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Chapter 16

Lean Systems


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Lecture Outline

Basic Elements of Lean Production Benefits of Lean Production

Implementing Lean Production

Lean Services Leaning the Supply Chain

Lean Six Sigma

Lean and the Environment

Value Stream Mapping

Copyright 2011 John Wiley & Sons, Inc. 16-2


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Lean Production

Doing more with less inventory, fewer workers,less space

Just-in-time (JIT) smoothing the flowof material to arrive just as it is

needed

JIT and Lean Production are used interchangeably

Muda waste, anything other than that which adds value to

product or service



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Waste in Operations



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Waste in Operations



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Waste in Operations



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Copyright 2011 John Wiley & Sons, Inc.

Basic Elements

1. Flexible resources2. Cellular layouts

3. Pull system

4. Kanbans

5. Small lots

6. Quick setups7. Uniform production levels

8. Quality at the source

9. Total productivemaintenance

10. Supplier networks

16-7Copyright 2011 John Wiley & Sons, Inc.


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Flexible Resources

Multifunctional workers perform more than one job general-purpose machines perform several basic

functions

Cycle time time required for the worker to complete one pass

through the operations assigned

Takt time paces production to customer demand



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Standard Operating Routine

for a Worker



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Cellular Layouts

Manufacturing cells comprised of dissimilar machines brought together to

manufacture a family of parts

Cycle time is adjusted to match takt time by

changing worker paths



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Cells With Worker Routes



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Worker Routes Lengthen

as Volume Decreases



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Pull System

Material is pulled through the system whenneeded

Reversal of traditional push system where materialis pushed according to a schedule

Forces cooperation

Prevent over and underproduction

While push systems rely on a predeterminedschedule, pull systems rely on customer requests



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Kanbans

Card which indicates standard quantity ofproduction

Derived from two-bin inventory system

Maintain discipline of pull production

Authorize production and movement of goods



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Sample Kanban



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a) Two-bin inventory system b) Kanban inventory system

Reordercard

Bin 1

Bin 2

Q - R

Kanban

RR

Q = order quantity

R= reorder point - demand during lead time

Origin of Kanban


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Types of Kanban

Production kanban authorizes production ofgoods

Withdrawal kanban authorizes movement of

goods

Kanban square a marked area designated

to hold items

Signal kanban a triangular kanbanused to signalproduction at theprevious workstation

Material kanban used to order material in

advance of a process

Supplier kanban rotates between the

factory and suppliers



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Dual Kanban System



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Other Kanbans



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Other Kanbans



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Determining Number of Kanbans


where

N = number of kanbans or containers

d = average demand over some time period

L = lead time to replenish an order

S = safety stock

C = container size

No. of Kanbans =average demand during lead time + safety stock

container size

N =dL + S

C


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Determining Number of Kanbans


d = 150 bottles per hourL = 30 minutes = 0.5 hours

S = 0.10(150 x 0.5) = 7.5

C = 25 bottles

Round up to 4 (to allow some slack) or

down to 3 (to force improvement)

N= =

= = 3.3 kanbans or containers

dL + S

C

(150 x 0.5) + 7.5

2575 + 7.5

25


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Small Lots

Require less space and capital investment Move processes closer together

Make quality problems easier to detect

Make processes more dependent on each other



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Inventory Hides Problems



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Less Inventory Exposes Problems



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Components of Lead Time

Processing time Reduce number of items or improve efficiency

Move time Reduce distances, simplify movements, standardize

routings Waiting time

Better scheduling, sufficient capacity

Setup time

Generally the biggest bottleneck



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Quick Setups

Internal setup Can be performed only

when a process is

stopped

External setup

Can be performed in

advance

SMED Principles Separate internal setup

from external setup

Convert internal setup

to external setup

Streamline all aspects

of setup

Perform setup activities

in parallel or eliminate

them entirely



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Techniques for Reducing Setup Time



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Uniform Production Levels

Result from smoothing production requirementson final assembly line

Kanban systems can handle +/- 10% demandchanges

Reduce variability with more accurate forecasts

Smooth demand across planning horizon

Mixed-model assembly steadies componentproduction



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Mixed-Model Sequencing



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Quality at the Source

Visual control makes problems visible

Poka-yokes prevent defects from

occurring Kaizen

a system of continuousimprovement; change forthe good of all

Jidoka authority to stop the

production line

Andons call lights that signal quality

problems Under-capacity

scheduling leaves time for planning,

problem solving, and

maintenance



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Examples of Visual Control



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5 Whys

A key part in an effective Kaizen is finding theroot cause of a problem and eliminating it

