Many efforts have been devoted to mesh a volume with hexahedral elements. One of the proposed methods consist in : deforming the original volume such that its boundary normal vector is always aligned with one of the majors axis i.e. constructing a polycube, voxelizing the deformed volume and deforming it back to the initial position. This pipeline recently proposed by Gregson et al. generates nice results, but is not sufficiently robust. More specificaly, it is required to determine a priori what will be the normal of the surface of the deformed object. However, nothing ensures that there exists a deformation compatible with these constraints. We propose a method able to determine if there exists a deformation of the object boundary that respects the normal constraints, and an automatic solution to edit the constraints to make the deformation possible.