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Anomaly Detection in Small Correlated Datasets Using PCA and Local Outlier Factor: A Case Study in Quality Inspection of Incoming Materials for Stamping
Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.ORCID iD: 0000-0001-9889-6746
Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.ORCID iD: 0000-0002-7730-506x
Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.ORCID iD: 0000-0002-6526-976x
Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.ORCID iD: 0000-0002-1162-7023
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The increasing use of recycled materials in automotive manufacturing introduces variability in mechanical properties, posing challenges for quality assurance in stamping operations. This study presents a data-driven anomaly detection framework for pre-assessment of incoming sheet metal materials, aiming to prevent substandard coils from entering production. A small dataset of 54 tensile test samples of CR440Y780T-DP steel was analyzed using Principal Component Analysis (PCA) for dimensionality reduction and Local Outlier Factor (LOF) for unsupervised anomaly detection. PCA retained 84.2% of the dataset variance in two components, enabling effective visualization and anomaly identification. LOF, optimized via sensitivity analysis and expert input, flagged three samples as anomalous. Finite Element simulations of a Volvo XC40 sill reinforcement component revealed that two anomalies could significantly affect springback behavior, 1 potentially breaching tolerance limits. The study proposes an industrial implementation strategy integrating tensile testing and anomaly evaluation into the stamping plant workflow, offering a scalable solution for early detection of material deviations. These findings demonstrate the feasibility of combining PCA and LOF for robust, interpretable quality control in automotive sheet metal forming.

Keywords [en]
Unsupervised Learning, Anomaly Detection, Principal Component Analysis, Material Testing, Automotive Manufacturing, Sheet Metal Forming
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:bth-28886OAI: oai:DiVA.org:bth-28886DiVA, id: diva2:2014566
Available from: 2025-11-18 Created: 2025-11-18 Last updated: 2025-11-18Bibliographically approved
In thesis
1. Towards Sustainable and Intelligent Manufacturing Processes: Data-Driven Insights from Automotive Manufacturing
Open this publication in new window or tab >>Towards Sustainable and Intelligent Manufacturing Processes: Data-Driven Insights from Automotive Manufacturing
2025 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Global manufacturing is entering an era of unprecedented variability in material properties, driven by sustainability goals and market volatility. The adoption of recycled steels introduces supplier-specific differences, while cost-reduction strategies and geopolitical disruptions (tariffs, trade barriers, and resource shortages) further amplify process scatter. These dynamics challenge conventional quality control in automotive sheet metal forming and demand intelligent, adaptable production systems.

This dissertation addresses how data-driven methods can strengthen process robustness without major infrastructure changes. Three guiding hypotheses are explored: (H1) machine learning can provide insights into the impact of input variations; (H2) synthetic data can supplement or replace operational data for model development; and (H3) existing sensor signals can be reinterpreted to reduce reliance on additional instrumentation.

A hybrid methodology combining finite element simulations, stochastic modeling, and industrial press shop data was developed. Key contributions include: (1) generation of synthetic datasets for predictive modeling of draw-in and cushion force; (2) application of unsupervised learning for early detection of anomalous material batches; and (3) a novel process monitoring metric, process work, derived from existing sensors to monitor process health.

The findings provide a framework for integrating intelligent data-driven tools into legacy systems, supporting the transition toward resilient and sustainable manufacturing practices.

Place, publisher, year, edition, pages
Karlskrona: Blekinge Tekniska Högskola, 2025. p. 175
Series
Blekinge Institute of Technology Doctoral Dissertation Series, ISSN 1653-2090 ; 2025:16
Keywords
Data-Driven Manufacturing, Machine Learning in Manufacturing, Process Monitoring and Control, Sheet Metal Forming
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:bth-28765 (URN)978-91-7295-517-2 (ISBN)
Public defence
2025-12-16, C413A, BTH, Karlskrona, 09:15 (English)
Opponent
Supervisors
Available from: 2025-11-03 Created: 2025-10-15 Last updated: 2025-12-10Bibliographically approved

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Barlo, AlexanderSigvant, MatsPilthammar, JohanIslam, Md. ShafiqulLarsson, Tobias

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