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1、外文原文：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; and ensuring the core strength of the tools is sufficient to with
2、stand 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 programming concepts.Materials coatings and geometry are the three ele
3、ments 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 successful in the high-speed machining of aluminum.Minimize Built-U
4、p 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 generated by the adhering aluminum dulls the tool so it can no longe
5、r 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 concentration to achieve the fine grain structure and the materi
6、als 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 built-up edge on the tool rendering it ineffective.The secret is
7、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 provides a tool of sufficient hardness so as to not dull quickly w
8、hen 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 nitrides, zirconium nitrides, diamond, and diamond-like coatings
9、(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 makes them unsuitable for an aluminum application. The PVD coati
10、ng 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 which it is applied. The surface”peaks and valleys” created by t
11、his 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 aluminum, which easily bonds with a cutting surface of the same mat
12、erial. 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 aluminum at very high speeds, the performance of an uncoated coarse-gr
13、ained 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 inert surface. These coatings have been found to significantly im
14、prove 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 value, adding about 20%-25%to the total tool cost. But, this co
15、ating 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 aluminum is a very soft material, and the federate is usually increas
16、ed 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 elongation. A sharp cutting edge will create high shearing and also high surfac
