How to calculate OEE Quality, what causes first pass yield losses, and the practical steps to reduce start-up waste and in-process rejects in food and FMCG manufacturing.
Quality in OEE measures first pass yield — the percentage of units produced that meet specification without rework. The formula is Quality = Good Units ÷ Total Units Produced. Total units includes everything that came off the line including rejects, rework and scrap. A unit that is reworked and eventually sold still counts as a quality loss because it wasn't right first time. The world-class target is 99% or higher. Quality is typically the strongest of the three OEE components, but when it drops it directly impacts material cost, labour time and customer service.
Quality losses are the most visible OEE losses because they produce physical waste you can see and count. But they're often harder to eliminate than downtime or speed losses because they have multiple root causes operating simultaneously. Here's how to break them down and address them systematically.
Quality losses fall into four broad categories, each with different causes and different improvement approaches.
Product produced during line stabilisation after a changeover or breakdown restart that doesn't meet specification. Often the largest single source of quality loss on multi-SKU lines.
Product rejected due to fill weight, seal integrity, dimensions or other in-process parameters drifting outside tolerance during steady-state production. Usually controlled by SPC and operator checks.
Product that fails inspection but can be brought back to specification — relabelling, recoding, repackaging. Counts as a quality loss even when eventually sold. Consumes significant secondary labour.
Start-up waste occurs during the unstable period after a line starts running following a changeover, breakdown or planned stop. The line is running but product parameters haven't yet stabilised within tolerance. On a high-changeover food line, this can represent the majority of all quality losses.
The fix is a defined changeover standard with explicit stabilisation criteria — measurable parameters (fill weight, seal strength, check weigher in control) that must be confirmed before full production resumes and output is counted as good. This converts vague "the line looks OK" judgements into objective pass/fail gates.
Quality improvement follows a different path to Availability or Performance improvement. It requires understanding root causes at a detailed level, not just recording that rejects happened.
Record every quality loss with a reason code. Run a weekly Pareto — the top 2 or 3 reasons typically account for 70–80% of all losses. Attack those first.
Create a written changeover standard with measurable criteria that must be met before production counts as first-quality. Eliminates guesswork at start-up.
Use SPC charts for critical parameters (fill weight, seal temperature, torque). Make variation visible in real time so operators can correct before rejects are produced.