Identification of Subassemblies by Leveraging Design Information in 3D Models

In the last decade, automatic subassembly identification is considered a topical problem in the industrial manufacturing field and actually it is a relevant not fully explored research subject. It results very challenging, both in the product design cycle and in the manufacturing phase, to deal with modern assemblies, due to their increasing complexity. In literature, it is a common strategy to introduce the Subassembly Identification (SI) concept to avoid working with all assembly's parts simultaneously [11, 4]. The idea is to break down the assembly into groups of connected parts which can be treated independently of one another. The SI offers support in the design phase for the identication of reusable components [13] and finds application in different assembly manufacturing tasks. Assembly Sequence Planning and Disassembly Sequence Planning methods exploit the assembly decomposition to limit the combinatorial explosion of the problem complexity. The recognition of independent components contained in an assembly allows to simplify the assembly line. Each of the components, in fact, can be produced separately, and then all of them are joined to make the final product. Further adding the stability hypothesis to the identified subassemblies is of particular interest to manage the production in parallel: place the production of a single product among multiple supplier industries or industrial robotic assemblers is certainly a solution to obtain a visible reduction in time and costs. In literature, works dealing with stable subassembly identification tend to focus on the specific methodology treated, without giving any general overview of the problem. Since no comprehensive and generally adopted subassembly definition exists for subassembly identification, our intent is to investigate the problem, pointing out the key concepts definitions, the main assumptions that have to be done and the techniques used for the identification. Then, we will show the issues that arise when dealing with industrial models, and some methods to address them are provided. Finally, exemplification of these concepts is proposed using the CAD model of a real ball valve.