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With China Plastic Machinery
With China Plastic Machinery
Also known as plastic molding processing. It is a general term for various processes that convert synthetic resins or plastic into plastic products. It is a large production department in the plastic industry. Plastic processing generally includes plastic batching, molding, machining, joining, modification and assembly. The last four processes are carried out after the plastic has been molded into finished products or semi-finished products, also known as plastic secondary processing.
Plastic processing has developed with the development of synthetic resins, and it has promoted the development of plastic machinery. Many plastic processing technologies are borrowed from rubber, metal and ceramic processing. The history of plastic processing can be traced back to the 1890s. After the birth of celluloid, it could only be made into blocks by molding because it was flammable, and then machined into sheets, which could be processed by thermoforming. This is the earliest plastic processing. Casting molding was successfully studied with the advent of phenolic resin; injection molding began in the 1920s and was used to process cellulose acetate and polystyrene; in the mid-1930s, soft polyvinyl chloride extrusion molding was successfully developed, and a single-screw extruder dedicated to plastic was introduced accordingly; in 1938, a twin-screw extruder was also put into production. In the early 1940s, polyurethane foam plastic were produced, and blow molding technology was used to produce polyethylene hollow products. The advent of the reciprocating screw injection machine in 1952 brought injection molding technology into a new stage. In the 1960s and 1970s, the newly developed plastic processing technologies included: various new molding methods for reinforced plastic, such as winding, pultrusion, sheet molding, reaction injection molding, structural foam molding, profile extrusion molding, sheet solid phase molding, co-extrusion, co-injection molding, etc. In the 1980s, plastic processing developed in the direction of high efficiency, high speed, high precision, energy saving, large-scale or ultra-small, ultra-thin, etc. Computer technology entered this field, raising the entire plastic processing technology to a new level.
In addition to polymers, the raw materials used in plastic processing generally also need to add various plastic additives (such as stabilizers, plasticizers, colorants, lubricants, reinforcing agents and fillers, etc.) to improve the molding process and the performance of the product or reduce the cost of the product. The additives and polymers are mixed and evenly dispersed into powder, also known as dry blends. Sometimes the powder needs to be processed into granules by plastic refining. Such powders and granules are collectively called compound materials or molding materials.
The key link in plastic processing. Plastic in various forms (powders, granules, solutions or dispersions) are made into products or blanks of the desired shape. There are as many as thirty molding methods. Its selection is mainly determined by the type of plastic (thermoplastic or thermosetting), the starting form, and the shape and size of the product. Common methods for processing thermoplastic include extrusion, injection molding, calendering, blow molding and thermoforming, and thermosetting plastic are generally processed by compression molding, transfer molding, and injection molding. Lamination, molding and thermoforming are methods of shaping plastic on a flat surface. The above plastic processing methods can all be used for rubber processing. In addition, there are casting methods using liquid monomers or polymers as raw materials. Among these methods, extrusion and injection molding are the most commonly used and are also the most basic molding methods.
The methods of joining plastic parts include welding and bonding. Welding methods are hot air welding using welding rods, hot melt welding using hot poles, high frequency welding, friction welding, induction welding, ultrasonic welding, etc. The bonding method can be divided into flux, resin solution and hot melt adhesive bonding according to the adhesive used.
The operation of assembling plastic parts into complete products by bonding, welding and mechanical connection. For example: plastic profiles are assembled into plastic window frames and plastic doors through sawing, welding, drilling and other steps.
Borrowing the processing methods of metal and wood, it is possible to manufacture plastic products with very precise dimensions or in small quantities. It can also be used as an auxiliary process for molding, such as sawing of extruded profiles. Because the properties of plastic are different from those of metals and wood, plastic have poor thermal conductivity, low thermal expansion coefficient and elastic modulus. When the clamp or tool is pressurized too much, it is easy to cause deformation, and it is easy to melt when heated during cutting, and it is easy to adhere to the tool. Therefore, when plastic are machined, the tools used and the corresponding cutting speeds must adapt to the characteristics of the plastic. Commonly used mechanical processing methods include sawing, shearing, punching, turning, planing, drilling, grinding, polishing, threading, etc. In addition, plastic can also be cut, punched and welded by lasers.
