Generally, manufacturing engineers are not required to have any specific certifications, but possessing and working towards certifications shows that a employee is engaged and interested in their field. A black-belt certification can be particularly desirable, but a CMfgE, PE, Lean Manufacturing, or other certification would still be viewed as a positive. It is important that you be prepared to discuss areas that you see as opportunity for future development and advancement in your career. Be sure to express where you would like to grow and how you would ask the employer to help you do so.