Virtual fixturing: Inspection of a non-rigid detail resting on 3-points to estimate free state and over-constrained shapes
Paper i proceeding, 2020

When the geometry of a non-rigid part or pre-assembly is measured fully clamped (over-constrained) in a measurement fixture, the spring-back information and influence from gravity forces are usually lost in the collected data. From the 3D-measurement data, it is hard to understand built in tensions, and the detail's tendency to bend, twist and warp after release from the measurement fixture. These effects are however important to consider when analyzing each part´s contribution to geometrical deviations after assembly. In this paper a method is presented, describing how free state shape and over-constrained shape of a measured detail can be virtually estimated starting from acquired data when the part or the preassembly is resting on only 3-points. The objective is to minimize the information loss, to spare measurement resources and to allow for a wider use of the collected data, describing the geometry. Part stiffnesses, part to part contacts and gravity effects are considered in the proposed method. The method is based on 3D-scanning techniques to acquire the shape of the measured object. Necessary compensations for part stiffnesses and gravity effects are based upon Finite Element Analysis (FEA) and the Method of Influence Coefficients (MIC). The presented method is applied to an industrial case to demonstrate its potential. The results show that estimated over-constrained shapes show good resemblance with measurements acquired when part is over-constrained in its measurement fixture.

Sheet metal



Virtual fixturing

Geometry assurance

Assembly simulation


Björn Lindau

Volvo Cars

Kristina Wärmefjord

Chalmers, Industri- och materialvetenskap, Produktutveckling

Lars Lindkvist

Chalmers, Industri- och materialvetenskap, Produktutveckling

Rikard Söderberg

Chalmers, Industri- och materialvetenskap

ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)

Vol. 2B-2020
9780791884492 (ISBN)

ASME 2020 International Mechanical Engineering Congress and Exposition, IMECE 2020
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