Large-scale mining machines in coal mine underground engineering are expensive to make, lack of spare parts, and have huge maintenance costs. Once damage occurs, the production line will be interrupted, causing significant economic losses. According to incomplete statistics, the annual cost of repairing large-scale coal mine equipment in China is tens of billions of yuan. Therefore, carrying out major equipment repairs and developing rapid, efficient, and sophisticated repair technologies not only have broad market demands, but also have significant economic and social benefits.
1. Looking forward to the application trend of 3D printing technology and its impact on human future production and lifestyle
According to the "Global 3D Printing Market 2017" report released by the US market research agency ReportsnReports, the global 3D printing market demand will grow at a rate of more than 20% per year, and will reach the scale of 5 billion US dollars in 2017.
The "Development and application of large-scale laser sintering molding equipment for the manufacture of complex parts and molds" in the "National High-tech Research and Development Plan (863 Plan) and the National Science and Technology Support Plan Manufacturing Field 2014 Alternative Project Recruitment Guide" states that "for The rapid manufacturing of complex parts and molds requires the development of large-scale laser sintering equipment suitable for the manufacture of wax molds, wax molds, sand molds, and nylon and other plastic parts. The precision of the parts is controlled within ± 0.1%, and the stacking efficiency reaches 1000cm3 / h , And formulate relevant technical standards ", the country passed on the strong development trend of 3D printing technology in China.
Next, we discuss the application and prospect of applying 3D printing laser repair technology to the maintenance of vulnerable equipment of mining machines, and promote the realization of rapid recovery of production and economic cost savings.
2.3D printing laser forming technology
The 3D printing laser forming repair technology is different from the previous repair technology. It uses metal powder as the material. With the support of CAD / CAM software, the CNC (computer numerical control) controls the laser head, the powder feed nozzle and the machine tool move according to the specified spatial trajectory. The parts are deposited / stacked layer by layer, and finally a three-dimensional solid close to the original part is generated. The core of the 3D forming and repairing technology lies in the three-dimensional model of the prosthesis and the laser three-dimensional shaping of the prosthesis. The three-dimensional model of the repaired body is generally obtained by CAD model processing software through Boolean operation.
3D forming repair technology uses some metallization alloying, body hardening, adding reinforcement and equal methods to make the cladding metal have certain strength / hardness, wear resistance, corrosion resistance, high temperature resistance and other properties to meet the special needs of the surface and solve The defect repairing problem of some assembly and bonding surfaces in the application can also make up for the problem of oversize in the metal processing process. 3D forming repair technology makes up for the defects of laser cladding technology in forming, and breaks through the technical limitation of laser cladding technology that can only coat a single layer or multiple layers of fusion layers on regular curved surfaces such as planes or cylinders. Free-form repair / repair on uneven or complex / shaped structure parts, and finally achieve accurate contour repair.
Laser three-dimensional forming repair technology can not only achieve the purpose of repairing parts, but also meet the needs of strengthening the repair area. The components and parts of mining equipment are complex in structure, the surface requires high strength and wear resistance, and the core requires high flexibility. At present, the laser cladding technology used in some mining equipment has no shaping function, so it is impossible to repair the original structure of the vulnerable parts of the mining equipment, and it can only be coated simply. 3D printing laser forming repair technology solves the defects of laser cladding technology in forming. It combines the characteristics of surface strengthening technology and three-dimensional forming, and is suitable for solving the repair problems of mining equipment. Although the development potential of 3D printing laser forming technology is huge, there are few application examples in the repair of mining equipment.
3. 3D printing laser repair application for mine vulnerable equipment
The wearing parts of mining equipment can be roughly summarized into three types: direct working parts, structural parts, and transmission system parts. These three types of parts have huge differences in the performance and requirements of industrial and mining environments. The above three types of parts The maintenance is the most important part of the normal production and maintenance of the mine. This article mainly discusses the application of 3D printing laser repair for the following three types of equipment parts.
