Copper Bar (also known as copper bus) products are mainly used in electric power, electronics, communications, heat, mold and other industries. With the development of the national economy and the increasingly fierce market competition, users have higher and higher requirements for the surface quality of copper bar products, the macroscopic description of the surface quality of copper bars can not completely cover the requirements of the market for the surface quality of copper bars. According to the statistical analysis of the complaints, the complaints of surface quality (including spots, pits, scratches, color difference and defects) accounted for 30.92% of the complaints. Surface quality is not only the first sense of the user aesthetic requirements, but also downstream users on the product production process and quality requirements. It is necessary to reduce or avoid the surface defects of copper bars by optimizing and improving the factors that affect the surface quality of copper bars.

1. Standard for surface quality of copper bars the standard for copper bars is GB/t5585.1(2005) copper, aluminum and their alloy bus bars for electrical purposes part 1: Copper and Copper Alloy bus bars, the surface quality requirements are: “The surface of the copper bar shall be smooth and smooth, and shall not have any defects that are not suitable for a good industrial product. There shall be no flash, burr and crack at the rounded corners and edges of the copper bar.” Due to the process, equipment, management and operation factors, at present, still rely on experienced personnel inspection, manual visual inspection. Although product standards are more comprehensive, testing methods are more flexible, but Operability, can not fully cover the user market on product quality requirements. 2. The surface quality index of copper bar can be divided into three main aspects: Smooth surface, smooth surface and surface defect. It is closely related to copper property, production technology, production management and production environment. 2.1 The influence factors of smooth surface of copper billet are mainly produced by continuous extrusion at present, and the surface of copper billet is cooled by coolant + alcohol. A small amount of alcohol is added to the coolant to reduce the oxide and obtain the desired surface. In the process of continuous extrusion cooling, the volatilization of alcohol will increase with the increase of the temperature of the coolant, and the oxidation of the billet surface will directly affect the surface quality of the Copper Bar, resulting in the increase of the production cost. 2.2 during the lubrication of a drawing die, relative motion between the tool and the surface of the workpiece occurs and friction occurs. Proper Lubrication, also known as process lubrication, is necessary. At present, the copper bar is mainly used with traditional drawing oil, because the traditional drawing oil mainly consists of mineral oil, volatile oil, boronized soap compounds and so on. The mineral oil is difficult to mix, contains harmful and flammable ingredients, difficult to clean and direct welding and other shortcomings. The volatile oil is flammable and toxic, which has little protective effect on tools and increases the content of volatile organic compounds (VOC) in the workshop. 2.3 surface defects caused by improper protection during production, storage and transportation. The products are in direct contact with iron or sharp objects, which lead to the surface of copper bar being damaged. Production Process Planning is not reasonable, the number of product transshipment, products constantly swing or move, so that the adjacent copper surface friction, resulting in copper surface scratch, scratch. 2.4 the ordinary copper bar (including the bulk copper bar) of packing quality is not tight, because of the friction between the copper bar and the copper bar in loading, unloading, lifting and transportation of the product, the surface of the product is bruised and scratched, in particular, the transport process of electrostatic injury (burn black spot) .

