Lean Six Sigma Project Examples
Practical Lean Six Sigma project examples mapped to DMAIC phases, showing the problem, baseline, root cause, improvement, control and results. These are illustrative examples based on common improvement scenarios — not claims about specific client projects.
Example 1: Reducing customer complaint response time
Average complaint response time was 6.2 days, exceeding the 3-day target.
6.2 days average, 23% of complaints unresolved within 5 days.
No standard acknowledgement process; complaints routed manually to 4 different teams.
Automated acknowledgement within 4 hours; single triage queue with routing rules.
CRM SLA alerts, weekly I-MR chart on response time, daily dashboard.
Average reduced to 2.1 days. 94% resolved within 5 days.
Tools used: SIPOC, fishbone diagram, Pareto chart, I-MR control chart, CRM SLA dashboard. Belt level: Green Belt.
Example 2: Reducing invoice processing errors
8.3% of invoices contained errors requiring rework, costing ~£12,000/month in delayed payments.
8.3% error rate, 350 invoices/month, 29 rework cycles average.
Manual data entry from 3 different formats; no validation at entry point; PO field optional.
Standardised invoice template; mandatory PO field; automated validation checks at entry.
Weekly error rate p-chart; monthly audit of sample invoices; control plan for the process owner.
Error rate dropped to 1.7%. Rework cycles reduced from 29 to 6/month. Savings ~£9,500/month.
Tools used: DMAIC, 5 Whys, Pareto chart, p-chart, process mapping, FMEA. Belt level: Green Belt.
Example 3: Reducing machine downtime in a production line
Unplanned downtime averaging 14.2 hours/week on CNC Line 3, reducing OEE by 11%.
14.2 hours/week downtime, OEE at 67%, 3.2 stoppages/week.
No preventive maintenance schedule; tool wear undetected until failure; coolant levels not monitored.
Implemented TPM (Total Productive Maintenance); sensor-based tool wear monitoring; daily coolant check sheet.
Weekly downtime Xbar-R chart; daily check sheet; maintenance dashboard reviewed at daily management board.
Downtime reduced to 4.1 hours/week. OEE improved to 79%. Stoppage frequency halved.
Tools used: OEE measurement, fishbone diagram, FMEA, Xbar-R control chart, TPM, control chart analysis. Belt level: Green Belt.
Example 4: Improving patient appointment scheduling in a clinic
18% no-show rate for appointments; clinic utilisation at 61% against a target of 80%.
18% no-shows, 61% utilisation, average wait time 14 days.
No appointment reminders; overbooking for certain slot types; no data on no-show patterns by day/time.
SMS reminders 48 hours before; data-driven slot allocation based on no-show patterns; waitlist system for cancellations.
Monthly no-show run chart; weekly utilisation report; clinic manager reviews at monthly performance meeting.
No-shows reduced to 7%. Utilisation improved to 78%. Average wait time reduced to 6 days.
Tools used: SIPOC, Pareto chart, run chart, data collection plan, process mapping. Belt level: Green Belt.
Example 5: Reducing defect rate in a welding process
Weld defect rate at 4.8% (target ≤ 1.5%), costing £18,000/month in rework and scrap.
4.8% defect rate, DPMO of 48,000, process capability Cpk = 0.72.
Welding parameters (current, gas flow, travel speed) not optimised; no controlled settings by material type; operator variation.
Design of Experiments to optimise welding parameters; standard parameter cards by material type; operator training and certification.
Daily Cp/Cpk monitoring; weekly p-chart on defect rate; parameter audit checklist; control plan updated.
Defect rate reduced to 1.2%. Cpk improved to 1.41. Savings £14,200/month.
Tools used: Process capability analysis, DOE (full factorial), ANOVA, p-chart, FMEA, control plan. Belt level: Black Belt (DOE required).
Lessons learned across these examples
- Define the problem precisely. Every successful project started with a clear, measurable problem statement — not a vague "things need to be better."
- Measure before you improve. Baseline data is what makes the improvement verifiable. Without it, you cannot prove the change worked.
- Root cause analysis is non-negotiable. In every example, the obvious cause was not the real cause. Fishbone diagrams and 5 Whys uncovered the actual drivers.
- Control is where projects fail. Without control charts, dashboards and ownership, improvements decay. A control plan keeps the gains.
- Match belt level to project complexity. Examples 1–4 are achievable at Green Belt. Example 5 requires Black Belt-level tools (DOE, ANOVA).
Frequently asked questions
Are these real projects?
These are illustrative examples based on common Lean Six Sigma project scenarios. They represent the types of problems, approaches and results you can expect — not claims about specific client engagements. The metrics, root causes and results are realistic but not tied to specific named organisations.
Do I need a project to get certified?
At Yellow and Green Belt level, most providers do not require a project submission — just the exam. At Black Belt level, some providers require a project. SimplicityHub's Green Belt assessment is exam-based with an optional project; Black Belt includes a project component.
What size of project is right for Green Belt?
A Green Belt project should have a clear problem, measurable baseline, a scope within one process or department, and achievable improvement within 2–4 months. Examples 1–4 above are typical Green Belt projects.
How do I choose a project?
Start with a pain point in your own work area — something that causes delays, errors, cost or customer complaints. Use a SIPOC diagram to scope it, then build a project charter. The best projects have a measurable baseline and a clear stakeholder who cares about the result.
What tools do I need for a DMAIC project?
The core tools are a project charter, SIPOC, data collection plan, Pareto chart, fishbone diagram, 5 Whys, and a control chart. You can access all of these free on SimplicityHub — see our calculators and DMAIC templates.
How long should a Lean Six Sigma project take?
A Green Belt project typically takes 2–4 months from Define to Control. A Black Belt project may take 4–6 months due to greater complexity. The timeline depends on data availability, stakeholder availability and the scope of the improvement.
Can I run a project without being certified?
Yes, but certification gives you the structured methodology and tools to do it properly. Many people start a project as part of their Green Belt training — the project becomes both a learning exercise and a real improvement for their organisation.
What if my project does not show improvement?
No improvement is still a result — it means the root cause was not correctly identified, or the solution did not address it. Go back to the Analyse phase, re-examine your data and root cause analysis, and try a different improvement. This is normal in DMAIC — it is an iterative process.