An applied methodology for tolerance design based on concurrent engineering

Tolerance design is an important part of the product development and manufacturing process. Studies show that using a reliable and efficient tolerance design method can effectively improve product quality and reduce manufacturing costs. Although numerous studies have been carried out in the area of tolerance analysis, combining the tolerance analysis with the concurrent engineering theory has been rarely studied so far. In order to resolve this shortcoming, a comprehensive tolerance design methodology based on concurrent engineering was proposed in the present study to shorten the product development cycle, improve product quality, and reduce manufacturing costs. To this end, experts from different engineering fields were employed to form a concurrent engineering team that works together. The tolerance design activities were divided into seven stages, including design requirements definition, dimension chain identification, initial geometric dimensioning and tolerancing, variation analysis, release technical specification, validation, and continuous improvement. Then the detailed work process of each stage is presented. Based on the Monte Carlo theory and 3D computer-aided tolerance software, a variation analysis framework was proposed. Finally, the gap between taillight and bodyside was considered a test case, and a specific operation method of tolerance design using this framework is expounded. In the studied cases, the calculated and measured mean value of the gap was 1.5 and 1.5368 mm, respectively, indicating the simulation error of 2.5 %. The obtained results show that the gap tolerance by the proposed method is consistent with the tolerance fluctuation in actual production.

Study of the effects of link tolerances to estimate mechanical errors in 3-RRS parallel manipulator

This paper presents the mechanical error estimation under the effects of link tolerances in a 3-degree-of-freedom (DoF) 3-RRS Spatial Parallel Manipulator (SPM). Position level kinematic analysis and workspace analysis in the form of reachable and orientation workspace are carried out initially. Then, the effect of link tolerances on individual link is studied at the position of mid-point and orientation of the movable platform. The corresponding mechanical errors are estimated. The effect of link tolerance variation is studied to know the pattern of mechanical error. The 3-D CAD model in SolidWorks is used to validate the results. The conclusions are drawn that lead to error minimization at the tolerance design stage.

Integrated approach enabling robust and tolerance design in product concept development

Along with the ever-increasing customer demands, early consideration of variation in terms of robust design is important to avoid expensive iterations in the product development. However, existing methods are detached from the development process and can therefore only be applied at a late stage or only with comprehensive expert knowledge. Especially in the concept stage, where the geometry of a product is not yet defined and the optimisation potential is high, effective solution proposals for systematic consideration of variation are lacking. Therefore, this paper describes a new integrated approach facilitating robust and tolerance design in the concept stage. The novelty of the approach using ontologies and graph-based visualisation is the close linkage of product development and tolerance knowledge, which allows automation and helps to avoid time- and cost-intensive iteration loops. As a result, a robust and tolerance-compliant concept design, an initial qualitative tolerance specification and instructions for the further tolerancing process are already available at the end of the concept stage. The applicability and the benefits of the approach are illustrated by representative case studies and a user study allowing a critical comparison between the conventional, mostly subjective procedure and the presented approach.