Inspection by exception: a new machine learning-based approach for multistage manufacturing

Moschos Papananias*, Thomas E. McLeay, Olusayo Obajemu, Mahdi Mahfouf, Visakan Kadirkamanathan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Manufacturing processes usually consist of multiple different stages, each of which is influenced by a multitude of factors. Therefore, variations in product quality at a certain stage are contributed to by the errors generated at the current, as well as preceding, stages. The high cost of each production stage in the manufacture of high-quality products has stimulated a drive towards decreasing the volume of non-added value processes such as inspection. This paper presents a new method for what the authors have referred to as ‘inspection by exception’ – the principle of actively detecting and then inspecting only the parts that cannot be categorized as healthy or unhealthy with a high degree of certainty. The key idea is that by inspecting only those parts that are in the corridor of uncertainty, the volume of inspections are considerably reduced. This possibility is explored using multistage manufacturing data and both unsupervised and supervised learning algorithms. A case study is presented whereby material conditions and time domain features for force, vibration and tempering temperature are used as input data. Fuzzy C-Means (FCM) clustering is implemented to achieve inspection by exception in an unsupervised manner based on the normalized Euclidean distances between the principal components and cluster centres. Also, deviation vectors for product health are obtained using a comparator system to train neural networks for supervised learning-based inspection by exception. It is shown that the volume of inspections can be reduced by as much as 82% and 93% using the unsupervised and supervised learning approaches, respectively.

Original languageEnglish
Article number106787
Number of pages15
JournalApplied Soft Computing Journal
Issue numberPart A
Early online date16 Oct 2020
Publication statusPublished - 1 Dec 2020


  • artificial neural network (ANN)
  • fuzzy c-means (FCM)
  • intelligent/smart manufacturing
  • machine learning
  • multistage manufacturing process (MMP)
  • principal component analysis (PCA)
  • UKRI
  • EP/P006930/1


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