Part XII: Industrial Engineering and Automobile Engineering Basics

Production Planning and Control

Production planning and control (PPC) encompasses the functions of planning, routing, scheduling, dispatching, and follow-up required to ensure that production activities proceed efficiently, meeting delivery commitments while making effective use of resources. Routing determines the sequence of operations and the machines/workstations through which a product will pass during manufacture. Scheduling assigns specific start and finish times to each operation, coordinating the timing across all workstations. Dispatching is the actual release of work orders and instructions to the shop floor, authorising production to begin. Follow-up (expediting) monitors actual progress against the plan, identifying and resolving delays or bottlenecks.

PERT and CPM

Programme Evaluation and Review Technique (PERT) and Critical Path Method (CPM) are project management techniques used to plan, schedule, and control complex projects consisting of many interrelated activities. Both techniques represent a project as a network of activities and events, but they differ in emphasis: CPM is typically used where activity durations are known with reasonable certainty (deterministic), commonly applied in construction and manufacturing projects, and places emphasis on the trade-off between project cost and duration ("crashing" activities). PERT is typically used where activity durations are uncertain (probabilistic), commonly applied in research and development projects, using three time estimates per activity (optimistic, most likely, and pessimistic) to calculate an expected duration and assess the probability of completing the project by a target date.

The critical path in either technique is the longest path through the network from start to finish, determining the minimum possible project duration; any delay in an activity on the critical path directly delays the entire project, whereas activities not on the critical path have some float (slack) — the amount by which their start or finish can be delayed without affecting the overall project completion date.

Inventory Control

Inventory control aims to maintain an appropriate stock of materials, ensuring smooth production while minimising the costs associated with holding inventory (storage, insurance, obsolescence, capital tied up) and the costs associated with running short of inventory (production stoppages, lost sales, rush order premiums). The Economic Order Quantity (EOQ) model determines the order quantity that minimises the total of ordering costs (which decrease per unit as order size increases, since fewer orders are placed) and carrying (holding) costs (which increase as order size increases, since more average inventory is held); the EOQ is the order quantity at which these two opposing costs are balanced, minimising total inventory cost.

ABC analysis classifies inventory items into three categories based on their value and consumption significance: A-items (a small percentage of items accounting for a large percentage of total inventory value, requiring tight control and frequent review), B-items (a moderate percentage of items with moderate value, requiring a moderate degree of control), and C-items (a large percentage of items accounting for a small percentage of total value, requiring only simple, loose control, since intensive management effort is not justified by their low value).

Quality Control

Quality control encompasses the techniques and activities used to ensure that a product or process meets specified quality requirements. Statistical Quality Control (SQC) uses statistical methods to monitor and control a process, commonly through control charts, which plot a process characteristic (such as a dimension, weight, or defect rate) over time against statistically calculated upper and lower control limits, allowing early detection of a process drifting out of statistical control before defective products are produced in large numbers.

Acceptance sampling is a quality control technique in which a random sample is drawn from a larger lot (batch), inspected, and the entire lot is accepted or rejected based on the sample's results, rather than inspecting every single item (100% inspection), which may be impractical, costly, or (in the case of destructive testing) impossible for the entire lot. Total Quality Management (TQM) is a broader organisational philosophy emphasising continuous improvement, employee involvement at all levels, and a strong customer focus, extending quality responsibility beyond a dedicated quality control department to the entire organisation.

Work Study — