12.3 TQM, Six Sigma, Lean & Continuous Improvement Methods

TQM, Six Sigma, Lean & Continuous Improvement Methods

Exam 2 asks you to match the methodology to the problem. A scenario describing wildly inconsistent output from a stable process points to Six Sigma. A scenario describing long lead times, bloated work-in-process, and material travelling four miles inside a plant points to Lean. A scenario describing a single escaped defect at a supplier points to 8D and a supplier corrective action request. Learning the vocabulary alone is not enough; learn the diagnosis.

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Total Quality Management (TQM)

TQM is an organization-wide management philosophy in which every function and every employee is accountable for continuously improving quality as defined by the customer. Its pillars:

1. Customer focus — the customer, internal or external, defines quality.
2. Total employee involvement — quality circles, empowered teams, suggestion systems.
3. Process-centred thinking — improve the process, not the individual.
4. Integrated system — quality is embedded across functions, including supply management.
5. Strategic and systematic approach — quality objectives cascade from strategy.
6. Continual improvement — PDCA operating permanently.
7. Fact-based decision making — measurement, not opinion.
8. Communication — sustained, two-way, including with suppliers.

TQM's engine is the PDCA / Plan-Do-Check-Act (Deming or Shewhart) cycle: plan a change, run it on a small scale, check results against the prediction, then act by standardizing the gain or re-planning. Many organizations use the variant PDSA (Plan-Do-Study-Act).

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Six Sigma

Six Sigma is a data-driven methodology that reduces variation and eliminates defects by managing process capability statistically. Its target is a process so capable that specification limits sit six standard deviations from the process mean.

Sigma Levels and DPMO

Because processes drift over time, the Six Sigma convention allows a 1.5-sigma long-term shift in the mean. This is why the headline figure is 3.4 defects per million opportunities rather than the 2 parts per billion a perfectly centred 6-sigma process would produce.

DPMO Calculation

$\text{DPMO} = \frac{\text{Number of Defects}}{\text{Units} \times \text{Opportunities per Unit}} \times 1{,}000{,}000$

Worked example. A supplier ships 12,000 printed circuit assemblies. Each assembly has 250 solder joints, and each joint is one opportunity for a defect. Incoming inspection and field returns identify 63 defective joints in total.

1. Total opportunities = $12{,}000 \times 250 = 3{,}000{,}000$
2. $\text{DPMO} = \frac{63}{3{,}000{,}000} \times 1{,}000{,}000 = \mathbf{21\ \text{DPMO}}$
3. Reading the table, 21 DPMO sits between the 5σ (233 DPMO) and 6σ (3.4 DPMO) rows — roughly 5.5 sigma, an excellent supplier.

Exam trap: defects per unit is not defects per million opportunities. Here defects per unit is $63 / 12{,}000 = 0.00525$, and defective units would be a third figure again. Read which denominator the item asks for.

The Two Six Sigma Roadmaps

Belt hierarchy: Yellow Belt (awareness and team participation), Green Belt (leads projects part-time), Black Belt (full-time project leader and coach), Master Black Belt (trains Black Belts and manages the program), Champion or Sponsor (executive who removes barriers and owns the business case).

Critical to Quality (CTQ) characteristics translate the Voice of the Customer into measurable, specification-bearing attributes — the bridge between a customer complaint and a control chart.

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Lean

Lean originates in the Toyota Production System and targets waste (muda) and flow. Its five principles: specify value from the customer's viewpoint, map the value stream, create flow, establish pull, and pursue perfection.

The Eight Wastes — DOWNTIME

Core Lean Tools

• Value Stream Mapping (VSM): maps material and information flow end to end, separating value-added time from total lead time. The headline metric is process cycle efficiency = value-added time ÷ total lead time.
• 5S: Sort, Set in order, Shine, Standardize, Sustain — workplace organization.
• Kanban: visual pull signal authorizing replenishment only on consumption.
• Poka-yoke: mistake-proofing so the error becomes physically impossible.
• SMED (single-minute exchange of die): setup reduction that makes small lots economic and therefore shrinks EOQ.
• Jidoka: automation with a human touch — the process stops itself when an abnormality occurs.
• Heijunka: production levelling to smooth volume and mix.
• Takt time: available production time ÷ customer demand, the drumbeat the line must match.

Lean vs. Six Sigma

Lean Six Sigma merges them: use lean to remove waste and shorten the value stream, then use Six Sigma to stabilize and centre what remains.

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Kaizen vs. Reengineering

• Kaizen — continuous, incremental, low-cost improvement driven by the people who perform the work. A kaizen event or blitz is a focused three-to-five-day cross-functional workshop targeting one process.
• Kaikaku / Business Process Reengineering — radical, discontinuous redesign of a process from a blank sheet, usually enabled by technology and carrying far higher cost and risk.

Exam scenarios that describe modest budget, engaged frontline staff, and an incremental target want kaizen. Scenarios describing a process that is fundamentally obsolete want reengineering.

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8D Problem Solving — the Supplier Corrective Action Discipline

When a supplier ships a nonconformance, the standard structured response is 8D, and Exam 2 tests it directly:

Exam trap: containment (D3) is not a corrective action. An item describing a supplier who "sorted the suspect lot and shipped good parts" has completed D3 only. Until root cause is verified at D4 and systemic prevention is applied at D7, the corrective action request must stay open.