Arc of radius 5.E-03 not possible between keypoints 3 and 5

请问哪位前辈可以给我解答一下，我在画半圆弧时，老出现这样的错误，但是我觉得我写的命令流语法没有错误啊？不解！:~
K,3,-0.005,0.005
K,4,0,0
K,5,0.005,0.005
LARC,3,5,4,0.005