First, the type, characteristics and suitable range of composite tools
The compound tool is a special tool that combines two or more holes of the same type or different types of hole machining tools. It can complete drilling, reaming, reaming, boring and boring in one process. The process is compounded by different processes, and has the characteristics of high efficiency, high precision and high reliability. The structural forms of composite cutters are: integral, assembled, indexable, and combined; composite types are: composite drill, composite hinge, composite expansion, composite concrete, composite concrete; drill collar, drill expansion, drilling chamfer, Expansion, drilling and expansion, expansion, expansion, drilling, drilling, drilling, hinges, hinges, etc.
The compound knife has the following characteristics: 1) It can process several surfaces simultaneously or sequentially, reduce maneuvering and auxiliary time, and improve productivity; 2) It can reduce the number of installations of the workpiece or the number of times of the fixture to reduce and reduce the positioning error; ) Reduce the complexity of the machine tool, reduce the number of machine tools, save costs, reduce manufacturing costs; 4) can ensure the mutual positional accuracy between the processing surfaces, high processing quality.
Composite tools are widely used in combination machine tools, automatic lines and special machine tools, and are used to process mechanical parts such as automobile engines, motorcycles, agricultural diesel engines, and cabinets.
Second, the innovation and development of composite tools
With the rapid development of the machinery industry, the machining difficulty is getting bigger and bigger, and the machining precision is getting higher and higher. The composite tool on the automatic line must meet the requirements of production beat, but also have reliability and high life, and should adapt to development. The need to reform and innovate traditional old-fashioned composite tools requires the application of new technologies and materials to improve the performance of composite machining tools.
Application of new materials on composite tools
Conventional composite tools generally use common high-speed steel and hard alloy, while the new composite tools use titanium-based hard alloy (cermet) and high-performance high-speed steel (including Co high-speed steel, powder high-speed steel, including New materials such as Al high speed steel), composite ceramics, CBN, and PCD, combined with different materials for composite tools: high-performance combination of high-speed steel and hard alloy, combination of high-speed steel and titanium-based hard alloy, high performance The combination of high-speed steel and CBN inserts, the combination of cemented carbide and PCD inserts, and the combination of cemented carbide and ceramic inserts enable the composite tool to achieve drilling, reaming, reaming, boring, and boring at the same speed. Process reliability requirements, such as our factory designed and manufactured high-performance high-speed steel material drilling hinge compound tool for a certain enterprise in Tianjin, the price is 5 times that of ordinary high-speed steel tool, but its performance is higher than ordinary high-speed steel tool More than 10 times, although the cost of a single tool has increased, its performance price advantage is reflected.
Application of Super Fine Mirror Surface Grinding Technology in Composite Tools
The quality of the cutting edge of the composite tool and the surface roughness of the front and back flank are the main factors affecting the precision, surface roughness and processing consistency of the machined workpiece. Reduce the surface roughness of the cutting edge and the front and back flank, improve the surface quality of the cutting edge and the front and back flank, to reduce the friction and adhesion between the chip and the tool face, and realize the composite machining instead of the grinding process. The application of super-fine mirror grinding technology can solve the problem of micro-shaped zigzag shape of the cutting edge, so that the cutting edge quality of the composite tool reaches the mirror surface, the surface roughness of the workpiece can reach Ra0.05～0.2μm, and the processing precision reaches IT5 level. .
Application of high strength low temperature brazing technology on composite tools
Blade brazed composite machining tools or composite tools with guiding structure are easy to produce blade cracks and guide portion annealing with general brazing technology, which seriously affects tool life. Because cemented carbide has high chilling property (74 ~ 87HRC) and high thermal hardness (resistant to 850 ~ 1400 ° C), but the thermal conductivity is poor, the welding performance is not good, the blade and the blade material are different, in the high temperature brazing joint Larger stress is generated, which is easy to produce blade cracks. Generally, high-temperature brazing is easy to cause partial annealing of the composite tool with guiding structure, and the hardness is reduced, thereby reducing tool life and machining accuracy. The use of high-strength low-temperature brazing technology not only ensures the quality of brazing but also effectively reduces the internal stress generated during brazing, which creates favorable conditions for improving the life of composite tools.
Application of CAD in composite tools
The compound machining tool combines two or more different tools of the same type and different types to realize one-time forming. This is not only a combination of ordinary tools. For composite tools, in different cutting conditions, both good chip removal performance and workpiece precision are guaranteed. The tool should have the best combination of space shape and shape. If you go to the hand and hand calculation according to the routine, it is more cumbersome and labor intensive. Some parameters need to be determined by trial production. CAD secondary development is used to build a 3D model, simulate machining, and extract the tool section parameters at any time to get the most. Good design solution, which can solve the problem of interference between the cutter chip and different forms of structure in different cutting conditions of drilling, reaming, boring and boring of composite tool, such as the processing of hydraulic plug threaded oil plug hole, The CAD-designed expanded composite tool is used. Another example is the processing of the fork hole on the car. Two sets of schemes are selected by CAD design: 1) Parabolic drill bit and blade angle reamer combined processing; 2) é•— reamer combination processing can meet the requirements of the workpiece design.
Third, design and manufacturing applications should pay attention to the problem
Design and manufacture should pay attention to the problem
For the design and manufacture of various diameter tolerances, tooth numbers, tooth shapes, geometric parameters and structural dimensions of composite tools, attention should be paid to the application and characteristics of the machining.
The load is large, the aperture is limited, and the tool is slender. At this time, a high-strength blade material is used.
The tool diameters of different parts of the composite tool are different, and the cutting speed is different. When the diameter difference is large, the tool with large diameter can use good tool materials, such as drilling and expanding compound knife, high-speed steel for drilling, and hard alloy blade for expansion. Or the carbide part of the drill part is selected, and the CBN insert is selected for the expansion part, and a combination application of various tool materials is implemented.
When designing a composite tool according to the machined workpiece and machining conditions, factors such as the cutting sequence or simultaneous machining sequence, tool structure, tool material selection, chip removal mode, and guide type should be considered.
Problems to be aware of when applying
Choose the right amount of cutting
Composite tools are mostly used on special machines, automatic lines or on general purpose machines. For automatic lines and special machines, the adjustment range of machine speed and feed speed is narrow. To ensure that the tool use effect is met, it is necessary to select the cutting amount. If the drilling and expansion compounding, the feed rate is limited by the drill bit, and the cutting speed is limited by the reamer. If the feed amount is determined by the reamer, the drill bit cannot bear, and if the cutting speed is determined by the drill bit, the quality of the reaming is difficult to ensure. The feed of the same type of composite tool should be selected by the tool with the smallest diameter, and the cutting speed should be selected by the tool with the largest diameter. Different types of composite tools generally have average values ​​of large and small diameters, and take into account the processing accuracy requirements, and comprehensively select the cutting amount.
CBN composite cutter is suitable for processing hardened steel, cast iron, superalloy, cobalt-based alloy. It is not suitable for processing aluminum alloy and general mild steel. It is also not suitable for low speed machining. The cutting speed should generally be no less than 30m/min.
PCD composite tools are suitable for the processing of aluminum alloys, copper alloys, zinc alloys and non-ferrous and non-metallic materials, and are not suitable for processing ferrous metals (steel, cast iron, etc.).
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