| 摘要 |
PROBLEM TO BE SOLVED: To stabilize the dimensional accuracy of both outer and inner lines to meet the tolerances of design values by setting an offset at the time of machining of the outer line and an offset at the time of the inner line separately from each other. SOLUTION: An end mill 4 reads an offset value at the time of machining of an outer line, reaches from the outer side of the outer line 2a of a scroll lap 2 to a center part 2b, and then temporarily moves away from the scroll lap 2 so as to cancel the offset for outer line machining. Then, the end mill reads the offset for inner line machining, and returns again to the center part 2b of the scroll lap 2. After that, the end mill extends from the inside of the inner line 2c to the outside so as to form the scroll lap 2. This two types of offset values for machining outer and inner lines are input into an NC device as macro variable after a deviation of outer and inner lines relative to the design value curves is confirmed based on the results of measurement of preceding machining. Thus, this end mill can adopt to a variation in the shape of the scroll laps for outer and inner lines.
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