Eng—Advances in Engineering· 2026Q2
Capacity Expansion and the Capability–Defect Gap After Automating a Screw-Fastening Station: A Lean Six Sigma DMAIC Case Study in an Automotive Safety-Components Production Line
- 0citations
- Q2SCImago
- 2026year
Short summary
Integrating an automated screw-fastener (OP8) increased rated capacity by 30.8% (117 to 153 parts/h), with OP8 contributing 8 parts/h, while Overall Equipment Effectiveness (OEE) remained high (88.0–91.7%). However, the new machine exhibited 2.3–3.0 times higher torque standard deviation and a defect rate 21 times higher than the previous machine, despite logged data appearing within specification.
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Key points
- Rated capacity increased by 30.8% (117 to 153 parts/h) after integrating an automated screw-fastener (OP8).
- OP8 contributed 8 parts/h to the capacity gain, while OEE remained high between 88.0% and 91.7%.
- Torque standard deviation on OP8 was 2.3–3.0 times higher than on the previous machines (OP6/OP7).
- The defect rate for poor screw-fastening reached 0.66% of OP8 output, approximately 21 times the rate of OP6, even when logged data was within specification.
AI-generated from the title and abstract; the full text is not read.
Abstract
Background: Automotive safety-component suppliers often must add capacity at short notice, and automation is common. This study quantifies the capacity, equipment-effectiveness, process-capability and nonconformity effects of integrating an automated screw-fastening machine (OP8) into an assembly line. Methods: An Action-Research DMAIC study combined 2024 monthly capacity, OEE and nonconformity records with ordered 100-part series of fastening torque and nut height from the original equipment (OP6/OP7) and OP8 for two product variants, analyzed with I-MR charts, resolution-aware Anderson-Darling tests, normal and Weibull capability indices with confidence intervals, and Brown-Forsythe, Hodges-Lehmann, Cliff’s delta and Welch tests. Results: Rated capacity rose from 117 to 153 parts/h (+30.8%), of which 8 parts/h (22% of the gain) is attributable to OP8; OEE remained at 88.0–91.7%. Torque standard deviation on OP8 was 2.3–3.0 times that on OP6 (Brown-Forsythe p < 0.001), whereas nut-height spread was 11–23% lower. Poor screw-fastening reached 0.66% of OP8 output in June, July and September, about 21 times the OP6 rate, although no logged reading was out of specification. Conclusions: Capacity increased, but capability indices computed from machine-logged, apparently screened data neither explained nor predicted the attribute defect rate, and the defect reduction cannot yet be credited to the improvement actions.
The authors' abstract, as published at the source. Eng—Advances in Engineering, 2026 · DOI ↗
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Statistics, Probability and UncertaintyDecision Sciences