Design-for Assembly (DFA) analysis of a product may indicate shortcomings of a design, without providing 'specific' guidance on redesigns for solving the problem. This paper introduces a computational tool, in development at USC, for assisting redesigns of mechanical assemblies for DFA. The system, named REV-ENGE, is based on a model of reverse engineering in order to incorporate design rationale into the redesign process. The system consists of three major parts: knowledge acquisition, construction of a default design plan, and case-based redesign. In particular, this paper focuses on to how a design plan, which serves as the basis for constructing a redesign plan, can be generated with user assistance. A simple example of a redesign of a container is illustrated. REV-ENGE produces redesign plans by constructing and modifying the original design plan, and facilitates the redesign process by providing a specific order and design actions to carry out, while considering design rationale.