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23-Ind-A4 Production Management · Undated paper

Question 2 of 8: The Seven Zeros

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

Notes on this paper

National Examinations — May 2019 — 17-Ind-A4 Production Management. Three-hour, closed-book exam; Casio or Sharp approved calculators only. Format: eight questions, each worth 20 marks (10/10 sub-part split per 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, Shingo, A Revolution in Manufacturing: The SMED System, and Shingo, Zero Quality Control: Source Inspection and the Poka-Yoke System — 5S, Five Whys, poka-yoke, SMED and lean root-cause analysis; R.W. Hall, Zero Inventories — the “seven zeros” JIT framework.

Question 2: The Seven Zeros (20 marks)

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.

Check — seven zeros defined individually
This question asks for the “seven zeros” as a standalone, 10/10 two-part question and explicitly requests each zero defined individually, so part (a) below gives seven distinct definitions, and part (b) gives the “why they work” argument.

(a) The Seven Zeros, Defined

The “seven zeros” is a just-in-time production framework (associated with R.W. Hall's Zero Inventories) that states the goal of a lean production system as seven simultaneous, idealized targets:

  1. Zero defects. Every unit produced conforms to specification the first time, achieved by building quality into the process itself (source inspection, poka-yoke, statistical process control) rather than sorting good parts from bad ones after the fact.
  2. Zero (excess) lot size. Produce and move parts in the smallest economically viable quantity — ideally one piece at a time — rather than in large batches sized around a slow changeover, so work-in-process and flow time are both minimized.
  3. Zero setups. Drive equipment changeover time toward nothing (the SMED philosophy of Question 3), which is what makes zero (excess) lot size economically possible in the first place.
  4. Zero breakdowns. Equipment is available whenever it is needed, achieved through total productive maintenance (TPM) — preventive and autonomous maintenance that catches wear before it causes an unplanned stoppage — rather than reactive repair after a failure.
  5. Zero handling. Minimize the non-value-added movement, transport, and touching of material between operations, since every extra handling step adds cost, flow time, and damage risk without adding value.
  6. Zero lead time. Compress the time from order (or raw-material release) to finished, shippable product toward nothing — the cumulative result of the other six zeros being achieved together, not a target pursued independently.
  7. Zero surging. Release work to the line at a level, uniform rate (heijunka) rather than in lumpy batches driven by upstream scheduling convenience, so downstream stations see steady, predictable demand instead of feast-and-famine capacity swings.

(b) Why the Seven Zeros Work

They work because each of the seven targets attacks one specific root cause of waste or variability, and driving all seven toward zero together — rather than trading one off against another — is what lets a line run with minimal buffers while still meeting demand: zero defects removes rework and scrap (a quality-driven variability source that otherwise forces extra WIP and inspection buffers); zero setups is what makes zero lot size economically viable, since a large batch only exists in the first place to amortize a slow changeover, and small batches directly shorten flow time; zero breakdowns removes machine-availability variability; zero handling minimizes non-value-added motion and damage risk between operations; zero lead time is the cumulative result of the other six being achieved; and zero surging prevents the plant from absorbing demand shocks as sudden capacity spikes. By Little's law, flow time $W$ and work-in-process $L$ are locked together at a given throughput $\lambda$ ($L=\lambda W$) — every one of the seven zeros is, in effect, another way of shrinking $W$ (or the variability that forces a buffer around $W$), so pursuing all seven together compounds rather than conflicts, which is why the framework treats them as one integrated target rather than seven separate initiatives.