time distribution and process parameters, as well as the reaction mass and the outside heat transfer, etc., ordinary extruder is often not competent, precision extrusion molding machine for a variety of complex reactive extrusion process provides the necessary equipment condition.
(4) high-speed extrusion basis: According to reports, the Japanese company’s D30 IKEGAI single screw extruder speed up to 3000r/min, output of up to 300kg / h. Foreign conical twin-screw extruder for the production of PVC pipe, single output of up to 1100 ~ 1500kg / h; parallel twin plastic trays screw extruder screw diameter over 300mm, aspect ratio up to 100, the maximum speed reached screw 1500r / min, WP’s ZSK133 series of machine production reached 7000 ~ 11000kg / h. The medical catheter wire speed can reach 250m/min, the film speed can reach 500m/min, coated cable line speed can reach more than 500m/min. At the same time high-speed extrusion, molding process must be implemented to ensure precise control. If you can not guarantee the accuracy of molding, the production speed is higher, the more waste. In this sense, it can be said of the high precision of the foundation.
(5) products to reduce material consumption needs: extrusion molding products due to lower waste caused by geometric accuracy is very alarming, produced using conventional extrusion equipment, plates, sheets, film, tube wall thickness uniformity generally up 8-10%, the resulting waste of material is about 8%. In recent years, China’s plastic products according to production 21000kt as the base, the annual production of extruded products 12600kt calculation, China’s annual geometric precision extrusion products due to lower than 100 million tons wasted resin. If 20% of the products using sophisticated extrusion technology and equipment to produce, you can save China’s annual consumption of 100,000 tons resin, over $ 800 million economic benefit.
Domestic and foreign technology and equipment Precision extrusion gap
Current domestic extrusion equipment sales of 8,000 units / year, with sales of 30 billion yuan, more than 2,000 imported extrusion equipment sets / year, imports about 200 million U.S. dollars (about 2 billion yuan), imports of extrusion equipment mainly for large and sophisticated equipment, the unit price for the domestic equipment 8 to 10 times its value significantly higher vac tray than the domestic equipment.
Imported extrusion equipment mainly large diameter solid wall pipe and corrugated pipe production line, geomembrane packaging design production lines, biaxially oriented film (BOPP, BOPET, BOPA, BOPS, etc.) production line, drip irrigation pipe production line, medical tubing production line, audiovisual film base and sensitive film Base production line, with a large petrochemical equipment twin screw extrusion granulation, and a variety of multi-functional laboratory extruder. These extrusion equipment imported at high prices have been able to enter the Chinese market, mainly rely on technical superiority, specifically in high-precision, high speed and high efficiency, high reliability.
U.S. PEI (Precision Extrusion, Inc.) Company for the production of precision medical tubing extrusion machine, using special design and manufacturing technology, as well as statistical process control technology, making sections of extruder temperature deviation can be controlled within 1 , pipe wall thickness deviation can be controlled within 2%. In contrast, high-precision temperature control extrusion equipment is generally 5 ~ 10 , pipe wall thickness deviation of more than 10%, can not meet the production of medical catheters, fiber optics and other high-precision products requirements. Such high-precision extrusion equipment is mainly dependent on imports.
Yielding extrusion equipment both in the actual level, or on the level of processing with foreign advanced level there are 15 to 20 year gap. In real-time monitoring of process parameters and product parameters, as well as the adoption of advanced control technology gaps are large, advanced high-precision online testing instrument is mainly dependent on imports, domestic few, and the gap with foreign products more than 10 years.
design standards and technical innovation capability gaps: foreign advanced plastic machinery processing enterprises have a strong design and technical innovation, such as Japan’s Nissei company has five technology research center, which has 376 injection molding technology engineers, accounting for 46.1% of total number of employees, patented technology 1470. In contrast, the domestic plastic machinery enterprises in university or professional and technical personnel less than 10%, less of independent intellectual property rights, development of new products generally imitation, CAD, CAE, CAM application is still in its infancy, most companies do not have the substantial technological innovation.
mechanical and electrical industries at home and abroad on the overall level of the gap: Foreign plastics machinery manufacturing industry commonly used CAD, CAE, CAM technology, and high-precision CNC machining center. Recent development of high-speed milling spindle speeds up to 40000 ~ 100000r/min, and to get the surface roughness of Ra 1mm; than 1mm ultra precision finishing technology and collector, chemistry, ultrasound, laser and other technologies integrated in together composite processing, plastic processing machinery will greatly enhance the level. Foreign screw face runout error is less than 0.01mm; screw diameter error can be controlled within 0.005mm less; screw and barrel outer surface of the inner surface roughness Ra is not more than 0.2mm; injection molding machine template geometric tolerance is not plastics products greater than 0.02mm / 1000mm. China imported from abroad in recent years, a number of high-precision machining equipment, but the overall level of foreign advanced clamshell packaging level there is a big gap.
