Practical Implications in Tolerance Analysis of Sheet Metal Assemblies: Experiences from an Automotive Application

Abstract

Over the past years, several approaches for variation simulation of sheet metal assemblies have been presented. However, there are few reports on validation of the methods compared to real production inspection data. Often, the validation consists of comparing the simulation result from different methods against each other and not to real inspection data. In practice, variation simulation methods are difficult to use due to practical implications. This paper illustrates some of the implications and modeling aspects related to sheet metal assembly variation analysis. The tolerance analysis and validation is done by analyzing a real sheet metal assembly with the production inspection data that is used to monitor the process. The aim is to analyze how consistent the result from the tolerance analysis is with the inspection data. Finally, some modeling aspects and techniques will be discussed.

Assembly sequence influence on geometric deviations propagation of compliant parts

“…The state space model has been extended by Loose et al (2009) with the development of an analytical derivation to describe features deviations controlled by GD&T characteristics. For tolerance analysis some aspects such as assembly sequence, contact modelling, we refer to Dahlström et al (2005), and fixture layout, referring to Huang et al (2007), need to be incorporated to find a correlation between simulated variations and actual ones. Söderberg et al (2007) presented a tool for non-rigid variation simulation and visualization based on…”

A Case Study – Resistance Spot Welding Distortions According to Several Welding Sequences

“…In this context, for example (Shaoyun et al, 2006) present in their study geometrical models for both slip and butt joints. Besides, (Dahlström et al, 2007) added placing of parts in a fixture, clamping and joining of parts together to sheet metal assembly variation analysis. (Moos & Vezetti, 2015) introduced welding sequence to the variational assemblies together with the effects of fixturing and resistance spot welding process (for example welding cap closure).…”

Dimensional Metrology of Flexible Parts: Identification of Geometrical Deviations From Optical Measurements

“…Sheet metal assembly consists in joining together one or more parts the characteristics of which are to be largely flexible and of complex forms. The process is often modelled as four sequential steps [1] The simulation allowing understanding how dimensional variations propagate is based on a Finite Element Approach (FEA) which requires the finest definition of part geometry [1] [2] [3]. In fact, actual geometry deviations may affect boundary conditions as shown in figure 1 [2]: the displacement at the point Pt1 not only depends on the displacement DL1 but is also affected by the form deviation.…”

“…In addition, real part surfaces are measured on inspection points using a classical measuring system: a CMM equipped with a contact probe. It is important to notice that to make simulation consistent, mesh nodes and inspection data must be coincident [2] [3]. As a result, the geometry of the surface is only acquired in a few measuring points which strongly depend on the initial meshing of the surfaces.…”

“…As a result, the geometry of the surface is only acquired in a few measuring points which strongly depend on the initial meshing of the surfaces. This may affect the finite element simulation [2]. Moreover, as it is well-known that part set ups influence flexible plate parts' deflections under their own weight [4], parts are measured in the exact position of the assembly to integrate the weight effect.…”