Manufacturing Process Driven Tolerance Analysis of Casting Parts
Year: 2010
Editor: Andreas Dagman; Rikard Söderberg
Author: Voss, Ralf; Meerkamm, Harald; Wartzack, Sandro
Section: Robust Design
Page(s): 11-20
Abstract
Part design, manufacturing process and used materials are strongly interconnected with each other. Especially when coming to tolerance issues, this fact is obvious: Manufacturing processes to create the designed part using certain materials lead to a certain range of deviations. On the other hand, the designer has to guarantee the functionality of the part. Hence, he has to know if the required tolerance zone can be obtained by the manufacturing process. Only by considering both “sides of the coin” a good tolerance management can be achieved that leads to a fast ramp-up time and low scrap rates in later production. Due to the complexity of real manufacturing processes in regards to deviations, the designer has to be supported in these tasks by appropriate methods and tools. In this paper an approach for the manufacturing process driven tolerance analysis of casting parts is presented. The concept focuses on the gravity die casting with lost cores, a widely used casting process. The approach integrates the results of different manufacturing simulations to an overall tolerance analysis model. This model shall support the designer in evaluating the deviations from the manufacturing process in comparison to the required tolerance zones. To verify the approach in regards to the chosen methodology, a demonstrator part is developed. The part is a simplified geometry of a cylinder head for an automobile combustion engine. Key Characteristics (KCs) are defined on the part consisting of wall thicknesses in inner parts of the geometry. Those KCs are measured in an analysis of the manufacturing process of a real cylinder head of a leading car manufacturer. The analysed process chain consists of the steps: Sand core production, assembly of sand cores, casting, heat treatment and machining. Especially the first three steps are crucial in the development of deviations on the defined KCs in this process. As a first part of the simulation approach, a shrinkage and distortion simulation is performed on the demonstrator part. The software Magmasoft 4.6 (a development prototype) is used for this purpose. A method to convert the output is presented to import the results into the overall tolerance analysis model.
Keywords: Dimensional Management, Computer Aided Tolerancing, Casting Parts, Manufacturing Simulation, Tolerance Process Chain