Product ontology is often constructed by explicating the domain ontology in a formal ontology language. The OWL Web Ontology Language has been positioned as a standard language. It requires technical expertise to directly represent the domain in OWL. An alternative way is to let a domain expert provide a conceptual representation of the domain, and to mechanically translate it into the corresponding OWL codes. We have developed a modeling tool called PROMOD to achieve this process in the product domain. We employ an Extended Entity-Relationship for conceptual model, enriched with modeling elements specialized for the product domain. We present how each element may be technically represented in OWL. We also provide a modeling scenario to demonstrate the practical feasibility of the tool in the field.