Just-in-Time System

Dr S G Deshmukh

Difficulty in Production ! Demand is uncertain and variable. Same equipment and people are used to make a

variety of products. Switching products takes time.(imagaine changing

over from say dark shade to light shade in a paint manufacturing !)

Things may go wrong(Murphy’s law!) Materials are defective. Deliveries are variable (late). Equipment fails, people make mistakes, etc. And so many other reasons..

Solution 1: Use Inventory Use inventory to:

Match supply with varying demand. Act as a buffer Allow production of a variety of products on

the same equipment, tools etc. Overcome defective materials, late

deliveries, equipment failures, mistakes, etc.

Forecast demand based on classical methods Produce in large lots (to reduce expensive

setups) & economics of scale PUSH product to customer.(even if he/she

doesn't want !) Large lot sizes mean:

Large work-in-process inventories. Large final product inventories. Slow response to changes and defects. Opaque view of the ground !

“Typical “ Production

Use just-in-time to identify and solve problems that create inventory. Reduce setup costs to switch products. Expose yourself to problems rather than

hiding under the cover of inventory ! Eliminate defective materials, late

deliveries, equipment failures, mistakes, etc.

Solution 2: Use Just-In-Time

“Just-in-Time” Production Produce in small lots to replenish stock

actually sold. Sales PULL product (and parts) through

plant. Get pulse of the market ! Small lot sizes mean:

Small work-in-process inventories. Small final product inventories. Quick response to changes and defects.

What is Waste?

Waste is ‘anything other than the minimum amount of equipment, materials, parts, space, and worker’s time, which are absolutely essential to add value to the product.’

— Shoichiro Toyoda President, Toyota

Different Kinds of Waste Waste from Over-production Waste of Motion Transportation waste Processing waste Defective Products Excess Inventory Information waste Energy waste Manpower waste

Elimination of Waste• JIT attempts to eliminate all costs (waste) that DO

NOT ADD any value to a product.• Machining, Packaging, Assembling etc. add value

to a product BUT Moving, Storing, Counting, Sorting etc add COST but No Value to a product. Hence try to eliminate them.

Management philosophy of continuous and forced problem solving.

Supplies and components are ‘pulled’ through system to arrive where they are needed when they are needed.

Originated in Japan; Popularized by Toyota; now used globally.

What is Just-in-Time?

Large Lot Sizes = Large Inventory

Time

Inventory Level

Lot Size 200 Average inventory = 100

Average inventory = (Lot size)/2

To Lower Inventory, Reduce Lot Size

Time

Inventory Level

Lot Size 200

Average inventory = (Lot size)/2

Lot Size 80

Average inventory = 40

Steps to Reduce Setup Time Separate setup into preparation (while

machine is running) and actual setup (while machine is stopped). Do as much as possible while the machine

is running. Move material closer and improve

material handling. Standardize and improve tooling.

Comment… INVENTORY is an Undesirable

cost. By LOWERING it, Hidden quality

and Production impediments are revealed.

Simplif ication and Elimination through Problem Solving, continuous improvement is the key.

JIT Just-in-time (JIT): A highly coordinated

processing system in which goods move through the system, and services are performed, just as they are needed,

JIT lean production JIT pull (demand) system JIT operates with very little “fat”

American Production and Inventory Control American Production and Inventory Control Society (APICS) definition of JITSociety (APICS) definition of JIT

• "a philosophy” of manufacturing

• based on planned elimination of all waste and continuous improvement of productivity.

• encompasses successful execution of all manufacturing activities required to produce final product,

• from design engineering to delivery and including all stages of conversion from raw material onward.

Goals of JIT

A manufacturing process that is so streamlined, cost eff icient, quality oriented and responsive to customer, that it becomes a strategic weapon. The goals in most cases consists of :

Produce product only on demand. Produce a perfect quality product. Reduce the cost of manufacturing. Integrate and to optimize every step of

manufacturing process. Develop manufacturing Flexibil i ty Keep commitments made to customers and

suppliers

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

JIT Through … Product design Process design Personnel/organizational

elements Manufacturing

planning and control

Enabler : Product Design Standard parts Modular design Highly capable production systems Concurrent

engineering Use of CAD/CAM Use of CFD

Enabler .. Process Design Small lot sizes Setup time reduction Manufacturing cells Limited work in process Quality improvement Production flexibility Little inventory storage

