wapperdude, well, of course I'm doing it properly at the beginning. But my drawing is quite complicated and modifying often, almost every time joining, then trimming, changing something, joining again and so on. I think the problem is visio is changing some values if it is not in inch (try arraying shapes 10mm x 4mm squares, you will see default positions with 3.99999 and 10.00001 steps). When trim and join operations are done this differences tell visio that it is not a circular arc any more, so it defines elliptical arc instead. Normally after checking what is present in dxf file I am deleting the erronous segments, redrawing that segment with circular arc, then dxf is corrected. I may have more than 60 parts to be cut with laser cnc, modifying all erronous shapes this way is quite time consuming and subject to other errors. I also tried if 'Fit curve' changes elliptical arcs to nearest circular arc but it is not working as I expected.
