Crazy Circles in CAD Drawings

Crazy Circles in CAD Drawings


When you see wild, crazy circles in drawings, it is due to the arc start and end angles getting reversed

instead of tracking a small section of an arc, it tracks the opposite part which is a nearly complete circle

in gcode G2 and G3 codes might be swapped - in dxf the 50 and 51 arc group codes might be swapped, or the 42 polyline bulge factor group code is negated

not sure how that happens but its not a rare phenomenon - some software either reads or writes those codes backwards

the way the arcs here repeat vertically suggests there is a series of tiny nearly straight nearly vertical arcs with a substantial radius and a miniscule included angle subject to rounding errors on the x coordinates of the arc end points - especially if the y coordinates straddle the arc centerline -

as shown in the exagerated colored diagram - the problem is in getting the red part of the arc instead of the blue part

Top Bottom