PET preform injection moulding equipment or bottle injection molding machine is mainly related to two aspects: preform injection moulding machine, preform mould.
The progress of the main performance of PET preform injection moulding machine
PET bottle injection moulding machine main performance with the progress of science and technology and constantly put forward new requirements. In the mid-1980s, the application of PET bottles was in the initial stage, and hot runner technology was still in the development stage, especially hot runner technology used in PET preform moulds is not mature enough, group cavity PET preform moulds are still in the research and development stage, so there are no particularly high-performance requirements for PET bottle injection moulding machines, for example, Daoben Machinery introduced the main features of the company’s PET preform injection moulding machine, mainly introduced the screw and nozzle to adapt to the PET preform injection moulding research and development, other aspects have not been touched.
With the development of hot runner technology, the development of group cavity moulds, especially the application of PET bottles in a geometric progression of growth, the performance requirements of PET preform injection machine put forward more and more high requirements, PET preform injection moulding machine to adapt to the development of the market, its mechanism and structure control and other aspects of the performance of special injection moulding machine is further reflected in the performance characteristics of the main performance in the high-speed, high efficiency, precision and other aspects.
Evolution of main mechanisms and structures of PET Bottle Injection Moulding Machine
Explore the fascinating journey of PET preform injection molding machines as they evolve to enhance efficiency, precision, and reliability. Delve into the advancements in mechanisms and structures that revolutionize the manufacturing process, ensuring superior quality and productivity in the production of PET preforms.
Mould closing mechanism:
Cavity moulds for PET bottle blanks have the inherent characteristics of high precision and low rigidity compared with moulds for ordinary plastic products. The price of a set of PET preform cavity moulds even exceeds the price of the main bottle injection moulding machine. Therefore, the clamping mechanism must be able to play a good role in protecting the mould. To achieve this function, the clamping mechanism must have sufficient rigidity, excellent clamping and opening speed characteristics, uniform deformation of the mould and good deformation repeatability.
What type of clamping mechanism is suitable to meet the above requirements?
This is a point that needs to be clarified in the design. Clamping mechanism mainly has an elbow-rod clamping mechanism and hydraulic clamping mechanism, the elbow-rod clamping mechanism is divided into single-point, four-point, five-point clamping mechanisms, hydraulic clamping mechanism and single-cylinder and four-cylinder synchronous clamping mechanisms. The elbow rod-clamping mechanism by its inherent characteristics determines the distribution of clamping force uniformity, institutional accuracy of long-term stability can not meet the high requirements, which is not conducive to the protection of high-precision group cavity moulds, clamping mechanism precision imbalance will destroy the accuracy of the mould and its service life, although to improve the accuracy of processing precision can improve the accuracy of the clamping mechanism to make up for the lack of performance of the elbow rod-clamping bottle injection moulding machine, but not fundamentally!
Overcome its inherent shortcomings. A four-cylinder synchronous hydraulic clamping mechanism, due to the hydraulic rigidity of the soft, in the high-pressure clamping force distribution uniformity, improved, the protection of mould performance has improved, but because of the four-cylinder is not possible to achieve the ideal synchronous high-pressure clamping mould. The single-cylinder hydraulic clamping mechanism of its inherent characteristics of the accuracy of mould protection can achieve the ideal state, in the clamping force distribution uniformity, mould low-pressure protection, clamping force stability and other aspects of excellent performance, is the first choice of precision injection moulding machine clamping mechanism.
According to the above brief analysis, it can be seen that to play good performance protection for PET preform group cavity moulds, the PET bottle injection moulding machine clamping mechanism should be preferred to the single-cylinder hydraulic clamping mechanism.
At present, most of the domestic injection moulding machine manufacturing enterprises adopt the elbow lever type clamping mechanism as the clamping mechanism of PET preform injection machine.
Progress of Injection Moulding Mechanism:
PET preform injection moulding machine injection plasticising mechanism is in the process of continuous development, to the high-speed and efficient direction of technological progress. At the initial stage of PET bottle blank injection moulding machine, the main research is how to reduce the production of acetaldehyde in the plasticising and injection process, improve the transparency, the application of PET bottle blank group cavity moulds, reduce the manufacturing cost of PET bottle blanks, Focus on the research and development of high speed and high efficiency, high speed and high efficiency refers to the high quality and high speed moulding, instead of referring to the high speed of injection, PET’s inherent characteristics do not allow a high speed of injection, and the high injection speed is not allowed, but the high injection speed is not allowed. PET injection moulding if the material temperature is too high, the screw shear force is too large or the rotational speed is too fast are easy to produce acetaldehyde and lead to acidification, usually after moulding PET bottle acetaldehyde content must be less than 3ppm.
High-speed injection plasticising is an important feature of the technological progress of PET preform injection moulding machine. High-speed, high-yield, can enable investors to lower investment to achieve greater output and high returns. To achieve high-speed injection plastic, from the mechanism, structure, control aspects of the breakthrough innovation.
