Transcript Cellular Manufacturing

Just-in-Time and Lean
Systems
The Philosophy of JIT - Lean
System (Production)
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Central (1st) belief: All waste (non value items)
must be eliminated (started at Toyota Motor Co.)
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excess inventory
backup equipment
anything (time, energy, space, human activity) that
does not contribute to the value of the product/service
Other beliefs:
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2. Broad view that entire organization must focus on
serving customers
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rather than focusing on their own jobs, employees know that
they are ALL ultimately responsible for serving the customer
(eliminate “it’s not my job” attitude)
The Philosophy of JIT - Lean
System (Production)
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3. JIT is built on simplicity- the simpler the better
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4. Focuses on improving every operation- Kaizen
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Continuous improvement: An organization is never
perfect and can always be improved in some way
5. Install simple visible control systems
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Encourages empl. to think about problems->simple sol.
Make all waste visible: open and clean floor space
6. Flexibility to produce different models/features
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Able to change volume
Able to produce variety of products
Three Elements of JIT
I. Elements of JIT Manufact.
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1.Inventory reduction exposes problems
2. Kanbans & pull production systems
3. Small lots & quick setups
4. Uniform plant loading
5. Flexible resources
6. Efficient facility layouts
1. Role of Inventory Reduction
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Inventory = Lead Time (less is better)
Inventory hides problems
2. The Pull System
2. The Pull System
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The amount produced at any one time
is the amount in one container
Kanban cards coordinate the pull
production system:
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Production cannot take place unless a
container is empty and a production
kanban has authorized production
A full container cannot be withdrawn
unless a withdrawal kanban authorizes it
Number of Kanbans Required
DT  S
N
C
N = number of containers
D = demand rate at the withdraw station
T = lead time from supply station
C = container size
S = safety stock = % of D*T (percent of
demand during lead time)
Computing the No. of Kanbans: an aspirin manufacturer has converted
to JIT manufacturing using kanban containers. They wish to determine the
no. of containers at the bottle filling operation which fills at a rate of 200
per hour. Each container holds 25 bottles, it takes 30 minutes to receive
more bottles, safety stock is 10% of demand during LT.
Round down: improvemen. in the op. needed; Round up: excess inventory
S ol u ti on:
D  200bottl e s pe r h ou r
T  30 m i n u te s .5 h ou r
C  25 bottl e s pe r con tai n e r
S  0.10(de m an
d)(T)  0.10(200)(
.5)  10 bottl e s
DT  S (200)(.5) 10
N
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 4.4 k an bancon tai n e rs
C
25
Q u e sti on: rou n du p or down ?
3. Small Lot Sizes & Quick
Setups
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Small lots mean less average inventory and
shorten manufacturing lead time
Small lots with shorter setup times increase
flexibility to respond to demand changes
Strive for single digit setups- < 10 minutes
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The goal: set up time = 0 sec. and lot size = 1
Setup reduction process is well-documented
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External tasks- do as much preparation while
present job is still running
Internal tasks- simplify, eliminate, shorten steps
involved with location, clamping, & adjustments
4. Uniform Plant Loading
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A “level” schedule is developed so that the same mix of
products is made every day in small quantities
Leveling the schedule can have big impact along whole supply
chain
Weekly Production Required
A
B
C
D
E
Traditional Production Plan
Monday
Tuesday
AAAAA
BBBBB
AAAAA
BBBBB
JIT Plan with Level Scheduling
Monday
Tuesday
AABBBB
AABBBB
CDEE
CDEE
10 units
20 units
5 units
5 units
10 units
Wednesday
BBBBB
BBBBB
Thursday
DDDDD
CCCCC
Friday
EEEEE
EEEEE
Wednesday
AABBBB
CDEE
Thursday
AABBBB
CDEE
Friday
AABBBB
CDEE
5. Flexible Resources
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Moveable, general purpose equipment:
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Portable equipment with plug in power/air
E.g.: drills, lathes, printer-fax-copiers, etc.
