Abstract

Data-driven modeling and fault detection of multi-stage manufacturing processes remain challenging due to the increasing complexity of the manufacturing process, the lack of structural data, data multi-dimensionality, and the additional difficulty when dealing with large data sets. The implementation of add-on sensors and establishing data acquisition, transfer, storage and analysis has the potential to facilitate advanced data modeling techniques. However, besides the associated costs, dealing with high-volume multi-dimensional data sets can be a major challenge. This paper presents a novel methodology for early fault identification of multi-stage manufacturing processes using a statistical approach. The major advantage of the proposed methodology is its reliance on only the product quality measurements and basic product manufacturing records, given the presence of peer sets. This leads to a feasible faultidentification solution in a sensor-less environment without investing costly data collection systems. The developed methodology transforms the end-of-process quality measurements to a process performance metric based on a density-based statistical approach and a peer-to-peer comparison of the machines at one stage of the process. This approach allows one to be more proactive and identify the problematic machines that could be affecting product quality. A case study in an actual multi-stage manufacturing process is used to demonstrate the effectiveness of the developed methodology.

Highlights

  • Statistical Process Control (SPC) has been widely employed in industrial operations to detect the changes in the process through monitoring process/quality variables over time and so to determine if the process is in control

  • Unlike the Shewhart and Cumulative Sum (CUSUM) control charts which use the current samples for statistical testing, the Exponentially Weighted Moving Average (EWMA) chart uses previous values multiplied by a weighting factor

  • This paper introduces a novel methodology for identifying the root cause of the anomalies that affect the product quality in multi-stage manufacturing processes

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Summary

INTRODCUTION

With the increasing productivity of manufacturing systems, multi-stage manufacturing processes are a commonly used. Further developments from the traditional SPC methods to address this problem include the regressionadjustment method developed by Hawkins (Hawkins, 1993), and applied in multiple case studies by others This method regresses quality variables on subsets of the other quality variables and monitor the residuals from the regression models for each stage. It is clear that existing methods will not suffice and a multivariate multistage monitoring approach based on only the quality measurements of the finished products needs to be considered. This paper introduces a novel methodology for fault identification in a multistage environment, given basic product manufacturing records and the presence of peer sets, where only multiple quality characteristics from the final manufacturing stage are available and no expert knowledge is needed.

TECHNICAL APPROACH
Development of Product Inspection Metrics for Anomaly Detection
Density-based Product Inspection Metric
Weighted feature summation
RESULTS AND DISCUSSIONS
CONCLUSIONS
FUTURE WORK

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