I apologize if this question has been asked earlier. I am trying to make rounded corner square opening in a cube object of 4:1:0.25 ratio using the boolean feature. It works fine if I use just a standard cube. The opening edges are crisp. But if I use an object from the splin that has a pre-set rounded corners and then use it in the boolean mode, the opening becomes dramaticly distorted. I did the RTFM bit. I could not see anything that would give me a clue. Any suggestions? Thanks

The booleen combinations are very unpredictable with most curved surfaces unless you have a very high poly count on the srfaces. You may create the cube with the rounded corner openings within the free form modeler. Start with a box on the cross section, add a round corner box inside on the same cross section, group them and combine as compound. Then just extrude them to proper width.