With the expansion of the application range of PET bottles, a higher performance requirement has been put forward for the injection molding equipment of PET flask. The development of PET bottle in China has been promoted, which has promoted the development of Chinese PET bottle blank injection molding equipment. But we should be soberly aware that the domestic PET bottle billet plastic molding equipment can not enter the large enterprises, like the soldiers in the market to beat, not a climate. In this paper, the author puts forward some opinions for reference according to the situation that he knows.

The injection molding equipment of the PET bottle is mainly related to two aspects: the blank injection molding machine and the blank mold.

1. Some important problems in the scientific and technological progress of the blank injection molding machine of PET bottle.

Domestic PET bottle billet injection molding machine mainly develops single - layer PET bottle blank injection molding equipment. Although a certain amount of PET injection molding equipment has been developed in China, its quality and technical level are at least 20 years apart from the international advanced level. Domestic PET bottle production of the largest unit, not a PET bottle blank injection molding equipment is domestic, which illustrates this problem. The author believes that the injection molding equipment of PET bottle is a high-end equipment, which is different from the development of ordinary injection molding equipment. Domestic PET bottle preform injection molding machine, some units to research and development as a common medium and low-end products research and development, the change of screw barrel as PET injection molding machine, in this way, development took a wrong path from the start, so have to go to always wandering at the low level. First of all, it is necessary to correct the development idea and develop the PET bottle billet injection molding machine as a high-end product to develop the high performance PET bottle billet injection molding machine.

1.1 progress of the main performance of the blank injection molding machine of PET bottle.

The main performance of the PET injection molding machine is constantly making new demands with the progress of science and technology. In the mid - 1980 - s, the application of PET bottles in the initial stage, the hot runner technology still under development, especially the technology used in PET bottle preform mould of hot flow path is not enough mature, group of PET bottle preform mould cavity are still in development stage, so the performance requirements for PET preform injection molding machine is not particularly high requirements, for example, the new Italian much plastic machinery co., LTD. In Shanghai in 1987 to introduce the company's main characteristics of PET preform injection molding machine, mainly introduced the screw and the nozzle in order to adapt to PET bottle preform injection molding of the research and development, on the other side has not hit. With the development of hot runner technology, group of cavity mould development, especially the application of PET bottles into the growth of the geometric series, PET bottle preform injection molding machine to the performance requirements of higher and higher demands are proposed, PET bottle preform injection molding machine in order to adapt to the development of the market, its organization and structure control further reflect the performance characteristics of special injection molding machine, main performance at high speed, high efficiency, precision and so on.

1.2 progress of the main body and structure of PET bottle billet injection molding machine.

1.2.1 closing mechanism.

Before the application of the group cavity mold of PET bottle billet, the research on the performance of the mold of the injection molding machine of PET bottle was not paid enough attention, for example,

In 1987, Italy new plastic machinery co., LTD. Introduced the company's PET bottle billet injection molding machine in Shanghai. With the use of PET bottle preform group of cavity mould clamping mechanism of PET preform injection molding machine puts forward new requirements, the clamping mechanism must be able to long-term parallelism between the template and the precision of the mould clamping force, clamping force stability.

The mold of the mould of PET bottle billet is compared with that of ordinary plastic products, which has the inherent characteristics of high precision and small rigidity. The price of a set of molds for a set of PET bottles exceeds the price of the host. Therefore, the mold closing mechanism must be able to play a good role in protecting the mold. In order to achieve this function, the mould mechanism must have sufficient rigidity, the speed characteristic of the model, the mould deformation and the deformation repeatability.

In order to meet the above requirements, what kind of mold closing mechanism should be adopted? This must be clear in development. Clamping mechanism mainly include toggle clamping mechanism and hydraulic clamping, toggle clamping mechanism is divided into single fulcrum, four fulcrum, five fulcrum clamping mechanism, hydraulic pressure clamping mechanism and single cylinder clamping mechanism and four cylinder synchronization. Toggle clamping mechanism is determined by the inherent characteristics of its own distribution uniformity of the clamping force and the long-term stability of the institutions precision can't meet the higher requirements, which is harmful to protect the high precision of cavity die, mold clamping mechanism precision imbalances would destroy the mould precision and service life, while improve the machining precision can improve the precision of the clamping mechanism, compensate for toggle clamping machine for the lack of performance, but it can not fundamentally overcome its inherent shortcomings. Four cylinder synchronous hydraulic clamping mechanism, as a result of hydraulic soft rigidity, when the high voltage clamping mould clamping force distribution uniformity of the improved, on the properties of mold protection has been improved, but as a result of four cylinder impossible ideal synchronous high pressure tight mould. Single cylinder hydraulic clamping mechanism itself inherent characteristics of the protection of the precision of the mould can reach the ideal state, in the mould clamping force distribution uniformity, the mould low pressure protection, clamping force stability has excellent performance, is the preferred precision injection molding machine clamping mechanism. According to the above brief analysis, it can be seen that, in order to have good performance protection for the molds of the PET bottle, the mould and mould mechanism of the PET bottle billet injection molding machine should be the preferred single cylinder hydraulic model mechanism.

