LMT Tools Trochoidal milling significantly reduces manufacturing costs

Editor: Briggette Jaya

Germany – Unknown to many, this very special milling strategy was developed some decades ago. But it was only through the availability of modern machine tools with fast and dynamic controls in combination with appropriate CAM software that the true performance potential of trochoidal milling could be unleashed, LMT Consultant Dr Diethard Thomas explains.

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Low cutting forces beneficial to dimensional accuracy of thin-walled workpieces.
Low cutting forces beneficial to dimensional accuracy of thin-walled workpieces.
(Source: LMT)

The LMT Tools Group is known to work very closely with well-known software companies from the field of CAM programming and has been able to confirm the expected advantages upon the operation of innovative cutting tools. The low cutting forces and their even distribution along the entire cutting edge length are said to allow for higher processing speeds, thus leading to significantly shorter production times with both increased tool life and workpiece quality. This strategy has been proven to also be beneficial when processing high-strength and hardened materials.

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Much is different compared to the past

The cutter still rotates at constant speed. However, as opposed to conventional slot and edge milling tools, this tool does not perform any linear feed motions with constant chip load. Rather, it moves very quickly on curved paths, so-called trochoids. The tool constantly circulates, approaching the contour of the workpiece while travelling in a curved path. It then produces a chip and quickly moves to the next curved path. The superposition of feed and circular motion is said to have a positive impact on operation conditions. The chip load fz , the radial depth of the cut ae and the wrap angle β constantly change. The programming system programs the parameter in such a way that the mean chip thickness and thus the stress on the cutting blades remain constant. According to LMT, this avoids machine spindles and an excessive and uneven distribution of force on the cutting blades.

The maximum wrap angle is claimed to be significantly lower than 180°, for example, when milling a full slot with a tool diameter that equals the slot width. When using trochoidal milling to cut a slot, the milling cutter diameter must be 30% less than the slot width in order to enable circular motion. The respective smaller wrap angle, together with the resulting reduced cutting forces, also allow for using a larger cutting edge length, i.e., the workpiece can be processed, if necessary, in a single pass, without changing the axial feed again. This is said to also save time and production costs.

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