The offset when operate the cirular polygon

There is a circular shape, which has a circular void, I want to use 1 mil width of the line to cur the void, making the circular shape has no void. Process: the polygon of shape = poly1; the polygon of void = poly2; the polygon of cut line = poly3; Use axlAirGap get the minimum distance between the circular void and the outline border of circular shape. according to the endpoints of axlAirGap result, create the 1 mil width cut line. get the polygon of the cut line (that is, poly3); result = axlPolyOperation(poly1 poly3 'OR); Issue: The graphical result of the combined position is offset. And the original shape is not completely overlap. How should I solve this offset problem? How can i get the right result. Thank you!