At present, most of the domestic injection molding machine manufacturers use the toggle joint mold mechanism as the molding mechanism of the molding PET bottle billet injection molding machine. Users of PET bottle preform injection molding equipment also have fully understanding, therefore, never a set of import expensive PET bottle preform group of mold cavity into the ordinary toggle clamping mechanism with injection molding machine. The injection molding machine of the PET bottle of the toggle mechanism determines that the market of the injection molding machine can only enter the low-end PET bottle billet and cannot enter the high-end market of the injection molding machine of the PET bottle.

1.2.1 the progress of injection plasticizer.

The injection molding mechanism of PET bottle billet injection molding machine is in the process of continuous development. In the initial stage of the injection molding machine of the PET bottle, the main research is how to reduce the production of acetaldehyde in the plasticized injection process and improve the transparency. Group of the cavity mould of the application of PET bottle preform, reduce the manufacturing cost of PET bottle preform, focuses on research and development of high efficient, high speed high efficiency refers to the high quality high speed molding, high injection speed, rather then PET itself features do not allow the high injection speed, PET injection molding if material when the temperature is too high, rotating speed of screw shear force is too large or too fast when are easy to produce acetaldehyde and lead to acidification, usually after molding of acetaldehyde content in PET bottles must be less than 3 PPM. Deviations in the quality of PET bottle preform put forward higher request, for example, within 50 grams of tube billet quality biggest negative deviation of 0.5 grams, 50 grams of quality in the check system of tube rounds maximum negative deviation was 1.5, 70 g, 70 g the quality check system of tube rounds maximum negative deviation was 2.5, 100 grams, so accurate measurement is the research and development of subject.

The high speed injection molding is an important characteristic of the technological progress of the injection molding machine. High speed and high yield can enable investors to obtain higher output and higher returns with lower input. In order to achieve high speed injection plasticization, innovation is carried out from the aspects of mechanism, structure and control.

The common coaxial first-line injection plasticizer has limited productivity and quality improvement by its structural features. There are only two ways to improve the plasticizing capacity, namely, to improve the plasticizing speed or increase the diameter of the screw. There are basically two ways to improve the plasticizing quality of PET, which is to reduce the plasticizing temperature or prolong the retention time in the cylinder. To improve the plasticizing speed, because the increase of shear rate will accelerate the production rate of acetaldehyde, it cannot be taken, so it can only improve the plasticizing ability by increasing the diameter of the screw. To reduce plasticizing temperature or prolong the retention time of molten material in the cylinder can improve the plasticizing quality, but also reduce the plasticizing ability. Therefore, to achieve the simultaneous improvement of plasticizing capacity and plasticizing quality, we must develop new injection molding mechanism to meet the requirements of high speed and efficiency. According to the characteristics of the plasticizing injection, the injection and the function of plasticizing, from the conventional one line is divided into two line type, namely the plasticizing and two functions by a conventional injection parts is divided into two parts, the plastic screw independence movement, plunger independent injection, injection and non-interference in each other between plasticizing, plasticizing do not take up the forming cycle, to improve the quality of plasticizing and improve plasticizing capability. Plasticizing screw diameter, is increased by improving the plasticizing capacity, at the same time, due to the plasticizing, independently of the cycle, can prolong residence time in the barrel, melting improve mixing uniformity of plasticizing material; At the same time, due to the appropriate extension of plasticizing time, it can provide sufficient time for low temperature plasticization and reduce the probability of material emergency heating and thermal decomposition due to excessive shear of materials.

The design of plastic screw has a great influence on the melting, mixing uniformity and melt temperature of PET. The injection molding of PET bottle embryo should be low cut and low compression ratio (about 2:1). The feeding section should be longer, and the transition section and metering section should be shorter.

