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ISQA 459 Mellie Pullman. JIT. Just-In-Time (JIT) Defined. JIT can be defined as an integrated set of activities designed to achieve high-volume production using minimal inventories (raw materials, work in process, and finished goods).

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just in time jit defined
Just-In-Time (JIT)Defined
  • JIT can be defined as an integrated set of activities designed to achieve high-volume production using minimal inventories (raw materials, work in process, and finished goods).
  • JIT also involves the elimination of waste in production effort.
  • JIT also involves the timing of production resources (e.g., parts arrive at the next workstation “just in time”).
the japanese approach to productivity
The Japanese Approach to Productivity
  • Elimination of waste
  • Efforts concentrated on shop floor
  • Respect for people
  • Quality improvement focus
waste in operations
Waste in Operations

(1) Waste from overproduction

(2) Waste of waiting time

(3) Transportation waste

(4) Inventory waste

(5) Processing waste

(6) Waste of motion

(7) Waste from product defects

jit demand pull logic

Vendor

Fab

Sub

Vendor

Fab

Final

Assembly

Customers

Sub

Fab

Vendor

Fab

Vendor

JIT Demand-Pull Logic
traditional conveyance

A

A

B

B

C

C

Traditional Conveyance

Sporadic and Infrequent Deliveries from Individual Suppliers

mixed load delivery

A

ABC

B

C

Mixed-Load Delivery

Regular and Frequent Deliveries from Many Suppliers

minimizing waste group technology
Minimizing Waste: Group Technology
  • Using Departmental Specialization for plant layout can cause a lot of unnecessary material movement.

Saw

Saw

Saw

Grinder

Grinder

Heat Treat

Lathe

Lathe

Lathe

Press

Press

Press

minimizing waste group technology1
Minimizing Waste: Group Technology
  • Revising by using Group Technology Cells can reduce movement and improve product flow.

Grinder

1

2

Lathe

Press

Saw

Lathe

Heat Treat

Grinder

Press

Lathe

A

B

Saw

Lathe

minimizing waste uniform plant loading
Minimizing Waste: Uniform Plant Loading

Suppose we operate a production plant that produces a single product. The schedule of production for this product could be accomplished using either of the two plant loading schedules below.

Not uniform Jan. Units Feb. Units Mar. Units Total

1,200 3,500 4,300 9,000

or

Uniform Jan. Units Feb. Units Mar. Units Total

3,000 3,000 3,000 9,000

How does the uniform loading help save labor costs?

mixed batch example
Mixed Batch Example
  • Company produces three products with a mixed model assembly line.
    • Operates 16 hours per day for 250 days/yr.
    • Determine the mixed model MPS for a daily batch.
    • Determine minimum batch MPS and the mix schedule for a day.
calculations
Calculations

For every unit of #3 (minimum batch), we need twice as many #2 and 4 times

As many #1 so for minimum batch:

Produce during each day produce #1,1,1,1,2,2,3 - repeated 20 times

mixed batch example1
Mixed Batch Example
  • Company produces four products with a mixed model assembly line.
    • Operates 8hours per day for 250 days/yr.
    • Determine the mixed model MPS for a daily and hourly batch .
    • Determine mix schedule for a day.
minimizing waste just in time production

Management philosophy

  • “Pull” system though the plant

WHAT IT IS

  • Attacks waste
  • Exposes problems and bottlenecks
  • Achieves streamlined production

WHAT IT DOES

  • Employee participation
  • Industrial engineering/basics
  • Continuing improvement
  • Total quality control
  • Small lot sizes

WHAT IT REQUIRES

  • Stable environment

WHAT IT ASSUMES

Minimizing Waste: Just-In-Time Production
minimizing waste inventory hides problems

Machine

downtime

Scrap

Vendor

Change

delinquencies

Work in

orders

process

queues

Engineering design

Design

(banks)

redundancies

backlogs

Decision

Paperwork

Inspection

backlogs

backlog

backlogs

Minimizing Waste: Inventory Hides Problems

Example: By identifying defective items from a vendor early in the production process the downstream work is saved.

