The principle is that a new surface is wrapped around the existing geometry so it takes over its shape and then the original geometry is removed.
Normal error is a common error in triangular mesh, so it is very important to repair it.
When applying the unify function to a part, only the outer triangles will be preserved and all the inner triangles will be thrown away.
Powerful and effective model repair algorithms. 99% of the 4447 not solid models in Thingi10k dataset can be successfully fixed.
The model you want to be 3D Printed must be watertight, so it is very important to repair it.