Mesh union problem - for 3d print

I would like to fiy and 3d print a broken handle for a large toolbox. The remaining part was scanned in. I take the left side where it is untuched and I mirrored it. Then I tried to make a MESH union in RHINO and also in Grasshopper. It worked none of them. Is there better approach make a good printable file?


You can cut the shape in the middle and use mirror but the problem it is not full symmetrical ; you need some work on it