CAD Refactoring and the Art of Computer Aided Design Model Maintenance

Abstract

Introduction: Solid modelling is a common way to communicate and store geometric information. Solid models allow drafters to abstract complex constructs enabling them to be better understood and shared. Leveraging the computer-based nature of models a ords continuous improvement and re nement of models via version control and the ability to store the history of a model's evolution. The abstractions also support the use and reuse of part geometry resulting in more e cient, less error-prone and compressed product development cycles [9, 12]. However, with particularly long-life products, solid modelling still poses challenges for the long-term management of product data (among which geometry data). Kasik et al. [5] discusses a range of challenges for which two underlying themes of interoperability and reuse are evident. In addition to the two longer-term underlying themes, the type of abstraction applied by the engineer during the initial design of the CAD model will also impact current activities. For example, artefacts, such as intersections between surface geometry, can cause issue in the subsequent generation of Computer Aided Manufacturing (CAM) code and/or meshes for simulation. Given that geometry may be constructed with di erent design intent [7], it is important to understand which construction can be reused at a lesser cost. A consequence will be alleviating the drafter of further cognitive load, so that the drafter can continue to design in the way that works best for them or they believe works best. The subject of changing structure of a system/code base without a ecting its external behaviour is of great interest in programming and is referred to as refactoring. This eld also cites the need for refactoring to simplify source code for long-term maintenance and support, providing underlying performance enhancements introduced by new techniques and copying with the growing complexity of a project. All of which are analogous to the issues and aims of engineers/engineering management. Given the parallels in both the problem and solution, the authors propose refactoring as an approach to re-structure the relationships between design entities in a CAD model. The following sections discuss relevant literature in CAD, Technical Debt, Refactoring, and Graph Representation which provide the foundations for CAD refactoring. Throughout the sections the same artefact is represented in the context of the topic discussed.