Just-in-Time

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Chapter 6

• Just-in-Time

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1  Introduction

• The term Just-in-time is used to refer to a
  repetitive production system in which both the
  movement of goods during production, and delivers
  from suppliers, are carefully timed so that at
  each step of the process the next (usually small)
  batch arrives for processing just as the
  preceding batch is completed.

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Origin of JIT

• The JIT approach was developed at the Toyota
  Motor Company of Japan by Mr. Taiichi Obno and
  several of his colleges. Taiichi became
  eventually vice president of manufacturing.
• The development of JIT in Japan was influenced by
  the fact Japan is a crowed country with few
  natural resources.
• The JIT and supermarkets.

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Benefits of JIT (1)

• Inventory levels are drastically reduced.
• The production period is greatly reduced.
• Product quality is improved. And cost of scrap
  and rework is reduced.
• Reduced space with inventory and
  materials-handling equipment.

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Benefits of JIT (2)

• Reduced manufacturing lead-time.
• Fewer workers.
• Promotes teamwork Workers are closer together so
  that they communicate more easily, work out
  problems more efficiently.
• Greater flexibility in work assignments and in
  changing production mix

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3. Key thought ---eliminating waste

• Waiting waste
• Transportation waste
• Work-in-process waste
• Inventory waste
• Waste of unneeded production steps
• Waste of unnecessary human motions (motion and
  effort)
• Defective products
• Overproduction waste

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eliminating waste figure

• Figure 14.3 ( P.546)

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4. Main points of JIT
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4.1 A pull system (1)

• In a push system, when work is finished at a
  workstation, the output is pushed to the next
  station or in the case of the final operation,
  it is pushed on to final inventory.
• Traditional production systems use the push
  approach.

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4.1 A pull system (2)

• In a pull system, control of moving the work
  rests with the following operation each
  workstation pulls the output from the preceding
  station as it is needed output of the final
  operation is pulled by customer demand or master
  schedule.
• JIT systems use the pull approach to control the
  flow of work, with each workstation gearing its
  output to the demand presented by the next
  workstation.

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4.2 Kanban production control

• Kanban means card.
• Types of Kanban
• There are two types of Kanban cards a
  conveyance card (C-kanban) and a production card
  (P-Kanban).
• Figure 14.4 (p. 548)
•   Knaban operation
• Kanban operation Rules.
• Figure 14.5 (p.549)

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4.3 Small lot sizes

• Small lot sizes yield a number of benefits that
  enable JIT systems to operate effectively.
• Less work-in-process inventory
• Reduce carrying costs, space requirements and
  clutter in the workplace
•   Less quality cost
•   Greater flexibility in scheduling
• Ideal lot size is one unit.

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4.4 Few, reliable suppliers (1)

• Supplier development and suppliers undergo
  fundamental changes.
• ------ Subcontractor networks and
  co-producers.
• Long-term relationships with suppliers.
• Delivery schedules, product quality, and mutual
  trust and cooperation become the primary basis
  for supplier selection.
• Suppliers are encouraged to extend JIT methods to
  their own suppliers.

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4.4 Few, reliable suppliers (2)

• Suppliers are ordinarily located near the buying
  firm's factory.
• Shipments are delivered directly to the
  customer's production line.
• Exact quantities.
• Near-perfect quality

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4.5 Quick, low-cost setups (1)

• Small lots and changing product mixes require
  frequent setups. Unless these are quick and
  relatively inexpensive, the time and cost to
  accomplish them is prohibitive.

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4.5 Quick, low-cost setups (1)

• Suitable setup tools and equipment
• Simplify setup procedures and methods
• Transform inside-setup-work to outside-setup-work
  
• Group technology
• Multipurpose equipment
• Train workers

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4.6 U-layout
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Multifunctional workers
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4.7    Preventive maintenance and repair
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4.8    A cooperative Spirit
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5 Comparison of JIT and general philosophy
Factors JIT General management Philosophy
Inventory Do away with it An asset. Against forecast errors, machine problems, late vendor deliveries. More inventory is "safer"
Lot size Immediate needs only Formulas. EOQ
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5. Comparison (2)
Setups Make them insignificant. Rapid changeover Low priority issue
Suppliers Coworkers part of the team, Few, long-term relationship Daily lot size delivery Adversaries. Multiple sources are the rule, and to play them off against each other.
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5. Comparison (3)
Quality Zero defects Tolerate scrap
Equipment maintenance Constant and effective Minimal breakdown As required
Lead times Keep them short more lead time
Workers Team Multifunctional Less cooperation
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6. Conditions

• Stabilize production schedules
• Make the factories more focused
• Improve product quality
• Good cross-train workers
• Good and reliable suppliers
• Good delivery conditions
• Preventive maintenance, etc.