High - speed injection molding is an important characteristic of PET bottle billet injection molding machine. High-speed plasticizing injection is not high speed injection and high plasticizing, instead the injections and plasticizing organic union, from the aspects of organization, structure, control on innovation, achieve minimal total time and plasticizing injection. In most domestic units, the so-called PET bottle billet injection molding machine basically only increases the diameter ratio of the screw and makes some changes in other screw parameters, which can not meet the high speed performance requirements. [3] HUSKY Canada exhibited in 2006 Shanghai international exhibition on the rubber and plastic injection of PET bottle preform for PET bottle preform injection molding machine, combined with the company's leading international hot runner mold, forming a 96 bottle preform, cycle is less than 7.5 seconds, basically reached 100% pass rate. High-speed machine structure is the main characteristics of plasticizing efficiency is high, the plasticizing plasticizing injection mechanism and two functions by a conventional injection parts is divided into two parts, the plastic screw independence movement, plunger, independent injection screw plasticization, molten material flow to open, will melt into the plunger store material cavity, measuring the melt flow closed, then, plunger note material into the cavity, in this way, plasticizing do not take up the forming cycle, improve the productivity. Remarkably screw injection material, the machine in injecting molten material movement is screw injection is not simple straight forward but rotating forward movement, the direction of rotation with the plasticizing direction of rotation. The author believes that in order to adapt to the plasticization of PET, reduce in the process of charging into the air, the solid material to fill in the process of feeding screw groove, in the process of injecting molten material into to cavity, plasticizing the screw rotation, to discharge into the barrel of the solid material in the air, at the same time, reduced the plasticizing time, shorten the production cycle. In order to reduce the axial temperature difference of the melting material, improve the quality of the bottle billet, adopt the large diameter screw to plasticize, shorten the plasticizing stroke, and plasticize the trip around 1D. This design idea is worthy of our reference.

2. Develop multi-layer co-injection flask equipment.

Multi - layer composite bottle is the development direction, the development of multi - layer billet equipment is the premise. We are basically still blank in this respect, the international development is very fast. NPE Kortec company in 2003 at the exhibition demonstrated a "Ultra" of 144 cavity injection mold, and the injection molding machine in Husky Canada, in the production of carbonated beverage bottle with multilayer parison, produced 35000 m/h, led the world, the value of our study. The blow molding of multi-level injection bottle is basically similar to the blow molding of single layer PET bottle. The multi-level injection bottle is specially developed for beer packaging. It has three layers and five layers. Domestic zhuhai zhongfu import equipment production of three - layer PET beer bottles. Each year, China produces about 24 million tons of beer per year, requiring about 4.4 billion beer bottles per year, which is a large market. Therefore, it is necessary to accelerate the development of the multi-layer co-injection bottle billet equipment.

3. The group cavitation of the mould of PET bottle billet.

It is the main way to improve the production efficiency and reduce the production cost. The main factors of restricting production efficiency of single layer bottle preform mould, bottle preform mould research and development and manufacturing in China far behind the international level, hot runner technology and used is not closed, advanced bottle preform mould for imported equipment. Internationally, the mold cavity number of the injection moulds of single-layer billets has reached 144 in the past four years, and NPE2006 in Chicago, USA (nettstal -Maschinen).

AG) introduced a 192 cavity PET bottle preforming machine at the exhibition, which is already in Reading, Berkshire Bottling in Pennsylvania.

Works company. Emile heskey company in Canada (Husky Injection Molding Systems

Also in NPE2006, it showed a Husky with about 650 tons of mode-lock force.

HyPET injection molding machine is designed for the 216 cavity PET bottle preformed mold, which is applied to Amcor PET in the United States.

Packaging company. And we can only reach 48 cavities, its technology and quality level is far below the international advanced level, can not enter the domestic well-known PET bottle billet production company. Group cavity PET bottle mould is the main work direction of PET bottle forming equipment. In order to be suitable for the forming of the mould of the group cavity PET bottle, the mechanism, structure and control system of the PET injection molding machine should be innovated accordingly.

Many mould r&d units in China have also made a lot of achievements in the research and development of PET bottle billet mould. A certain number of PET bottle billet moulds have been exported, and some have replaced the imported PET flask mould. Guangzhou China by precision machinery co., LTD adopts CAD/CAM computer aided design/manufacturing, with great series of PET bottle preform mould, design of hot runner, absorbing the foreign advanced technology, using free cut gate design, hot runner nozzle temperature control alone. It is the first of its kind in China. The mould is produced in full automatic condition without the frequent operation of the staff, so as to reduce the labor force of the workers. Key parts of the mold (core and cavity, mold) using German mirror surface rust steel and heat treatment (HRC45), ensure the quality of the service life of the mold with a bottle (normal use of maintenance free, 1.5 million times the minimum wall thickness difference is less than 0.1 mm). Zhejiang Huang Yanyu sheng polyester mold factory manufacturing has a 12 cavity, a 16 cavity, a series of 48 PET bottle preform injection mold cavity, absorption of Germany, Japan, Canada and other countries of advanced technology, after years of careful research, successfully developed a new generation of YS2 a 16 cavity preform injection mold series, with domestic injection molding machine to produce imported PET bottle preform quality.

