In the DFG project 'Method for knowledge-based tolerance allocation and function-oriented process design', we are working together with the Department of Product Life Cycle Management (PLCM) at the Technical University of Darmstadt to develop the scientific basis for knowledge-based and partially automated tolerance allocation. We are also researching function-oriented process planning, taking into account product and manufacturing information for machined components.
In machining, process-related uncertainties are unavoidable. These are taken into account during product development through tolerances to ensure the functionality of the component. At this stage, the exact manufacturing process plan is usually not yet known. Tolerance allocation is therefore based on expert knowledge. This can lead to increased manufacturing and inspection costs due to overly tight tolerances. This is exacerbated by inconsistent knowledge transfer processes, for example when hiring new employees or purchasing new machine tool.
The development of ontology-based assistance systems for knowledge-based tolerance allocation and function-oriented process planning promises an efficient solution. The development of such a system, which bridges the interface between development and manufacturing, should enable the specification of the first manufacturing parameters and precise tolerance allocation. In doing so, we take into account both the manufacturing effort and the achievable tolerances based on the availability of tools and machine tools.
Within the project, we are analysing components that are manufactured by 3-axis milling processes. These components are represented by a combination of form elements from ISO 14649-10. The experimental study and the measurement of these form elements enable the creation of a model for predicting form errors. Furthermore, we are developing a method for tolerance analysis using Skin Model Shapes and an auxiliary body-based method for estimating the manufacturing effort for complex geometries.
The heuristic rules for the tolerance allocation will be developed on the basis of the ontology-based knowledge representation, which is to be completed in an early project phase. These rules take into account both the achievable tolerances and the manufacturing effort. This provides the basis for the implementation of an assistance system that enables knowledge-based tolerance allocation and function-oriented process planning as early as the product development phase.
Contact:
For further information, please contact Andrii Skryhunets, Institute of Production Engineering and Machine Tools at Leibniz Universität Hannover, on telephone +49 511 762 18351 or by email (skryhunets@ifw.uni-hannover.de).
