The nature of the load of the injection moulding machine is constant torque class, with hard mechanical characteristics and high dynamic characteristics requirements, so a special inverter for injection moulding machines should be used. The special inverter for injection moulding machines is based on the general purpose inverter with an additional 0~1A signal conversion link to improve the performance of use. Considering the time required for each stage of the injection moulding process, the acceleration and deceleration time of the inverter should be short, generally 1 second, so the capacity of the inverter should be increased appropriately. Ningbo Haishi Plastic Machinery recommends the use of a constant torque frequency converter dedicated to Zhengyi injection moulding machines. Due to the special nature of the injection moulding machine process, various faults will be encountered in the transformation, the following are the problems commonly encountered in the transformation of the injection moulding machine frequency and processing methods.

1. No change in frequency of the inverter

As the inverter adopts the injection molding machine valve control current signal for speed control, the frequency display after the operation of the inverter is 0.0 (some inverters show 0) phenomenon, the main reason for the signal polarity reversal; signal to take the wrong; signal wiring port and parameter settings do not match; injection molding machine auxiliary power failure, etc., this failure should first identify the category of injection molding machine valve control is the current signal, voltage signal or pulse control signal (some models), and whether the signal positive and negative polarity and inverter control terminals correspond.

2. Noisy oil pump

Some injection moulding machines will make abnormal noise after the operation of the frequency converter, then the noise source should be judged where, is from the motor or oil pump, if the noise of the oil pump may be caused by: injection moulding machine hydraulic oil is too little, there is air inhalation; injection moulding machine oil filter or oil blockage; injection moulding machine oil pump vane wear more serious; encounter the situation should first check the injection moulding machine oil pump, troubleshooting before running, in addition when injection moulding in low speed In addition, when the injection molding is at low speed and high pressure, the noise of the oil pump will be abnormal, and the speed signal will be increased appropriately.

The injection molding machine has the ability to mold complex appearance, precise size or dense plastic products with metal inserts, and is widely used in national defense, mechanical and electrical, automotive, transportation, building materials, packaging, agriculture, education and health and people's daily life in various fields. In the rapid development of the plastics industry today, injection moulding machines occupy an important position in terms of quantity or variety, and their total production accounts for 20% - 30% of the entire plastic moulding equipment, thus becoming the fastest growing plastic machinery, production of the largest number of machines. According to relevant statistics, from 1996 to 1998, China exported 8383 sets of injection moulding machines (sets) and imported 42959 sets of injection moulding machines (sets), of which the output of China's injection moulding machines reached 20000 sets in 1998, and its sales accounted for 42.9% of the total sales of plastic machines.

China's plastic processing enterprises are scattered all over the country, the technical level of equipment varies, most processing enterprises need technical transformation of their equipment. In the past few years, China's plastic machine industry has made remarkable technological progress, especially the gap between the technical level of injection moulding machines and foreign brand-name products has been greatly reduced, and significant improvements have been made in the level of control, the internal quality of products and the appearance of the shape. The choice of domestic equipment, with a smaller investment, can also produce products of comparable quality to imported equipment. These have created conditions for the technological transformation of enterprises. The development status of China's injection moulding machines At present, China produces more manufacturers of injection moulding machines, according to incomplete statistics, there are more than 60. There are two types of injection moulding machines: vertical and horizontal. According to the products produced can be divided into ordinary type and precision injection molding machine. One-time injection volume 45-51000g; clamping force 200-36000kN; processing raw materials are thermosetting plastics, thermoplastics and rubber three. Thermoplastics include polystyrene, polyethylene, polypropylene, nylon, polyurethane, polycarbonate, plexiglass, polysulfone and (acrylonitrile/butadiene/styrene) copolymer (ABS). In terms of the products processed, there are single-colour, two-colour general and precision plastic products. The main manufacturers of the above products all have their own series, each with its own characteristics. For example, Guangdong Zhende Plastic Machinery Factory Co., Ltd. produces the Jieba CJ series of injection moulding machines, which are available in both CNC and computer-controlled forms for each specification. Ltd. in Zhejiang Province produces the HTF80X-HFT3600X series of injection moulding machines, which can be used to produce a variety of high-precision thermal plastic products. The machines use linear movement sensors to control injection, mould closing and ejection, and adopt multiple CPU electronic control systems, large format colour LED displays and full computerised automatic control.

Ordinary horizontal injection moulding machine is still the leading direction of development of injection moulding machine, its basic structure almost no major changes, in addition to continue to improve its control and automation level, reduce energy consumption, manufacturers according to the changes in the market is developing to the direction of combination series, such as a model of injection moulding machine configuration of large, medium and small injection device, combined into a standard type and combination type, increasing the flexibility, expanding the scope of use,? This has increased flexibility, expanded the range of use and improved economic efficiency.

In recent years, the injection moulding machine manufacturers in the world's industrialized countries have been improving the functions, quality and auxiliary equipment of common injection moulding machines, as well as the level of automation. At the same time, they are vigorously developing and developing large injection moulding machines, special injection moulding machines, reaction injection moulding machines and precision injection moulding machines to meet the needs of producing plastic alloys, magnetic plastics and plastic products with embedded parts.

Injection moulding machine is currently one of the fastest developing plastic machines in China, and the gap between the level and the developed industrial countries is relatively small. However, mainly refers to ordinary injection moulding machines, in most varieties of extra-large, various special, dedicated and precision injection moulding machines, some products are still blank, which is the main gap with the industrial developed countries