4. The forming cycle of the PET bottle is high.

The high speed molding cycle is a comprehensive embodiment of the performance of the PET bottle. Overall, the molding cycle is shorter and more productive. Extruder of the developed countries has been widely used modern electronic and computer control technology, the technological parameters of the whole process of lines such as melt pressure and temperature, paragraphs body temperature, the main screw and feed screw speed, feed feed rate, the proportion of all kinds of raw materials, such as current voltage of the motor parameters online testing, and USES the microcomputer closed-loop control. Some companies have adopted online remote monitoring, diagnosis and control, and control the extrusion molding production line. This is very beneficial to ensure the stability of process conditions, improve product accuracy and improve production efficiency. Netstal PET - Line model of the company caused a sensation in NPE2006 exhibition hall, the clamping force of the this kind of machine is about 600 tons of 192 cavity preform machine, casting more than 90000 hours per bottle preform, the machine of von berg systeme cycle time of just 7.4 seconds. HUSKY Canada exhibited in 2006 Shanghai international exhibition on the rubber and plastic injection Hy400 PET bottle preform preform special injection molding machine, combined with the company's leading international hot runner mold, forming a mold 96 bottle preform, cycle is less than 7.5 seconds, basically reached 100% pass rate. High-speed machine structure is the main characteristics of plasticizing efficiency is high, the plasticizing plasticizing injection mechanism and two functions by a conventional injection parts is divided into two parts, the plastic screw independence movement, plunger, independent injection screw plasticization, molten material flow to open, will melt into the plunger store material cavity, measuring the melt flow closed, then, plunger note material into the cavity, in this way, plasticizing do not take up the forming cycle, improve the productivity. Remarkably screw injection material, the machine in injecting molten material movement is screw injection is not simple straight forward but rotating forward movement, the direction of rotation with the plasticizing direction of rotation. The author believes that in order to adapt to the plasticization of PET, reduce in the process of charging into the air, the solid material to fill in the process of feeding screw groove, in the process of injecting molten material into to cavity, plasticizing the screw rotation, to discharge into the barrel of the solid material in the air, at the same time, reduced the plasticizing time, shorten the production cycle. In order to reduce the axial temperature difference of the melting material, improve the quality of the bottle billet, adopt the large diameter screw to plasticize, shorten the plasticizing stroke, and plasticize the trip around 1D.

5. Integration of r&d system.

The research and development of injection molding equipment for PET bottle is different from that of injection molding machine. General injection molding machine research and development, basically be purely injection molding machine research and development, the research and development staff to grasp the mold, molding, plastic raw materials, such as the requirement of knowledge is not high, at present a big proportion of injection molding machine research and development personnel to these don't know. PET bottle preform injection forming group has expanded by cavity to cavity, so the PET bottle preform injection equipment is injection molding machine, mold, injection process, as well as the raw material into a system of four combinations, especially before all must be integrated closely combination, be short of one cannot. According to the development requirements of the injection molding equipment of the PET bottle, only the knowledge of the four sides can be fully understood and mastered, so as to develop the high-end PET bottle blank injection molding equipment. International PET bottle preform injection molding equipment, research and development of the PET preform injection molding machine and PET bottle preform mould as a system, especially for hot runner technology and used in PET bottle preform mould, accounted for in the world leading position, make the host and mould both match each other to achieve the best condition, maximum production capacity, make the PET bottle preform injection molding equipment to achieve the best performance. Domestic PET bottle preform injection molding equipment research and development system, the disconnect between four, not to become a closely the development of the industrial chain, research and development of the host does not understand how the host matching with mold, mold did not understand the mould development how to match with the host. Research and development of the host unit that PET bottle preform injection molding equipment research and development is the PET injection molding machine research and development, the PET injection molding machine research and development that is plasticizing injection device research and development, the PET plasticizing injection device research and development that is the screw of the research and development, so the domestic research and development of the so-called PET injection molding machine just put screw improvement, stay at the international level in the 1980 s. The unit of the research and development host lacks the understanding of the mold of the PET bottle, not to mention the development of the mould for the PET bottle. In such a level of knowledge and research and development system, it is impossible to develop high-end PET bottle blank injection molding equipment.

6 conclusion

In this paper, the present status of PET bottle preform injection molding equipment and discusses the development direction, fully shows the great prospects for development our country PET bottle plastic molding equipment, at the same time, we should see the PET bottle plastic molding equipment and industrial developed countries differ greatly. The typical international PET bottle billet injection molding machine production equipment is Canada's HUSKEY.

PET injection molding machine, the internationally recognized leader in the, so, we should carefully study its characteristics, the characteristics, performance characteristics, develop more PET bottle preform injection molding machine has a performance advantage. In the market internationalization today, domestic PET bottle injection moulding equipment, if there is no technical advantage in performance, the developed equipment can only be exhibited, cannot be a commodity.