Industrial engineering Study Guide

📖 Core Concepts Industrial Engineering (IE) – Design, improve, and install integrated systems of people, materials, information, equipment, and energy. Interdisciplinary Basis – Merges math, physical & social sciences with engineering analysis & design. Primary Objectives – Reduce waste, streamline operations, boost overall performance. Key Principles – Lean manufacturing, Six‑Sigma, information systems, process capability. Major Sub‑disciplines – Work design, operations research, engineering economics, facilities & energy, quality & reliability, ergonomics, supply‑chain, logistics, healthcare. 📌 Must Remember Frederick Taylor (1911) – Father of IE; introduced scientific management, time studies, standardized work. Therbligs – 18 elemental motions identified by Frank & Lillian Gilbreth for manual‑work analysis. Gantt Chart – Visual schedule tool by Henry Gantt; shows task dependencies & timelines. Moving Assembly Line – Henry Ford’s innovation cut car‑assembly time from >12 h to 1 h 33 min. Deming (1950s) – Pioneered variance minimization & quality improvement. Kaizen & Kanban – Japanese continuous‑improvement & pull‑system concepts adopted in the 1970s. Theory of Constraints (Goldratt) – Identify & manage bottlenecks to improve throughput. Supply Chain Focus (1990s) – IE shifted toward end‑to‑end material, information, and financial flow coordination. 🔄 Key Processes Time‑Study/Work Measurement Observe task → Break into therbligs → Record time for each → Establish standard time. Gantt Chart Creation List activities → Define duration → Set dependencies → Plot bars on timeline. Lean Six‑Sigma DMAIC Define → Measure → Analyze → Improve → Control. Theory of Constraints Flow Identify constraint → Exploit it → Subordinate other processes → Elevate constraint → Repeat. Kanban Pull System Set card limits → Produce only when downstream demand signals → Reduce inventory. 🔍 Key Comparisons Taylorism vs. Gilbreth’s Therbligs – Taylor = macro‑level standardization; Gilbreth = micro‑level motion analysis. Lean vs. Six‑Sigma – Lean = waste elimination & flow; Six‑Sigma = variation reduction & statistical quality. Gantt Chart vs. PERT – Gantt = time‑line bar chart; PERT = probabilistic network analysis (not in outline). Theory of Constraints vs. Traditional Optimization – TOC focuses on the single bottleneck; traditional OR seeks global optimum via linear programming. ⚠️ Common Misunderstandings “IE is only about factories.” – IE applies to services, healthcare, logistics, and any system involving people & resources. “Lean = no inventory ever.” – Lean aims for minimal inventory, not zero; safety stock may still be needed. “Six‑Sigma replaces lean.” – They complement each other; Six‑Sigma adds statistical rigor to lean’s waste focus. 🧠 Mental Models / Intuition System Thinking – View the whole process as interconnected; a change in one part ripples through the rest. Bottleneck Principle – The overall output can’t exceed the capacity of the slowest step. Pareto 80/20 – 80 % of problems often stem from 20 % of causes; target high‑impact improvements first. 🚩 Exceptions & Edge Cases Standard Time Validity – Works only when worker skill, tools, and environment remain constant. Kanban Limits – In highly variable demand, strict card limits may cause stock‑outs; buffer zones become necessary. Theory of Constraints – If multiple constraints exist (balanced line), TOC’s single‑constraint focus must be adapted. 📍 When to Use Which Time‑Study vs. Simulation – Use time‑study for repetitive manual tasks; use simulation for complex, stochastic systems. Gantt Chart vs. Kanban – Gantt for fixed‑date project planning; Kanban for continuous production/flow environments. Lean vs. Six‑Sigma – Lean for obvious waste (overproduction, transport); Six‑Sigma when defects/variability dominate. Operations Research (OR) Models – Apply linear/integer programming when decisions have clear objective functions and constraints. 👀 Patterns to Recognize Repeated Waste Types – Overproduction, waiting, transport, extra processing, inventory, motion, defects (the 7 wastes). Bottleneck Symptoms – Queue buildup upstream, idle downstream resources, high work‑in‑process (WIP). Therblig Clusters – Frequent “grasp” and “release” motions indicate potential for tool redesign. 🗂️ Exam Traps Confusing “Kaizen” with “Kanban.” – Kaizen = continuous improvement mindset; Kanban = visual pull‑system tool. Assuming All IE Overlaps Are Redundant. – Overlap with OR, ergonomics, etc., is intentional for integrated solutions, not duplication. Mixing Up Standard Time vs. Cycle Time. – Standard time includes allowances; cycle time is the pure work time. Selecting Six‑Sigma for Simple Waste Issues. – Over‑engineering; lean tools are faster and less resource‑intensive.