"It is not only feasible to imagine the processing of nickel - chromium alloy 718 and other high temperature alloys (HRSAs) at the speed of processing aluminum," said Melissa Singher, a senior product engineer at the U. S.. The secret lies in the SX9 ceramic end mills produced by the cutting tool manufacturer.

Singher said: "in the use of SX9 mills to process superalloys (such as Inco 718 and 625), it is suggested that the speed is 2000 to 3000 SFM (surface feed / minute), with a minimum speed of about 1000 SFM. For example, in general, the minimum speed of a 0.5 inch vertical milling cutter is 8000r/min. To obtain the best performance, the spindle speed should be within the range of 15000 to 20000r/min. The feed rate is usually 0.0011 to 0.0013 IPT (inch / every blade), and the feed speed should exceed 100 ipm/min (inch / minute) when the 4 edge end milling cutter is used for 20000r/min cutting.

Singher says that a large number of spatters with spark chips will be quickly ignited, and the cutters will quickly prepare for the chip recycling, which is a very effective metal cutting process. It is worth noting that under proper machining technology, the working life of the tool can be as long as 10-25min. Singher explains that SX9 is a kind of SiAlON or silicon aluminum nitride ceramics, which ingeniously combines the strength of silicon nitride with the heat resistance and wear resistance of alumina. It is reported that the cutting edge design can withstand the extreme heat and pressure generated by high-speed machining of HRSA.

Singher added that working hardening is a common phenomenon at such a high cutting speed. This is also the reason why the end mills are mainly used for rough machining. Therefore, a cemented carbide end mill with a diameter of at least 0.3 cm (0.012 inches) is usually required for finishing. Here are some basic rules of thumb for SiAlON end mills.

Because of the high temperature, the continuous tool path can reduce the thermal shock of the tool.

When machining core, the inclination angle of 1.5 degree and 50% of conventional feed speed should be used.

Ceramic end mills are not suitable for machining titanium materials because the heat generated during processing will produce adverse reactions to the material.

Use the 6 edge end mill instead of the 4 edge milling cutter as far as possible to maximize productivity.

In addition, high speed and high balance hydraulic or heat shrinkable chuck or shaft should be selected as far as possible. No cutting fluid is used, instead of direct injection of a chuck with a strong convective air, which can prevent the expansion of a large amount of cutting heat produced during the process.

Finally, although the price of the ceramic cutter is much higher than that of the high quality hard alloy, the higher productivity in the use of the ceramic end mills is easy to balance the cost increase caused by the price.

Singher said: "because of the intense competition atmosphere in the engine parts industry, we have seen that the first and two tier sub contractors are very interested in this product. These companies really see their potential productivity of 15-40 times higher than that of carbide end mills, thus greatly reducing the manufacturing time of complex HRSA parts.

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