• Development of metal cutting technology tend to talk

    2014-06-28 507

    Development of metal cutting technology tend to talk
    From the development history of the tool, from late nineteenth Century to mid twentieth Century, tool materials with high speed steel as the main representative; 1927 Germany first developed the cemented carbide tool material and widely applied; in twentieth Century 50 time, Sweden and America respectively synthesized diamond cutting tool, then enter with the ultra hard material as the representative of the period. In twentieth Century 70 time, people use high-pressure synthesis techniques in the synthesis of polycrystalline diamond (PCD), to solve the natural diamond rare, expensive problems, so that the scope of application of diamond tools is extended to multiple areas of aviation, aerospace, automotive, electronics, stone etc..
    The selection of tool materials is cutting the foundation of success. Compared with the hard alloy, PCD tool speed can reach 4000m/min, and only its 1/4 hard alloy. From life perspective, PCD tool generally can increase 20 times. From the processed surface quality of the watch, the effect of PCD hard alloy is better than 30%-40%. In addition, CBN (made of boron nitride) development of superhard material tool and the surface coated cutting tools of machining technology advances are not.
    Over the past 100 years, the cutting speed of the tool to continuously improve, brought the change processing efficiency, further expand the processing scope brought. The biggest sign of cutting, high speed cutting (highspeedcutting, referred to as HSC) development.
    A high speed machining system involves many aspects. Only from the machining process, the traditional machining, a machining workpieces such as mold, need to go through the blank annealing the rough machining and finish machining - quenched - EDM for electric spark machining and special finishing and polishing procedures manual. High speed machining requires only rough quenching - rough machining, semi finishing and finishing and superfinishing process, from the process, reduces three, the processing time compared to the traditional processing method can shorten about 30%-50%; in the processing of small size parts, this advantage is especially obvious. What is more, the past some enterprises producing complex mold, basically need 3, 4 months can be delivered for use, high speed cutting, only half a month will be completed.
    A high speed machining system, composed of two parts the tool and technology. And cutting some factors related to the choice of cutting tool material, cutting tool system structure, the tool needs to be processed edge shape. And technology is closely related to the CAD/CAM system selection, tool path planning, cutting parameters and cooling and lubrication process.
    Since the popularization of high speed cutting in half a century, from 1950 to 2000, the processing efficiency is improved by 4-5 times. Of course, need to be mentioned is, high speed cutting is generally made of the processing object to define the scope of "high speed".
    Tool for all the processing cost is small. A manufacturing process of automobile industry as an example we analysis: investment accounted for 35% of the total cost of machine tools and other equipment; energy consumption equipment work accounted for 7%; the normal operation of the enterprise cost accounts for 27%; cooling and lubrication costs accounted for 17%; the direct labor accounts for 9%; tool 4%. Similarly, the cost of mass production machining aluminum alloy workpieces, cooling and lubricating accounted for 16%; the tool 4%; other processing costs accounted for 80%. As can be seen, the tool in the entire cost, accounts for only a small part of the. However, do not ignore it, the 4% cost of the tool, it may affect the overall processing efficiency 10%-15%.
    The tool, there are three key factors, cost, efficiency, life. Some experiments show that, if the tool cost is reduced by 30%, the overall cost reduced about 1%; if the tool life 50%, the overall cost reduced about 1%; however, if it is possible to improve the optimization of cutting parameters, tool machining efficiency, 20% so, each part can reduce more than 15% of the overall cost.
    Of course, to improve the production efficiency of machine, should not only reduce machining time workpiece by high speed cutting, still need to vigorously compression processing auxiliary time (including the adjustment of the machine, running test, air travel, braking air operation, the workpiece feeding and clamping, tool change time), standby time and fault downtime, because in many varieties of small batch production conditions, effective cutting time of general machine only accounted for all of its time of 25%-35%. Visible, in addition to the high-speed cutting, processing, how to more effectively, is one of the important issues in manufacturing industry.
    At present, the green machining technology has become a global hot, the green, environmental protection, high efficiency, including the economic. From the environmental point of view, one is to reduce the high-speed and efficient processing bring energy consumption, on the other hand, coolant and lubricant selection is very important. As mentioned above, a high percentage of coolant cost share in the overall cost, achieve about 16%. Lubricating and cooling effect and the whole processing efficiency is very relevant, especially for difficult to machine materials, such as titanium alloy, cutting to a certain extent, must be properly cooling. With the development of high-speed cutting, cutting coolant pouring, often hot cracking, resulting in reduced tool life, this point needs to be improved.
    In short, in the processing technology, high precision, high efficiency, low cost, environmental protection, and the predictable results, will be the trend. This predictability, refers to the processing result must be predictable, controllable, rather than random. This requires the operator to a deeper understanding of the processing technology.