LEAN system

Supporting goals

• A balanced system, smooth, rapid flow of materials and/or work

• Supporting goals:– Eliminate disruption– Make the system

flexible– eliminate waste,

especially exess inventory

Value• That customer is

willing to pay• That changes products

color, function, shape, other attributes so that the product is getting closer to the customers requirements

• That we do right at first time

Wastes• Those processes which directly do not create

value for customers (muda, mura, muri) :– that are not necessary, and must be eliminated– That are necessary, because these are

supporting value-add processes, cannot be eliminated (like transporting)

• Muda – 7 wastes of lean• Mura – not leveled workflow• Muri – overloading of workers and assets

There are 7 wastes in LEAN (TIMWOOD):

• Inventory • Overproduction • Waiting• Unnecessary

transportation• Processing waste• Inefficient work

methods• Defects

Lean thinking

Operation

Traditional improvement

Lean improvement

Non value-add process

Value-add process

JIT Building Blocks

• Process design

• Product design

• Personnel/organizationalelements

• Manufacturing planning and control

Process Design

• Small lot sizes

• Setup time reduction

• Manufacturing cells

• Limited work in process

• Quality improvement

• Production flexibility

• Little inventory storage

Benefits of Small Lot Sizes

Reduces inventory

Less storage space

Less rework

Problems are more apparent

Increases product flexibility

Easier to balance operations

Setup time

• reducing changeover time ( because small lots require frequent setups)

• SMED (single minute exchange of die)

–External

–Internal activities.

Manufacturing cells

• In Functional Manufacturing similar machines are placed close together (e.g. lathes, millers, drills etc)

• In Cellular Manufacturing systems machines are grouped together according to the families of parts produced.

• The major advantage is that material flow is significantly improved, which reduces the distance travelled by materials, inventory and cumulative lead times.

Quality improvement

• Kaizen – continuous improvement of the system

• Jidoka (Autonomation) – automatic detection of defects during production. It consist two activities:– One for detecting defects

when they occur– Another for stopping

production to correct the cause of defects.

• Poka Yoke safeguards built into the process to reduce the possibility of errors.

Work flexibility• Overall goal of lean is to achieve the ability to process mix of

products in a smooth flow.• One potential obstacle is bottlenecks, which occur when portions of

the system become overloaded. Because of – The absence of workers cross trained workers– Not leveled workflow use takt time

• Example: – Total time per shift is 480 minutes per day– There are two shifts per day– There are two 20-minutes break and a 30 minutes lunch break per shift.– Daily demand is 80 pieces

• Net time available per day= 2*(480-20*2-30)=820minutes• Takt time=820minutes/80 pieces=10,25 minutes• If the actual cycle time is higher, our customers won’t get their

needs, if the actual cycle time is lower, there will be overproduction, and we have to inventory surplus products.

Inventory storage

• Inventory storage is a waste, • a buffer which can cover up problems, partly

because inventory makes them seem less serious.

Product Design• Standard parts – fewer parts to deal with lower training costs

• Modular design – easy to satisfy different needs

• Highly capable production systems – quality is designed into the product and the production process

• Concurrentengineering

Personnel/Organizational Elements

• Workers as assets

• Cross-trained workers

• Continuous improvement

• Cost accounting

• Leadership/project management

Manufacturing Planning and Control

• Level loading

• Pull systems

• Visual systems

• Close vendor relationships

• Reduced transaction processing

• Preventive maintenance

Mixed model sequencing

• the sequence (on the base of setup time and setup cost – let it be now A,C,B)

• how many times the sequence should be repeated (determine the smallest integer)

• how many units to produce

Model Daily quantity Units per cycle

A 10 10/5=2

B 15 15/5=3

C 5 5/5=1

Pull/Push Systems

• Pull system: System for moving work where a workstation pulls output from the preceding station as needed. (e.g. Kanban)

• Push system: System for moving work where output is pushed to the next station as it is completed

Visual system

• Kanban- a manual system responds to signals of the need for delivery of parts and materials (both to the factory and between the workstation)– Production kanban– Conveyance kanban

Traditional Supplier NetworkTraditional Supplier Network

BuyerBuyer

SupplierSupplierSupplierSupplier SupplierSupplier SupplierSupplier

SupplierSupplier

SupplierSupplierSupplierSupplier

Figure 12.4a

Tiered Supplier NetworkTiered Supplier NetworkFigure 12.4b

SupplierSupplier

SupplierSupplier

SupplierSupplier

SupplierSupplierSupplierSupplier SupplierSupplier

BuyerBuyer

SupplierSupplierFirst Tier SupplierFirst Tier Supplier

Second Tier SupplierSecond Tier Supplier

Third Tier SupplierThird Tier Supplier

Comparison of JIT and Traditional

Factor Traditional JIT

Inventory Much to offset forecast errors, late deliveries

Minimal necessary to operate

Deliveries Few, large Many, small

Lot sizes Large Small

Setup; runs Few, long runs Many, short runs

Vendors Long-term relationships are unusual

Partners

Workers Necessary to do the work

Assets

Table 12.3

Preventive maintenance

• Total Productive Maintenance – operators responsible for the equipments they use

• Housekeeping – 5S– Sort– Straighten– Sweep– Standardize– Self-discipline

Thank you for your attention!