Ordinary coaxial one-line injection plasticizing mechanisms by the desire of their structural characteristics limit productivity and quality improvement. To improve the plasticizing capacity, there are only two ways, that is, to increase the plasticizing speed or to increase the diameter of the screw; to improve the quality of PET plasticizing, there are two ways, that is, to reduce the plasticizing temperature or to increase the melt residence time in the cylinder. Increasing the plasticizing speed, due to increase the shear rate will accelerate the rate of production of acetaldehyde, which can not be taken, so only by increasing the diameter of the screw to improve the plasticizing capacity. Reducing the plasticizing temperature or increasing the residence time of the melt in the barrel will improve the plasticizing quality, but at the same time reduce the plasticizing capacity.
Therefore, to achieve the simultaneous improvement of plasticising capacity and plasticising quality, it is necessary to develop a new injection plasticising mechanism that meets the requirements of high speed and high efficiency. According to the characteristics of injection plastication, the injection and plastication functions are divided into two lines from the conventional one-line type, i.e. the two functions of plastication and injection are divided into two parts from the conventional one-part, the plastication is an independent movement of the screw and the plunger is an independent injection, there is no interference between the two, and the plastication does not take up the forming cycle, so as to achieve the improvement of both the plastication quality and the plastication capacity. By increasing the diameter of the plasticising screw, the plasticising capacity can be increased. At the same time, since the plastication is independent of the cycle, the residence time of the molten material in the cylinder can be extended to improve the uniformity of material mixing and plastication; at the same time, since the plastication time can be appropriately extended, it can provide enough time to achieve low-temperature plastication, reducing the chances of the material being subjected to excessive shear, which may result in the rapid temperature rise of the material and thermal decomposition.
Plasticising screw design has a greater influence on PET melting, mixing uniformity and melt temperature.PET preform injection should use low shear, low compression ratio screw (about 2:1), the feed section should be made longer, the transition section and metering section should be made shorter.
High-speed injection and plastication is an important feature of PET preform injection moulding machine. High-speed injection and plastication is not high-speed injection and high-speed plastication, but the organic combination of injection and plastication, from the mechanism, structure, control aspects of innovation, to achieve the minimum total time of injection and plastication. Most of the domestic units of the so-called PET preform injection moulding machine is basically just to increase the length and diameter ratio of the screw and make some changes in other screw parameters, which can’t meet the performance requirements of high-speed at all. Canada HUSKY company in 2006 Shanghai International Rubber and Plastics Exhibition on display in the injection of PET preforms PET preforms special injection moulding machine, combined with the company’s international leading hot runner moulds, forming a mould of 96 preforms, the cycle is less than 7.5 seconds, the pass rate basically reached 100%. The main feature of the high-speed structure of the bottle injection moulding machine is the high efficiency of plasticising, plasticising and injection mechanism of plasticising and injection of two functions from the conventional one part into two parts, plasticising for the independent movement of the screw, the plunger independent injection, the screw plasticising is completed, the melt runner opens, the molten material is injected into the plunger storage cavity, measurement, melt runner closes, and then the plunger injected into the cavity, so that the plasticising does not take up the cycle of moulding, improve productivity.
In this way, plasticising does not take up the forming cycle, improving productivity. It is worth mentioning that the screw injection action, the machine in the melt injection action, the injection of the screw is not simply a straight line forward movement, but rotating forward movement, the direction of rotation with the direction of rotation of the plasticising. The authors believe that in order to adapt to the PET plasticising, to reduce the entry of air in the charging process, so that the solid material in the charging process to fill the screw groove, in the process of extruding the molten material into the injection cavity, the plasticising screw rotates and extrudes, which is conducive to discharging the air that enters the barrel of solid material, and at the same time, reduce the plasticising time and shorten the production cycle. To reduce the axial temperature difference of the melt and improve the quality of the preforms, the large-diameter plasticising screw is used to shorten the plasticising stroke, and the plasticising stroke is about 1D.
PET bottle preform mould group cavity:
PET bottle preform mould group cavity is the development direction of PET bottle preform mould, is to improve production efficiency and reduce production cost of the most important way. The main factor limiting the production efficiency of single-layer preforms is the mould. Many of China’s mould R & D units in the PET preform mould research and development has also made a lot of achievements, a certain number of PET preform moulds have been exported, there are also some have replaced the imported PET preform moulds.
PET preform injection moulding equipment research and development, different from the injection moulding machine research and development. General injection moulding machine research and development, basically is pure injection machine research and development, on the research and development personnel to master the mould, injection technology, plastic raw materials and other knowledge requirements are not high, at present, not a small proportion of injection moulding machine research and development personnel on these do not understand. PET bottle blank injection moulding has been developed by the development of multi-cavity to the group of cavities, so the PET bottle blank injection equipment is the injection moulding machine, moulds, injection technology, as well as raw materials, four will be a combination of systems, especially the first, the first is a combination of systems. A system of combinations, especially the first three must become a tightly integrated combination, one can not do without the other.
