Comparison of Spatial Math Models for Tolerance Analysis: Tolerance-Maps, Deviation Domain, and TTRS

Abstract

This paper presents a comparison of degree of freedom (DOF) based math models, viz., tolerance-maps, deviation domain, and TTRS, which have shown most potential for retrofitting the nuances of the ASME/ISO tolerance standards. Tolerances specify allowable uncertainty in dimensions and geometry of manufactured products. Due to these characteristics and application of tolerances, it is necessary to create a math model of tolerances in order to build a computer application to assist a designer in performing full 3D tolerance analysis. Many of the current efforts in modeling tolerances are lacking, as they either do not completely model all the aspects of the ASME/ISO tolerance standards or are lacking the requisite full 3-D tolerance analysis. Some tolerance math models were developed to suit CAD applications used by the designers while others were developed to retrofit the ASME/ISO tolerance standard. Three math models developed to retrofit the ASME/ISO standard, tolerance-maps, deviation domain, and TTRS are the main focus of this paper. Basic concepts of these math models are summarized in this paper, followed by their advantages and future issues. Although these three math models represent all aspects of the ASME/ISO tolerance standard, they are still lacking in one or two minor aspects.

A statistical method to identify main contributing tolerances in assemblability studies based on convex hull techniques

“…Every control point u Usually, convex hull techniques are used for worst case tolerance analysis (Ameta et al, 2011). The stack-up domain is compared with a functional domain which represents the functional requirements.…”

“…A characteristic parameter is the volume |C pi,pj | := Vol(C pi,pj ) of C pi,pj . Although the domain volume is not used in the DD approach, it is used in T-Maps R (Ameta et al, 2011). However, the 'relative' clearance domain volume |C dev pi,pj |/|C nom pi,pj | in the DD approach is similar to the T-Map R approach.…”

A comprehensive study of tolerance analysis methods for rigid parts with manufacturing signature and operating conditions

“…However, there is a growing interest in considering working conditions and operating windows in CAT (Anselmetti et al 2010). These computer models for tolerance simulation and analysis make severe simplifications about observable geometric deviations, since they are reduced to rotational and translational feature defects (Polini 2012, Ameta et al 2011. This leads to results with large ranges of uncertainty and a discrepancy between the virtual models and the observed reality.…”

A review of representation models of tolerance information

“…During the past few decades, a variety of interpretation models, such as offsetting model [2][3][4], parametric model [5][6][7], vector equation model [8,9], variational surface model [10], kinematic model [11][12][13], generalized interval model [14], degree of freedom (DOF) model [15][16][17], and tolerance-map model [18][19][20], have been proposed. Benefited from the gaining popularity, in the same period, researchers have also carried out extensive reviews upon this subject, such as the reviews of Liu et al [21], Hong and Chang [22], Marziale and Polini [23][24][25], Ameta et al [26], Polini [27], and Chen et al [28].…”