A practice of asking why? repeatedly until theunderlying cause is identified (usually requiring

five questions) Simple, yet powerful technique for finding theroot cause of a problem



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Total Productive Maintenance (TPM)

Breakdown maintenance

Repairs to make failed machine operational

Preventive maintenance

System of periodic inspection and maintenance to

keep machines operating

TPM combines preventive maintenance and

total quality concepts



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TPM Requirements

Design products that can be easily produced onexisting machines

Design machines for easier operation,changeover, maintenance

Train and retrain workers to operate machines Purchase machines that maximize productivepotential

Design preventive maintenance plan spanninglife of machine



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5S Workplace Scan


Seiri

(sort)

Seiton

(set in order)

Seisou(shine)

5S ScanKeep only what you

need

A place for

everything and

everything in its

place

Cleaning, and

looking for ways tokeep clean and

organized

GoalUnneeded equipment, tools, furniture;

unneeded items on walls, bulletins; items

blocking aisles or stacked in corners;

unneeded inventory, supplies, parts; safety

hazards

Items not in their correct places; correct places

not obvious; aisles, workstations, & equipment

locations not indicated; items not put away

immediately after use

Floors, walls, stairs, equipment, & surfaces not

clean; cleaning materials not easily accessible;lines, labels, signs broken or unclean; other

cleaning problems

Eliminate or Correct


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Seiketsu

(standardize)

Shisuke(sustain)

5S ScanMaintaining and

monitoring the first

three categories

Sticking to the rules

GoalNecessary information not visible; standards

not known; checklists missing; quantities and

limits not easily recognizable; items cant be

located within 30 seconds

Number of workers without 5S training; numberof daily 5S inspections not performed; number

of personal items not stored; number of times

job aids not available or up-to-date

Eliminate or Correct

5S Workplace Scan


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Supplier Networks

Long-term supplier contracts

Synchronized production

Supplier certification

Mixed loads and frequent deliveries

Precise delivery schedules

Standardized, sequenced delivery

Locating in close proximity to the customer


B fi f L P d i


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Benefits of Lean Production

Reduced inventory

Improved quality

Lower costs

Reduced space requirements

Shorter lead time

Increased productivity


B fit f L P d ti


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Benefits of Lean Production

Greater flexibility

Better relations with suppliers

Simplified scheduling and control activities

Increased capacity

Better use of human resources More product variety


I l i L P d i


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Implementing Lean Production

Use lean production to finely tune an operating

system

Somewhat different in USA than Japan

Lean production is still evolving

Lean production is not for everyone


L P d ti P bl


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Lean Production Problems

Highly variable demand

Large variety of low-volume products

Custom engineered products

Mass production parts

Unexpected changes in demand or supply


L S i


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Lean Services

Basic elements of lean production apply equally

to services

Most prevalent applications

lean retailing

lean banking lean health care


L i th S l Ch i


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Leaning the Supply Chain

pulling a smooth flow of material through aseries of suppliers to support frequentreplenishment orders and changes in customerdemand

Firms need to share information and coordinatedemand forecasts, production planning, andinventory replenishment with suppliers andsuppliers suppliers throughout supply chain


L i th S l Ch i


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Leaning the Supply Chain

Pull a smooth flow of material through the

system

Build a highly collaborative business

environment

Adopt the technology to support your system

Consider near shoring


L Si Si


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Lean Six Sigma

Lean and Six Sigma are natural partners forprocess improvement

Lean Eliminates waste and creates flow

More continuous improvement Six Sigma

Reduces variability and enhances processcapabilities

Requires breakthrough improvements


V l St M i (VSM)


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Value Stream Mapping (VSM)

A tool for analyzing process flows and

eliminating waste

Specialized icons related to

lean production

material and information flows aha Kaizen bursts


VSM Sh


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VSM Shapes


VSM f Milli & W ldi


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VSM for Milling & Welding


VSM f E R


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VSM for Emergency Room



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Copyright 2011John Wiley & Sons, Inc.

All rights reserved. Reproduction or translation of this

work beyond that permitted in section 117 of the 1976United States Copyright Act without express permission

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