This presentation was made at the 2019 NAFEMS World Congress in Quebec Canada
3D scanning technology is a powerful tool allowing to create a digital twin of an existing part. Thanks to recent developments in the field, some commercial handheld 3D scanners can deliver the same precision as metrology tools like Coordinate Measuring Machines (CMM). Significant advantages of the handheld 3D scanner are portability, reduced sensitivity to environmental changes and it allows for inspection of the entire part surface instead of simply digitalizing discrete points. Tool makers and manufacturers using injection molding have already integrated handheld 3D scanners into their daily toolbox to help increase the quality and repeatability of their parts.
This paper focuses on the joint use of numerical simulation and 3D scanning to predict the stresses and strains in a complex mechanical assembly, where dimensional tolerances played a key role in load and stress distribution. This paper is based on an engineering project which involved the failure root cause analysis of tooling used to produce a composite helmet.
Repeated failures of the tooling used to produce helmets has forced the use of innovative methods to determine the source of the problem and apply the necessary corrections. Finite element analysis (FEA) is favoured tool to determine the stresses and displacements caused by the operating loads. However, because of the complexity of the tooling, simply considering the operating loads and using the nominal dimensions of the 3D geometries did not allow to clearly identify and reproduce without a doubt the cause of premature wear and failure.
To identify source of the problem, parts were digitized using 3D scanning technology and virtually assembled using dimensional analysis software. This made it possible to measure the gaps at critical assembly interfaces with a high level of precision. Then, by using a non-linear contact algorithm which varied part offsets in the FEA model, coupled with a dimensional analysis of the different tooling 3D scans, it was possible to reproduce the problematic failures. Complex freeform surface interfaces were modelled in FEA at their nominal dimensions, and contacts were segmented locally. Dimensional analysis of the tooling allowed to retrieve the possible interference and gaps. Different tool combinations were analysed to understand the interaction between tolerances and load distribution.
|Date||18th June 2019|