tailieunhanh - Metal Machining - Theory and Applications Episode 1 Part 3

Tham khảo tài liệu 'metal machining - theory and applications episode 1 part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | A forward look 33 Fig. Sales of insert cutting tips in Japan 1980 to 1996 compete with grinding processes. Attention is also being paid to environmental issues how to machine without coolants which are expensive to dispose of to water treatment plant. Developments in milling have a different emphasis from turning. As has been seen the intermittent nature of the milling process makes it inherently more expensive than turning. A strategy to reduce the force variations in milling without increasing the average force is to increase the number of cutting edges in contact while reducing the feed per edge. Thus the milling process is often carried out at much smaller feeds per edge - say to mm - than is the turning process. This results in a greater overall cutting distance in removing a unit volume of metal and hence a greater amount of wear other things being equal. At the same time the intermittent nature of cutting edge contact in milling increases the rate of mechanical and thermal fatigue damage relative to turning. The two needs of cutting tools for milling higher fatigue resistance and higher wear resistance than for similar removal rates in turning are to some extent incompatible. At the same time a productivity push exists to achieve as high removal rates in milling as in turning. All this leads to greater activity in milling development at the present time than in turning development. Perhaps the biggest single and continuing development of the last 20 years has been the application of Surface Engineering to cutting tools. In the early 1980s it was confidently expected that the market share for newly developed ceramic indexable insert cutting tools for example the alumina tools considered in Section would grow steadily held back only by the rate of investment in the new more powerful and stiffer machine tools needed for their potential to be realized. Instead it is a growth in ceramic titanium nitride titanium carbide and alumina coated .