Lecture Principle of inventory and material management - Lecture 28

Lecture 28 - Just­in­Time Manufacturing (Continued). The contents of this chapter include all of the following: JIT layout, distance reduction, increased flexibility, inventory, reduced variability, reduced setup cost, JIT scheduling, kanban, JIT quality tactics, lean operations.

Just­in­Time Manufacturing (Continued)

Books

• Introduction to Materials Management, Sixth Edition, J. R. Tony Arnold, P.E., CFPIM, CIRM, Fleming  College, Emeritus, Stephen N. Chapman, Ph.D., CFPIM, North Carolina State University, Lloyd M.  Clive, P.E., CFPIM, Fleming College

• Operations Management for Competitive Advantage, 11th Edition, by Chase, Jacobs, and Aquilano, 2005,  N.Y.: McGraw­Hill/Irwin.

• Operations Management, 11/E, Jay Heizer, Texas Lutheran University, Barry Render, Graduate School of  Business, Rollins College, Prentice Hall

Reduce waste due to movement

JIT Layout Tactics

Build work cells for families of products

Include a large number operations in a small area Minimize distance

Design little space for inventory

Improve employee communication

Use poka-yoke devices

Build flexible or movable equipment

Cross-train workers to add flexibility

þLarge lots and long production lines

with single-purpose machinery are being replaced by smaller flexible

volume or designs change

þ Applicable in office environments as

well as production settings

þ Facilitates both product and process

improvement

flexibility and efficiency

the passing on of important

information about the process

þWith little or no inventory buffer,

getting it right the first time is

critical

in very small lots

there is no storage

Inventory is at the minimum level necessary 

to keep operations running

JIT Inventory Tactics

Use a pull system to move inventory

Reduce lot sizes

Develop just-in-time delivery systems with suppliers Deliver directly to point of use

Perform to schedule

Reduce setup time

Use group technology

Inventory level

Process downtime Scrap

Setup time Late deliveries

Quality problems

Inventory  level

Reduce Variability

Scrap

Setup  time

Late deliveries

Quality  problems

Process  downtime

average inventory is 100

þIdeal situation is to have lot sizes of

one pulled from one process to the next

þOften not feasible

desired setup time

D = Annual demand = 400,000 units

d = Daily demand = 400,000/250 = 1,600 per day

p = Daily production rate = 4,000 units

Q = EOQ desired = 400

H = Holding cost = $20 per unit

S = Setup cost (to be determined)

2DS H(1 - d/p)

S = = = $2.40(Q2)(H)(1 - d/p)2D (3,200,000)(0.6)800,000Setup time = $2.40/($30/hour) = 0.08 hr = 4.8 minutes

sizes

and reduces average inventory

preparation prior to shutdown and changeover

Use one-touch system to eliminate adjustments (save 10 minutes) Step 4

Step 5 Training operators and standardizing work procedures (save 2 minutes)

Initial Setup Time

Step 2

Move material closer and improve material handling (save 20 minutes)

Step 1

Separate setup into preparation and actual setup,

doing as much as possible while the machine/process is operating

(save 30 minutes)

Step 3

Standardize and improve tooling (save

inside and outside the organization

JIT Scheduling Tactics

Communicate schedules to suppliers

Make level schedules

Freeze part of the schedule

container of material to be produced

pulls material through

the process

signals are used, but

the system is still called

a kanban

on boxes

Work cell

assembly

Final assembly Kanban

contact, a card can be used

contact, a light or flag or empty spot on the floor may be adequate

quantity or parts

are several components or different lot sizes

thought of as a build authorization and the kanban a type of pull system that

initiates actual production

limit on the amount of work-in-process between cells

two-card system can be used with one two-card circulating between the user and storage area and the other between the storage area and the producer

or Containers

produce a container of parts

needed

Number of kanbans

(containers)

Demand during Safety

lead time + stock Size of container

=

Production lead time = 2 days

(Wait time +

Material handling time +

Processing time)

Demand during lead time = 2 days x 500 cakes = 1,000

Number of kanbans = = 51,000 + 250250

delayed material

of inventory

disposal costs, wasted space, and

labor

þStrong relationship

quality because JIT exposes poor quality

problems are exposed sooner

allows simpler JIT systems to be used

Use statistical process control

Empower employees

Build fail-safe methods

(poka-yoke, checklists, etc.)

Expose poor quality with small lot JIT

Provide immediate feedback

þ Build an organizational culture and value

system that stresses improvement of all processes

þ Part of everyone’s job

þ People are treated as

knowledge workers

þ Engage mental and

physical capabilities

þ Empower employees

þ Work shall be completely specified as to

content, sequence, timing, and outcome

þ Internal and external customer-supplier

connection are direct

þ Product and service flows must be simple and

direct

þ Any improvement must be made in accordance

with the scientific method at the lowest possible level of the organization

þDifferent from JIT in that it is externally

focused on the customer

customer wants

þOptimize the entire process from the

customer’s perspective

produce perfect parts

manufacturing are used in services

End of Lecture 28