Plastic molding processing technology has been widely used in the production of many high-tech products, such as auto parts, 3C electronic products, connectors, displays, mobile phones, plastic optical lenses, biomedical application products, and general daily necessities, etc. With the trend of diversification of product usage and variability in functional requirements, plastic molding processing technology is booming day by day.
Overview of Plastic Machinery
The general term for various machinery and devices used in the plastics processing industry. Certain general-purpose machinery and equipment such as fluid and solid conveying, separation, crushing, grinding, and drying also occupy an important position in the plastics processing industry, so they are often listed as plastic machinery.
According to the production process of plastic products, plastic machinery can be divided into four categories: plastic compounding machinery, plastic molding machinery, plastic secondary processing machinery, and plastic processing auxiliary machinery or devices. Plastic compounding machinery is used in the manufacture of various forms of plastic compounding materials, including kneaders, plastic mixing machines (open mills and internal mixers), pelletizers, screening machines, crushers, and grinders. Plastic molding machinery, also known as plastic primary processing machinery, is used for the molding of plastic semi-products or products, including compression molding machines, injection molding machines, extruders, blow molding machines, calenders, rotational molding machines, foaming machines, etc. Plastic secondary processing machinery is used for reprocessing and post-processing of plastic semi-products or products, including thermoforming machines, welding machines, heat sealing machines, hot stamping machines, vacuum evaporation machines, flocking machines, printing machines, etc. Metal processing machine tools are also commonly used for secondary processing of plastics. Plastic processing auxiliary machinery or devices are used to rationalize the plastic processing process, including automatic metering and feeding device, automatic scrap recycling device, automatic injection molding product removal device, injection mold quick replacement device, injection mold cooling machine, automatic thickness measurement device, and raw materials transportation and storage equipment, etc. Such auxiliary machinery or devices have become an indispensable part of modern plastic processing automation.
The perfection of plastic machinery directly affects the quality, output, and cost of plastic semi-products or products, so it must be able to adapt to changes in temperature and stress during plastic compounding and processing, as well as the resulting changes in the properties of molten materials, and to adapt to chemical corrosion and special conditions such as mechanical wear. The specialization of plastic grades, the development of engineering plastics, the emergence of composite materials, the development of large-scale, lightweight, and thin-walled plastic product structures require plastic machinery to achieve: complete sets for product production purposes; high-speed, labor-saving, Automation to improve the production efficiency of products; to ensure the precision of product specifications and quality with the smallest error; low energy consumption, less space, easy and safe operation, and maintenance.
Plastic industry development
Compared with metal, stone, wood, plastic has the advantages of low cost and strong plasticity. It is widely used in the economy and daily life. The plastic industry occupies an extremely important position in the world today. The production of plastic products has developed rapidly all over the world for many years. China's production of plastic products has always been at the forefront of the world rankings. Among them, the production of many plastic products has ranked first in the world, and China has become the world's largest producer of plastic products. From 2001 to 2010, the average annual growth rate of China's plastic product output remained above 15%. In 2010, China's total output of plastic products reached 58.3 million tons.
What are the types of plastic machinery?
There are many types of plastic machinery. According to the processing technology, it is divided into three categories: extruder, injection molding machine, and blow molding machine.
The extruder extrudes the molten plastic through a fixed-shaped extrusion port under the action of a screw and cuts it after being shaped by water cooling under the action of a tractor. It is mainly used for the continuous production of various products with the same cross-section, such as pipes, rods, and profiled materials. It can also be used for plastic modification and granulation.
The basic mechanism of extrusion is: a screw rotates in the barrel and pushes the plastic forward. The screw is an inclined surface or slope, wound on the center layer. The purpose is to increase the pressure to overcome the greater resistance. As far as an extruder is concerned, there are three types of resistance to overcome: the friction of solid particles (feed) against the barrel wall and the friction between them during the first few revolutions of the screw (feed zone); The adhesion on the wall of the cylinder; the flow resistance inside the melt when it is pushed forward. Divided into a single screw extruder and twin-screw extruder.
Injection molding machine
The injection molding machine injects molten plastic into the mold, and the product becomes the product after cooling. It has a wide range of uses. Depending on the plastic, the place of use is also different. The injection molding machine is the most used processing machine in the plastic processing industry. Not only a large number of products can be directly produced by the injection molding machine, but it is also a piece of key equipment for the injection stretch blowing process.
Blow molding machine
Blow molding is a common method for manufacturing hollow thermoplastic products. The main products are tube films and hollow containers. The blow molding machine can plasticize the preformed product by heating, and then enter the mold to blow molding. This method is mainly used for high-speed and high-yield PET bottles and BOPP bottle production is a two-step process; blow molding can also be combined with the injection molding process to become an injection stretch blow integrated machine, which is also a common method for producing PET containers; blow molding process can also be combined with the extrusion process, extrusion Blow molding equipment has a wider range of applications and can produce more products. Products include multilayer composite films and various polyolefin hollow containers, which are widely used in the food, medicine, and cosmetics industries.
The film blowing machine heats and melts the plastic particles and then blows them into a film. There are many types of film blowing machines, including PE, POF, and so on. The new material is blown out with brand-new particles, the color is uniform, clean, and the bag stretches well. Some people use recycled plastic bags to make particles. These kinds of particles are usually called old materials. When they are made into particles, they are usually gray. When making bags, pigments are usually added to make the bags unevenly colored, brittle, and easy to break. The price is lower. Although it is a recycled plastic bag, there is still a big difference between the waste bag in the bag making process and the garbage plastic in the usual sense. The most important factors in the work of the film blowing machine are three factors: temperature (machine temperature, indoor temperature), two spirals, and three cooling systems.
