Computer aided rapid tooling process selection and manufacturability evaluation for injection mold development

Abstract

Injection mold development lead time has been reduced presently by over 50% by employing rapid prototyping based tooling methods. Rapid tooling methods however, have certain limitations in terms of mold material, accuracy, surface finish, and mold life. The relevant process knowledge, especially for newer routes, is not very well established, resulting inconsistent or inappropriate rapid tooling (RT) process selection and mold design incompatibility. This paper presents a computer aided rapid tooling process selection and manufacturability evaluation methodology for injection molding, supported by mold cost estimation models and RT process capability database. Rapid tooling process selection is based on process capability mapping in quality function deployment (QFD) against a set of tooling requirements that are prioritized through pairwise comparison using analytical hierarchal process (AHP). The mold manufacturability for the selected RT process is carried out using fuzzy-analytic hierarchy process (fuzzy-AHP) to identify problem features, if any. This is followed by estimating the cost of RT mold and comparing it with a conventional mold, using cost models developed based on the concept of cost drivers and cost modifiers. The entire methodology has been implemented in a software program using Visual C++ in Windows environment and demonstrated on an experimental mold as well as industrial cases. The proposed methodology enables selecting an appropriate rapid tooling process for a given injection mold requirement, and identifying critical features that could be modified to improve manufacturability, thereby achieving better quality and lower cost of molded parts along with shorter lead time.