Chapter 13 Lean Systems

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Chapter 13 Lean Systems
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APICS Definition of JIT

• A philosophy of manufacturing based on planned
  elimination of waste continuous improvement of
  productivity. ...

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APICS Definition of JIT

• The primary elements of just-in-time are to
• Have only required inventory when needed,
• Improve quality to zero defects,
• Reduce lead times by reducing setup times, queue
  lengths, lot sizes,
• Incrementally revise operations themselves, and
• Accomplish these things at minimum cost.

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APICS Definition of Lean Manufacturing

• A philosophy of production that emphasizes
  minimization of amount of all resources
  (including time) used in various activities of
  enterprise. It involves
• Identifying eliminating non-value-adding
  activities,
• Employing teams of multi-skilled workers,
• Using highly flexible, automated machines

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Calculate Number of Containers
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Traditional View of Manufacturing

• Key objective was to fully utilize capacity so
  that more products were produced by fewer workers
  machines.
• How? With large queues of in-process inventory
  waiting at work centers.
• Workers machines never had to wait for product
  to work on, so capacity utilization was high
  production costs were low.
• Result products spent most of their time in
  manufacturing just waiting

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JIT Manufacturing Philosophy

• Main objective of JIT manufacturing is to reduce
  manufacturing lead times
• This is primarily achieved by drastic reductions
  in work-in-process (WIP)
• The result is a smooth, uninterrupted flow of
  small lots of products throughout production

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Characteristics of Lean Systems Just-in-Time

• Pull method of materials flow
• Consistently high quality
• Small lot sizes
• Uniform workstation loads
• Standardized components and work methods
• Close supplier ties
• Flexible workforce
• Line flows
• Automated production
• Preventive maintenance

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Pull vs. Push System

• Pushproduction of item begins before customer
  demand
• Pullproduction of item is triggered by customer
  demand

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Consistently High Quality

• Eliminate scrap rework to achieve uniform
  product flow
• Quality at the sourceworkers serve as their own
  quality inspector
• Supplier quality must be 3? or better
• Stopping assembly line probably means missed
  deliveries

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Small Lot Sizes

• As small as possible to eliminate carrying
  inventory
• Small lots cut lead times
• Small lots help achieve level workload
• But, small lots
• Increase setups
• Drive shorter setup times

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Reducing Inventoriesthrough Setup Time Reduction

• Central to JIT is reduction of production lot
  sizes so inventory levels are reduced
• Smaller lot sizes result in more machine setups
• More machine setups, if they are lengthy, result
  in
• Increased production costs
• Lost capacity (idle machines during setup)
• Answer is REDUCE MACHINE SETUP TIMES

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Uniform Workstation Loads

• Same quantity and type products each day
• Difficult to impossible in a job shop
• Mixed-model assembly
• Produce a mix of products in small lots

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Working Toward Repetitive Manufacturing

• Reduce Setup Times Lot Sizes to Reduce
  Inventories
• Change Factory Layout to Allow Streamlined Flows
• Convert Process-Focused Layout to Cellular
  Manufacturing (CM) Centers
• Install Flexible Manufacturing Systems (FMS)
• ..more

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Working Toward Repetitive Manufacturing

• Standardize Parts Designs
• Train Workers for Several Jobs
• Implement Preventive Maintenance (PM) Programs
• Install Effective Quality Control Programs
• Develop an Effective Subcontractor Network

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Standardized Components Work Methods

• Productivity tends to increase with increased
  repetition
• Standardization of components reduces raw
  material inventory requirements

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Closer Supplier Ties

• Close relationship required
• Frequent delivery often directly to the assembly
  line
• Consistently high quality
• JIT manufacturers usually seek
• Local suppliers
• Reduced inventory in suppliers warehouse also
• Long-term partnerships with suppliers

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Flexible Workforce

• Workers can perform multiple jobs
• Workers rotate to other jobs based on vacations,
  relieve bottlenecks, or even relieve boredom

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Line Flows

• Can reduce setups
• One worker multiple machines (OWMM)
• One worker may follow product through entire
  manufacturing operation

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Automated Production

• Important part of JIT
• However, for some tasks humans consistently
  outperform machines

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Preventive Maintenance

• Scheduled downtime to maintain equipment reduce
  unscheduled maintenance
• Use skilled technicians to maintain high-tech
  machines

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Changes Required for JIT

• JIT requires certain changes to factory way it
  is managed
• Stabilize production schedules
• Make factories more focused
• Increase work center capacities
• Improve product quality
• Cross-train workers
• Reduce equipment breakdowns
• Develop long-term supplier relations

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Eliminating Waste in Manufacturing

• Make only what is needed now.
• Reduce waiting by coordinating flows balancing
  loads.
• Reduce or eliminate material handling shipping.
• Eliminate unneeded production steps.
• Reduce setup times increase production rates.
• Eliminate unnecessary human motions.
• Eliminate defects inspection.

