DURING the past half-century, many ideas have come and gone as to what the best materials are for rotary draw bending tools. This is not surprising because of the many advances in materials, heat treatments, and coatings during this period. What may be surprising is that the materials that were the right stuff in the middle of the 20th century remain, for the most part, the best choices for tooling at the beginning of the 21st century. What does best mean? The best material for a tube bending tool is the most cost-effective one. This refers to the ratio of tool life to tool cost, which usually is expressed as the per-bend cost of the tool. Cost-effectiveness must take into account process control, or the stability of the tube bending machine's operation, which in turn determines productivity. In terms of tool life, this translates into exhausting that life through wear rather than failure. A tool failure often causes a process failure, which can shut down a tube bending machine.
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