Capable of being setup to do many different
things with minimal setup time
Multifunctional workers:
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Workers assume considerable responsibility
Cross-trained to perform several different duties
Trained to also be problem solvers
6. Effective Facility Layouts
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Workstations in close physical proximity to
reduce transport & movement
Streamlined flow of material
Often use:
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Cellular Manufacturing (instead of process
focus)
U-shaped lines: (allows material handler to
quickly drop off materials & pick up finished work)
Traditional Process Focused Layout
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Jumbled flows, long cycles, difficult to schedule
JIT Cellular Manufacturing
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Product focused cells, flexible equipment, high
visibility, easy to schedule, short cycles
II. JIT and TQM- Partners
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Build quality into all processes
Focus on continuous improvement - Kaizen
Quality at the source- sequential inspection
Jidoka (authority to stop line)
Poka-yoke (fail-safe all processes, i.e. prevent
defects from occurring: “foolproof”)
Preventive maintenance- scheduled
Work environment- everything in its place, a
place for everything
III. Respect for People: The Role
of Employees
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Genuine and meaningful respect for associates
Willingness to develop cross-functional skills
Actively engage in problem-solving (quality circles)
Everyone is empowered
Everyone is responsible for quality: understand both
internal and external customer needs
Associates gather performance data
Team approaches used for problem-solving
Decisions made from bottom-up
Everyone is responsible for preventive maintenance
The Role of Management
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Responsible for culture of mutual trust
Serve as coaches & facilitators
Support culture with appropriate incentive
system including non-monetary
Responsible for developing workers
Provide multi-functional training
Facilitate teamwork
Supplier Relationships and JIT
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Use single-source suppliers when possible
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Build long-term relationships
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Work together to certify processes
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Co-locate facilities to reduce transport if possible
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Stabilize delivery schedules
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Share cost & other information
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Early involvement during new product designs
Benefits of JIT
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Smaller inventories
Shorter lead times
Improved quality
Reduced space requirements
Lower production costs
Increased productivity
Greater flexibility
Implementing JIT
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Implementation needs a designated “Champion”
Make quality improvements
Reorganize workplace
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Reduce setup times
Reduce lot sizes & lead times
Implement layout changes
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Remove clutter & minimize storage
Cellular manufacturing & close proximity
Switch to pull production
Extend methods to suppliers
JIT - Problems
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Companies that use JIT have experienced a
variety of problems.
 Production
systems need to be not only
reliable, but also flexible to switching “on the
fly” to meet an unexpected production change.
Typical problems involve:
 equipment downtime
 the coordination and timing of subassembly
production
 setup losses
 lack of supply reliability
 use of forecasts in production (push, not pull
system)
JIT - Problems (example)
One of the factories of Aisin, a brake-part
supplier of Toyota that accounted for
80% of Toyota’s purchased brake-parts,
was destroyed by fire. This fire was a
major problem since the supplier had
only a three day supply of parts in its
warehouse. At the time, both Toyota and
Aisin were using all of their plants at full
capacity. It was estimated that Toyota
might miss selling 50,000 cars as a result
of the fire.
JIT in Services
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Most of the JIT concepts apply equally to
Service companies
Cellular layouts, product focused, & flexible
employees shorten response times
Service inventory, “paperwork”, should be
eliminated, simplified, examined for “waste”
“Fail-safe” all processes from Orders-Payment
Team based organizations
JIT in Services
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McDonald’s has implemented JIT in their program
“Made for You.” This program, which was
implemented a few years ago in the restaurants,
consists of a making food to order. It consists of
computerized kitchens with the use of some robotic
technology. For example, machines dump fries into a
basket, lower the basket into the oil and then remove
the fries when done. The company revamped its
point of service software, toasters, prep tables and
holding bins. The prep tables were redesigned for a
smooth, more efficient, work flows.
The easiest aspects of JIT to apply in services are the
use of multifunction workers, cycle time reductions,
setup time reductions, parallel processing, and
workplace reorganization.
Chapter 07 problems
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Problem 2:
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a.
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D = 10 thermostats per hour
T = 30 minutes = ½ hour
C = 5 thermostats per container
N = = = 1 Kanban (D*T)/C = 10*0.5/5
b.
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S = 2 thermostats
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N = = = 1.4 Kanbans (D*T +S)/C = (5 + 2)/5
Chapter 07 problems
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Problem 4:
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a.
D = (50 units/hour)(1 hour/60 minutes) = 0.8333
units/minute
T = 30 minutes
C = 10 per container
N = (0.8333)(30)/10 = 2.5 containers
b.
As the system improves, the cycle time decreases, hence the
lead time T decreases, and therefore the number
N = (DT + S)/C of containers needed decreases (N may be
rounded down to 2)
Chapter 07 problems
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Problem 6:
T = 30+5 min. to transport = 35 min.
C = 20 units per container
N = 5 containers
S = 20% of the demand during lead
time = .2(DT)
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N = (DT + S)/C --> NC = DT + S --> DT = NC - S
DT = NC - S = NC - %DT
DT + %DT = NC
(1+%)DT = NC --> D = NC/(1+%)T
D = NC/1.2T = 5(20)/(1.2*35) = 2.38 units per
minute =142.86 units per hour