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1、外文译文院 （系）： 机电学院 专 业： 机电技术教育 姓 名： 杜 显 峰 学 号： 20040315033 指导老师： 陈 锡 渠 New tools maximize new machine designsThe primary tooling concerns when machining aluminum are: minimizing the tendency of aluminum to stick to the tool cutting edges; ensuring there is good chip evacuation form the cutting edge; an
2、d ensuring the core strength of the tools is sufficient to withstand the cutting forces without breaking.Technological developments such as the Makino MAG-Series machines have made tooling vendors rethink the any state-of-the-art machine technology. It is vital to apply the right tooling and program
3、ming concepts.Materials coatings and geometry are the three elements in tool design that interrelate to minimize these concerns. If these three elements do not work together, successful high-speed milling is not possible. It is imperative to understand all three of these elements in order to be succ
4、essful in the high-speed machining of aluminum.Minimize Built-Up EdgeWhen machining aluminum, one of the major failure modes of cutting tools the material being machined adheres to the tool cutting edge. This condition rapidly degrades the cutting ability of the tool. The built-up edge that is gener
5、ated by the adhering aluminum dulls the tool so it can no longer cut through the material. Tool material selection and tool coating selection are the two primary techniques used by tool designers to reduce occurrence of the built-up edge.The sub-micron grain carbide material requires a high cobalt c
6、oncentration to achieve the fine grain structure and the materials strength properties. Cobalt reacts with aluminum at elevated temperatures, which causes the aluminum to chemically bond to the exposed cobalt of the tool material. Once the aluminum starts to adhere to the tool, it quickly forms a bu
7、ilt-up edge on the tool rendering it ineffective.The secret is to find the right balance of cobalt to provide adequate material strength, while minimizing the exposed cobalt in the tools for aluminum adherence during the cutting process. This balance is achieved using coarse-grained carbide that pro
8、vides a tool of sufficient hardness so as to not dull quickly when machining aluminum while minimizing adherence.Tool coatingsThe second tool design element that must be considered when trying to minimize the built-up edge is the tool coating. Tool coating choices include TiN, TiAIN, AITiN, chrome n
9、itrides, zirconium nitrides, diamond, and diamond-like coatings(DLC). With so many choices, aerospace milling shops need to know which one works best in an aluminum high-speed machining application.The Physical Vapor Deposition (PVD) coating application process on TiN, TiCN, TiAIN, and AITiN tools m
10、akes them unsuitable for an aluminum application. The PVD coating process creates two modes for aluminum to bond to the toolsthe surface roughness and the chemical reactivity between the aluminum and the tool coating.The PVD process results in surface that is rougher that the substrate material to w
11、hich it is applied. The surface”peaks and valleys” created by this process causes aluminum to rapidly collect in the valleys on the tool. In addition, the PVD coating is chemically reactive to the aluminum due to its metallic crystal and ionic crystal features. A TiAIN coating actually contains alum
12、inum, which easily bonds with a cutting surface of the same material. The surface roughness and chemical reactivity attributes will cause the tool and work piece to stick together, thus creating the built-up edge. In testing performed by OSG Tap and Die, it was discovered that when machining aluminu
13、m at very high speeds, the performance of an uncoated coarse-grained carbide tool was superior to that of one coated with TiN, Ticn, TiAIN, or ALTiN. This testing does not mean that all tool coatings will reduce the tool performance. The diamond and DLC coatings result in a very smooth chemically in
14、ert surface. These coatings have been found to significantly improve tool life when cutting aluminum materials.The diamond coatings were found to be the best performing coatings, but there is a considerable cost related to this type of coating. The DLC coatings provide the best cost for performance
15、value, adding about 20%-25%to the total tool cost. But, this coating extends the tool life significantly as compared to an uncoated coarse-grained carbide tool.GeometryThe rule of thumb for high-speed aluminum machining tooling designs is to maximize space for chip evacuation. This is because alumin
16、um is a very soft material, and the federate is usually increased which creates more and bigger chips.The Makino MAG-Series aerospace milling machines, such as the MAG4, require an additional consideration for tool geometry-tool strength. The MAG-Series machines with their powerful 80-hp spindles will snap the tools if they are not designed with sufficient core strength.In general, sharp cutting edges should always be used to avoid aluminum elon
