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A recent development in the field of coatings is the application of diamond films to cemented carbide tools by means of CVD, etc., so that tools with complex shapes or chipbreakers can also have the properties of diamond tools. In addition, a soft coating such as MoS2 is now being applied to the tool to improve the lubrication state during the cutting process and improve the metal cutting performance.
5. Application of new tool holder and tool clamping technology
In line with the application of CNC machine tools and the development of high-speed machining, many problems in the cutting process must be reconsidered from the perspective of high speed, such as the connection of the tool and the tool holder, the connection of the tool holder and the machine tool spindle, the rapid tool change problem, cutting The vibration problems of the system and the corresponding dynamic balance of the tool system have led to the rapid development of various new tool holder and tool clamping techniques.
At present, there are many German HSK series tool holders used in the automotive industry. The HSK shank is a new type of high-speed tapered shank. Its interface adopts the over-positioning method of simultaneous positioning of the tapered surface and the end surface, which eliminates the axial positioning error. The shank is hollow and the length of the cone is short, which is beneficial to processing. The center tool changer is lighter and faster, and has higher repetitive mounting precision. The shank and the main shaft are locked by the expansion claws. Under the centrifugal force generated by high-speed rotation, the shank can be firmly locked and applied on the high-speed machining center. very common.
The CAPTO shank is also a new type of shank. The shank is not a conical type, but a triangular cone type. The rib is a circular arc type, and the hollow short cone structure with a taper of 1:20 is also the same. The conical surface and the end surface are simultaneously contacted and positioned, and the conical polygonal structure can realize the torque transmission without sliding in both directions, and the transmission key is no longer needed, which is beneficial to the dynamic balance. This shank is not easily deformed and has low wear and thus has consistent positional accuracy.
In addition, the tool holders used in high-speed machining include the KM series tool holders from the United States and the BIG-PLUS tool holders from Japan. However, HSK shanks are mostly used in machining center machines used in the automotive industry.
In terms of the clamping technology of the tool, the hot-sleeve holder is a newly developed technology in recent years. It is characterized by a hydraulic tool holder with comparable or higher precision, but the price is much cheaper than the hydraulic tool holder, just like To adjust the tool length, a special hot-sleeve tool changer is required. However, if the hot-sleeve tool used in production is large in size, it is economically cost-effective and it is also possible to improve tool life. Companies such as Chery Automobile and Shenlong Automobile have adopted this hot-sleeve holder in new projects.
6. Proposal of cutting tribology and its application in metal cutting
The development of metal cutting theory has been around for many years, and tribology has evolved since the 1960s. However, most of the research in the field of tribology focuses on the research of friction, wear and lubrication of general motion pairs and the development of corresponding tribological techniques. This pair of special friction pairs composed of tools and workpieces occurs during the cutting process. Various tribological phenomena, tribological properties, and corresponding tribological solutions have not been studied. In the theory of metal cutting, although it is often said that the friction and lubrication that occur during the cutting process, it is inevitable to talk about the wear of the tool, but it also rarely uses the theory and technology accumulated by the contemporary tribology, so it is necessary The concept of cutting tribology is proposed. The theory of tribology and metal cutting theory are combined to establish the theory of cutting tribology that adapts to the special friction process of the cutting process. It is verified by practice and in turn guides the problems of production and metal cutting. Solution and tool optimization.
In fact, the tool and the workpiece being machined form a pair of friction pairs. The lubricating medium or the various products formed during the cutting process form a tribological system. During the metal cutting process, the system is subjected to severe friction. The frictional wear effect on the desired workpiece occurs, and undesired tool wear also occurs. The influencing factors of this system are equipment, fixture, workpiece material, lubrication medium, lubrication method, tool material, tool geometry, cutting parameters, etc. .
The application of cutting fluid in machining is very common, but its lubrication, cooling and other effects are not well understood by everyone. Recently, we have encountered such a problem in the machining of an aluminum inline four-cylinder engine cylinder head. The hydraulic tappet hole of the workpiece is processed by a PCD reamer with a guide bar, using a water-based emulsion. When changing the liquid, another emulsion of similar grade on the surface is used in the process. As a result, the surface roughness of the processed workpiece is suddenly deteriorated, which exceeds the requirements specified in the drawings, and the sharpening or adjustment of the cutter is improved anyway. The method, or changing the different cutting parameters, is that the qualified product cannot be processed, so the cutting fluid has to be replaced by the original cutting fluid. Surprisingly, the surface finish of the workpiece becomes good immediately, which fully meets the requirements of the drawings. In order to obtain the high confidence of the test results, and then continue to test once, and then the cutting fluid with poor performance in the previous test was exchanged into the machine tool, it was found that the qualified parts could not be completely processed, so the process can only be used in the process. The cutting fluid used in the test proves the correctness of the test results again, and also shows the matching and correct lubrication of the tribological system. The importance of quality and lubrication methods. Therefore, in the process control of metal cutting, it is necessary to strictly control the cutting fluid and its lubrication methods including the cutting fluid type, concentration, cleanliness, pH value, flow rate, pressure, etc. as process control parameters, so as to ensure controlled Machinability and good processing quality and high production efficiency.
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