A Modelica Library to Simulate Geometrical and Dimensional Deviations in Process Assemblies

The main goal of production quality paradigm is a joint improvement of production rate and conformity, while minimizing the waste of resources. This paradigm is aligned with the Zero-Defect Manufacturing (ZDM) approach, which aim is the defect removal in manufactured products. Simulation tools offer a high flexibility to analyse complex systems such as multi-stage manufacturing systems, allowing to optimize the required production rates and the quality of the products. To this end it is necessary to develop simulation models that integrate the discrete behaviour of products flow, and the spread of quality characteristics during the process. This work is focused on the modelling of the geometrical quality characteristics that depend on the deviations induced when the part is held by a processing fixture. For the modelling of this behaviour, Modelica language is selected because of its ability to integrate the modelling of multi-physical systems, including the discreet behaviour necessary to simulate the materials flow. For that purpose, this paper presents a Modelica library for the definition of simulation models able to analyse geometrical and dimensional deviations produced in process assemblies composed of a piece and a fixture. The use of Modelica language, which modelling is based on equations, requires the definition of a mathematical structure, based in this case on the TTRS (Technologically and Topologically Related Surfaces) model.