Special Issue: Geometric Tolerancing

Abstract

In 1989 a small group of researchers gathered at Jerusalem, Israel under the sponsorship of CIRP (International Academy for Production Engineering) to address the emerging problem of computer-aided tolerancing (CAT), which is situated prominently at the interface between product design and manufacturing. Since then, such CIRP CAT meetings have been held as working seminars and conferences at an approximate frequency of once in 2 yr. The latest edition of the CIRP CAT conference was the 13th in this series and was held at Zhejiang University, Hangzhou, China during May 11–14, 2014. We are pleased to bring a selection of ten papers that were presented at that conference to this special issue. These papers cover a wide spectrum of current, international research in CAT.Standards play an important role in CAT. In the paper titled “A Portrait of an ISO STEP Tolerancing Standard as an Enabler of Smart Manufacturing Systems,” the authors introduce a recently published international standard for the exchange of human-readable three-dimensional presentation as well as machine-readable representation of tolerances. They portray this standard as an enabler of digital, also known as smart, manufacturing. In the paper titled “Formal Language for GeoSpelling,” the authors propose a syntax for a formal language to capture the semantics of the ISO geometrical product specifications standards that cover all dimensional and geometrical tolerancing. They envision GeoSpelling to be generic enough to cover not only standardized specifications but also other kinds of geometrical specifications.Tolerances influence process plans in computer-aided manufacturing. The paper titled “A Framework for Explicating Formal Geometrical and Dimensional Tolerances Schema from Manufacturing Process Plans for 3D Conformance Analysis” positions tolerancing information formally and explicitly in computer-aided manufacturing process planning. It proposes a method to determine datum flow chain in manufacturing and to compare it to design specifications. A related problem is analyzed in the paper titled “Welding Simulation of Non-Nominal Structures with Clamps.” It proposes a method to simulate variations in components and fixtures, and to combine them with welding simulation, thereby simulating geometric variation in a welded assembly. The influence of manufacturing processes on the surface quality is the topic of another paper titled “Manufacturing Signature for Tolerance Analysis,” which investigates the effects of manufacturing signature in tolerance stack-up analysis.Continuing the theme of manufactured surface variation, in the paper titled “Geometrical Simulation of Multiscale Toleranced Surface with Consideration of the Tolerancing Principle,” the authors propose a method for geometrical modeling of multiscale surface variation. They also propose a multilevel display of such surface variations. In the paper titled “Comparison of Analysis Line and Polytopes Methods to Determine the Result of a Tolerance Chain,” the authors explore functional surfaces in mechanisms, and how they are related to maximum and minimum material conditions in an assembly. Recently, industrial interest has moved beyond just the surface to the interior of manufactured parts. To address this need, the paper titled “Numerical Analysis of the Feldkamp-Davis-Kress Effect on Industrial X-ray Computed Tomography for Dimensional Metrology” proposes a method for improving the accuracy of X-ray computed tomography for nondestructive verification of manufactured parts.Most of the current tolerance analyses to date have used ideal geometric forms. Recognizing that manufactured parts have nonideal forms, new geometric models called “skin models” have emerged as a more realistic way to model such nonideal forms. The paper titled “Contact and Mobility Simulation for Mechanical Assemblies Based on Skin Model Shapes” presents an approach for a skin model based simulation of contact and mobility for assemblies. A related paper titled “Comparison of Skin Model Representations and Tooth Contact Analysis Techniques for Gear Tolerance Analysis” examines four skin model representations for gear tolerance analysis.We want to express our special gratitude to Professors Mathieu, Xiang, Jianrong, Yang, and Ravani for their help in the selection and review of the papers appearing in this special issue.