23-Ind-A4 Production Management · December 2014
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Technical Examinations — December 2014 — 98-Ind-A4 Production Management. Three-hour, closed-book exam; Casio or Sharp approved calculators only. Format: seven questions, each worth 20 marks (sub-part weights as tabulated on the front page); only the first five questions appearing in the answer book are marked, so candidates effectively choose 5 of 7. All seven are solved below for completeness. The paper asks for point-form answers wherever possible; the solutions below use full working for clarity.
Reference texts: Nahmias & Olsen, Production and Operations Analysis (7th ed., Waveland/McGraw-Hill) — forecasting, inventory (EOQ) and aggregate planning; Sipper & Bulfin, Production: Planning, Control, and Integration — production-management systems; Hillier & Lieberman, Introduction to Operations Research (11th ed.) — LP formulation and project scheduling (CPM/PERT); Pinedo, Scheduling: Theory, Algorithms, and Systems (5th ed.) — parallel-machine scheduling, makespan and tardiness; Hopp & Spearman, Factory Physics (3rd ed.) — variability and production-system inefficiency; Womack, Jones & Roos, The Machine That Changed the World — history of mass production and lean; Ford, My Life and Work (1922) and standard histories of the moving assembly line; Juran & Godfrey, Juran's Quality Handbook (5th ed.) — the quality trilogy; Hopp & Spearman, Factory Physics, Ch. 7 — Little's law.
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
Taiichi Ohno was the Toyota production engineer who, from the 1950s onward, built the Toyota Production System (TPS) — the direct ancestor of what the West later called "lean manufacturing." His central new idea was Just-In-Time (JIT) production: rather than pushing large batches through a plant based on a forecast and warehousing the surplus, each process pulls exactly the parts it needs, exactly when it needs them, from the process before it, using a kanban card as the pull signal. The significance of this idea is hard to overstate — it inverted the entire logic of mass production. Where Ford-style mass production treated large batch sizes and high machine utilization as the path to low cost, Ohno showed that eliminating the seven wastes (overproduction, waiting, transport, over-processing, inventory, motion, defects) by pulling only what is needed, in small lots, with rapid changeovers (enabled by SMED), could achieve lower cost, higher quality, and far shorter lead times simultaneously. JIT together with jidoka (automation with a human touch, stopping a line the instant a defect is detected) is the two-pillar foundation of TPS, and every modern pull-based, low-inventory manufacturing system worldwide traces its lineage to Ohno's work at Toyota.
Henry Ford's new idea was the moving assembly line, introduced at the Highland Park plant in 1913 for Model T production. Rather than have workers move to a stationary chassis to perform many different tasks (as in craft production), Ford brought the work to a fixed sequence of stationary workers on a continuously moving conveyor, with each worker repeating one narrow task. The significance is that this combined Adam Smith's division-of-labour principle with Eli Whitney-style interchangeable parts and, crucially, paced the whole line at a fixed cycle time set by the conveyor speed — the entire plant's throughput became a single, controllable number. This cut the time to assemble a chassis from roughly 12.5 person-hours to about 1.5 person-hours within a few years, and enabled Ford to cut the Model T's price repeatedly while raising the famous "$5 day" wage, simultaneously making the car both affordable to buy and (via the higher wage) affordable for his own workforce. The moving assembly line is the direct ancestor of every paced production line in modern manufacturing, and "Fordism" as an economic term describes the resulting model of mass production paired with mass consumption.
Joseph Juran's new idea was to reframe quality management as a management discipline rather than a purely statistical/inspection discipline, formalized as the "Juran Trilogy": quality planning (designing the product/process to meet customer needs), quality control (monitoring performance and correcting deviations, statistically or otherwise), and quality improvement (breaking through to a new, better level of performance via structured projects). He also popularized applying the Pareto principle to quality — the observation that a small fraction of defect causes ("the vital few") typically account for the large majority of quality losses, which is the theoretical basis for prioritizing improvement effort using Pareto charts. The significance of Juran's contribution is that it moved quality from being "the inspection department's job" (catching defects after the fact) to being a company-wide management responsibility spanning strategic planning, daily operations, and continuous improvement projects with an explicit cost-of-quality business case — a shift that underlies TQM, ISO 9001, and Six Sigma alike.
Eli Whitney is credited (along with contemporaries such as Honoré Blanc in France) with popularizing interchangeable parts, most famously demonstrated in an 1801 exhibition where he assembled muskets from a pile of individually-manufactured components in front of U.S. government officials. His new idea was manufacturing each part to a fixed tolerance against a standard gauge or jig, rather than hand-fitting each part to one specific finished assembly (the prevailing craft-production practice). The significance is foundational: without interchangeable parts, neither Ford's moving assembly line nor any modern mass-production system could function, because a paced line requires that any unit of part X fit any unit of assembly Y without hand-fitting. Interchangeability also enabled a separate, and equally important, second-order effect — it made field repair and spare-parts logistics possible (a broken part could be swapped for any equivalent replacement), which is why the concept spread first through military procurement (muskets, and later firearms and machinery) before becoming the default assumption of all of manufacturing.
John Little's new idea, formally proved in 1961, is Little's Law: in any stable system, the average number of items in the system (work-in-process, $L$) equals the average arrival/throughput rate ($\lambda$) multiplied by the average time an item spends in the system (flow time, $W$): $L=\lambda W$. The significance is its extraordinary generality — the proof makes almost no assumptions about the arrival process, service-time distribution, or queue discipline, so the relationship holds equally for a single machine, an entire factory, a hospital, or a software system's request queue, as long as the system is in steady state. This makes it one of the very few universal, "free" quantitative levers available to an operations manager: since $\lambda$ is usually fixed by market demand, the only way to shorten $W$ (customer lead time) is to reduce $L$ (work-in-process), which is the direct theoretical justification for WIP-capping techniques such as kanban and CONWIP that Ohno's TPS (Question 1(i)) also relies on.