3. Surface quality control surface quality control is the entire process control from the production of copper bar to the product packaging, is a fine management, careful operation of the systems engineering, each process is the key to control the surface quality of products. 3.1 ensure that the cooling system of continuous extrusion machine is normally cooled by lubricant additive liquid + water. The cooling system of continuous extrusion machine is normal or not, which has a great influence on the quality of the blank surface. One is to reform the cooling water channel of continuous extrusion machine to ensure that the cooling water temperature is in an ideal state. Through the improvement of cooling water channel of continuous extrusion machine and the use of lubricant additive liquid, the surface quality of billet is improved obviously, and the surface of billet is bright, bright and non-oxidized. . 3.2 A water-based lubricant is used to lubricate the drawing die. The lubricant is a water-soluble drawing oil Water-soluble stretching oil has a very high lubrication effect, in plastic deformation to provide high-efficiency lubrication film, can effectively improve the surface quality of products, effectively reduce scratches, scratches and other phenomena. With super extreme pressure anti-wear performance, is conducive to protect the mold, prolong the life of the mold. The cooling performance is good, the drawing oil is completely dissolved in water, and the comprehensive use cost is saved greatly. Easy to clean products, economic safety, stable effect, clean the workshop environment. The product has high wettability and can effectively improve the roughness and accuracy of the product. Excellent anti-rust performance, will not corrode the sensitive metal. Environmentally friendly products, additives do not contain sulfur, phosphorus, in line with environmental requirements, no impact on the skin . Because the lubricant contains a lot of water, easy to deteriorate, in the use of the process should pay attention to maintenance and monitoring, according to the requirements of regular replacement. Through the use of water-based lubricant, the surface color of copper bar is bright and uniform, and the surface quality has been improved obviously. The surface quality of the lubricant before and after the change to the drawing die is shown in figure 3 . 3.3 optimization of production processes and process routes, in order to avoid the scratch, bump and scratch on the surface of copper bar in the process of stretching, straightening, sawing, packing and so on, it is necessary to arrange the production process reasonably, select the most suitable process route and reduce the lifting times. Reduce the secondary damage to the surface of copper bar where in direct contact with the product are wrapped with soft glue or cloth to avoid the surface of copper bar knock, bump and scratch. Each layer of copper surface are non-woven fabric interlayer, to ensure that the copper surface does not scratch . 3.4 optimisation of packaging, standardisation of packaging, with the length of 6000mm copper bar as the standard, the method of packing and fastening with PVT tape at 5 points of each sling is adopted, that is, the method of bulk packing or simple packing with thin film is changed before, adopt 3 ~ 5 points of equidistant textile tape packing plus PVT tape packing and fastening, at least not less than 3 points, through the optimization of the packing method, avoid the surface of the copper bar to be bruised, scratched or scraped, in particular, the transport process to avoid the occurrence of electrostatic injury (burn black spot) . Before and after the optimization of packaging see figure 4 and figure 54 At present, the surface quality inspection of copper bars relies on the visual observation and judgment of operators and inspectors, and lacks unified standards and quantitative concepts Although the requirement of surface quality of copper bar is higher and higher, the controllability of surface quality of copper bar and the accuracy of test results are still not ideal due to the influence of process, equipment, management and operation . With the quantitative requirement of surface quality of copper bar and the requirement of modern production management, the inspection method of observing and judging the surface quality of copper bar by the visual inspection of operators and inspectors will inevitably be eliminated in the end. The surface defect inspection technology of plate and strip with machine vision as the core has become the focus of the present research. Will be further promoted in the industry and use. 5. Conclusion (1) with the more and more intense market competition and the higher requirement of surface quality of copper strip, high surface quality has become an important index to measure the quality of Copper Strip (2) the control and improvement of the surface quality of copper bars is a comprehensive project, it involves many factors, such as production technology, equipment level, production environment and personnel quality, etc. . Only when all aspects cooperate closely and avoid all kinds of adverse factors, can better surface quality of copper strip be obtained The main factors affecting the surface quality of the copper bar are the surface finish of the blank, the drawing and lubrication, the protection of each working procedure in the production process and the packing method, through the process optimization and improvement, fine management and careful operation, the surface quality of the copper bar was significantly improved, and the number of complaints of surface defects was reduced from 30.92% to 17.54% . (3) on-line automatic surface defect detection technology is an ideal equipment for surface quality detection in copper bar production, it realizes the quantification of the surface defect of Copper Bar, provides the basis for the judgment of the surface quality and the optimization of the process, and greatly improves the reputation of the product quality. The on-line automatic surface defect detection technology instead of the visual inspection method will be further promoted and used in the industry. 

Source: The