Turning a 3d model into a mold

A customer needs a mold of a 3d object I created for them. Is there a way to take the object I already modeled and turn it into essentially a 'negative space' within Adobe Substance 3d Modeler which I can place into a block of substance ultimatey creating the 3d layout for the mold? I would then create the proper breaks and pour holes for them to 3d print.