JIT (Just-in-Time)
JIT (Just-in-Time)
Section titled “JIT (Just-in-Time)”Overview
Section titled “Overview”Just-in-Time (JIT) is an integrated set of activities for high-volume production with minimal inventory. It means producing what is needed, when it is needed, and no more. Anything over the minimum is considered waste. JIT was pioneered by Japanese manufacturers in the early 1980s and is applied primarily to repetitive manufacturing environments.
JIT is like having groceries delivered RIGHT when you need them:
Old way (Push System):
- Buy 50 cans of soup “just in case”
- Pantry is FULL
- Soup expires before you use it
- Wasted money and space!
JIT way (Pull System):
- Buy 1 can today for dinner
- Store delivers 1 can tomorrow for tomorrow’s dinner
- Pantry is EMPTY but you always have food!
The Seven Wastes (TIMWOOD):
- Transportation (moving stuff unnecessarily)
- Inventory (extra stuff sitting around)
- Motion (walking to get tools)
- Waiting (parts waiting for next machine)
- Overproduction (making too much)
- Over-processing (polishing what customers won’t see)
- Defects (fixing mistakes)
Memory: “Right stuff, right time, right amount!”
Core Concept
Section titled “Core Concept”JIT is a production philosophy that aims to eliminate all waste by producing only what is needed, when it is needed, and in the quantity needed. The fundamental principle is that anything over the minimum required is waste.
Key Principles:
- Eliminate Waste: Any activity that doesn’t add customer value is waste
- Pull System: Production is triggered by actual customer demand, not forecasts
- Continuous Flow: Products move through the system without stopping
- Ideal Lot Size = One: Process items one at a time for maximum efficiency
- Drive Inventory to Zero: Low inventory exposes hidden problems (like lowering water reveals rocks)
The Rocks in Water Analogy:
- High inventory = high water level = problems (rocks) are hidden
- Low inventory = low water level = problems (rocks) become visible
- Goal: Drive all inventory queues to zero to expose and fix problems
Components / Framework
Section titled “Components / Framework”| Component | Description | Source |
|---|---|---|
| Pull System | Production triggered by downstream demand via Kanban signals | MGH_book.pdf |
| Waste Elimination | Seven wastes: TIMWOOD (Transportation, Inventory, Motion, Waiting, Overproduction, Over-processing, Defects) | MGH_book.pdf |
| Ideal Lot Size | One unit at a time for optimal flow | MGH_book.pdf |
| Repetitive Manufacturing | JIT is applied to repetitive manufacturing environments | MGH_book.pdf |
| Continuous Improvement | Kaizen culture to eliminate waste continuously | Chapter1.pptx |
| Quality at Source | Defects caught and fixed immediately where they occur | MGH_book.pdf |
Example
Section titled “Example”From Slides and Real-World:
Toyota (Pioneer): Seats arrive at assembly plant in exact sequence of cars on assembly line, 2 hours before installation. Supplier located nearby enables this. Result: Zero seat inventory.
McDonald’s: Cooks burgers to order during off-peak (pull), but makes some in advance during peak (hybrid). Holds for 7 minutes max, then discards — balances JIT with speed requirement.
Dell Computers: Components arrive at factory based on actual customer orders. Assembly begins after order is placed online. Customer receives custom PC in 3-5 days, Dell holds minimal inventory.
Implications
Section titled “Implications”JIT has significant implications for organizations:
- Cost Reduction: Less capital tied up in inventory, reduced storage costs, less handling
- Quality Improvement: Problems surface quickly when inventory is low, forcing immediate resolution
- Space Savings: Less warehouse space needed for raw materials and finished goods
- Supplier Relationships: Requires close partnerships with reliable suppliers for frequent, on-time deliveries
- Risk Exposure: No buffer inventory means supply disruptions halt production immediately
- Cultural Change: Requires workforce empowerment, cross-training, and continuous improvement mindset
Related Concepts
Section titled “Related Concepts”- Lean Manufacturing: Broader philosophy that includes JIT as a core component
- Kanban: Visual signaling system used to implement pull production
- Kaizen: Continuous improvement culture essential for JIT success
- Takt Time: Production rate matched to customer demand rate
- Heijunka: Production leveling to smooth demand variations
- SMED: Single Minute Exchange of Dies for quick changeovers
Quick Summary
Section titled “Quick Summary”- JIT = produce what is needed, when needed, no more [MGH_book.pdf]
- Pioneer: Japanese in early 1980s [Chapter1.pptx, Slide 18]
- Anything over minimum is waste [MGH_book.pdf]
- Applied to repetitive manufacturing [MGH_book.pdf]
- Ideal lot size = one [MGH_book.pdf]
- Low inventory exposes hidden problems (rocks in water analogy) [MGH_book.pdf]
- Goal: drive all inventory queues to zero [MGH_book.pdf]
- Seven wastes: TIMWOOD (Transportation, Inventory, Motion, Waiting, Overproduction, Over-processing, Defects)
Exam Tips:
- JIT is NOT zero inventory — it’s MINIMUM necessary inventory
- Pull system = downstream demand triggers upstream production
- Low inventory = good because it exposes problems to fix
- JIT requires reliable suppliers, quality at source, skilled workers
Sources
Section titled “Sources”- Chapter1.pptx [Slide 18]
- IPPTChap007.pptx [Slide 4]
- MGH_book.pdf