Just-in-time manufacturing Study Guide

📖 Core Concepts Lean Manufacturing – Produces only what the customer needs, when it’s needed, and eliminates non‑value‑added activities. Just‑In‑Time (JIT) – An inventory strategy that delivers parts exactly when required; a subset of Lean that focuses mainly on inventory waste. Two Pillars of TPS Just‑In‑Time – Supplies the right quantity at the right time. Jidoka – Builds quality in by automatically stopping a process when a defect occurs. Andon System – Visual/audible signal that pin‑points the location of a problem so supervisors can act quickly. Seven Types of Waste (Muda) – Inventory, Overproduction, Over‑processing, Transportation, Excess Motion, Waiting, Defects. Five Lean Principles (Womack & Jones) – Value, Value‑Stream, Flow, Pull, Perfection. 5S Workplace Organization – Sort, Set in Order, Shine, Standardize, Sustain. Kanban Pull System – Cards or signals that authorize production only when downstream demand creates a need. Takt Time – The pace required to meet customer demand; defines how fast each unit must be produced. Value‑Stream Mapping (VSM) – Visual map of material and information flow used to spot waste. SMED (Single‑Minute Exchange of Die) – Reduces setup time by separating internal and external setup tasks. --- 📌 Must Remember Lean vs. JIT – Lean = waste elimination in all processes; JIT = waste elimination in inventory only. Jidoka = “automation with a human touch”; any abnormality → stop the line. Andon alerts who and where a problem exists. The 7 Muda are the core checklist for waste identification. 5S order: Sort → Set → Shine → Standardize → Sustain. Kanban Types – Production Kanban (authorizes making) vs. Withdrawal Kanban (authorizes moving). SMED Goal – Changeover ≤ 10 minutes (single‑digit minutes). Pull vs. Push – Pull = downstream demand triggers upstream production; Push = schedule drives production regardless of demand. --- 🔄 Key Processes Implementing 5S Sort: Remove unnecessary items. Set in Order: Assign labeled locations. Shine: Clean & inspect daily. Standardize: Document the first three steps. Sustain: Audit, train, and reinforce habits. Kanban Pull Cycle Downstream consumes a part → pulls a withdrawal Kanban. Withdrawal Kanban signals upstream → triggers a production Kanban. Production Kanban authorizes making a fixed quantity. Andon Activation Operator detects defect → presses Andon button. Signal lights/audible alarm → line stops & supervisor intervenes. SMED Setup Reduction List all setup activities. Separate into internal (machine stopped) vs. external (can be done while running). Convert as many internal tasks to external as possible. Streamline and time each step to achieve ≤ 10 min total. --- 🔍 Key Comparisons Lean vs. JIT – Lean eliminates waste everywhere; JIT focuses only on inventory waste. Mechanical Jidoka vs. Human Jidoka – Sensors stop machines automatically vs. operators manually stopping the line. Production Kanban vs. Withdrawal Kanban – Authorizes making parts vs. authorizes moving parts downstream. 5S vs. Standard Workplace Organization – 5S is a structured, step‑by‑step method; generic organization may lack the sustain phase. --- ⚠️ Common Misunderstandings “Lean = no inventory” – Lean aims to right‑size inventory, not eliminate it entirely; some buffer may be necessary for reliable suppliers. “Jidoka is only about machines” – Human‑driven stops are equally critical; the Andon system empowers operators. “Kanban eliminates all planning” – Kanban replaces push planning with pull signals; demand forecasting still matters. “SMED is only for large factories” – Any operation with changeovers can apply the internal/external task split. --- 🧠 Mental Models / Intuition “Pull = Let the customer pull the rope” – Visualize a rope; you only pull (produce) when the customer pulls (orders). “Waste is anything that does not move the product toward the customer” – Treat every activity as “value‑adding?” → if not, it’s waste. “Andon is a fire alarm for the line” – When a defect appears, the alarm (Andon) alerts everyone instantly. --- 🚩 Exceptions & Edge Cases Supply‑Chain Fragility – Very small order sizes may clash with suppliers’ minimum order quantities; a safety stock buffer may be needed. High‑Variability Demand – Lean’s reliance on accurate forecasts can break down; consider hybrid push‑pull or decoupling points. Non‑Manufacturing Environments – In services (e.g., healthcare), “inventory” translates to patient waiting time; adapt waste categories accordingly. --- 📍 When to Use Which Use 5S when workstations are cluttered, causing motion waste or hiding abnormalities. Deploy Kanban when downstream demand is variable and you need a visual pull signal. Apply SMED when long changeovers create bottlenecks or excess inventory. Implement Andon/Jidoka when defect detection is slow or quality problems recur. Choose VSM for cross‑functional projects that require a big‑picture view of material and information flow. --- 👀 Patterns to Recognize Repeated stop‑and‑go signals → Likely a Jidoka/Andon issue. Large batch sizes with high inventory → Overproduction waste. Long travel distances between workstations → Transportation waste. Workers waiting for parts or instructions → Waiting waste; consider pull or Kanban. Extra steps not required by the customer → Over‑processing waste. --- 🗂️ Exam Traps “Lean eliminates all inventory” – Wrong; Lean reduces excess inventory, not all stock. Confusing JIT with Lean – JIT is a subset; exam may list “Lean” when they mean “JIT” – watch the scope of waste addressed. Selecting “Kanban” for scheduling long‑lead‑time items – Kanban works best for short‑lead, high‑frequency parts; long‑lead items may need a master schedule. Assuming SMED is a tool for quality – SMED targets setup time, not defect reduction (that's Jidoka). Mixing up the 5S steps – Remember the exact order; “Sustain” always comes last. ---