Just-in-time Systems

Just-In-Time Systems

What is JIT ? • Producing only what is needed, when it is needed • A Practical philosophy • An integrated management system. • JIT’s mandate: Eliminate all wastes & Variations.

Basic Elements of JIT 1.Flexible resources 2.Cellular layouts 3.Pull production system 4.Kanban Replenishment control 5.Small-lot production 6.Quick setups 7.Aligned production 8.Quality at the source 9.Total Productive Maintenance 10. Supply Chain Management- networking

• • • • • • •

Examples of Waste

Watching a machine run Waiting for parts Non- Standard batches of parts Overproduction Moving parts over long distances Storing inventory Searching for tools, consumables, parts, gauges • Machine breakdown • Re- work / pair / make / do

Flexible Resources • Multi – functional / skilled workers • General purpose machines • Multi use – Tool / Fixtures / Jigs

Standard Operating Routine

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 Machines

Enter

Worker 2 Worker 1

Exit Key:

Product route Worker route

Worker 3

• • • • •

Kanban Replenishment Control System Kanban indicates standard quantity of production / supply for replenishment Derived from two-bin inventory system Kanban maintains discipline of pull production Production Kanban authorizes production Withdrawal Kanban authorizes movement of goods

A Sample Kanban Part no.: 7412 Description: Slip rings

From : Machining M-2

Box capacity

25

Box Type

A

Issue No.

3/5

To: Assembly A-4

Kanban Squares X

X

X

X X

Flow of work Flow of information

X

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 sto ck containersize dL + S N= C

No. of kanbans =

where – – – – –

N = number of Kanbans d = demand over defined time period L = lead time to produce parts S = safety stock C = container size

Small-Lot Production • Requires less space & capital investment • Moves processes closer together • Makes quality problems easier to detect • Makes processes more driven by each other

Inventory Hides Problems

Bad Design Lengthy Setups Inefficient Layout

Poor Quality Machine Breakdown

Unreliable Supplier

Lower Levels Of Inventory To Expose Problems

Bad Design Poor Lengthy Quality Setups Machine Inefficient Unreliable Breakdown Layout Supplier

SMED Principles 1. Separate internal setup from external setup 2. Convert internal setup to external setup 3. Streamline all aspects of setup 4. Perform setup activities in parallel or eliminate them entirely

Reducing Setup Time • • • • • •

Preset desired settings Use quick fasteners Use locator pins Prevent misalignments Eliminate tools Make movements easier

Quality At The Source • Jidoka is authority to stop production line • Andon lights signal quality problems • Visual control makes problems visible • Poka-yoke prevents defects

Kaizen • Continual improvement • Requires total employment involvement • Essence of JIT is willingness of All to – – – – –

spot quality problems halt production when necessary generate ideas for improvement analyze problems perform different functions

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 • Design products that can be easily produced on existing machines • Design machines for easier operations, changeover, maintenance • Train & retrain workers to operate machines • Design preventive maintenance plan spanning life of machine

Visual Control Tool board

Visual kanbans

Work station

Library shelf

How to sensor

30-50

Machine controls

Good

Better

Best

Trends In Supplier Policies

1. Locate near to the customer 2. Use small, side loaded trucks and ship mixed loads 3. Consider establishing small warehouses near to the customer or consolidating warehouses with other suppliers 4. Use standardized containers and make deliveries according to a precise delivery schedule 5. Become a certified supplier and accept payment at regular intervals rather than upon delivery

Benefits Of JIT 1. Reduced inventory 2. Improved quality 3. Lower costs 4. Reduced space requirements 5. Shorter lead time 6. Increased productivity

7. Greater flexibility 8. Better relations with suppliers 9. Simplified scheduling and control activities 10. Increased capacity 11. Better use of human resources 12. More product variety

JIT Implementation • Use JIT to finely tune an operating system • From Japan-TPS to Allover in World • JIT requires evolving all time • JIT is for everyone

JIT In Services • Competition on speed & quality • Multifunctional department store workers • Work cells at fast-food restaurants • Just-in-time Sale of - ? • Construction firms receiving material just as needed