Chapter 11: JustInTime Manufacturing Systems

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Chapter 11Just-In-Time Manufacturing Systems
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Agenda

• PULL Versus PUSH System
• Types of Kanbans
• Kanban Planning and Control Models
• Singal Kanban
• Other Types of Kanbans
• Alternative JIT Systems
• JIT Purchasing
• Total Quality Control and JIT
• Difficulties and Benefits of JIT Implementation

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Pull Versus Push System

• A kanban is a card attached to a standard
  container that issues the production and
  withdrawal of parts between workstations
• Differences short-term scheduling and PC
• Pull system based on kanban that represents the
  immediate requirements of the next stage
• Push system based on the work orders that issued
  for one planning horizon

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Types of Kanbans

• Withdrawal Kanban to pass the authorization for
  movement of parts from one work center to another
• Production Kanban to release an order to the
  preceding process to build parts equal to the lot
  size specified on the card.

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Types of Kanbans

• Flow of withdrawal and production Kanbans and
  their interaction

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Rules for Operating Kanban

• Rule 1 No withdrawal of parts without a kanban
• Rule 2 the subsequent process comes to withdraw
  only what is needed
• Rule 3 do not send the defective parts to the
  subsequent process
• Rule 4 the preceeding process should produce
  only the exact quantity of parts withdrawn by the
  subsequent process
• Rule 5 smoothing of production
• Rule 6 fine tuning of production using kanban

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Kanban Planning and Control Models

• Deterministic the number of Kanbans
• Notations
• y number of kanbans
• D demand per unit time
• Tw waiting time of kanban
• Tp processing time
• A container capacity (lt10 of daily
  requirement)
• ? a policy variable
• Model

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Example 1
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Solution
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Kanban Planning and Control Models

• A Probabilistic Cost Model for Determining
  Optimal Number of Kanbans
• Notations
• p(x) density function for the number of Kanbans
  required
• cn holding cost per container per unit time at
  a work center
• cs cost of a shortage per container per unit
  time at a work center
• x the actual requirement for the kanbans
• Model n kanbans circulating in the system.

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Example 2
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Kanban Planning and Control Models

• Relationship between JIT manufacturing, setup
  time, and cost
• JIT lot size approaching unity
• JIT not to permit shortages
• Notations
• A setup cost C unit cost
• i annual inventory carrying cost rate
• D demand rate P production rate
• Total variable cost
• Optimal economic production quantity

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Example 3

• Consider a product with the following data
• Unit cost, C100.00
• Annual inventory carrying cost rate, i 10
• Demand rate, D 10,000 units per year
• Production rate, P 15,000Units paer year.
• Determine optimal lot sizes for various values of
  setup costs varying from 400 to0.00016

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Signal Kanban

• Used for systems with large setup time relative
  processing times
• A signal kanban triggers the production of a lot
  that consists of more than one container at a
  time
• Types of signal kanban
• Raw material ordering kanban rectangular,
  withdraw material from the preceding stage
• Production ordering kanban triangular, trigger
  the production
• Calculations
• Minimum lot size per setup
• Production signal kanban position
• Material-ordering signal kanban position

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The flow of signal kanbans
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Other Types of Kanbans

• Express Kanban
• Used when shortages of parts occur
• Presence in a red post, trigger
• a button for the machine line making the part is
  switched on, activating a light on the light
  board
• The worker at the location where the light has
  come on must immediately produce the part and
  deliver it personally to the subsequent process
• Emergency Kanban used as a temparary measure to
  make up for the defective units and other
  uncertainties
• Through Kanban used for adjacent work centers

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Alternative JIT Systems

• Periodic pull system the manual information
  processing time of a kanban method was replaced
  by on-line computerized processing.
• Constant WIP system (CONWIP) CONWIP production
  cards are assigned to the entire production line.
  Used for large number of part types or
  significant setup times systems
• Long pull system the control encompasses more
  than one work station.

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JIT Purchasing Activities

• Determining the purchase lot size small
  quantities with more frequent deliveries
• Select suppliers smaller number of nearby
  suppliers, ideally one, good relationships
• Evaluating suppliers product quality, delivery
  performance, price with 0 defectives
• Receiving inspection extended to the suppliers
  plant
• Negotiating and bidding process lowest price,
  product quality, long-term relationship
• Determining mode of transportation both inbound
  and outbound freight and on-time delivery
• Determining product specification an interaction
  between the supplier and buyer is encouraged to
  evolve the design specifications leading to least
  manufacturing costs without sacrificing
  functional requirements
• Paperwork less formal paperwork
• Packaging exact quantities in small standard
  containers

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Total Quality and JIT

• TQC requires a commitment from every one
• JIT no defects ? have a TQC program
• TQC responsibilities
• Design proper specifications for
  manufacturability, quality and reliability of
  products
• Purchasing quality parts from the suppliers
• Manufacturing quality products meeting design
  specifications and training the workers about
  process control and their responsibilities for
  quality production
• QC department setting and implementation of
  quality standards, inspection procedures, audit
  programs for supplier and manufacturing line,
  coordination of quality problems between supplier
  and manufacturer
• Sales and service dept. providing quality (after
  sales) service and feed back on the product
  performance to the design, manufacturing, and QC
  departments

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Principles of Quality for each worker

• Process control
• Easy-to-see quality
• Insistence on compliance
• Line stop
• Correcting ones own errors
• 100 check
• Project-by-project improvement

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Quality Culture action plans

• Establish TQC teams in the factory
• Establish standard procedures for detecting and
  solving problems
• Establish good housekeeping practices in the
  plant
• Reinforce JIT manufacturing practice
• Establish a feedback mechanism to monitor
  customer quality needs and change quality
  standards to met customer satisfaction
• Establish a quality inspection information system
  with the suppliers t to eliminate receiving
  inspection
• Develop and organize quality training programs on
  a regular basis. Involve suppliers in such
  programs

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Difficulties and Benefits of JIT Implementation

• Difficulties
• Frequent changes in production planning
• Inaccurate forecasting procedures resulting in
  under-or over forecasting of demand
• Equipment failures create capacity problems
• Employee turnover, absenteeism, etc.
• Benefits
• For a company increase productivity, better
  quality, reduced leadtime, etc.
• For functional areas manufacturing, engineering,
  purchasing, sales and marketing, etc.