Production Flexibility Reduce downtime by reducing changeover

time Multi-tools, workstations Use preventive maintenance to reduce

breakdowns Cross-train workers to help clear bottlenecks Use many small units of capacity Use off-line buffers Reserve capacity for important customers

Enabler : Personnel/Organizational Elements

Workers as assets Cross-trained workers Belief in improvement by workers Continuous improvement Cost accounting Organic element of human being !! Leadership/project management

Enabler ..Planning & Control

Level loading Pull systems Visual systems (Andon ,

alarms etc.) Close vendor relationships Reduced transaction

processing Preventive maintenance

Models for supplier

Arms Length Model Closed, Competitive Evaluation on lowest bid

Data/Information sharing very limited

Inspection based quality regime

No shared R&D

Partnership Model Collaboration based Multi-criteria evaluation of

sources Sharing of data/information

encouraged Participative attitude towards

quality Shared R&D

Buyer Supplier Relationship Buyer Action Attributes Supplier Action Attributes Joint Action Attributes Outcome Attributes

Buyer Action… Fewer suppliers Long term contract Increased volume to suppliers Supplier evaluation/certification Training and audit Freight consolidation Stable production schedule Performance evaluation

Supplier Action.. SPC Close proximity Quality circle Flexible suppliers Reduced set ups Increased customer support

Joint Action Mutual trust & cooperation Information sharing Joint design & development Continuous improvement

Outcome … Frequent & reliable deliveries Small shipment Reduced paperwork Shared perceptions Flexibility in everything !

Benefits Cooperation, reduced inventory, quality at low cost, better planning and control, less paperwork improved communication

Kanban as a Control System Kanban: Card or other device that

communicates demand for work or materials from the preceding station

Kanban is the Japanese word meaning “signal” or “visible record”

Paperless production control system Authority to pull, or produce comes

from a downstream process.

Kanban..• fixed quantity bins or containers or pallets used to signal

replenishment needs

• (reminiscent of traditional two-bin system of stock control).

• When first bin empty, new full bin moved in within usage time from the second bin).

• With well-designed floor layouts, system adds considerably to efficiency of operational environment.

• integration of computer systems internally & externally with suppliers systems so Kanban data & instructions can flow between linked systems.

Youtube on JIT (10.56 minutes) https://www.youtube.com/watch?

v=CBFKBf1rOyo

Frank Sinatra sings JIT…(2.18 minutes)

https://www.youtube.com/watch?v=RIcQ26arWAs

NPTEL session By Prof G Srinivasan (IIT Madras) on JIT (51 minutes)

https://www.youtube.com/watch?v=Zjx7zCjLjyw

JIT objective: Frequent on-time deliveries of small lots of high quality.

Buyer and supplier form JIT partnerships to eliminate: Unnecessary activities. In-plant inventory. In-transit inventory. Poor suppliers.

Suppliers

Transitioning to a JIT System Get top management commitment Decide which parts need most effort Obtain support of workers Start by trying to reduce setup times Gradually convert operations Convert suppliers to JIT Prepare for obstacles

Barriers to migration Management may not be committed Workers/management may not be

cooperative Suppliers may

resist Why?

Benefits of JIT Systems Reduced inventory levels High quality Flexibility Reduced lead times Increased productivity

Benefits of JIT Systems ..cont’d

Increased equipment utilization Reduced scrap and rework Reduced space requirements Pressure for good vendor relationships Reduced need for indirect labor

Benefits of JIT.. Contd. Part Cost: Low scrap, Low Inventory Quality: Fast detection, Corrections Design: Fast Response to

Engineering changes Administration Efficiency: Fewer

suppliers, minimal expedit ing, less paper work

Productivity: Reduced rework/Inspection delay, reduced parts

JIT exposes quality problems by reducing inventory.

JIT limits number of defects produced with small lots.

JIT requires TQM. Statistical process control. Worker involvement & empowerment. Immediate feedback.

Quality

JIT is flow…

JIT Is Flow is Hirano and Furuya’s book which gives an extensive practical overview of JIT/Lean.

http://www.amazon.com/Jit-Is-Flow-Hiroyuki-Hirano/dp/0971243611

Interesting book..

https://store.kobobooks.com/en-US/ebook/toyota-supply-chain-management-a-strategic-approach-to-toyota-s-renowned-system

Toyota Global.. http://www.toyota-global.com/company/vision_philosophy/toyota_production_system/just-in-time.html

Summary JIT as a philosophy Attack on elimination of waste Pull based system Critical Factors

Involvement of top management Simplified processes Orientation towards inventory