Model Based product Definition for improved transfer of tolerance information between digital manufacturing systems (Enhanced use of PMI)

Model-Based Definition (MBD) implies that the 3D CAD model with 3D annotations is used for all communication between all parties involved in the design and manufacture of a product. MBD relies entirely on the machine readability of the annotation. This means that the type of annotation, its content and the geometric entities to which it refers, the so-called semantic references, can be interpreted by software. This PhD study aims to establish how effective this communication is. The research focuses on geometry, annotations and neutral exchange formats. It considers how accurately geometry can be transferred from one CAD system to another and what can affect this accuracy. For annotations, the focus is on machine readability. This study investigates available options in different CAD systems. The conclusion when exporting to STEP AP242 is that they are not always equivalent and that the designer should be aware of this. Finally, a software package has been developed to help designers and manufacturers avoid as many of the problems identified in this research as possible. This software package analyses, identifies and lists the annotations present in the model and indicates which annotations may cause issues for other manufacturing stakeholders. This could be the lack of semantic references or the loss of data when exporting to STEP. In the latter case, it is possible to automatically convert these annotations to another type where no data is lost. The software has been developed, used and tested by a number of people in the manufacturing environment who have provided valuable feedback on the GUI and functionality. Although the original goal could not be met because of limitations in the library’s APIs, the software can be considered a success in the context of this study.