The purpose is to beautify the surface of plastic products, which usually includes: mechanical modification, that is, using filing, grinding, polishing and other processes to remove burrs and burrs on the parts, and correct the size, etc.; coating, including coating the surface of the parts with paint, using solvents to brighten the surface, and covering the surface of the products with patterned films, etc.; coloring, including painting, printing and hot stamping; metal plating, including vacuum coating, electroplating and chemical silver plating. Among them, hot stamping is to transfer the colored aluminum foil layer (or other patterned film layer) on the hot stamping film to the parts under heating and pressure. Many household appliances, building products, daily necessities, etc. use this method to obtain metallic luster or wood grain patterns.
The Chinese government has a series of policies to promote the development of the plastic industry, and will vigorously promote the stable and sustainable development of the entire industry
In order to cope with the impact of the international financial crisis, implement the government's overall requirements on maintaining growth, expanding domestic demand, and adjusting the structure, ensure the stable development of light industry, accelerate structural adjustment, and promote industrial upgrading, the government has issued the "Light Industry Adjustment and Revitalization Plan", and listed plastic as one of the three key industries for planning.
As one of the pillar industries of light industry, the total industrial output value, total assets, number of employees, and export volume of the plastic products industry have accounted for more than 10% of the total light industry. Therefore, the adjustment and revitalization of the plastic processing industry is directly related to the revitalization and development of the entire light industry, and occupies a pivotal position.
In the process of responding to the international financial crisis, the central and local governments have taken a series of powerful measures to help enterprises solve difficulties and overcome difficulties with enterprises.
The main measures are: First, support backbone enterprises to "go global" through various means and set up logistics centers and distribution centers in major sales markets. Second, establish economic and trade cooperation zones and actively promote the construction of overseas industrial parks and economic and trade cooperation zones. Third, continue to support the construction of foreign trade professional markets, build border trade professional markets for light industrial products in Southeast Asia, Central Asia, Northeast Asia and other regions, establish China's light industrial product trade centers in the Middle East, Northern Europe, Russia and other regions with conditions, strengthen external publicity, and facilitate the entry and exit of goods and personnel. Fourth, give full play to the role of processing trade and support enterprises to expand processing trade. Fifth, improve the foreign trade service system, such as establishing a service platform and training system for the management of technical regulations and standards of light industrial export products abroad, as well as a quality and safety case notification, return verification, early warning and emergency response system, to improve the quality management level of enterprises and maintain the image of Chinese products. Simplify the customs clearance and inspection procedures for the export of light industrial products, reduce relevant charging standards, improve customs clearance efficiency, and promote trade facilitation. The introduction of these favorable policies has gradually shown its positive role in promoting the plastic processing industry to cope with the crisis and develop healthily and rapidly.
As we all know, China's plastic processing industry has a high degree of marketization and strong adaptability. Its products also have a high cost-effectiveness in the international market. The further expansion of the domestic demand market provides a broad market space for the development of light industry. As long as we seize the opportunity, make full use of the market-driven mechanism, and make up our minds to actively take comprehensive measures, we can achieve the adjustment and revitalization of the plastic processing industry. Both the government and enterprises realize that this international financial crisis is an opportunity for reshuffle. As long as we have firm confidence, seek opportunities in crisis, judge the situation, and focus on the present and the long-term, we can turn crisis into opportunity and gain greater development space. Such as the following aspects:
Inorganic chemicals, chemical printing and dyeing, organic raw materials, polymers/resins, plastic and rubber, chemical equipment, coatings and paints, chemical reagents, foreign exhibitions, Chinese exhibitions, exhibition information, insulating electrical materials and equipment, epoxy flooring, electronic materials, adhesives, paints and coatings, fiberglass and construction industries
Processing shrinkage marks
Plastic processing shrinkage is one of the most common problems in plastic processing. For plastic products with high surface quality requirements, shrinkage is even more difficult. Therefore, with the continuous improvement of plastic processing technology, it is imperative to minimize the problem of plastic processing shrinkage and improve product quality.
In plastic processing, the shrinkage formed at thicker locations of plastic parts, such as ribs or protrusions, is more serious than that at adjacent locations. This is because the cooling rate of thicker areas is much slower than that of surrounding areas. The different cooling rates lead to depressions at the joint surface, which are familiar shrinkage marks. This defect seriously limits the design and molding of plastic products, especially large thick-walled products such as beveled casings of TV sets and display casings. In fact, shrinkage marks must be eliminated on products with strict requirements such as daily electrical appliances, while plastic processing shrinkage marks are allowed for some products with low surface quality requirements such as toys.