online detection and automatic control of the level of the gap: Foreign precise extrusion equipment, widely used laser-based, optical, electromagnetic, ultrasonic, inductive, air induction principles such measuring devices. The first three methods for measuring the dimensions of the extrudate, after four kinds of products used to measure the wall thickness. Laser measuring instrument frequently used to measure the outer diameter of the cable pipe and coated according to a different measurement range, a resolution of 0.001 ~ 0.01 mm. In automatic control, in addition to outside the PLC control, fuzzy control technology, neural network control technology, statistical process control technology and other advanced control technology in precision extrusion equipment has played a pivotal role. The domestic extrusion equipment control technology PLC control only in the initial stage, mostly for simple open-loop control or joint control, the lack of online measuring instruments and advanced control software, so the closed-loop control is rarely used.
Precision extrusion technology in the production of plastic pipe applications
According to projections, by 2005 China’s plastic pipe production will reach 1.2 million tons, of which building drainage pipe, outdoor water pipe, underground drainage pipes, electrical plastic pipe casing accounts for more than 60%. Currently, the construction of the vast majority of plastic pipes are used to produce homemade pipe production equipment.
Precision plastic pipe extrusion system is characterized in ordinary pipe extruder based on the increase of weightlessness metering hopper, melt pump, pipe wall thickness measuring instrument and other devices online, while using statistical process control system (SPC system) replaced The traditional instrument control system or PLC control system. Modern precision extrusion line traction machine also uses the host and replace DC servo motors and variable frequency motor, plastic case in order to achieve true digital control.
Precision extrusion technology prospects
Extrusion development of the theory makes it according to the requirements of molding, precision designed extrusion process and extrusion molding equipment. To achieve stable extrusion extrusion equipment for the purpose of the new innovations of modern machining technology continues to improve, the adoption of advanced control technology for precision extrusion technology provides a great space for development. The precision molding, functional molding, reactive extrusion molding requirements, as well as two-way stretch, functionally graded materials, micro-foam molding process requirements, is a precision extrusion technology development of a powerful driving force. Precision extrusion technology, plastics processing industry will have a huge impact, very broad application prospects.
Precision Extrusion will become high value-added processing industry: in people’s concept, extrusion is highly efficient, low-value-added plastic processing methods, but sophisticated extrusion technology development and applications will change this state, Some precision molding products processing, can bring high added value, and even be able to play the role of Midas touch. In medical plastic catheter, for example, some foreign companies have been able to produce dialysis tubing, artificial blood vessels, stents and other precision with interventional therapy products, the price of these products is generally several hundred times the value of its raw materials more, some more than one million times.
Precision extrusion production equipment is a prerequisite for precision extrusion products, development of precision extrusion equipment for plastics machinery manufacturers to bring huge business opportunities and profits. Precision extrusion equipment currently is the value of the price of generic extrusion equipment 5 to 10 times more than our precision extrusion equipment still in its infancy, the development is very big.
for precision response polymer extrusion and functionally graded materials processing: In addition to the modern plastics extruder reaction function, but also has the function of chemical reactor, the material in the extruder can complete bulk polymerization, chemical grafting , a key to obtain a copolymer, coupling / crosslinking controllable degradation, functional modification of the functional groups, the preparation of the polymer alloy, nano / polymer composite material, etc. Reactive extrusion process requires strict control of the reaction temperature, pressure, residence time distribution and process parameters, as well as the reaction mass and the outside heat transfer, etc., while the ordinary extruder is often not competent. Precision extrusion molding machine can achieve precise control of the extrusion process parameters to clear plastic packaging meet the different requirements of the reaction system.
Since the 1957 discovery crystal polymers, as well as the theory put forward since the molecular chain folding, polymer morphology and microstructure cause for great concern. Along with X-ray diffraction, electron microscopy, small-angle neutron scattering, the new surface probe, atomic force microscopy and other advanced testing technology, people on the polymer structure – morphology – deepening understanding between the performance. It has been cut through the extrusion molding process to control the direction and intensity (or stretching field control), prepared by uniaxially or biaxially oriented structure of the self-reinforced material; through the cooling process control, as well as shear, tensile and vibration induced field, get a different crystal structure. By molding process control, access aggregation structure changes according to certain rules of functionally graded materials to achieve the mechanical, optical, electrical and other properties gradient requirements. The aggregation structure control technology, both extrusion process requires precise control, precision extrusion technology can be expected in the preparation of functionally graded materials play an important role….