materi lean production

Copyright 2006 John Wiley & Sons, Inc. Beni Asllani

University of Tennessee at Chattanooga

Lean Production

Operations Management - 5th Edition

Roberta Russell & Bernard W. Taylor, III

Copyright 2006 John Wiley & Sons, Inc. 15-2

Lecture Outline

w Basic Elements of Lean Productionw Benefits of Lean Productionw Implementing Lean Productionw Lean Services


Lean Production

w Doing more with less inventory, fewer workers, less space

w Just-in-time (JIT)n smoothing the flow of material to arrive

just as it is neededn JIT and Lean Production are used

interchangeablyw Muda

n waste, anything other than that which adds value to the product or service


Waste in Operations


Waste in Operations (cont.)


Basic Elements

1. Flexible resources2. Cellular layouts3. Pull production system4. Kanban production control5. Small lot production6. Quick setups7. Uniform production levels8. Total productive

maintenance9. Supplier networks


Flexible Resources

w Multifunctional workersn perform more than one jobn general-purpose machines perform

several basic functionsw Cycle time

n time required for the worker to complete one pass through the operations assigned

w Takt timen paces production to customer demand


Standard Operating Routine for a Worker


Cellular Layouts

w Manufacturing cellsn comprised of dissimilar machines brought

together to manufacture a family of partsw Cycle time is adjusted to match takt time

by changing worker paths


Cells with Worker Routes


Worker Routes Lengthen as Volume Decreases


Pull System

w Material is pulled through the system when needed

w Reversal of traditional push system where material is pushed according to a schedule

w Forces cooperationw Prevent over and underproductionw While push systems rely on a predetermined

schedule, pull systems rely on customer requests


Kanbans

w Card which indicates standard quantity of production

w Derived from two-bin inventory systemw Maintain discipline of pull productionw Authorize production and movement of

goods


Sample Kanban


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

Reorder card

Bin 1

Bin 2

Q - R

Kanban

R R

Q = order quantity R = reorder point - demand during lead time


Types of Kanban

w Production kanbann authorizes production of

goodsw Withdrawal kanban

n authorizes movement of goods

w Kanban squaren a marked area designated

to hold items

w Signal kanbann a triangular kanban

used to signal production at the previous workstation

w Material kanbann used to order material in

advance of a processw Supplier kanban

n rotates between the factory and suppliers


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


Determining Number of Kanbans: Example

d = 150 bottles per hour L = 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 25

75 + 7.5 25


Small Lots

w Require less space and capital investment

w Move processes closer togetherw Make quality problems easier to

detectw Make processes more dependent

on each other


Inventory Hides Problems


Less Inventory Exposes Problems


Components of Lead Time

w Processing timen Reduce number of items or improve efficiency

w Move timen Reduce distances, simplify movements, standardize

routingsw Waiting time

n Better scheduling, sufficient capacityw Setup time

n Generally the biggest bottleneck


Quick Setups

w Internal setupn Can be performed

only when a process is stopped

w External setupn Can be performed

in advance

w SMED Principlesn Separate internal setup from

external setupn Convert internal setup to external

setupn Streamline all aspects of setupn Perform setup activities in

parallel or eliminate them entirely


Common Techniques for Reducing Setup Time


Common Techniques for Reducing Setup Time (cont.)


Uniform Production Levels

w Result from smoothing production requirements

w Kanban systems can handle +/- 10% demand changes

w Smooth demand across planning horizon

w Mixed-model assembly steadies component production


Mixed-Model Sequencing


Quality at the Source

w Visual controln makes problems visible

w Poka-yokesn prevent defects from

occurringw Kaizen

n a system of continuous improvement; change for the good of all

w Jidokan authority to stop the

production linew Andons

n call lights that signal quality problems

w Under-capacity schedulingn leaves time for planning,

problem solving, and maintenance


Examples of Visual Control


Examples of Visual Control (cont.)


Total Productive Maintenance (TPM)

w Breakdown maintenancen Repairs to make failed machine operational

w Preventive maintenancen System of periodic inspection and

maintenance to keep machines operatingw TPM combines preventive maintenance

and total quality concepts


TPM Requirements

w Design products that can be easily produced on existing machines

w Design machines for easier operation, changeover, maintenance

w Train and retrain workers to operate machinesw Purchase machines that maximize productive

potentialw Design preventive maintenance plan spanning

life of machine


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

number of daily 5S inspections not performed; number of personal items not stored; number of times job aids not available or up-to-date

Keep only what you need

A place for everything and everything in its place Cleaning, and

looking for ways to keep clean and organized

Maintaining and monitoring the first three categories Sticking to the rules

Seiri (sort)

Seiton (set in order)

Seisou (shine)

Seiketsu (standardize)

Shisuke (sustain)

5S Scan Goal Eliminate or Correct


Supplier Networks

w Long-term supplier contractsw Synchronized productionw Supplier certificationw Mixed loads and frequent deliveriesw Precise delivery schedulesw Standardized, sequenced deliveryw Locating in close proximity to the customer


Benefits of Lean Production

w Reduced inventoryw Improved qualityw Lower costsw Reduced space requirementsw Shorter lead timew Increased productivity


Benefits of Lean Production (cont.)

w Greater flexibilityw Better relations with suppliersw Simplified scheduling and control activitiesw Increased capacityw Better use of human resourcesw More product variety


Implementing Lean Production

w Use lean production to finely tune an operating system

w Somewhat different in USA than Japanw Lean production is still evolvingw Lean production isnt for everyone


Lean Services

w Basic elements of lean production apply equally to services

w Most prevalent applicationsn lean retailingn lean bankingn lean health care


Copyright 2006 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information herein.

materi lean production

Documents