The reasons for the formation of plastic processing shrinkage marks may be one or more, including processing methods, component geometry, material selection, and mold design. Among them, geometry and material selection are usually determined by the raw material supplier and are not easy to change. However, there are many factors on mold design on the mold manufacturer that may affect the plastic processing shrinkage link. Cooling runner design, gate type, and gate size may have a variety of effects. For example, a small gate such as a tube gate cools much faster than a tapered gate. Premature cooling at the gate reduces the filling time in the cavity, which increases the chance of shrinkage marks. For molders, adjusting processing conditions is one way to solve the problem of plastic processing shrinkage. Filling pressure and time significantly affect shrinkage. After the part is filled, excess material continues to fill the cavity to compensate for the shrinkage of the material. A filling phase that is too short will lead to increased shrinkage and ultimately more or larger shrinkage marks. This method of solving plastic processing shrinkage itself may not reduce shrinkage marks to a satisfactory level, but molders can adjust filling conditions to improve shrinkage marks.
Plastic processing molding Plastic processing thermoplastic plastic commonly used methods include extrusion, injection molding, calendering, blow molding and thermoforming, plastic processing thermosetting plastic generally use compression molding and transfer molding.
Plastic processing jointing Plastic processing methods for joining plastic parts include welding and bonding.
Surface modification of plastic processing Plastic processing hot stamping is to transfer the colored aluminum foil layer (or other patterned film layer) on the hot stamping film to the workpiece under heating and pressure.
In plastic machinery processing, various plastic processing faults are often encountered. What kind of professional terms are more accurately expressed in the plastic machinery industry for these faults? Let's analyze the professional terms of plastic processing faults one by one.
1. Short injection: In plastic processing, the appearance of plastic parts is incomplete due to insufficient filling of the cavity.
2. Overfill flash: During the plastic processing molding process, the residual material overflows into the gap between the mold joint surfaces and remains on the plastic parts.
3. Weld mark: A linear mark on the surface of the plastic part, which is caused by the diversion and convergence of several streams of material in the mold during injection or extrusion. The molten material is not completely fused at the interface and cannot be fused into one, resulting in a fusion mark, which affects the appearance quality and mechanical properties of the plastic part.
4. Flow marks: Due to the improper flow of the molten material in the mold cavity, the surface of the plastic part produces annual ring-shaped, spiral-shaped or cloud-shaped wave-shaped uneven defects.
5. Surface turbidity: refers to the cracks with gaps on the surface of the plastic part and the damage formed thereby. The phenomenon of cracks on the outside or inside of the plastic part caused by long-term or repeated application of stress lower than the mechanical properties of the plastic is called stress cracking; the phenomenon of sudden and complete rupture of the plastic part due to constant load for a certain period of time at a specific temperature is called stress cracking; the cracks and ruptures of some thermoplastic parts due to excessive exposure to higher temperatures are called thermal stress cracking.
6. Compression cracking: refers to the obvious cracks in one or several layers of reinforcement materials on the outside of the laminated plastic that can be seen through the resin layer covering the surface.
7. Wrinkle cracking: A defect in which the surface of the laminated plastic is cracked and obviously separated.
8. Wrinkle: During the plastic processing, one or more layers of the surface of the plastic part have creases or wrinkles.
9. Cracking and whitening: The more obvious fine cracks on the surface of plastic parts are called cracks, and the frost-like fine cracks similar to cracks are called whitening. Cracking and whitening are fine cracks without cracks. Environmental stress cracking will occur when plastic parts are exposed to a certain chemical environment or under stress conditions.
10. Silver streak: Needle-shaped silver-white frost-like fine lines produced on the surface of plastic parts along the material flow direction.
11. Stripe: Linear stripe defects on the surface or inside of plastic parts.
12. Stripe: Due to poor dispersion or mixing of colorants and other reasons, mica flake-like dark spots are produced on the surface of plastic parts.
13. Orange peel pattern: The uneven appearance defect like orange peel produced on the surface of plastic parts.
14. Cell streak: It refers to the cell layer in foam plastic that is very different from its inherent cell structure.
15. Black spots: During the plastic processing and molding process, the molten material is overheated and decomposed under high temperature and high pressure conditions, resulting in black carbonized spots on the surface of the plastic part.
