With the rapid development of the chemical industry and the continuous expansion of chemical products in international trade, the demand for large extruded hollow containers has grown rapidly. The 1000-liter IBC barrels have grown at a faster rate in recent years and have grown at a rate of 8% in Europe. The United States has grown at a rate of 25% and is replacing the double-L-ring barrel. The increase in demand for large extrusion blown hollow containers has led to the development of large extrusion blown hollow plastic molding machines. Shanghai Huawang Industry Co., Ltd. developed a 1000L large hollow plastic molding machine in 1998, which filled the domestic gap and produced 1000LIBC barrels and hollow trays. Several famous extrusion blown plastic molding machine manufacturers in the world have successively introduced large-sized extrusion blown hollow plastic molding machines. In recent years, the equipment has had many new developments, and there have been significant advances in energy saving and high efficiency.

R&D priorities 1 Improving production efficiency Shortening the production cycle and increasing production efficiency are important aspects of the technological progress of large extrusion blown hollow plastic molding machines. China's large extrusion blow-molded hollow plastic molding machines are much less efficient than international large-size hollow plastic molding machines of the same specifications, so we can't just be satisfied with the equipment's ability to form products, but should be used for research and development in improving production efficiency. . The main factors related to production efficiency are plasticizing ability and blow-molding cooling time.

(1) Improve plasticizing capacity (extruded plasticizing production capacity)
Increasing plasticizing capacity is a prerequisite for improving production efficiency. The plasticizing capacity of extruders prepared on domestic large-scale extruded blow-molding hollow plastic molding machines is generally lower than the plasticizing capacity of extruders of the same specifications in the world, so the molding cycle is long and the energy consumption is high. The extruders prepared by some domestic units on large extrusion blown hollow plastic molding machines generally use conventionally designed extruders. They have not made profound studies on the special characteristics of extruders required for large-scale extrusion blown hollow plastic molding machines. Staying in the concept of universal extruder, only satisfied with the plastic extrusion, not to pursue high plasticizing ability.

Improve the plasticizing ability, that is to improve the plasticity and conveying capacity of the screw barrel. In the international market, extruders prepared on large extrusion blow-molding hollow plastic molding machines have previously adopted the "IKV" structure with forced cooling by forced feeding. “IKV” structure, which mainly has deep and wide longitudinal grooves with different shapes in the liner of the feeding zone of the barrel, and at the same time, the forced cooling structure is designed in the feeding area, which greatly improves the transportation efficiency, 0.3-0.5 increase to 0.6-0.85, plus a reasonable design of the barrier and mixing sections, the plasticizing ability of the extruder is more than 50% higher than that of the conventional designed extruder, and the extrusion volume is stable. Domestic production of φ150/25 extruder, when processing HMWHDPE powder, its plasticizing capacity only reached 250kg/h, German Krupp company's “IKV” structure of φ150/25 extruder is processing 70% new material and 30% HMWHDPE blended with comminuted material has a plasticizing capacity of 600 kg/h and a nominal specific power of only 0.3 kw/kg.h-1. The "IKV" structure has not been adopted on domestic extruders and it is worth considering. Of course, the "IKV" structure also has some drawbacks, such as serious wear of the screw and barrel, high energy away from the cooling water, etc. Therefore, when designing the screw and barrel, we should combine the actual situation and continue to adopt new materials. Technology, on the basis of the "IKV" structure, continues to research and improve and improve the plasticizing and plasticizing quality. Of course, some manufacturers have made achievements in improving the plasticization capacity. Guangdong Jinming Plastic Equipment Co., Ltd. has developed a high-output screw that can process 100% of new material and can also process 100% of powder and 100% of reclaimed material. The output is more than 40% higher than the conventionally designed screw output.

(2) Shortening blow molding time The key to shortening the blow molding time is to improve the performance of the blow molding system. The main technical specifications of the blow molding system are blowing pressure and gas temperature. The blow molding equipment we are now equipped with is a conventional air compressor, which uses conventional blowing pressure and cannot meet the need for rapid inflation and cooling of large hollow products. The wall of large hollow plastic products is thick, so the performance of the blow molding system not only relates to the production efficiency, but also relates to the quality of the products, especially the strength of the bonded seam of the parison. The key to improving the quality of products is to increase the air blowing pressure and use low-temperature dry high-pressure air blow molding. German company Beke cools the air to -350C to -450C, blow molding, strengthens the cooling of the inner wall of the product, makes the cooling rate of the inner and outer walls of the product uniform, greatly improves the quality of the product, and the cooling time is shortened by no less than 20%. , Increased production efficiency.

