Posted by Bill S. on October 12, 2000 at 00:17:59:
In Reply to: distortion in gear after hobbing posted by harsh gupta on October 09, 2000 at 05:59:21:
You may be experiencing material stresses that are inherent in the bar material at manufacturing, such as pre-heat treated or highly worked/cold-drawn bar stock or forgings. Also, to a lesser extent, stresses can accumulate during machining of the blank.
A machined blank that inspects well after machining can "relax" or distort when some of the internal stresses are later relieved by thermal drawing and/or hobbing. These small distortions can contribute to pronounced runout on gearshafts as the length to diameter ratio increases.
You might try having the raw-cut blanks or forgings stress-relieved or drawn prior to machining to see if this reduces distortion after hobbing.
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