From: Weakness Ranking Method for Subsystems of Heavy-Duty Machine Tools Based on FMECA Information
Category | Description | Reference value of failure frequency | OPR score |
---|---|---|---|
Class I | Occur frequently | > 20% | 10 |
Class II | Occur sometimes | 10%–20% | 9, 8, 7 |
Class III | Occur occasionally | 1%–10% | 6, 5, 4 |
Class V | Occur less | 0.1%–1% | 3, 2 |
Class V | Occur rarely | < 0.1% | 1 |