3.1. Mining machine vulnerable direct working parts 3D printing laser repair
The vulnerable parts of mining equipment are direct working parts, such as picks of roadheaders and coal shearers, scrapers of scraper conveyors, scraper chains and sprockets, and crawler plates of roadheaders and combined miners , Track wheels, tooth plates, ring gears of crushers, etc. The characteristic of this type of worn parts is that the working conditions are extremely harsh, often subject to strong scratches and violent impacts. The vulnerable forms are generally surface wear or internal cracks.
This type of parts is a consumable part of mining equipment, with serious wear and frequent replacement. For example, the cutting head and pick seat of the roadheader are made of quenched and tempered ZG35CrMnSi, ZG40CrNiMo and other cast steel materials. The general tooth surface and near surface hardness are HRC49 ～ HRC54. The structure has a certain arc appearance shape. The coating technology can strengthen the surface, but the pick or the tooth seat often suffers from uneven wear, forming an irregular geometric appearance. The laser cladding technology cannot be repaired or needs to be processed after repair, and the laser three-dimensional forming repair technology not only can It achieves the appearance with high dimensional accuracy, and can meet the needs of strengthening and non-sparking of tungsten-cobalt alloy picks.
Such as the scraper conveyor sprocket, the general material is 40Cr and other hardenable materials, which are tempered. The sprocket chain socket is thick, and problems such as quenching or unhardening are likely to occur during heat treatment, so the hardness of the sprocket can only be limited to the range of HRC45 ～ HRC50, and the laser three-dimensional forming repair technology can make the sprocket chain socket repair the hardness Reached above HRC50.
3.2, 3D printing laser repair of vulnerable parts of mining machine
The vulnerable equipment of the mining machine includes mechanical structural parts, which generally need to meet the structural strength of the equipment itself, and also need to have a certain resistance to wear and impact. Such parts are generally moderately damaged, and replacement frequency is low. However, some imported large-scale mining equipment parts and accessories have a long supply cycle and are expensive. After the parts are easily damaged, 3D printing laser repair can not only make the equipment run normally in a short time, but also save a lot of equipment maintenance costs. The materials of such parts are generally high-strength structural steel, wear-resistant steel and other steels, and some structures require cast iron and cast steel.
The wear parts of mining equipment generally require high strength / hardness, good wear resistance, and certain toughness. The laser forming and repairing technology has the advantages of concentrated energy, small heat-affected zone, fine internal grains, uniform structure and excellent performance. In addition, the laser forming repair technology can use CNC (computer numerical control) technology to form the same structure as the original part with the support of CAD / CAM software to achieve the effect of near net forming. The parts repaired by this technology not only have smooth and smooth appearance, small structural distortion, but also the mechanical properties can reach the level of traditional forgings, which is much higher than that of ordinary arc welding and argon arc welding.
3.3. Mining machine vulnerable mechanical transmission 3D printing laser repair
Another part of the vulnerable parts of the mining machine are mechanical transmission system parts, such as gears, splines, shafts, etc. The failure types of such parts are generally broken teeth, wear and other forms, and the replacement frequency is relative to the first and second types low. Gears and spline parts are generally made of carburized / nitrided steel, and shaft parts are generally made of 40Cr, 35CrMo, 40CrNiMo with good hardenability. Such parts are generally expensive, and the processing dimensional accuracy requirements are higher. Cannot be used if injured. In particular, imported large-scale coal equipment for mining has no replacement parts. Once such parts are damaged, the equipment cannot continue to work.
3.4 Features and advantages of 3D laser printing repair technology
1) Digital manufacturing: digitize the product structure with the help of CAD and other software, and drive the machinery and equipment to be processed into devices; digital files can also be transferred through the network to realize the production mode of decentralized manufacturing.
2) Dimensional reduction manufacturing (layered manufacturing): That is, the three-dimensional structure object is first decomposed into a two-dimensional layered structure, and the three-dimensional objects are accumulated layer by layer.
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