Practical guide · Quality management
How to improve product quality in manufacturing: 7 steps
Short answer
To improve product quality, find where defects start, fix the root cause of the biggest one, and change the process so it cannot happen again. In order: define good and count defects, rank them with a Pareto, find the root cause, error-proof the step, write the fix into the work instruction, check it with audits and control charts, then train people to keep it. Inspection alone only sorts good from bad.
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The short answer
Quality improves when you stop catching defects at the end and start preventing them where they begin. That means measuring defects in a way that points to a place and a cause, fixing the process instead of the single part, and making the fix stick. The same seven steps apply whether you are asking how to improve quality in production, in a factory or in quality control, because all of them come down to finding and removing causes.
The sequence below is the short version. Our post on how to improve production quality in manufacturing goes deeper on each step, and the quality improvement page shows how LeanSuite tracks the work.
Seven steps to improve product quality
- 1
Define what good looks like, and measure defects
Write down the specification and what counts as a defect for each product. Then count defects in a consistent way, by type, line, shift and product, with a defect check sheet. You cannot improve what you only guess at.
- 2
Find where defects start, with a Pareto
Rank defect types from biggest to smallest with a Pareto chart and pick the top one. Build it by count and by cost, because the order can change. A few causes usually account for most of the loss.
- 3
Find the root cause, not the symptom
Ask why until you reach a condition you can change for good, using the 5 Whys or a fishbone. The root cause analysis guide and the problem solving methods guide help you choose the method.
- 4
Error-proof the process
Redesign the step so the mistake is impossible or is caught on the spot. This is poka-yoke: a fixture that only fits one way, a sensor that stops the machine, a checklist that cannot be skipped. Record that it works with an error-proofing verification log.
- 5
Standardise the fix in a work instruction
Write the new way into the work instruction or SOP, with pictures where you can, and remove the old version. A fix that lives in one person's head goes away when that person does. The SOP template is a starting point.
- 6
Check with audits and control charts
Audit that the standard is followed, and plot the key measurement on a control chart so drift shows up before parts go out of tolerance. Open non-conformance reports for anything that still escapes, and follow them to closure.
- 7
Train and sustain
Train everyone who does the job on the new standard, check understanding at the line, and review the defect numbers at the daily meeting. Then go back to step 2: the next biggest defect is now the top bar.
An illustrative example
This example is made up. A plant that makes drilled metal brackets sees returns for holes that are out of position. The team starts a check sheet and finds that most rejects come from one drilling fixture on the second shift.
The first answer people give is that the second shift is careless. The team asks why instead. The fixture can hold the bracket two ways, one of them rotated, and the work instruction does not show the correct way. The fix is a locating pin that stops the bracket going in rotated, a photo added to the instruction, and a first-piece check logged each start-up. A control chart on hole position confirms the process is centred. The operators did not change. The process did.
Common mistakes
| Mistake | What goes wrong | Do this instead |
|---|---|---|
| Inspecting quality in | More checkers find more defects, but the cause is still there and cost goes up | Use inspection to measure, and spend the effort on preventing the defect at the source |
| Blaming operators | People hide mistakes, so the same defect returns | Ask what made the error easy to make, then error-proof the step |
| Fixing the symptom | Parts are reworked or sorted and the cause is untouched | Go to the root cause before changing anything |
| Working on everything at once | Effort is spread thin and no defect type really falls | Start with the top Pareto bar and finish it |
| No standard after the fix | The defect slowly comes back | Update the work instruction, train and audit it |
For the scrap and rework side of the same work, see how to reduce scrap and rework. For how prevention and checking fit together, see quality assurance vs quality control.
Go deeper
This page is the short version. These guides cover each part in full.
- How to Improve Production Quality in ManufacturingThe full blog guide, with more detail on each step.
- Quality at the Source: Building Quality Into the Production ProcessHow to stop a defect at the step where it is made.
- Right First Time in ManufacturingThe principles and steps for getting it right the first time.
- Why Defects Reach CustomersHow defects get past quality control, and how to close the gaps.
- Poka-Yoke Error-Proofing MethodsMethods for making a mistake impossible or obvious.
- Control Charts: Reading and Interpreting Manufacturing DataHow to read the signals that tell you a process is drifting.
All our articles on this subject are in the quality management topic.
Free templates and tools
- Defect check sheetTally defects by type and day, with units inspected, defect rates, a location sheet and the week's Pareto.
