YThis paper presents a methodology using various tools to gather evidence of project-based learning for developing engineering problem-solving skills. It is part of a study abroad program designed for Japanese engineering students from mechanical, electrical and IT disciplines. In a project-based activity, the final product is assessed for learning outcomes, but the processes used to arrive at the final product also need to be evaluated carefully. In this case study, we used learner-centered processes to enable us to observe progress towards learning outcomes, and to gain insight into the thinking processes that enable success in project-based learning. Central to evaluating this process is a team workbook (either physical or electronic) including drawings, photographs and descriptions, which records all decisions, discussions and rationales for the complete design lifecycle of the project. The workbook enables us to review rejected designs, and to discuss with students both during and after the project reasons for rejections and revisions. Our case study includes three projects; The main project currently consists of conceiving, designing, building and testing a drone using a 3D printer. As students become familiarized with using the 3D printer, they recognize the need to optimize its operation to overcome printer limitations. The CAD designs are revised several times before students produce parts that can be used in the final product assembly. Keeping copies of early CAD designs serves as an excellent record of learning progress, and gives good insight into the thinking processes of project-based problem solving. The use of the 3D printer for rapid prototyping also enable students to observe directly the results of poor decision-making, without compromising their final product. If a good record of these early rejected parts is kept, together with the CAD design files, these can be used both as useful evidence of learning, and as a powerful teaching tool to explain theory and reasons for industry practice.