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Chapter 7 – Just-in-Time and Lean Systems

JIT philosophy Meaning of waste in JIT Differences bet. “push” and “pull” systems Key elements of JIT manufacturing Explain the elements of TQM and their role in

JIT Describe the role of people in JIT and why

respect for people is so important Understand impact of JIT on service and

manufacturing

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Just-in-Time (JIT) Philosophy

Toyota developed JIT system in Japan, after WWII Driven by a need survive after the devastation

caused by the war JIT gained worldwide prominence in the 1970s JIT philosophy means getting the right quantity of

goods at the right place and the right time JIT is an all-encompassing philosophy found on

eliminating waste or anything that does not add value (i.e., more than just inventory reduction)

A broad JIT view is one that encompasses the entire organization

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The Philosophy of JIT - continued

Often termed “Lean Systems” Broad view that entire organization must focus

on the same goal - serving customers JIT is built on simplicity- the simpler the better Focuses on improving every operation-

Continuous improvement - Kaizen Visibility – all problems must be visible to be

identified and solved Flexibility to produce different models/features

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Waste in Operations

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Waste in Operations (cont.)

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Waste in Operations (cont.)

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Three Elements of JIT

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Three Elements of JIT - continued JIT manufacturing focuses on production

system to achieve value-added manufacturing

TQM is an integrated effort designed to improve quality performance at every level

Respect for people rests on the philosophy that human resources are an essential part of JIT philosophy

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Elements of JIT Manufacturing JIT Manufacturing is a philosophy of value-added manufacturing

Achieved by Inventory reduction - exposes problems Kanbans & pull production systems Small lots & quick setups Uniform plant loading Flexible resources Efficient facility layouts

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Role of Inventory Reduction Inventory = Lead Time (less is better) Inventory hides problems

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The Pull System

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Number of Kanbans Required

N = number of containersD = demand rate at the withdraw stationT = lead time from supply station C = container sizeS = safety stock

C

SDT N

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down?or up round:Question

containers kanban 4.425

10(200)(.5)

C

SDTN

bottles 10.5)0.10(200)(d)(T)0.10(deman S

containerper bottles 25C

hour .5minutes 30T

hourper bottles 200D

:Solution

Computing the Number of Kanbans: an aspirin manufacturer has converted to JIT manufacturing using kanban containers. They wish to determine the number of containers at the bottle filling operation which fills at a rate of 200 per hour. Each container holds 25 bottles, it takes 30 minutes to receive more bottles, safety stock is 10% of demand during LT.

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Small Lot Sizes & Quick Setups Small lots mean less average inventory and

shorten manufacturing lead time Small lots with shorter setup times increase

flexibility to respond to demand changes Strive for single digit setups- < 10 minutes Setup reduction process is well-documented

External tasks- do as much preparation while present job is still running

Internal tasks- simplify, eliminate, shorten steps involved with location, clamping, & adjustments

Ultimate goal is single unit lot sizes

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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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Common Techniques for Reducing Setup Time

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Common Techniques for Reducing Setup Time (cont.)

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Common Techniques for Reducing Setup Time (cont.)

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Examples of Visual Control

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Examples of Visual Control (cont.)

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Uniform Plant Loading A “level” schedule is developed so that the same mix

of products is made every day in small quantities Leveling the schedule can have big impact along whole

supply chain

Monday Tuesday Wednesday Thursday FridayAAAAA BBBBB BBBBB DDDDD EEEEEAAAAA BBBBB BBBBB CCCCC EEEEE

Monday Tuesday Wednesday Thursday FridayAABBBB AABBBB AABBBB AABBBB AABBBBCDEE CDEE CDEE CDEE CDEE

5 units5 units10 units

Weekly Production Required

Traditional Production Plan

JIT Plan with Level Scheduling

ABCDE

10 units20 units

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Flexible Resources Moveable, general purpose equipment:

Portable equipment with plug in power/air E.g.: drills, lathes, printer-fax-copiers, etc. Capable of being setup to do many different

things with minimal setup time

Multifunctional workers: Workers assume considerable responsibility Cross-trained to perform several different duties Trained to also be problem solvers

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Effective Facility Layouts Workstations in close physical proximity

to reduce transport & movement Streamlined flow of material Often use:

Cellular Manufacturing (instead of process focus)

U-shaped lines: (allows material handler to quickly drop off materials & pick up finished work)

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Traditional Process Focused Layout

Jumbled flows, long cycles, difficult to schedule

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JIT Cellular Manufacturing Product focused cells, flexible equipment,

high visibility, easy to schedule, short cycles

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Cells with Worker Routes

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Worker Routes Lengthen as Volume Decreases

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JIT and TQM- Partners Build quality into all processes Focus on continuous improvement - Kaizen Quality at the source- sequential inspection Jidoka (authority to stop line) Poka-yoke (fail-safe all processes) Preventive maintenance- scheduled Work environment- everything in its place, a

place for everything

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Respect for People: The Role of Employees

Genuine and meaningful respect for associates Willingness to develop cross-functional skills JIT uses bottom-round management – consensus

management by committees or teams Actively engage in problem-solving (quality

circles) Everyone is empowered Everyone is responsible for quality: understand

both internal and external customer needs

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Respect for People: The Role of Employees

Associates gather performance data Team approaches used for problem-

solving Decisions made from bottom-up Everyone is responsible for preventive

maintenance

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The Role of Management

Responsible for culture of mutual trust Serve as coaches & facilitators Support culture with appropriate

incentive system including non-monetary

Responsible for developing workers Provide multi-functional training Facilitate teamwork

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Supplier Relationships and JIT

Use single-source suppliers when possible Build long-term relationships Work together to certify processes Co-locate facilities to reduce transport if

possible Stabilize delivery schedules Share cost & other information Early involvement during new product

designs

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Benefits of JIT

Reduction in inventories Improved quality Shorter lead times Lower production costs Increased productivity Increased machine utilization Greater flexibility

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Implementing JIT Starts with a company shared vision of

where it is and where it wants to go Management needs to create the right

atmosphere Implementation needs a designated

“Champion” Implement the sequence of following steps

Make quality improvements Reorganize workplace Reduce setup times

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Implementing JIT - continued Reduce lot sizes & lead times Implement layout changes

Cellular manufacturing & close proximity Switch to pull production Develop relationship with suppliers

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JIT in Services Most of the JIT concepts apply equally to

Service companies Improved quality such as timeliness, service

consistency, and courtesy Uniform facility loading to provide better

service responsiveness Use of multifunction workers Reduction in cycle time Minimizing setup times and parallel

processing Workplace organization