WORK CELL DESIGNWORK CELL DESIGN

Principles for Implementing Lean Manufacturing

Cellular Flow

Definition

Cellular Flow Manufacturing is a method of organizing manual and machine operations in the most efficient combination to maximize value-added content and minimize waste.

Cellular Flow

Lean Building Blocks

Quick Changeover

Standardized Work

Batch Reduction

Teams

Quality at Source

5S System Visual Plant Layout

POUS

Cellular/FlowPull/Kanban TPM

ValueStreamMapping

Continuous Improvement

Cellular Flow

Cellular Manufacturing Benefits•Simplified scheduling and communication•Minimal inventory needed between processes•Increased visibility• provide quick feedback and problem resolution

•Development of increased product knowledgeDevelopment of increased product knowledge• workers are trained to understand the total workers are trained to understand the total

processprocess•Shorter lead times Shorter lead times • Small lots and one piece flow Small lots and one piece flow • to match customer demandto match customer demand

Work Cell – Realization of a Lean Work Cell – Realization of a Lean ProcessProcess•A work cell’s effectiveness is not separable from related A work cell’s effectiveness is not separable from related elements:elements:- The product(s)The product(s)

- Workers must be able to manufacture and assemble the product to meet Workers must be able to manufacture and assemble the product to meet customer demand customer demand [DFA, DFM][DFA, DFM]

- A breadth of products often must be accommodated by a single A breadth of products often must be accommodated by a single manufacturer manufacturer [Product families][Product families]

- The people(s)The people(s)- Work cells must produce varying products and varying rates to meet Work cells must produce varying products and varying rates to meet

customer demand customer demand [Product families, Takt time][Product families, Takt time]- Work cells must be designed such that workers can safely and Work cells must be designed such that workers can safely and

repeatedly perform necessary steps to meet customer demand. repeatedly perform necessary steps to meet customer demand. [Human [Human factors]factors]

Principles for Implementing Lean Manufacturing

Cellular Flow

The Five Step Cell Design Process

• Group Products

• Establish Takt Time

• Review the Work Sequence

• Balance the Process

• Design the Cell Layout

Cellular Flow

Product Grouping Considerations• Similar Process/Resource Requirements

• Changeover/Set-up Times

• Process Time Variation

• Demand vs. Capacity

Cellular Flow

Product Grouping Tool:The Product/Process Matrix

Product PortfolioProduct Portfolio•““The set of different product offerings that a The set of different product offerings that a company provides. Products can be unique, company provides. Products can be unique, share common systems, and/or production share common systems, and/or production methods.”methods.”

•Product portfolio architecture – “system Product portfolio architecture – “system strategy for layout out components and strategy for layout out components and systems on multiple products”systems on multiple products”

•3 Portfolio Architectures3 Portfolio Architectures1.1.Fixed unsharing Fixed unsharing – each product is unique, no sharing of – each product is unique, no sharing of

components, typically very high volume components, typically very high volume 2.2.Modular platform Modular platform - share modules, components, or systems to - share modules, components, or systems to

meet the needed variety - common elements are called the meet the needed variety - common elements are called the platform and each supported product is called a variant platform and each supported product is called a variant

3.3.Massively customizableMassively customizable – varies to meet customer need – – varies to meet customer need – either by customer (e.g. car seat) or manufacturereither by customer (e.g. car seat) or manufacturer

- Otto and Wood, 2000

Cellular Flow

The Five Step Cell Design Process• Group Products

• Establish Takt Time

• Review the Work Sequence

• Balance the Process

• Design the Cell Layout

More on Takt Time More on Takt Time •Takt time can change!! Takt time can change!! •What can you change to match takt time?What can you change to match takt time?

- Number of peopleNumber of people- Number of cells (requires investment in machinery) Number of cells (requires investment in machinery)

•Takt Time Rounding Rules:Takt Time Rounding Rules:•Crew size Crew size calculation for an assembly line doing one piece calculation for an assembly line doing one piece

flow paced to Takt Time is:flow paced to Takt Time is:- Crew size = Sum of Manual Cycle Time / Takt TimeCrew size = Sum of Manual Cycle Time / Takt Time

•If Manual Cycle Time = 1,293 seconds and a Takt time = If Manual Cycle Time = 1,293 seconds and a Takt time = 345 sec345 sec

•Crew size = 1,293 person-seconds / 345 secondsCrew size = 1,293 person-seconds / 345 seconds•Crew size = 3.74 peopleCrew size = 3.74 people•In this case the crew size will be 4 people since 3 people In this case the crew size will be 4 people since 3 people

would not be able to meet customer demand. would not be able to meet customer demand.

