operations

Lean six sigma

process improvement philosophy combining lean and six sigma to improve quality, efficiency, and customer satisfaction

• Lean: Focuses on eliminating waste and non-value-added activities.

• Six Sigma: Focuses on reducing variation and defects through data and statistical analysis.

• Together: Improve quality, reduce costs, shorten lead times, and increase efficiency.

six sigma helps reduce

improve process capability by reducing variation and defects

6 sigma performance

approx 3.4 defects per million opportunities (DPMO) → accuracy → 99.99966%

DMAIC → 5 step process for improving existing processes when the causes of problems are unknown

→ Define

→ measure

→ analyze

→ improve

→ control

5 lean principles

1. Identify Value — determine what customers consider valuable.

2. Map the Value Stream — identify activities that create value and those that create waste.

3. Create Flow — ensure work moves smoothly without unnecessary interruptions.

4. Establish Pull — produce based on actual customer demand.

5. Pursue Perfection — continuously improve the process.

Lean tool → 5S

organize workplaces to improve efficiency and safety

Lean tool → just in time

produce only what is needed, when needed

Lean tool → Kaizen

continuous improvement through small, ongoing changes

Lean tool → Kanban

visual signals that control workflow and inventory

Lean tool → poka yoke

error-proofing to prevent or immediately detect mistakes

Lean tool → pull system

production triggered by customer demand

Lean tool → standard work

documented best known method for completing tasks

Lean tool → value stream mapping

maps material and info flows to identify waste

Lean tool → visual factory

uses visual cues to communicate status and problems quickly

8 wastes of lean (DOWNTIME)

D — Defects → Errors requiring correction or rework

O — Overproduction → Producing more than needed

W — Waiting → Idle time between process steps

N — Non-Utilized Talent → Not fully using employees' skills or ideas

T — Transportation → Unnecessary movement of materials

I — Inventory → Excess materials or finished goods

M — Motion → Unnecessary movement by workers

E — Extra Processing → Performing more work than customers require

nominal group technique

Individuals generate ideas independently, share them, then rank options

Lean waste → Defects

Errors requiring correction or rework

Lean waste → Overproduction

Producing more than needed

Lean waste → Waiting

Idle time between process steps

Lean waste → Non-Utilized Talent

Not fully using employees' skills or ideas

Lean waste → Transportation

Unnecessary movement of materials

Lean waste → Inventory

Excess materials or finished goods

Lean waste → Motion

Unnecessary movement by workers

Lean waste → Extra Processing

Performing more work than customers require

Multivoting

Team members vote to narrow a large list of options.

Vroom-Yetton Decision Model

Helps leaders determine how much team participation a decision requires.

Weighted Scoring Model

Quantitatively compares alternatives using weighted criteria.

Check Sheet

Collect and tally data consistently

• Example: Recording how many products have scratches, dents, or missing parts.

Pareto Chart

• Identify the most important problems

• based on 80/20 rule → Approximately 80% of problems may come from 20% of causes

Run Chart

Track performance over time

• Example: Tracking customer complaints each month

• Run Chart vs. Control Chart: Run charts show patterns over time; control charts add statistical limits to evaluate process stability.

Scatter Diagram

Identify relationships between variables

Flowchart

Map process steps and decisions

• Example: Customer places order → Inventory checked → Order processed → Product shipped.

Fishbone Diagram (cause and effect)

Identify possible root causes

• Often combined with brainstorming and the 5 Whys technique.

Histogram

Show the frequency distribution of data

Six Major Cause Categories (6 Ms)

Man, Machine, Method, Material, Measurement, and Mother Nature

6 Ms → Man

Workers, training, staffing, and skills

6 Ms → Machine

Equipment, tools, and technology

6 Ms → Method

Procedures and processes

6 Ms → Material

Raw materials and components

6 Ms → Measurement

Data collection, gauges, and calibration

6 Ms → Mother Nature

Environmental conditions

defects per unit formula

DPU = total defects / total units

Tollgates

Critical checkpoints that must be completed before advancing to the next DMAIC phase.

Three Define Phase Tollgates:

1. Map the process.

2. Define customer needs and requirements.

3. Create a project charter.

Project Identification Process:

Select the project using a weighted scoring model → Map the process using SIPOC → Formally authorize the project using a charter.

SIPOC Diagram

SIPOC: A high-level process map that documents a business process from beginning to end.

Letter	Meaning	Description
S	Suppliers	Who provides resources?
I	Inputs	What resources are needed?
P	Process	What activities occur?
O	Outputs	What does the process produce?
C	Customers	Who receives the outputs?

Purpose of SIPOC

• Establish a shared understanding of a process.

• Identify process boundaries.

• Clarify suppliers, inputs, outputs, and customers.

• Support improvement planning during Define.

Seven Steps to Create SIPOC:

• Choose a process.

• Define the Process (4–10 high-level steps).

• Identify Outputs (typically 3–4).

• Identify Customers.

• Identify Inputs.

• Identify Suppliers (at least one for each input).

• Share and validate the diagram.

Project Charter

A formal document authorizing an improvement project and outlining its objectives, scope, resources, responsibilities, and expected results.