Robustness Evaluation of Product Concepts based on Function Structures

Abstract

Due to the varying environment conditions as well as the manufacturing induced deviations, the properties of products vary. In order to still meet the increasingly tightening of functional requirements, tolerancing as well as Robust Design practices became integral parts of the product development. However, despite the fact that the robustness of a product is mainly determined by its conceptual design in early design stages, these activities are usually carried out at the end of the design process. In order to overcome this shortcoming, this contribution shows a method that supports the selection of robust principal solutions and thus contributes to the design of product concepts, which are less sensitive to variations. The novelty lies in the adaption and combination of robust design criteria for the quantitative robustness evaluation in the conceptual design stage. First the product characteristics, which are relevant for the product robustness are determined on the basis of the function structure. By using an adopted VMEA and a newly developed evaluation matrix, this allows a thorough robustness evaluation of product concepts. The method is exemplary shown for a lifting table.

Integration of robust and tolerance design in early stages of the product development process

“…4. Since the basic procedure of the individual methods [namely 'prioritization of FKCs and robustness evaluation of principle solutions' (Goetz et al 2019), 'graph-based tolerancing' (Goetz et al 2018a) and 'CAD-based tolerance analysis' (Goetz et al 2018b)] has already been comprehensively described, the focus of this contribution is primarily on the presentation of the entire methodology and its continuous application to a product to demonstrate the general usability of the approach when thoroughly linking it to the product development process. In combination with the methods already described in the previous contributions, the proposed approach covers the early stages of the product development process from task classification to preliminary design and thereby creates a link to the detail design, where numerous established tools for the final product verification already exist.…”

“…Since this means that a first validation of elementary tolerances is already done in the preliminary design, expensive iterations in the final tolerance definition in the detail design stage can be reduced. The general possibility of integrating the individual methods within the product development process has already been demonstrated in preliminary work using various case studies, see Goetz et al (2018aGoetz et al ( , b, 2019. In the following, the basic procedure of the required steps is described in the subsequent sections.…”

“…Instead, with respect to high usability in the design environment, a FMEA-or rather VMEA-oriented approach was developed to quantify the significance of individual FKCs across the different levels of the function structure with respect to the overall product. While the general procedure of the VMEA is maintained, the individual factors for the calculation of the customized variation risk priority number (VRPN) are modified, as comprehensively described in Goetz et al (2019). Besides the evaluation of the significance of each function or FKC, it primarily respects possibly occurring variation and thus allows a quantified characterization of the importance of each element of the extended function structure.…”

“…6. As comprehensively described in Goetz et al (2019), established robustness criteria such as those described in Sect. 2.2 are used and individually weighted for this purpose.…”

“…Since the detailed application of the single methods described in Sects. 3.2-3.5 has already been shown using a scissor lift table and a coinage machine in Goetz et al (2018aGoetz et al ( , b, 2019, this section focuses on the continuity and integration into the design process.…”