Question 1 of 7: Just-in-Time Production

Question 1: Just-in-Time Production (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.

(a) Definition of JIT and Seven Fundamental Concepts

Just-in-time (JIT) production is a manufacturing philosophy, developed within the Toyota Production System, whose goal is to produce and deliver exactly the right items, in exactly the quantity needed, at exactly the time they are needed — no earlier and no later — so that inventory, and the costs and defects it hides, are driven toward zero rather than carried as a buffer against an unmanaged process.

Seven of its fundamental concepts:

1. Pull production (kanban). Nothing is produced until a downstream signal (a card, an empty bin, an electronic kanban) authorizes it, so material is drawn through the plant by actual consumption rather than pushed ahead of schedule based on a forecast.
2. Small lot sizes / level scheduling (heijunka). Producing in small, frequent batches (ideally one-piece flow) smooths the demand each upstream process sees and shrinks the inventory needed between stages.
3. Setup-time reduction (SMED). Driving changeover time toward single-digit minutes is what makes small-lot production economical — without it, small lots would be swallowed by setup cost.
4. Standardized work. A single, documented best method and takt-time-paced work content per station, so cycle-to-cycle variability — a major source of line imbalance — is minimized.
5. Jidoka / quality at the source. Any operator or machine that detects an abnormality stops the line immediately rather than passing a defect downstream, so problems are visible and fixed at their origin instead of accumulating in inventory.
6. Visual control (andon). A visible signal (light, board, cord-pull) makes the current status of the line — running, waiting, stopped for a problem — obvious to everyone at a glance, so response is immediate rather than discovered later.
7. Total elimination of waste (muda). Every activity that does not add value from the customer's perspective — overproduction, waiting, excess transport, excess inventory, unnecessary motion, over-processing, defects — is systematically targeted for removal.

(b) A Situation Where JIT Will Not Work Well

Consider a manufacturer of highly customized, low-volume aerospace subassemblies that sources several critical, long-lead-time components from a small number of overseas specialty suppliers whose own delivery reliability is poor and whose lead times run several months. Attempting to run this operation under classic JIT — pulling small lots against a kanban signal with little or no buffer stock — will not work well.

The reason is that JIT's entire logic depends on high-frequency, reliable, short-cycle replenishment: a pull signal is only useful if the upstream source can respond to it quickly and predictably. Here, demand for any given configuration is low and irregular (each aircraft build is close to a one-off), so there is no stable consumption rate for a kanban loop to regulate against, and the long, unreliable overseas lead times mean that by the time a shortage is signalled, the part cannot arrive in time regardless of how quickly the signal propagates. Running with near-zero buffer stock under these conditions would expose the line to frequent, costly stoppages rather than the smooth, low-inventory flow JIT is meant to deliver — the variability and uncertainty JIT is designed to expose and eliminate are, in this case, structural facts of the supply base that no amount of internal pull-system discipline can fix. A more appropriate strategy is a hybrid approach: JIT/pull scheduling for the high-volume, reliably-sourced components, paired with strategic (buffer) stock and longer-horizon forecasting for the small set of critical, unreliable, long-lead-time items.