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People Make JIT Work

• JIT has strong element of training involvement
  of workers.
• Culture of mutual trust teamwork must be
  developed.
• Attitude of loyalty to team self-discipline
  must be developed.
• Another crucial element of jit is empowerment of
  workers, giving them authority to solve
  production problems.

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Elements of JIT Purchasing

• Cooperative long-term relationship between
  customer supplier.
• Supplier selection based not only on price, but
  also delivery schedules, product quality,
  mutual trust.
• Suppliers usually located near factory.
• Deliveries directly to production line.
• Parts delivered in small, standard-size
  containers with minimum of paperwork in exact
  quantities.
• Delivered material is of near-perfect quality.

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Benefits of JIT

• Inventory levels drastically reduced
• Frees up working capital for other projects
• Less space is needed
• Customer responsiveness increases
• Total product cycle time drops
• Product quality is improved
• Scrap rework costs go down
• Forces managers to fix problems eliminate waste
  .... or it wont work!

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Uncovering Production Problems

• We Must Lower Water Level!

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Lot Size and Cycle Inventory
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Lot Size and Cycle Inventory
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Lot Size and Cycle Inventory
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Lot Size and Cycle Inventory
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Lot Size and Cycle Inventory
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Kanban Production Control

• At core of JIT manufacturing at Toyota is kanban,
  an amazingly simple system of planning
  controlling production.
• Kanban, in Japanese, means card or marquee.
• Kanban is means of signaling to upstream
  workstation that downstream workstation is ready
  for upstream workstation to produce another batch
  of parts.

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Kanbans Other Signals

• There are two types of kanban cards
• A conveyance card (c-kanban)
• A production card (p-kanban)
• Signals come in many forms other than cards,
  including
• An empty crate
• An empty designated location on floor

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Conveyance Kanban
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Production Kanban
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Flow of Kanban Cards Containers
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Containers in a Kanban System

• Kanban is a simple idea of replacement of
  containers of parts, one at a time
• Containers are reserved for specific parts, are
  purposely kept small, always contain same
  standard number of parts for each part number
• At Toyota containers must not hold more than
  about 10 of days requirements.
• There is minimum of two containers for each part
  number, one at upstream producing work center
  one at downstream using work center

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Single-Card Kanban System
Receiving post
Storage area
Kanban card for product 1
Kanban card for product 2
Empty containers
Full containers
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Single-Card Kanban System
Receiving post
Storage area
Kanban card for product 1
Kanban card for product 2
Empty containers
Full containers
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Single-Card Kanban System
Receiving post
Storage area
Kanban card for product 1
Kanban card for product 2
Empty containers
Full containers
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Single-Card Kanban System
Receiving post
Storage area
Kanban card for product 1
Kanban card for product 2
Empty containers
Full containers
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Single-Card Kanban System
Receiving post
Storage area
Kanban card for product 1
Kanban card for product 2
Empty containers
Full containers
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Single-Card Kanban System
Receiving post
Storage area
Kanban card for product 1
Kanban card for product 2
Empty containers
Full containers
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Single-Card Kanban System
Receiving post
Storage area
Kanban card for product 1
Kanban card for product 2
Empty containers
O2
Fabrication cell
O3
O1
Full containers
O2
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Single-Card Kanban System

• Each container must have a card
• Assembly always withdraws from fabrication (pull
  system)
• Containers cannot be moved without a kanban
• Containers should contain the same number of
  parts
• Only good parts are passed along
• Production should not exceed authorization

Part Number 1234567Z Location Aisle 5 Bin
47 Lot Quantity 6 Supplier WS
83 Customer WS 116
KANBAN
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Lean Systems in Services

• Consistently high quality
• Uniform facility loads
• Standardized work methods
• Close supplier ties
• Flexible workforce
• Automation
• Preventive maintenance
• Pull method of materials flow
• Line flows

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Operational Benefits

• Reduce space requirements
• Reduce inventory investment
• Reduce lead times
• Increase labor productivity
• Increase equipment utilization
• Reduce paperwork and simple planning systems
• Valid priorities for scheduling
• Workforce participation
• Increase product quality

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Implementation Issues

• Organizational considerations
• Human cost of JIT systems
• Cooperation and trust
• Reward systems and labor classifications
• Process considerations
• Inventory and scheduling
• MPS stability
• Setups
• Purchasing and logistics