2 The head of the high-performance storage type head single-layer large-sized blown hollow container is a storage type head. The containers produced by China's large-scale extrusion blown hollow plastic molding machines are basically single-layered, for example, 200L double-L-ring barrels, IBC barrels, etc. The single-layer large hollow container is formed of HMWHDPE raw material. HMWHDPE is a crystalline plastic with strong molecular orientation, and the “elastic memory” effect of the melt is strong. Therefore, the storage material head must be able to achieve sufficient molecules in the melt. The time rearranges the distribution, broadens the distribution of the melt flow MWD, and reduces the radial temperature gradient of the melt, so as to increase the strength of the melt fusion zone and the quality of the parison surface, so as to ensure that the melt within the extruded parison does not crack. In order to improve the product strength; high-performance storage type head must have a reasonable flow channel structure, can fully meet the plastic melt molding process requirements, can achieve rapid color change refueling. One of the main features of improving the performance of the stocking head is to increase the strength of the melt fusion zone. At present, there are also many domestic use of melt fusion seam zone poor strength of the single-layer heart-shaped envelope flow design of the storage type head. The double-layered heart-shaped enveloping flow path storage head is a high-performance storage type head, the principle of which is to divide the fusion joint into two and staggered distribution, and the parison is covered by a complete melt layer Improve the melt fusion zone strength, widely used in the world. The advanced structure and advanced design methods can achieve the best results. The application of CAD is a necessary method to achieve high performance in the storage head of a dual-layer heart-shaped enveloping flow path. The computer software currently used in the head design is FLOW2000 large-scale computer analysis software and three-dimensional mold design software PRO/ E et al., At present, the design of the storage type heads in China is basically not using advanced CAD methods and is based solely on experience. This is the main reason for the low performance of the storage type heads in China. First-in-first-out, fast color-change refill, and easy-to-clean are the important characteristics of high-performance storage-type heads. The positive approach is to use advanced CAD methods with high-quality steel and precision processing equipment and advanced CAE processing methods.

3 The machine lifting mechanism of the domestic large-scale extrusion blow-molded hollow plastic molding machine is mostly a sprocket chain mechanism. Practice has proved that due to its own defects, the transmission mechanism is inconvenient to adjust and easy to bite, especially above 200L. The machine lift mechanism. However, because some units copied each other and did not make fundamental reforms, they are still in use. Therefore, a substantial reform must be made to the large-scale extrusion blow-molded machine lifting mechanism in China, and the single-driven sprocket chain synchronous lifting mechanism should be changed to two or four synchronous drive mechanisms to eliminate the phenomenon of seizure.

4 Clamping mechanism Clamping mechanism should have high movement accuracy, high speed, easy loading and unloading molds and other properties. At present, the mold clamping mechanism of large-scale extrusion blow-molded hollow plastic molding machines in China follows the structure of a small-sized hollow container molding machine mold clamping mechanism, adopts three-bar linkage of four-pull rods or four-bar linkages and its expansion structure. The main disadvantages are: Uneven stress of the template. , The phenomenon of easy to increase the mold, at the same time due to the presence of the rod, the space of the mold is subject to certain restrictions, so that the manipulator's operating space is constrained.

Boltless tie bar clamping mechanism is a kind of clamping mechanism developed in recent years. It has the characteristics of large clamping force, uniform distribution, easy loading and unloading of moulds, large capacity and energy saving, and the use of small coefficient of friction and movement in the guide movement. Smooth, high-precision ball linear guide, rapid shifting of the mold by the servo motor through the ball screw to achieve, high-pressure mold clamping is a template on the plug into another template on the locking sleeve, distributed in a template on both sides Two or more pairs of clamping cylinders tighten another template to achieve high pressure mode locking, and vice versa, high pressure mode opening.

Synchronously driven hydraulic rodless clamping mechanism. Taiwan's Fengji Iron Works Co., Ltd.'s tie bar-less mold clamping mechanism is different from the plug-type tie-barless mold clamping mechanism, the largest specification to achieve VSE (DCE)-150 (screw diameter), it is synchronized with the two sets of hydraulic drive mechanism synchronization Driving each template separately, because the template center is driven by the force of the cylinder, it can reduce the weight of the template, reduce the amount of lock deformation, loading and unloading the mold is easier, the larger the module capacity, more suitable for manipulator operation, performance than Pin-type tie-barless mold clamping mechanism has more advantages and is worth popularizing and applying.

5 Optimizing the wall thickness of parison wall thickness control products is a major goal pursued by manufacturers of large extrusion blown hollow plastic molding machines. The same technology is also a key technology. The prominent problem in hollow containers produced in China is that the wall thickness is not uniform, and the parison wall thickness control system is divided into an axial wall thickness distribution system (AWDS) and a radial wall thickness distribution system (PWDS), which can work in conjunction with each other. Get the best parison and more ideal wall thickness distribution. At present, most large extrusion blown plastic molding machine manufacturers in China only use the axial wall thickness distribution system. The system only controls the thickness distribution of each axial section, but the extruded parison is in the horizontal section. It is still in the shape of a circle of equal thickness, but it is still not the best distribution of wall thickness for products that have a part with a greater tensile requirement in a symmetrical direction. Radial wall thickness distribution system for optimal control of wall thickness in products with large tensile requirements in the symmetric direction, allows the extrusion of parisons to have a non-circular cross-section change in a desired section, which improves product quality. Improving the uniformity of the thickness of the inner and outer surfaces of the curved part is of great importance. At the same time, it can also reduce the weight of the product under the premise of guaranteeing the quality of the product. Taking a 1000L container as an example, a radial wall thickness distribution system can be used to reduce the weight. %-10%. There are two types of radial wall thickness distribution systems: flexure rings that change the thickness of the preform by controlling the deformation of a thin-walled flexible ring in one or two symmetrical directions by an electro-hydraulic servo system; To achieve a change in the thickness of the embryo margin repair form. As an alternative to the radial wall thickness distribution system, the core mold modification method, that is, the function of controlling the axial wall thickness distribution system, corrects the specific position of the core mold, and approximately obtains the non-radial position. The amount of round change.

The embryo wall thickness control servo system has not yet been able to produce a system that meets the performance requirements in China, and in particular, the radial wall thickness distribution system is still blank, which to some extent hinders the technological progress of large hollow plastic molding machines.