The development history of plastic profiles in China

The development history of plastic profiles in China

For a long time, plastic profile extrusion has been a relatively weak category in my country’s plastics processing industry. The single-screw extruder is used, and the extrusion die is at a relatively low speed (about 1 m/min). ) Produce profiles with relatively simple cross-sections. Since the mid-1980s, in order to accelerate the development of the plastic door and window industry, my country has begun to import a large number of foreign advanced twin-screw profile extrusion molding production lines. In this way, billions of dollars have been spent to raise the production level of plastic profiles in my country to a new level. However, the development of plastic profiled doors and windows has a large demand for extrusion dies. However, the few or dozens of extrusion dies introduced with the extrusion unit are far from meeting the needs of changes and development in the architectural door and window market. At that time, the international market price for extrusion dies that could meet the requirements of these advanced extrusion units was about 30,000 to 40,000 US dollars, or even more expensive. However, the inability to provide a good supporting system in China has become one of the main factors restricting further development.

　　This situation and the resulting business opportunities have promoted the research and development of extrusion dies. Because of this, the domestic research and development work on extrusion dies is basically carried out with imported extrusion dies as samples. There are more surveying and mapping imitations, less experimental research, and less mechanism research and exploration. However, the extrusion die is very practical and has not yet formed a strict theory and a fixed model. The design and manufacture of extrusion dies in our country has achieved rapid development with the introduction of advanced foreign extrusion dies and the active participation of some universities.

However, the design of the extrusion die must solve the problems of the non-Newtonian characteristics of the molding compound flow and the comprehensive effects of mold release expansion, traction deformation, and cooling shrinkage of the molded parison, and is affected by the extrusion unit (mainly screw and barrel). Molding compound formula (including formula components and mixing conditions) and operation process (temperature, speed, cooling water and vacuum) and other aspects. Therefore, it is very difficult to design a high-quality extrusion die with simple surveying and imitating. Especially in the face of the continuous improvement and development of complex profiled materials and raw material formulations, as well as the continuous improvement of the quality and production efficiency requirements of profiled products, the lack of theory and experimentation has become more apparent. In addition, limited to perceptual experience, and relying too much on repeated debugging and repairing, the result will inevitably be more failures and a lot of waste of manpower, energy and raw materials during the debugging and repairing process, and it is also difficult to stably obtain high Quality extrusion die. However, market demand has a huge driving force. For more than ten years, my country's extrusion die has formed a considerable production capacity with the development of the plastic door and window industry. It is understood that there are currently more than five or six domestic manufacturers that actually deliver more than 200 sets of extrusion dies each year, and there are more mold factories that provide a large number of extrusion dies.

　　 In 1999, the total number of domestically produced extrusion dies actually delivered for use has exceeded 3000 sets. In addition to the single-cavity extrusion die for single melt extrusion, a multi-cavity, two-color co-extrusion, soft and hard co-extrusion, post-co-extrusion, co-extrusion of recycled materials and low-foaming steel-plastic co-extrusion have also been manufactured. Extrusion and other types of extrusion dies. The production speed of the plastic profile of the extrusion die has also been continuously improved. The domestic leading extrusion die has achieved an extrusion speed of 2.5 m/min or more for the main profile. The application of computer high-tech means has further promoted the development of extrusion moulds in our country. A practical CAD system for extrusion moulds has been successfully developed and connected with the wire-cut CNC machine tools to realize CAD/CAM integration. Coordinate wire cutting machine tools (more than ten imported) and imported abrasive flow extrusion grinding and polishing machine tools process the extrusion die cavity, which greatly improves the production efficiency and manufacturing accuracy. The mold industry formulated and implemented the plastic extrusion mold industry standard in 1998-JB/T 8744-8746-1998, which is even more mature.