Cellular Flow

Example from http://www.gemba.com/uploadedFiles/Know%20Your%20Takt%20Time.pdf

Cellular Flow

The Five Step Cell Design Process• Group Products

• Establish Takt Time

• Review the Work Sequence

• Balance the Process

• Design the Cell Layout

Cellular Flow

Steps in the Process

① Observe and document the tasks each worker performs

- Observe, don’t just ask

- The steps are defined (explicitly or implicitly) by the designer

② Break operations into observable segments

③ Study machine capacity, cycle times, and changeover times

④ Look for value-added and non-value-added elements

Cellular Flow

The Five Step Cell Design Process• Group Products

• Establish Takt Time

• Review the Work Sequence

• Balance the Process

• Design the Cell Layout

Cellular Flow

Combine Work to Balance the Process

0

10

20

30

40

50

60

Seco

nds

1 2 3 4 5

Operation Work Content

Before

0

10

20

30

40

50

60

Seco

nds

1 2 3 4

Operation Work Content

After

Cellular Flow

Standard Work Combination Sheet – Example

Date: 8/20/00

Manual Auto Walk

14 2 2

24 11 2

36 2 2

14 4 6

Part Name: Circulation Pump Takt Time: 27 seconds

Step # Work Content TimeDescription

Work Content Graph (1.5 sec/div)

Manual Machine Walking

Work Sequence: 7 of: 15 Quota: 1,000 per shift

Total = 24

Pick up shaft and rotor; load, assemble, unload

Unload, load, start

Pick up 2 nuts & bracket; load, assemble, unload

273 6 9 12 15 18 21 24

Cellular Flow

Alternative Work Combinations

Market demand = 220,000 units per year Takt time = 27 seconds

Lathe Mill Mill Inspect

Drill

Drill

TestDrillPack

1 2 3 4 5

10 9 8 7

627

seconds 27

seconds

Inspect

27 secon

ds

Cellular Flow

Staffing For Increased Demand

Market demand = 312,000 units per year Takt time = 19 seconds

Lathe Mill Mill Inspect

Drill

Drill

TestDrillPack

1 2 3 4 5

10 9 8 7

6

Inspect

19 second

s 19 seconds

19 seconds

19 second

s

Cellular Flow

The Five Step Cell Design Process• Group Products

• Establish Takt Time

• Review the Work Sequence

• Balance the Process

• Design the Cell Layout

Cellular Flow

Design Goals for All Work Areas • Flexible output

• Lot size of 1

• Point of Use Storage (POUS)

• Mixed models

• Visual management

• Source inspection

• Zero NVA activities

Cellular Flow

Water Pump Case StudyWater Pump Case StudyCirculation Pump Assembly Cell

Bearing

Ass’y

Motor Ass’y

Solder

Make Box

Pack

TestFinalAss’y

Wind Bobbi

n

WeldContac

tAss’y

Rivet

Bracket Ass’y

RotorAss’y

Lathe

BobbinAss’y Termin

alAss’y

Stator Ass’y

)

Cellular Flow

Water Pump Case Study

Testing

Packaging

Bobbin Winding

New U-Shaped Cell

Cellular Flow

Water Pump Case StudyWater Pump Case Study

Workplace Organization

Material flow chutes

Tools within reach

Cellular Flow

Water Pump Case Study Water Pump Case Study

Machining and Assembly

Material Flow Chute

Cellular Flow

Ergonomic Factors in Work Station (and Product) Design

Design the work to:• Minimize motion• Avoid unnatural postures and movements• Avoid sharp turns in motion• Make moves easy to perform without much concentration• Use hands and forearms instead of upper arms and shoulders for light work• Minimize lifting• Follow a rhythm

Cellular Flow

Tool and Material Design and Layout Guidelines• Place tools and materials close to and in front of the

operator

• Keep tools and materials in a designated place

• Design fixtures for specific purposes, not general purposes

• Combined usage tools are recommended when more than one tool is required

Cellular Flow

Ergonomic Resources

Ergonomic resources are understandable, practical, and affordable.

Fitting the Task to the Man: An Ergonomic Approach - Grandjean

The Measure of Man and Woman: Human Factors in Design – Tilley and Dreyfuss

Your FE Resource Guide

Cellular Flow

Cellular Flow