Why mould makers can’t treat cutting tool choice in isolation

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Settings important for best milling results

During high-feed operations, cutters should be run at full diameter engagement, but no less than half their insert width. Full diameter engagement is possible because high-feed cutters effectively direct cutting forces at the machine spindle in the axial direction to create balance. Cutters engaged at less than half their insert width will experience push and increased vibrations because the cut is unbalanced. For high-speed milling, the same types of tools (indexable insert cutters and solid-carbide end mills) used for high-feed milling are applicable as long as they have geometries conducive to using high spindle speeds and feed rates.

While high-feed end mills with long overhangs are effective in high-speed operations they cannot be run as fast as tools with shorter overhangs (unless specialised vibration dampening tool holders are used or cutting speeds are reduced significantly). When a tool with long overhang operates faster than recommended, excessive vibration can be the result, causing insert chipping and premature insert failure.

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Insert wear analysis points out problems of the process

Maximum tool life and predictable tool usage are critical in optimising mould machining operations. Mould makers must understand the various insert failure modes and examine used inserts to determine the root cause of failure. To assist in the examination of inserts, a stereoscope - with good optics, adequate lighting and a magnification of at least 20 times - can help identify failure modes that contribute to premature insert wear.