Cost of quality: what getting it wrong actually costs

Cost of quality is the total a business spends on getting things right plus the total it spends because things went wrong. Stated that way it sounds like an accounting exercise; its value is that it makes visible the second half, which never appears as a line in any budget and is usually several times larger than the first.

The four parts of cost of quality

• Prevention: training, better process design, supplier development, maintenance done before failure.
• Appraisal: inspection, testing, audits — the cost of finding out whether things are right.
• Internal failure: scrap, rework, re-testing, delays, the production time consumed by second attempts.
• External failure: returns, warranty work, credit notes, the engineer sent back out, and the customer who does not reorder.
• The last category is the most expensive and the least measured, because most of it never reaches an account code.

Why the invisible categories dominate

Prevention and appraisal are budgeted, so they are visible and easy to cut. Failure costs are absorbed: rework happens inside normal production hours, a credit note reduces revenue rather than appearing as a cost, a delayed delivery is handled by overtime nobody attributes to quality. The result is an organisation that can tell you precisely what inspection costs and has no idea what defects cost, which reliably produces the wrong decision — cutting the measurable spend and increasing the unmeasured one.

Estimate roughly rather than measuring precisely. A figure assembled in an afternoon from scrap records, credit notes and an honest guess at rework hours is accurate enough to change decisions, and waiting for a rigorous system means the number never exists at all.

What the ratio tells you

1. Mostly external failure: you are discovering problems after the customer does, which is the most expensive possible place.
2. Mostly internal failure: you are catching them, but late — the process produces defects and inspection finds them.
3. Mostly appraisal: you are inspecting quality in rather than building it, which is expensive and incomplete by nature.
4. Mostly prevention: the healthy position, and the one that takes years to reach.
5. Track the total as a percentage of turnover so it can be compared across periods rather than read as a raw figure.

Ettex Sheets is enough to hold the four categories with the sources behind each, which is more than most small manufacturers have and takes an afternoon to assemble. The internal failure half overlaps directly with first pass yield, since rework counted honestly there is the same money appearing in this calculation.