Technical development details of the hottest large

2022-10-24
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With the rapid development of chemical industry and the continuous expansion of chemical products in international trade, the demand for large extrusion blow hollow containers has increased rapidly. In recent years, 1000L IBC barrels have increased at a faster rate, 8% in Europe and 25% in the United States, and are replacing double L ring barrels. The increasing demand for large extrusion blow hollow containers has driven the development of large extrusion blow hollow plastic molding machines. Shanghai huawang Industry Co., Ltd. developed a 1000L large-scale hollow plastic molding machine in 1998, filling the domestic gap, and produced 1000libc barrels and hollow pallets. Several famous manufacturers of extrusion and blowing hollow plastic molding machines in the world have successively launched large-scale extrusion and blowing hollow plastic molding machines, and in recent years, the equipment has made many new developments, mainly in energy conservation, high efficiency and other aspects

research and development focus

1 improve production efficiency

shortening production cycle and improving production efficiency are important contents of technological progress of large-scale extrusion blow hollow plastic molding machine. The production efficiency of the large-scale extrusion blow molding machine in China is much lower than that of the large-scale hollow plastic molding machine of the same specification in the world, so we cannot only be satisfied that the equipment can form products, but should make research and development on improving production efficiency. The main factors related to production efficiency are plasticizing capacity and blow molding cooling time

(1) improve the plasticizing capacity (extrusion plasticizing production capacity)

improving the plasticizing capacity is a prerequisite for improving production efficiency. The plasticizing capacity of the extruder prepared on the large-scale extrusion blow hollow plastic molding machine developed in China is generally lower than that of the extruder of the same specification in the world, so the molding cycle is long and the energy consumption is high. The extruders prepared by some domestic units on large-scale extrusion and blowing hollow plastic molding machines generally adopt the extruders of conventional design. They have not made a deep study on the particularity of the extruders required by large-scale extrusion and blowing hollow plastic molding machines, and they still stay on the concept of general extruders, which are only satisfied with plasticizing and extrusion, and do not pursue high plasticizing capacity

improve the plasticizing capacity, that is, improve the plasticizing performance and conveying capacity of the screw barrel. In the world, the extruder prepared on the large-scale extrusion blow molding machine has long adopted the IKv structure with forced feeding and forced cooling. IKv structure, which mainly has deep and wide longitudinal grooves with different shapes on the bushing in the feeding area of the barrel, and at the same time, a forced cooling structure is designed in the feeding area, which greatly improves the conveying efficiency, from the conventional 0 5 to 0 85. In addition to the reasonable design of barrier section and mixing section, its plasticizing capacity is more than 50% higher than that of the conventional extruder, and the extrusion capacity is stable. When processing hmwhdpe powder, the plasticizing capacity of 150/25 extruder produced in China is only 250kg/h. When processing hmwhdpe mixed with 70% new material and 30% crushed material, the plasticizing capacity of 150/25 extruder of IKv structure of Krupp company in Germany is 600kg/h, and the nominal specific power is only 0.3kw/kg h-1。 IKv structure has not been adopted in domestic extruders, which is worth our thinking. Of course, IKv structure also has some defects, such as serious wear of screw and barrel, high energy taken away by cooling water, etc. Therefore, when designing screw and barrel, we should combine the actual situation and constantly adopt new materials and new technologies, and constantly study and improve on the basis of IKv structure to improve the plasticizing capacity and quality. Of course, some manufacturers have made achievements in improving the plasticizing capacity. Guangdong Jinming Plastic Equipment Co., Ltd. has developed a technology that can not only process 100% new materials, but also 5 Total spring stiffness: 300 ± 10kgf/cm. It can process high-yield screws with 100% powder and 100% recycled materials, and its output is more than 40% higher than that of conventional design screws

(2) shorten the blow molding cooling forming time

the key to shorten the blow molding cooling forming time is to improve the performance of the blow molding system. The main technical indicators of the performance of the blow molding system are the blowing pressure and gas temperature. The blow molding equipment we are now equipped with are conventional air compressors, which use conventional blowing pressure, which can not meet the needs of rapid blowing and cooling of large hollow products. The wall of large hollow plastic products is thick, so the performance of blow molding system is not only related to the production efficiency, but also related to the quality of products, especially related to the strength of parison bonding joint. Increasing the blowing pressure and using the low-temperature dry table 4. Comparing the new and old material standards of a certain Japanese automobile bumper with the dry high-pressure air blow molding is the key to shorten the blow molding cooling molding time and improve the product quality. BEKE company of Germany cooled the air to -350c to -450c for blow molding, which strengthened the cooling of the inner wall of the product, made the cooling rate of the inner and outer walls of the product uniform, greatly improved the quality of the product, shortened the cooling time by no less than 20%, and improved the production efficiency

