High efficiency machining in heat resistant alloys
Kohichi Ohta | OSG Corporation Applications Engineer
Ceramic end mills have been developed as an effective tooling solution for high efficiency roughing of heat-resistant super alloys (HRSA), which are widely used in the aerospace and energy industries. HRSA are classified as hard materials that are difficult to machine because of their excellent high-temperature strength and low thermal conductivity. HRSA materials such as Inconel 718 have a tendency to soften when temperature exceeds 700 Celsius, allowing easier cutting. As ceramic end mills have high-temperature tolerance, they are a perfect fit for these hard materials.
Ceramic end mills are roughing tools that machine dry. High efficiency roughing is achieved by applying the heat generated from the fast, dry cutting as a part of the cutting mechanism while machining in the designated temperature range where the strength of nickel-based metal decreases.
OSG’s ceramic end mill series employs an optimum ceramic grade ideal for high-speed machining at high-temperatures in difficult-to-machine materials such as Inconel 718, with roughing efficiency dramatically surpassing carbide end mills. Two types of ceramic end mills are included in the series – the CM-RMS peripheral cutting edge type and CM-CRE end cutting edge type.
Compared to carbide end mills, ceramic end mills are superior in hardness at high-temperatures. However, ceramic end mills’ resistance against transverse stress are less than half of carbide end mills, making them easily prone to unexpected breakage when used under inappropriate cutting conditions. To minimize sudden breakage, OSG’s CM-RMS features optimum flute geometry to enable smooth chip evacuation even at aggressive cutting condition. Its negative cutter form increases cutting edge rigidity to enable long tool life as illustrated in figures 1 and 2. The CM-RMS is available in 4-or 6-cutting edge specification to accommodate individual application needs.
Figure 1. Continuous use is possible with low level of cutting chip welding
4-flute peripheral cutting edge type
Figure 2. Stable machining free of breakage
6-flute peripheral cutting edge type
The CM-CRE end cutting edge type ceramic end mill does not only excel in flat surface milling, but also in 3D applications, such as the machining of turbine blades. Its large-diameter specification reduces the risk of breakage during machining and enables optimum cutting speed without being restricted by the capability of the machining center. Furthermore, the CM-CRE is regrindable and can be reincarnated by cutting away the used portion.
Ceramic end mills enable higher cutting speeds and longer tool life versus conventional carbide end mills, which would not be able to tolerate such high-temperature machining condition. For manufacturers who are in search of significantly greater productivity in hard rough milling operations, solid ceramic end mills may be the ultimate tooling solution.
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