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i take the stl files of that url. if i open with the program 3dslash , the holes go out. if i open with Simplify3D, to print it in my machine do the same. i send you 2 photos of piece B.
when i try to correct the pieces with Meshmixer, a lot of holes go out.
do you see something i do bad to print pieces?
wich program you use to desing pices?