Six Sigma Green Belt

Lean Concepts

Lean focuses on speed and flow by eliminating waste, while Six Sigma focuses on reducing variation and defects. Combined as Lean Six Sigma, the two approaches address both how fast and how well work is done. Lean thinking rests on five principles, applied in order:

➜

➜

➜

➜

Defined by the customer

Remove interruptions

Produce on customer

Improve continuously

Every step that delivers

and delays

demand

value

Related lean concepts include just-in-time (JIT), producing only what is needed, when it is needed, in the quantity needed; takt time, the pace of customer demand (available time ÷ demand); gemba, the actual place where work is done; jidoka, stopping automatically when an abnormality occurs so defects are not passed on; and heijunka, leveling the mix and volume of production.

Value Analysis

Value analysis sorts every activity into one of three categories so that improvement effort goes to eliminating waste.

VA Ratio = Value-Adding Time ÷ Total Lead Time

Many processes have ratios below 10%, which signals a large opportunity to cut lead time.

The Eight Wastes (Muda)

Lean identifies eight types of waste. The mnemonic DOWNTIME helps recall them. Recognizing waste is the first step toward eliminating it.

Waste	Description	TypicalCountermeasure
Defects	Productsorservicesthatfailrequirements requiring ,	Errorproofing rootcauseelimination ,
	inspection rework scrap orwarrantycost , , ,
Overproduction	Makingmore orearlier thanneeded;createsinventoryand , ,	Pullsystems productiontotakt ,
	hidesproblems
Waiting	Workstallsforapprovals information equipment orearlier , , ,	Balanceworkloads removebottlenecks ,
	steps
Non-utilized talent	Employeeskillsandideasnotused	Involvepeopleinimprovement
Transportation	Unnecessarymovementofmaterialsorinformationbetween	Co-locate steps improve layout ,
	processes
Inventory	Rawmaterial WIP orfinishedgoodsbeyondimmediateneed; , ,	Smallerbatches betterflow ,
	tiesupcapital

Waste	Description	TypicalCountermeasure
Motion	Unnecessarymovementofpeople:walking reaching , ,	5S workplaceorganization ergonomics , ,
	searching
Extraprocessing	Doingmorethanthecustomerrequires:excessprecision ,	Clarifycustomerrequirements
	redundantchecks

Transportation moves materials or products; motion is movement of people. Overproduction is often called the worst waste because it creates several others, especially inventory and waiting.

Value Stream Mapping

A value stream map (VSM) shows the material and information flow for an entire product family from supplier to customer. Process boxes carry data boxes (cycle time, changeover time, uptime, number of operators), inventory triangles show where work waits, and a timeline at the bottom separates value-adding time from total lead time. Teams draw a current-state map, design a future-state map using lean principles (continuous flow, pull, level loading, smaller batches), and then follow an implementation plan that sequences improvements, starting with quick wins.

Design for Six Sigma (DFSS) Methodologies

Design for Six Sigma builds quality into a new product, service, or process from the start, so that it meets its critical-to- quality (CTQ) requirements at launch. DMAIC fixes problems in something that exists; DFSS prevents problems by design. Because most of a product's cost and quality is locked in during design, DFSS is often more economical than later correction.

RoadMap	Phases	Focus
DMADV	Define·Measure·Analyze·Design·Verify	Newproduct service orprocess;themost , ,
		widelyusedDFSSroadmap
IDOV	Identify·Design·Optimize·Verify(Validate)	Productandengineeringdesign;optimizes
		designparameters
DMAIC(for	Define·Measure·Analyze·Improve·Control	Improvinganexistingprocess
comparison)

In DMADV, Verify confirms through pilots and testing that the design performs as required before full release. Verification checks that the design meets its specifications (built it right); validation checks that it meets the customer's actual needs (built the right thing).

Basic Failure Mode and Effects Analysis (FMEA)

FMEA systematically evaluates potential failures, their effects, their causes, and the controls in place, and it prioritizes risks for prevention or mitigation. It is a proactive, team-based tool completed before failures occur.

Ways each process step or component could fail

▼

Consequences for the customer or later steps

▼

How likely each cause is to happen

▼

How likely the failure is to be caught before it reaches the customer (10 = almost certainly not detected)

▼

Take action on the highest risks, then re-rate

RPN = Severity × Occurrence × Detection

Each rating is typically on a 1–10 scale, so RPN ranges from 1 to 1,000. S = 8, O = 4, D = 5 gives RPN = 160.

Example:Processfmeaworksheetrows

Step/FailureMode	Effect	Cause	S	O	D	RPN	Action
Labelprint:wrong	Productshippedtowrong	Manuallotentry	8	4	6	192	Barcodescanoflot(error
label	customer						proofing)
Fill:underfill	Shortweight;complaint	Nozzlewear	6	3	3	54	AddnozzletoPMschedule
Seal:weakseal	Leakintransit	Lowsealing temperature	7	2	7	98	1 Temperatureinterlockand alarm

Actions may reduce occurrence (prevent the cause) or improve detection; severity usually changes only through a design change, so it is the hardest rating to lower. Many organizations also require action on any failure mode with a very high severity rating regardless of its RPN.

Design FMEA and Process FMEA

Analyzes how the product design could fail to perform its

Analyzes how the manufacturing or service process could fail

intended function: materials, geometry, tolerances, and

to produce the design as intended: each process step, its

interfaces. Completed during design, before release to

failure modes, and its controls. Feeds the control plan.

production.

Six sigma = 3.4 DPMO (with the 1.5σ long-term shift).

Five lean principles: value, value stream, flow, pull, perfection.

DMAIC improves existing processes; DMADV and IDOV design new ones.

Eight wastes: DOWNTIME. Motion = people; transportation = materials.

Balanced scorecard: financial, customer, internal process, learning and growth.

RPN = S × O × D; severity is the hardest rating to reduce.

COQ: prevention, appraisal, internal failure, external failure.

DFMEA examines the design; PFMEA examines the process.