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Chapter 11. Just-In-Time and Lean Production. To Accompany Russell and Taylor, Operations Management, 4th Edition ,  2003 Prentice-Hall, Inc. All rights reserved. What is JIT ?. Producing only what is needed, when it is needed A philosophy An integrated management system

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chapter 11

Chapter 11

Just-In-Time and Lean Production

To Accompany Russell and Taylor, Operations Management, 4th Edition,  2003 Prentice-Hall, Inc. All rights reserved.

what is jit
What is JIT ?
  • Producing only what is needed, when it is needed
  • A philosophy
  • An integrated management system
  • JIT’s mandate: Eliminate all waste
basic elements of jit
Basic Elements of JIT

Flexible resources

Cellular layouts

Pull production system

Kanban production control

Small-lot production

Quick setups

Uniform production levels

Quality at the source

Total productive maintenance

Supplier networks

flexible resources
Flexible Resources
  • Multifunctional workers
  • General purpose machines
  • Study operators & improve operations
standard operating routine for a worker

Worker: Russell

Cycle Time: 2 min

Standard Operating Routine

Sheet 1

Order of Operations time

Operations :10 :20 :30 :40 :50 1:00 1:10 1:20 1:30 1:40 1:50 2:00

Pick up material

Unload/

load machine 1

Unload/

load machine 2

Unload/

load machine 3

Inspect/

pack

Standard Operating Routine for a Worker

Figure 11.2

cellular layouts
Cellular Layouts
  • Group dissimilar machines in manufacturing cell to produce family of parts
  • Work flows in one direction through cell
  • Cycle time adjusted by changing worker paths
manufacturing cell with worker routes

Cell 1

Worker 1

Worker 2

Worker

3

Manufacturing Cell with Worker Routes

Figure 11.3

worker routes lengthened as volume decreases

Cell 1

Cell 2

Worker 2

Worker 1

Worker 3

Cell 3

Cell 4

Cell 5

Worker Routes Lengthened as Volume Decreases

Figure 11.4

the pull system
The Pull System
  • Material is pulled through the system when needed
  • Reversal of traditional push system where material is pushed according to a schedule
  • Forces cooperation
  • Prevent over and underproduction
kanban production control system
Kanban Production Control System
  • Kanban card indicates standard quantity of production
  • Derived from two-bin inventory system
  • Kanban maintains discipline of pull production
  • Production kanban authorizes production
  • Withdrawal kanban authorizes movement of goods
the origin of kanban

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

Bin 1

Kanban

Bin 2

Reorder

card

Q - R

R

R

Q = order quantity

R = reorder point - demand during lead time

The Origin of Kanban

Figure 11.5

types of kanbans
Types of Kanbans

Figure 11.6

types of kanbans17
Types of Kanbans

Figure 11.6

types of kanbans18
Types of Kanbans

Figure 11.6

types of kanbans19
Types of Kanbans
  • Kanban Square
    • Marked area designed to hold items
  • Signal Kanban
    • Triangular kanban used to signal production at the previous workstation
  • Material Kanban
    • Used to order material in advance of a process
  • Supplier Kanbans
    • Rotate between the factory and suppliers
determining number of kanbans

average demand during lead time + safety stock

container size

No. of Kanbans =

dL + S

C

N =

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

determining the number of kanbans

75 + 7.5

25

dL + S

C

(150 x 0.5) + 7.5

25

N = =

= = 3.3 kanbans or containers

Determining the Number of Kanbans

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)

Example 11.1

small lot production
Small-Lot Production
  • Requires less space & capital investment
  • Moves processes closer together
  • Makes quality problems easier to detect
  • Makes processes more dependent on each other
components of lead time
Components of Lead Time
  • Processing time
    • Reduce number of items or improve efficiency
  • Move time
    • Reduce distances, simplify movements, standardizeroutings
  • Waiting time
    • Better scheduling, sufficient capacity
  • Setup time
    • Generally the biggest bottleneck
smed principles
SMED Principles

Separate internal setup from external setup

Convert internal setup to external setup

Streamline all aspects of setup

Perform setup activities in parallel or eliminate them entirely

uniform production
Uniform Production
  • Results from smoothing production requirements
  • Kanban systems can handle +/- 10% demand changes
  • Smooths demand across planning horizon
  • Mixed-model assembly steadies component production
quality at the source
Quality at the Source
  • Jidoka is authority to stop production line
  • Andon lights signal quality problems
  • Undercapacity scheduling allows for planning, problem solving & maintenance
  • Visual control makes problems visible
  • Poka-yoke prevents defects
visual control
Visual Control

Figure 11.9

visual control34
Visual Control

Figure 11.9

visual control35
Visual Control

Figure 11.9

kaizen
Kaizen
  • Continuous improvement
  • Requires total employment involvement
  • Essence of JIT is willingness of workers to
    • Spot quality problems
    • Halt production when necessary
    • Generate ideas for improvement
    • Analyze problems
    • Perform different functions
total productive maintenance tpm
Total Productive Maintenance (TPM)
  • Breakdown maintenance
    • Repairs to make failed machine operational
  • Preventive maintenance
    • System of periodic inspection & maintenance to keep machines operating
  • TPM combines preventive maintenance & total quality concepts
tpm requires management to
TPM Requires Management to:
  • Design products that can be easily produced on existing machines
  • Design machines for easier operation, changeover, maintenance
  • Train & retrain workers to operate machines
  • Purchase machines that maximize productive potential
  • Design preventive maintenance plan spanning life of machine
supplier policies
Supplier Policies

Locate near to the customer

Use small, side loaded trucks and ship mixed loads

Consider establishing small warehouses near to the customer or consolidating warehouses with other suppliers

Use standardized containers and make deliveries according to a precise delivery schedule

Become a certified supplier and accept payment at regular intervals rather than upon delivery

benefits of jit
Benefits of JIT

Reduced inventory

Improved quality

Lower costs

Reduced space requirements

Shorter lead time

Increased productivity

Greater flexibility

Better relations with suppliers

Simplified scheduling and control activities

Increased capacity

Better use of human resources

More product variety

jit implementation
JIT Implementation
  • Use JIT to finely tune an operating system
  • Somewhat different in USA than Japan
  • JIT is still evolving
  • JIT isn’t for everyone
jit in services
JIT In Services
  • Competition on speed & quality
  • Multifunctional department store workers
  • Work cells at fast-food restaurants
  • Just-in-time publishing for textbooks
  • Construction firms receiving material just as needed