Since the introduction of technological innovation in the 1950s, screw-type plastic injection molding machines have been in existence for more than 50 years. At present, 80% of the engineering plastics industry uses injection molding. In recent years, due to the growing demand for injection products in the automotive, construction, household appliances, food, and pharmaceutical industries, the development and improvement of injection molding technology has been promoted. China's plastic machinery sales in 2000 were around 7 billion yuan, with a record of about 85,000 units, of which about 40% were injection molding machines. From the perspective of major producing countries such as the United States, Japan, Germany, Italy, and Canada, the output of injection molding machines is increasing year by year, accounting for the largest proportion of plastic machinery.

 

    1. Technical level and development trend of plastic injection molding machine

 

    From the advent of injection machines, the clamping force is 1000-5000kN, and the small and medium-sized injection machines with injection volume of 50-2000g account for the vast majority. In the late 1970s, large-scale injection machines were rapidly developed due to the development of engineering plastics, especially in automobiles, ships, aerospace, machinery, and large household appliances. The United States is the most obvious. In 1980, there were about 140 large-scale injection molding machines with a clamping force of 10,000 kN or more in the United States. In 1985, it increased to more than 500. Japan's famous machine company has successfully manufactured the world's largest injection molding machine with a clamping force of 120,000 kN and an injection volume of 92,000 g.

 

    Since the 1980s, CAD/CAE/CAPP/CAM computer application technology has been widely used in the plastic machine manufacturing industry, which has promoted the rapid development of the research and development and manufacturing level of China's injection molding machines. A group of national high-tech enterprises represented by Ningbo Haitian Co., Ltd. have successively introduced software such as computer aided design and analysis from UGS and PTC of the United States to realize three-dimensional parametric modeling, mechanism motion simulation, and original masterpieces. Analysis, accurate analysis and calculation of stress distribution, stress peaks and dangerous areas in high stress areas, help designers to quickly understand, evaluate and modify the design plan to ensure the reliability of the rationality of important parts structure. In order to ensure high-quality design output to high-quality product output, the old processing methods have been difficult to adapt to the requirements of technology and quality competition. In the "Eighth Five-Year Plan" and "Ninth Five-Year Plan", Haitian Company has invested a total of 200 million yuan to form a processing center branch in accordance with the scientific method of rolling development. A new large-scale assembly plant of 50,000 square meters, a 100,000 square meter sheet metal and structural parts processing plant, a new 10,000 square meter test workshop and laboratory, and a new three-dimensional automatic warehouse with 5,928 warehouse locations. Purchased two flexible processing lines from OKUMA, Germany, and added them to a fleet of more than 40 machining centers. The National 863 Program - Zhejiang Haitian CIMS Project was implemented, and the K3 system was successfully applied to realize computer integrated management such as production planning, materials and costs. The introduction of IMAN system realizes computer integrated management of product technical data creation and tracking, product structure and version, query of product attributes and associated data, and information transfer to K3 system.

 

    In 2000, Haitian achieved a sales income of 860 million yuan in this year, a foreign exchange earning of 10 million US dollars, a profit tax of 200 million yuan, and 100 large-scale injection molding machines with international level in the 1990s. Two major technologies of international advanced level were carried out. The development of equipment, one is the injection molding machine's protective door, distribution box and other metal parts on the surface of the plastic injection line to form mass production capacity, and the second is the injection molding machine screw and barrel bimetal spraying process into mass production, so that key components have been Three complete series are formed, which are the HTW and HTFX series of toggle-type clamping, the HTK series of direct-pressure mode-locking, and the HTD series of servo motor control. The basic parameters are from 580kN to 36000kN, and the injection weight is from 70g to 51,460g, which is in the leading position in China.

 

    Haitian Company pays great attention to the development of international injection machines and strives to catch up with the development of advanced productivity. The international mold shift speed has been increased from 20-30m/min to 40-50m/min, and the highest is 70m/min. Haitian's small and medium-sized machines have already entered the 40-50m/min level, and the mainframe is at the level of 30-35m/min. The injection speed has increased from the past 100 mm/s to the current 250 mm/s, and some have reached 450 mm/s. The electric injection molding machine developed by Nippon Steel Works has reached 900mm/s. Haitian brand injection molding machines generally exceed 130mm/s. Accelerate to 450mm/s with an accumulator. The injection pressure has increased from the previous 120-150 MPa to the current 180-250 MPa. Japan's SN120P machine has reached 460MPa, and its product shrinkage rate is almost zero, product tolerance can be guaranteed at 0.02-0.03mm, wall thickness can be guaranteed to 0.l-0.2mm. Energy saving from the past flow ratio and pressure proportional control to variable control or quantitative control, variable frequency speed control, servo control technology injection molding machine, energy consumption is only 30% of traditional machines, Haitian company using variable frequency servo technology injection molding machine The energy consumption is only 50% of the traditional. The high efficiency of the injection molding machine is mainly reflected in the fast working cycle and short product cycle, which is generally more than 24% higher than in the past. The mold opening and pre-molding of high-efficiency injection molding machines are generally completed simultaneously. Both core pulling and ejection are completed in the mold opening. The fastest injection molding machine at the daily exhibition, the working cycle is only 1 second. The control technology of the injection molding machine has undergone the development process of relay, contactor control and programmable controller control and special computer control. Since the late 1960s, the company's first application of computer control technology, after the rapid development since the 1980s, is not a simple motion control, but includes melt temperature, injection pressure, injection speed, dwell time, cooling process and hydraulic pressure. Comprehensive control of various parameters of the loop. In the past, most of them used open-loop control and are currently moving toward closed-loop control. The Klaus Maffei PM control system in Germany, through the clamping force, cavity pressure and filling process control, makes the product quality error accurate to 0.15%. The gap between Haitian's control technology and today's international advanced level is still relatively large. The special computer we independently developed has certain reliability and stability, anti-interference ability, feedback response sensitivity, resolution accuracy, etc. with Siemens, Baba Kangmen, etc. distance. In addition, the motion accuracy and comprehensive error of the hardware need to be further improved.