Example: By identifying defective work by employees upstream, the downstream work is saved.

minimizing waste kanban production control systems
Minimizing Waste: Kanban Production Control Systems

Withdrawal kanban

Storage Part A

Storage Part A

Machine Center

Assembly Line

Production kanban

Material Flow

Card (signal) Flow

determining the number of kanbans needed
Determining the Number of Kanbans Needed
  • Setting up a kanban system requires determining the number of kanbans (or containers) needed.
  • Each container represents the minimum production lot size.
  • An accurate estimate of the lead time required to produce a container is key to determining how many kanbans are required.
the number of kanban card sets
The Number of Kanban Card Sets

k = Number of kanban card sets (a set is a card)

d = Average number of units demanded over some time period

L = lead time to replenish an order (same units of time as demand)

S = Safety stock expressed as a percentage of demand during lead

time

C = Container size

example of kanban card determination problem data
Example of Kanban Card Determination: Problem Data
  • A switch assembly is assembled in batches of 4 units from an “upstream” assembly area and delivered in a special container to a “downstream” control-panel assembly operation.
  • The control-panel assembly area requires 5 switch assemblies per hour.
  • The switch assembly area can produce a container of switch assemblies in 2 hours.
  • Safety stock has been set at 10% of needed inventory.
jit requirements design flow process
JIT Requirements: Design Flow Process
  • Link operations
  • Balance workstation capacities
  • Re-layout for flow
  • Emphasize preventive maintenance
  • Reduce lot sizes
  • Reduce setup/changeover time
jit requirements improve product design
JIT Requirements: Improve Product Design
  • Standard product configuration
  • Standardize and reduce number of parts
  • Process design with product design
  • Quality expectations
respect for people
Respect for People
  • Level payrolls
  • Cooperative employee unions
  • Subcontractor networks
  • Inverted pyramid management style
  • Small group involvement activities
jit requirements total quality control
JIT Requirements: Total Quality Control
  • Worker responsibility
  • Measure SQC
  • Enforce compliance
  • Fail-safe (Poke-yoke) methods
  • Automatic inspection
poke yokes address mistakes
POKE-YOKEs address Mistakes

DEFECTS

MISTAKES

  • Damaged parts
  • Missing parts
  • Reversed parts
  • Wrong parts
  • Wrong size or shape
  • Wrong chemical properties
  • Wrong physical properties
  • Wrong item shipped
  • Wrong label
  • Wrong package
  • Damaged finished product
  • Omitting a part
  • Omitting a process
  • Performing a process incorrectly
  • Performing a process on the wrong part
  • Performing a process in improper environmental conditions
  • Performing the wrong process
  • Setting up equipment incorrectly
  • Setting up a work piece incorrectly
  • Adjusting equipment incorrectly
  • Tooling set up incorrectly
  • Tooling adjusted incorrectly
  • Installing wrong part
  • Installing part incorrectly
jit requirements work with vendors
JIT Requirements: Work with Vendors
  • Reduce lead times
  • Frequent deliveries
  • Project usage requirements
  • Quality expectations
jit requirements reduce inventory more
JIT Requirements: Reduce Inventory More
  • Look for other areas where inventory hides
    • Stores
    • Transit
    • Carousels
    • Conveyors
mrp and jit
MRP and JIT
  • MRP is a planning system that does not do detailed shop floor scheduling
  • MRP requires fixed lead times which might actually vary with batch size
  • JIT excels at rapidly moving small batches of material through the system
mrp small bucket approach
MRP Small Bucket Approach
  • MRP “buckets” are reduced to daily or hourly
    • The most common planning period (time bucket) for MRP systems is weekly
  • Planned receipts are used internally to sequence production
  • Inventory is moved through the plant on a JIT basis
  • Completed products are moved to finished goods inventory which reduces required quantities for subsequent planned orders
    • Back flushing based on the BOM is used to deduct inventory that was used in production
mrp balanced flow
MRP Balanced Flow
  • Used in repetitive operations
  • MRP plans are executed using JIT techniques based on “pull” principles
  • Flows are carefully balanced with small lot sizes
mrp vs the supermarket
MRP vs. The Supermarket
  • Items used by many products are held in a common area often called a supermarket
  • Items are withdrawn as needed
  • Inventory is maintained using JIT systems and procedures
  • Common items are not planned by the MRP system