2 high performance storage head

the head for forming single-layer large extrusion blow hollow containers is a storage head. The containers produced by large extrusion blow molding machines in China are basically single-layer, such as 200L double L ring barrels, IBC barrels, etc. The single-layer large hollow container is formed from hmwhdpe raw materials. Hmwhdpe is a crystalline plastic with strong molecular orientation, and the elastic memory effect of the melt is strong. Therefore, the storage head must be able to make the molecules in the melt have sufficient time to rearrange although the temperature does not change the column distribution, broaden the MWD distribution of the melt flow, and reduce the radial temperature gradient of the melt, so as to improve the strength of the melt fusion seam area and the quality of the parison surface, Ensure that the melt inside the extruded parison does not produce cracking phenomenon to improve the strength of the product; The high-performance storage head must have a reasonable flow channel structure, which can fully meet the requirements of plastic melt molding process, and can realize rapid color change and material change. One of the main ways to improve the performance of the storage head is to improve the strength of the melt fusion seam. At present, the storage head designed by the single-layer heart-shaped envelope runner with poor strength in the melt fusion seam area is also widely used in China. The storage head with double-layer heart-shaped envelope flow channel is a high-performance storage head. Its principle is to divide the fusion joint area into two parts and stagger the distribution. The parison is covered by a complete melt layer, which improves the strength of the melt fusion joint area and is widely used internationally. The best effect can be achieved only with advanced structure and advanced design means. The application of CAD is a necessary method to make the storage head with double-layer heart-shaped envelope flow channel achieve high performance. The computer software used in the design of the head now includes flow2000 large-scale computer analysis software and three-dimensional mold design software pro/e, etc. at present, the design of the storage head in our country basically does not use advanced CAD means, and it is designed by experience alone, which is the main reason why the performance of the storage head in our country is not improved. First in first out, fast color change and material change, and convenient cleaning are important characteristics of high-performance storage head. The positive approach is to adopt advanced CAD means, high-quality steel, precision processing equipment and advanced CAE processing methods

3 machine lifting mechanism

most of the machine lifting mechanisms of domestic large extrusion blow hollow plastic molding machines are sprocket chain mechanisms. Practice has proved that this kind of transmission mechanism is inconvenient to adjust and easy to bite due to its own defects, especially in machine lifting mechanisms above 200L. However, because some units copied each other and did not make fundamental reforms, they are still in use. Therefore, the lifting mechanism of domestic large-scale extrusion and blowing hollow plastic molding machine must be substantially reformed, and the sprocket chain synchronous lifting mechanism driven by a single drive must be changed to two or four synchronous driving mechanisms to eliminate the phenomenon of seizure

4 clamping mechanism

the clamping mechanism should have the properties of high motion accuracy, fast speed, easy loading and unloading of molds, etc. At present, the clamping mechanism of large-scale extrusion blow hollow plastic molding machine in China adopts the structure of the clamping mechanism of small-scale hollow container molding machine, and adopts the three plate linkage and its extended structure of two or four pull rods. The main disadvantages are: the force on the formwork is uneven, and it is easy to expand the mold. At the same time, due to the existence of the pull rod, the space of the mold is limited, and the operating space of the manipulator is constrained

the plug-in pull-free clamping mechanism is a clamping mechanism developed in recent years. It has the characteristics of large clamping force and uniform distribution, easy loading and unloading of the mold, large capacitance modulus, energy saving, etc. the guiding motion pair adopts the ball linear guide rail with small friction coefficient, stable movement and high operation accuracy. The rapid mold movement is realized by the servo motor through the ball screw. The high-pressure mold locking is after the plug on one template is inserted into the locking sleeve on another template, More than two pairs of mold locking cylinders distributed on the left and right sides of one template tighten the other template to realize high-pressure mold locking, otherwise, it is high-pressure mold opening

hydraulic synchronous drive pull rod less clamping mechanism. The pull rod free clamping mechanism of Taiwan Fengji Iron Factory Co., Ltd. is different from the bolt type pull rod free clamping mechanism. The maximum specification reaches VSE (DCE) -150 (screw diameter). It uses two sets of mutually symmetrical hydraulic drive mechanisms to drive their respective templates synchronously and separately. Because the center of the template is driven by the force of the driving oil cylinder, it can reduce the weight of the template, reduce the locking deformation, make it easier to load and unload the mold, and have a larger capacitance modulus It is more suitable for the operation of manipulator, and has more advantages in performance than the bolt type non pull rod clamping mechanism, which is worth popularizing and applying

5 parison wall thickness control

the optimization of product wall thickness is a major goal pursued by large extrusion blow molding machine manufacturers, and it is also a key technology. The prominent problem of hollow containers produced in China is the uneven wall thickness. The parison wall thickness control system is divided into axial wall thickness distribution system (AWDs) and radial wall thickness distribution system (PWDs). The two interact with each other to obtain the best parison and more ideal product wall thickness distribution. At present, most domestic large-scale extrusion blow hollow plastic molding machine manufacturers only use the axial wall thickness distribution system, which only controls the thickness distribution of each axial section. However, because the extruded parison is still in an equal thickness circle in the horizontal section, it is still not the best wall thickness distribution for some products with large tensile requirements in a symmetrical direction. The radial wall thickness distribution system performs the best wall thickness control for products with large tensile requirements in the symmetrical direction, which can make the extruded parison change in a non-circular section in a required section. It is of great significance to improve the product quality and improve the thickness uniformity of the internal and external radius of curved parts. At the same time, it can also reduce the product weight on the premise of ensuring the product quality. Take 1000L container as an example, The radial wall thickness distribution system can reduce the weight by 5%-10%. There are two kinds of radial wall thickness distribution systems: the flexible ring type that changes the thickness of the embryo by controlling the deformation of the thin-walled flexible ring in one or two symmetrical directions through the electro-hydraulic servo system; Through the up and down movement of the shaped mouth ring, the lip repair to change the thickness of the shaped embryo is realized, which helps it carry out recycling education in all parts of the United States. As an alternative to the radial wall thickness distribution system, the core mold modification method, which has the function of axial wall thickness distribution system control, modifies the specific position of its core mold to approximately obtain the non-circular variation in the radial direction

Up to now, China has not been able to produce a system that meets the performance requirements of the

embryo wall thickness control servo system, especially the radial wall thickness distribution system is still blank, which hinders the technology of large-scale hollow plastic molding machine to a certain extent

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