- Pareto chart templateA tally sheet, the Pareto by count and by cost with the cumulative line and the 80% cut, and a before and after comparison. Excel sorts and draws it.
- Root cause analysis templateOne report from problem statement to proof: containment, evidence, analysis, verified causes, actions and the effectiveness check.
- 5 Whys templateA problem statement, a why chain that can branch, evidence for every answer, root causes and countermeasures that are checked.
- Error-proofing verification log (daily master-sample check)Each poka-yoke device proved every day or week with a known-bad sample, with missed checks counted and the hours and parts at risk worked out when one fails.
- X-bar and R control chart template25 subgroups with means and ranges, control limits from A2, D3 and D4, signal flags, both charts and a reaction log.
- Standard operating procedure (SOP) templateA full SOP in the hierarchical step format, from purpose and scope to the steps, records, revision history and approvals, with review checks and an SOP register.
- Quality inspection checklistAn in-process and final inspection record: measured characteristics, visual checks, a decision and first pass yield.
- Pareto chart makerPaste categories and counts: sorted bars, cumulative percentage line and the vital few at the 80% line, as a PNG or SVG.
- First pass yield (FPY) calculatorFirst pass yield at each step and rolled throughput yield (RTY) across the whole process.
- Scrap rate calculatorScrap rate, the cost of scrap per period and per year, and what reaching a target rate would save.
- Cost of poor quality (COPQ) calculatorTotal COPQ and cost of quality, and each as a share of revenue, from the four quality cost categories.
Doing this in LeanSuite
Quality Improvement
Log quality issues from the floor, trace each one to its root cause and follow the corrective action through to closure.
See Quality ImprovementNon-Conformance (NCR)
Moves non-conformance reports into an automated workflow and links each defect report to root-cause problem solving.
See Non-Conformance (NCR)AI Root Cause Analysis
Describe a problem, answer the AI's questions, and get the likely root causes and an action plan.
See AI Root Cause Analysis
See it on your own lines
Bring the problem you are working on to a 45-minute demo. Or look around with sample data first, or pilot LeanSuite on your own lines for 90 days, with the setup done by our team.
FAQ
Questions about how to improve product quality
Measure defects by type and place, rank them with a Pareto chart, find the root cause of the biggest one, error-proof the process step, write the fix into the work instruction, check it with audits and control charts, and train people on it. Repeat with the next biggest defect.
Make sure you are measuring the right things with gauges you trust, use control charts to see drift before parts fail, inspect at the step where a defect can be made rather than only at the end, and send every escape back to a root cause. Quality control tells you what happened, so pair it with prevention.
Build quality in at the step where the work is done. Give operators clear standards, stop the line when something is wrong, use error-proofing so mistakes cannot pass, and track defects by cause. Fixing the process is more lasting than sorting the parts afterwards.
Start by counting defects in a consistent way: by type, line, shift and product, on a simple check sheet. Without that data you cannot tell which problem is biggest. Once you have a couple of weeks of counts, rank them with a Pareto chart and begin with the top one.
Prevent the defect instead of finding it. Use error-proofing such as fixtures and sensors, make the work instruction clear, check the first piece at each start-up, and fix root causes. Inspection finds problems already made, while prevention stops them being made.
Quality assurance is about the process: the systems and standards that prevent defects. Quality control is about the product: the checks that find defects that got through. Improving quality needs both, with the stronger effect coming from prevention.
The common ones are a check sheet to count defects, a Pareto chart to rank them, the 5 Whys or a fishbone to find the cause, poka-yoke to error-proof the step, a work instruction to hold the fix, and a control chart to watch the process. Use them in that order, one defect at a time.
Related guides and tools
More method guides
- The 6 Ms of production
- Poka-yoke
- Model area 90-day plans
- Moving from Excel to one system
- Reducing machine downtime: a worked month
- Andon and jidoka
- Cycle time vs lead time, worked through
- Root cause analysis
- How many operators a line needs
- Reducing scrap and rework: a worked month
- Unsafe acts and unsafe conditions
- Just culture
- Stop-work authority
- Material review board (MRB)
- What is an NCR?
- Problem solving methods
- Quad chart
- OEE calculation
- Quality assurance vs quality control
- SOP meaning and format
- Job hazard analysis
- Near miss reporting
- Fishbone diagram
- Pareto chart
- Histogram
- Control chart
- What is a gemba walk
- What is lead time
- What is operational excellence
- Preventive vs predictive maintenance
Or browse the topics, the full library and the lean glossary.
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