The film blowing machine produces a film suitable for all kinds of high-grade film packaging. This kind of film can be widely used in light and heavy packaging due to its good barrier properties, freshness, moisture-proof, frost-proof, oxygen barrier, and oil resistance. Such as various fresh fruits, meat products, pickles, fresh milk, liquid beverages, medical supplies, etc.
In plastic machinery, the calender is usually combined with pilot devices such as material conveying, screening, metering, kneading and plasticizing, and subsequent devices such as separation, traction, embossing, cooling, thickness measurement, coiling, and cutting, as well as transmission, monitoring and heating. Equipment and other equipment constitute a complete calendering production line to produce soft and hard films, sheets, artificial leather, wallpaper, and floor coverings, and other products. There are many types of calenders in plastic machinery. The number of pressing rollers is divided into two rollers, three rollers, four rollers, and five rollers. The arrangement of pressing rollers can be divided into F, Z, S, and L types.
Different from other plastic machinery, the calender consists of a frame, a pressure roller and its adjusting device, a transmission system, and a heating system. The frame is usually made of cast iron and is directly installed on both sides of the cast iron or cast steel frame to support the roller bearings, cross-shaft or roller pre-bending device, roller adjusting device, lubricating device, and other auxiliary devices. The pressure roller is made of chilled cast iron and cast steel, and its aspect ratio is selected according to the bending strength of the pressure roller material, which is about 2.6 to 3.5. To compensate for the uneven thickness of the product caused by the bending deformation of the pressure roller, the pressure roller is mostly made into a waist drum shape, and the roller cross-device and the roller pre-bending device can also be used to eliminate the uneven thickness of the product. Each pressure roller is driven by a separate motor. Steam or superheated water is generally used for the heating of the pressure roller, and the temperature difference between the two ends is required to not exceed 1°C. Each pressure roller has an independent automatic heating system. Modern calenders use roller bearings instead of traditional sliding bearings to save energy, improve bearing life, and product thickness accuracy. According to the different calender specifications, the thickness of the soft PVC film produced is also different, ranging from 50 to 1000m, and the minimum thickness of the hard PVC film is 60m.
The full name is a closed plastic mixing machine. It is one of the main equipment for plastic compounding. According to the working principle, it can be divided into two types: intermittent and continuous. The main structural parameters of the internal mixer are the rotor speed, diameter, length, and the total capacity of the internal mixer.
The structure of the elliptical rotor type batch internal mixer consists of a mixing chamber, a rotor, an upper top bolt (pressing device), a lower top bolt (discharging device), heating, and cooling devices, and a transmission system. The working principle is: the mixture enters the mixing chamber from the feeding hopper, and is subject to constant changes in the gap between the two relatively rotating rotors, the gap between the rotor and the inner wall of the mixing chamber, and the gap between the rotor and the upper and lower top bolts. Kneading and friction make the plastic heat and plasticize, and mix it evenly. Intermittent mixers have tended to be standardized and serialized. The internal mixer has 4, 25, 50, 75, 150, 250, 380l specifications according to the total capacity. Since batch internal mixers are not suitable for continuous production, continuous internal mixers were developed in the 1960s. The more commonly used are rotor type continuous internal mixer and twin-screw mixer. There are many types of twin-screw mixers. Generally, it has the ability of forced conveying of materials, strong mixing function, short residence time of materials in the twin-screw, and good self-cleaning performance of the twin-screw, which can eliminate material accumulation in time and reduce material degradation, so the application is increasingly popular.
There are two types of molding machines used for thermoplastic plastic sheets: sheet and roll feeding type and single sheet feeding type. The sheet and roll feed type thermoforming machine feeds the roll-shaped sheet material or directly connects with the sheet extruder to form an assembly line. The single-sheet feed type thermoforming machine is named after the pre-cut sheet material is fed.
Continuous film and roll feeding thermoforming machines are quite popular. They can produce high-quality products at high speeds and supply them by mold specifications. The most popular ones are 60×60, 90×90, 125×106cm and other specifications. This type of thermoforming machine is often designed with a heating furnace whose length is 3 to 4 times the size of the longest mold. Most heating furnaces are electrically heated and installed on a rack that can be removed from the sheet conveying system. There are two main types of ovens: C frame type and drop door type. Thermoforming systems are mostly hydraulically or mechanically driven. Single-chip feed thermoforming machines can be divided into two types: rotary type and shuttle type. Rotary thermoforming machines are often used for mass production of products. There is a three-station standard thermoforming machine with a rotation of 120°; there are also four-station thermoforming machines with a heating station. The shuttle thermoforming machine has a forming station, and the sheet material is clamped on the clamping frame and then reciprocated above the heating furnace. It is also designed as a double-station thermoforming machine composed of two forming stations and an oven. The processing adaptability of this type of thermoforming machine is wide.
Plastic industry trends
- Starting from the development of plastic products, provide users of plastic machinery with a full range of services from products, process formulas, equipment, and after-sales services.
- Following the requirements of users, design and manufacture applicable equipment specifically for users to solve their technological difficulties.
- Timely learn from the technological development of related industries and apply the latest scientific and technological achievements to the industry. Such as the scientific and technological achievements of electronics, communication industry, automobile industry, and aerospace industry.
- Keep up with the progress of materials science and adapt new equipment to the processing of new raw materials.
- Establish the concept of equipment that is the key factor for users to succeed or fail in market competition, and strive for high-speed, high-efficiency, and energy-saving equipment operation.
- There are cases of optimization and reorganization among companies, but there is no large-scale alliance of large chemical companies. Since foreign professional collaboration is very mature, the scale of plastic machinery manufacturing enterprises will not be too large.