G900G00G54X21.Y0.S2500M3Z20.G01Z0.F2000X20.G02I-20.G01X21.G00Z100.M5M9G91G28Z0.Y0.M30刀在圆的外面,要圆的半径加刀的半径,在里面就减刀的半径
G2 I-20G3 I-20