1、 外文翻译 英文原文 : High-speed grinding -applications and future technology Abstract The basic mechanisms and the applications for the technology of high-speed grinding with CBN grinding wheels are presented. In addition to developments in process technology associated with high-speed machining, the grindi
2、ng machine, coolant system, and the grinding tool also need to adapt to high-speed machining. Work piece-related factors inurning the results of machining are also discussed. The paper concludes with a presentation of current research and future developments in the area of high-speed grinding, and t
3、he development of high-speed CBN camshaft grinding. All rights reserved. 1. Introduction More than 25 years of high-speed grinding have expanded the field of application for grinding from classical finish machining to high-performance machining. High-speed grinding offers excellent potential for goo
4、d component quality combined with high productivity. One factor behind the innovative process has been the need to increase productivity for conventional finishing processes. In the course of process development it has become evident that high-speed grinding in combination with preliminary machining
5、 processes close to the finished contour enables the configuration of new process sequences with high-performance capabilities. Using the appropriate grinding machines and grinding tools, it is possible to expand the scope of grinding to high-performance machining of soft materials. Initially, a bas
6、ic examination of process mechanisms is discussed that relates the configuration of grinding tools and the requirements of grinding soft materials. The effect of an effective and environmentally friendly coolant system is also investigated in addition to the effect of work piece-related variables on
7、 the suitability of using high-speed grinding techniques. 2. Theoretical basis of high-speed grinding In view of the random distribution of cutting edges and cutting-edge shapes, statistical methods are applied to analyses the cutting mechanism in grinding. The mean unreformed chip thickness, hcu, a
8、nd the mean chip length, lcu, are employed as variables to describe the shape of the chip. The unreformed chip thickness is dependent on the static density of cutting edges, Cstat, and on the geometric and kinematics variables 1,2: (1) where Vw is the work piece speed, VS the grinding wheel speed, a
9、e the depth of cut, deq the equivalent grinding wheel diameter, and ， ， are greater than zero. On the basis of this relationship, it can be established that an increase in the cutting speed, assuming all other conditions are constant, will result in a reduction in the unreformed chip thickness. The
10、work piece material is machined with a larger number of abrasive grain contacts. At the same time, the number of cutting edges involved in the process decreases. This leads to the advantages promised by high-speed grinding which is characterized by a reduction in grinding forces, grinding wheel wear
11、, and in work piece surface roughness. Consequently, increasing the speed of the grinding wheel can lead to an increase in the quality of the work piece material, or alternatively, an increase in productivity. The process technology depends on the characteristics and quality requirements of the work
12、 piece to be machined. As the cutting speed increases, the quantity of thermal energy that is introduced into the work piece also increases. An increase in cutting speed is not normally accompanied by a proportional reduction in the tangential grinding force, and thus results in an increase in proce
13、ss power. Reducing the length of time the abrasive grain is in contact with the work piece can reduce the quantity of heat into the work piece. An increase in the machining rate of the process is necessary for this to happen, where the chip thickness is increased to the level that applies to lower c
14、utting speeds without overloading the grinding wheel. Experimental results 3 illustrate that increasing the cutting speed by a factor of two while maintaining the same metal removal rate leads to a reduction in the tangential force but, unfortunately, leads to an increase in the amount of work done.
15、 Owing to constant grinding time, there is an increase in the process energy per work piece and, subsequently, in the total thermal energy generated. When the material removal rate is also increased the rising tangential force results in a further increase in grinding power. The quantity of thermal
16、energy introduced into the work piece is lower than the initial situation when the same-machined work piece volume applies despite the higher cutting speed and increased metal removal rate. These considerations show that machining productivity can be increased using high-speed grinding without havin
17、g to accept undesirable thermal effects on ground components. There are three fields of technology that have become established for high-speed grinding. These are 1. High-speed grinding with CBN grinding wheels. 2. High-speed grinding with aluminum oxide grinding wheels. 3. Grinding with aluminum ox
18、ide grinding wheels in conjunction with continuous dressing techniques (CD grinding). Material removal rates resulting in a super proportional increase in productivity for component machining have been achieved for each of these fields of technology in industrial applications 4,5 (Fig. 1). High equi
19、valent chip thickness of between 0.5 and 10 mm are a characteristic feature of high-speed grinding. CBN high-speed grinding is employed for a large proportion of these applications. An essential characteristic of this technology is that the performance of CBN is utilized when high cutting speeds are
20、 employed. 3. Grinding tools for high-speed grinding CBN grinding tools for high-speed machining are subject to special requirements regarding resistance to fracture and wear. Good damping characteristics, high rigidity, and good thermal conductivity are also desirable. Such tools normally consist o
21、f a body of high mechanical strength and a comparably thin coating of abrasive attached to the body using a high-strength adhesive. The suitability of cubic boron nitride as an abrasive material for high-speed machining of ferrous materials is attributed to its extreme hardness and its thermal and c
22、hemical durability. High cutting speeds are attainable above all with metal bonding systems (Fig. 2). One method that uses such bonding systems is electroplating, where grinding wheels are produced with a single-layer coating of abrasive CBN grain material. The electro-deposited nickel bond displays outstanding grain retention properties. This provides a high-level grain projection and large chip spaces. Cutting speeds of 280 m s-1 are possible 6. The service life ends when the abrasive layer wears out.