16. White spots or bright spots: In transparent or translucent plastic films, sheets or plastic parts, there are particles that are not fully plasticized. When light is transmitted, white spots can be seen. Such spots are called "fish eyes". If the material is opaque or colored, such spots are called white spots or bright spots.
17. Pockmarks: Regular or irregular small pits appearing on the surface of plastic parts, usually with a depth and width of about the same.
18. Filler spots: Obvious spots in plastic parts caused by the presence of fillers such as wood flour or asbestos.
19. Dark spots: Dark stains that appear in laminate structures with fabric as the base material.
20. Burnt and burnt spots: During the plastic processing, under high temperature and high pressure molding conditions, the melt is carbonized due to overheating decomposition, and the carbonized char is mixed in the melt, forming defects on the surface and inside of the plastic part.
21. Bubbles: During the plastic processing and mold filling process, if a large amount of gas remains in the melt, or the air in the mold cavity is not completely exhausted, the plastic part will form defects with small volume or a series of pores inside after molding.
22. Vacuum bubbles or dark bubbles: When the plastic part is cooled and solidified during plastic processing, due to the different cooling speeds inside and outside, sometimes the outer surface has been cooled and solidified, but the inside is still in a hot melt state. Once the center part cools and shrinks, vacuum holes will be generated inside the plastic part. These holes are generally called vacuum bubbles or dark bubbles, also known as shrinkage holes.
23. Pinholes: Pinhole-sized through-hole defects in plastic sheets or films.
24. Deflation: The defect of increased local density caused by the destruction of the cell structure of foam plastic during the manufacturing process.
25. Depression and shrinkage: During the cooling process of plastic processing, the surface of the plastic part is cooled and solidified first, and the internal or thick wall parts are cooled and solidified later, so that when the volume shrinks, the shrinkage speed inside and outside is inconsistent, and the surface of the plastic part is stretched by the internal part to form a depression, resulting in shallow pits or pits.
People's Daily Online, Beijing, March 29 (Reporter Sun Boyang) Yesterday, the website of the Ministry of Industry and Information Technology announced the economic operation analysis of the plastic processing industry in 2012. According to the data released by the Ministry of Industry and Information Technology, from January to December, the total industrial output value of plastic products enterprises above designated size increased by 15.04% year-on-year, and the growth rate slowed down compared with last year.
According to the data of the Ministry of Industry and Information Technology, in 2012, the growth trend of China's plastic products industry output and the total value of production and sales was stable, showing a warming trend. According to the statistics of the National Bureau of Statistics, the growth rate dropped by 12.5 percentage points compared with the previous year, and the growth rate slowed down significantly. The sales output value achieved in the whole year increased by 14.95% year-on-year, and the production and marketing rate reached 98.17%, which was 0.13 percentage points higher than that in 2011, and the production and marketing rate continued to maintain a high level. In terms of output, the output of plastic products in 2012 increased by 8.99% year-on-year. Among them, agricultural films increased by 7.74% year-on-year, foam plastic increased by 23.13% year-on-year; artificial leather and synthetic leather increased by 15.55% year-on-year, daily plastic increased by 14.43% year-on-year, and other plastic increased by 7.26% year-on-year. Except for daily plastic, artificial leather, synthetic leather, and foam plastic increased by more than 10% year-on-year, and other products increased by less than 10% year-on-year. Among them, agricultural plastic films and other plastic products had the lowest growth rate, which fell by 6.75 and 21.33 percentage points respectively compared with the same period last year.
The Ministry of Industry and Information Technology said that in the second half of 2012, the foreign trade situation of the plastic products industry showed signs of recovery. According to the statistics of the General Administration of Customs, from January to December, the total import and export value of plastic products in China increased by 16.55% year-on-year, among which the export volume increased by 5.79% year-on-year; the export value increased by 24.55% year-on-year, which was 16.65 percentage points higher than the growth rate of China's foreign trade export value in 2012 (7.9%), and the export growth rebounded. The export volume accounted for about 23.91% of the total output of plastic products in the country during the same period, showing the important position of the export market in the entire industry. In 2012, China's plastic product production basically met the needs of the Chinese market, causing the growth rate of plastic product imports to continue to decline. From January to December, the national plastic product import volume decreased by 3.46% compared with the same period last year; the import value decreased by 0.46% year-on-year.
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