23-Ind-A4 Production Management · May 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Technical Examinations — May 2018 — 17-Ind-A4 Production Management. Three-hour, closed-book exam; Casio or Sharp approved calculators only. Format: eight questions, each worth 20 marks (sub-part weights 10/10 as tabulated on the front-page marking scheme); candidates do two questions from Section A and three from Section B, and only the first five questions appearing in the answer book are marked. All eight 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/EPQ) and aggregate planning; Sipper & Bulfin, Production: Planning, Control, and Integration — production scheduling, JIT/kanban and shop-floor implementation gaps; 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 and days-off workforce scheduling; Hopp & Spearman, Factory Physics (3rd ed.) — variability, buffering, and production scheduling; Liker, The Toyota Way, and Shingo, A Revolution in Manufacturing: The SMED System — 5S, Five Whys, SMED and lean root-cause analysis.
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.
SMED (Single-Minute Exchange of Die) is a lean methodology, developed by Shigeo Shingo at Toyota, for reducing equipment changeover time — the time between the last good part of one production run and the first good part of the next — down to “single-digit minutes” (under ten). It works by separating every changeover task into two categories and then systematically shrinking both: (1) internal setup elements, which can only be done while the machine is stopped (removing the current die, bolting in the new one), are first correctly sorted apart from (2) external elements, which can be done while the machine is still running the previous job (fetching the next die and its tools, pre-checking bolt torque specs, staging fixtures on a cart beside the machine); internal steps are then converted to external wherever possible (pre-heating a die, pre-assembling a sub-fixture off-line); and finally both remaining internal and external elements are streamlined (quarter-turn clamps instead of bolts, guide pins for automatic alignment, standardized die heights that need no shimming).
Example. A stamping press changing dies between two part numbers originally takes 90 minutes: the operator waits for the crane to bring the next die (internal, but purely a waiting/logistics problem), unbolts eight mounting bolts of varying sizes, manually shims the new die to the correct height, and re-torques all eight bolts. Applying SMED: the next die is pre-staged on a cart beside the press and inspected while the current die is still running (external); the eight assorted bolts are replaced with quarter-turn clamps on a standardized die-base height (streamlining); and a locating pin fixes horizontal alignment automatically (eliminating the manual shim step). The changeover, now only “crane the pre-staged die in, engage four clamps, verify with a go/no-go gauge,” falls from 90 minutes to under 8 — enabling smaller batches (since setup no longer dominates the cost trade-off), which is precisely the enabler JIT/kanban production depends on.
Kanban is a pull-based visual signal system: a downstream station only produces (or a supplier only ships) when an empty kanban card or bin arrives, and the number of cards in circulation for a part sets a hard ceiling on the WIP for that part. Sizing that card count correctly assumes demand for the part is reasonably stable and repetitive, so a fixed number of cards, once tuned, keeps the line fed without either starving or over-producing.
Example situation: a job shop building highly customized, low-volume, engineer-to-order equipment — e.g., a manufacturer of one-off industrial test rigs, where each order has a different bill of materials, different routing through the shop, and no two consecutive jobs are alike. Kanban is not advisable here because: there is no repeating part number to attach a card to — kanban controls the replenishment of a specific, recurring item between two fixed points in a process, and a part built once and never again has no steady-state demand rate for a card count to be tuned against; demand and routing are both highly variable and unpredictable job-to-job, so any fixed number of cards is wrong almost immediately (too few cards starves the constantly-changing bottleneck resource, too many lets WIP balloon for parts that may never be ordered again); and kanban's core benefit — a simple, decentralized visual signal that avoids the overhead of a full scheduling system — is lost when routings differ every job, because there is no stable flow for the signal to regulate. A project-scheduling or MRP-based push system, which explicitly plans each unique job's due date and material requirements, fits this environment far better. By contrast, kanban is well-suited to the opposite case: a repetitive, high-volume assembly line consuming the same fasteners, sub-assemblies, or components shift after shift, where a stable average consumption rate makes a fixed card count both calculable and effective.
