Reducing_{CO2 emissions} has an impact on all areas of our lives. New fields of application are emerging and existing ones need to be adapted. The development of cutting tools is also affected. Because alternative drives, new lighter materials, energy-saving and resource-conserving concepts are more in demand than ever, but it must also be possible to machine them. Developers therefore see great potential in design changes to tools and new coatings, in new machining strategies - and in digital solutions that react to the existing framework conditions in real time.

Double service life with coating

New, lightweight aluminum-lithium alloys are all the rage. Conventional tools are quickly overwhelmed by these materials. This leads to an increasing demand for high-performance tools that are specially developed for this area of application.

iCut dynamically adjusts the feed rate to the cutting conditions. The production time per workpiece can be reduced and process reliability increased. © Walter

For example, aircraft components made from aluminum alloys often have a machining volume of up to 90 percent. Depending on the desired component geometry, numerous chamfers or cavities have to be milled out of the metal. The aim is to ensure stability and save weight. In order to produce the components economically and at the same time to a high quality, they must be machined using the high-speed cutting (HSC) process, with cutting speeds of up to 3,000 m/min. Cutting values that are too low lead to built-up edges - and therefore to rapid wear and frequent tool changes. High costs due to long machine running times are the consequence. It is therefore not without reason that the aluminum specialists among the machining companies demand above-average cutting data and tool life as well as particularly high process reliability.

The tool developers at Walter AG show how such a complex requirement profile can be handled with the design of the M2131 ramping milling cutter. The 90° milling cutter is fitted with a new type of indexable insert with the designation WNN15. Behind this is a new PVD coating, which is produced using the so-called HiPIMS process. The term HiPIMS stands for "High Power Impulse Magnetron Sputtering". This technology is derived from the English word "sputtering" and involves sputtering with a magnetron. The special feature of the physical coating process is that it produces an extremely dense and smooth PVD coating. This greatly reduces friction and the tendency for built-up edge formation. At the same time, the process increases cutting edge stability and resistance to flank wear. The result is a maximum metal removal rate. Field tests have confirmed the advantages of HiPIMS indexable inserts compared to corresponding standard types. Increases in tool life of up to 200 percent were achieved. "We see an increasing demand for high-performance tools for aluminum machining - especially in aerospace technology, but also increasingly in the automotive industry," says Wolfgang Vötsch, Senior Product Manager Milling at Walter AG.

Dynamic milling - HPC versus HDC

More process reliability, faster processing - at ever lower costs and consistent quality. Many sectors are under this pressure, especially the supplier industry. The demands on surface quality and dimensional accuracy are often increasing at the same rate as the requirements for process reliability and cost-effectiveness. Added to this is the growing demand for materials that are lightweight or heat-resistant. Materials from the ISO M and ISO S material groups, which are often difficult to machine due to these properties.

Dynamic milling offers a solution that provides both productivity and process reliability. More and more metalworking companies are therefore opting for it.

The main differences between conventional high-performance cutting (HPC) and high dynamic cutting (HDC) lie in the movement of the milling cutter - and in the forces that are generated. With HPC, the milling tool moves at relatively shallow cutting depths; with HDC, the CAD/CAM control system adapts the paths that the tool describes during machining to the shape of the workpiece. This prevents empty paths or at least shortens them. In addition, the cutting depth with the HDC is significantly greater than with the conventional HPC. This also reduces travel distances because the entire tool length can be used right from the start.

The pressure angle is usually very large with HPC. The forces that occur are correspondingly high. This in turn quickly leads to signs of wear on the tool and the machine spindle. In contrast, dynamic milling is characterized by high process stability and a long tool life. The pressure angle is usually chosen to be small for HDC. This means that the forces acting on the tool and machine are significantly lower than with HPC. Higher cutting parameters, less idle travel and more process stability result in a clearly higher metal removal rate for HDC milling compared to HPC.