Trochoidal milling | With high feed rates to deep cuts
Trochoidal milling enables the machining industry to achieve marked rationalised potential with regard to tool costs and processing times and to reduce machine tool stress in many areas of application. What must be emphasised here on the one hand is the manufacture of engine components for the aviation and astronautic industry and exhaust turbines for the motor vehicle industry. On the other hand, this milling technology is implemented for the manufacture of structural and other small-scale production components in the tool and mould construction industry (hard machining) along with general engineering. The machining of high alloyed and hardened materials such as case-hardening steels or heat-resistant nickel base alloys can be made significantly more productive, cost-effective and resource- efficient by the use of trochoidal milling.
Viewed in general, the use of trochoidal milling technology makes sense in the manufacture of slots with a high aspect ratio and different slot widths. Very different slot widths or pocket sizes can thus be produced with a single tool. The available cutting length of the milling cutter is also better utilised due to increased cutting depths. Furthermore, due to the considerably optimised contact ratios in full cut compared to conventional milling (tool wrap angle 180°) the resulting machining forces are reduced. Especially due to the reduction of the acting radial force, thin-walled components can be manufactured with process reliability with the greatest precision whilst simultaneously preserving the machine tool. With regard to the material to be machined, trochoidal milling offers considerable advantages due to a reduction of chip length (regardless of the radial feed), an increased chip removal area and reduced machining stress (slot width small tool diameter, no chip congestion and multiple cutting of the chips) and resulting reduced thermo mechanical tool stress. Higher cutting data with simultaneously increased tool lives compared to the conventional full cut are thus achievable. For effective use of the trochoidal milling technology however, it is necessary to agree on the programming cycles of CNC controls in addition to using appropriate tool concepts.
Motivation
The drive for increased mobility with increasing performance and comfort requirements continues and is now stronger than ever. At the same time, mobility is a motor for employment and growth in Germany. Contradictory requirements such as tightened emission regulations and increasing quality requirements with simultaneous cost reduction are thus the primary drivers for ever more efficient drive solutions and their production strategies, both in aviation and the motor vehicle industry. The aviation branch in particular has seen constant growth in previous years. According to the German Aerospace Industries Association the growth in turnover for the entire branch was 7.8 % in 2013. The number of employees also increased by 4.8 % to 105,500 employees directly in aviation and astronautics. At the same time, the requirements increased with regard to engine technology, fuel consumption, pollutant and noise emissions. The higher combustion pressures and temperatures necessary to increase efficiency for example cause increasing material stresses. The manufacturers are thus compelled to substitute the most commonly used classic TiAl6V4 titanium alloy by materials with increased heat resistance, such as Ti6242, titanium aluminides (TiAl) or nickel base alloys. However, in addition to outstanding material qualities, these material alloys are characterised by their impeded machinability compared to TiAl6V4. A considerable increase in productivity and cost-effectiveness in machining of these high-performance materials for future turbine components is therefore a basic pre-requisite for the assurance of competitivity of manufacturing companies.
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