| 摘要 |
PROBLEM TO BE SOLVED: To obtain a motor stator core excellent in dimensional precision after punching out industrially by controlling the roundness of a cutting edge in a punching die with a prescribed formula according to elongation percentage of a non-oriented silicon steel sheet. SOLUTION: The motor core is manufactured by punching out the non- oriented silicon steel sheet containing by weight of <=4% Si and <=2% Al. The roundness of the cutting edge in the punching die is controlled with the following formula (1) according to the elongation percentage of the non-oriented silicon steel sheet. 3.0(El)-26.0>=R/D>=3.2(El)-58.8...(1). Wherein, El is the elongation of the steel sheet (%), R is the roundness of the cutting edge (μm) and D is outer diameter of the stator. The relation between the elongation of the steel sheet and the roundness shows high correlation and the larger the elongation is, the lower the roundness is. In the case of drawing the straight lines of the upper limit and the lower limit having the allowance under consideration of the dispersion, the following equations are obtd. (R/D)×100=3.0(El)-26.0, (R/D)×100=3.2(El)-58.8.
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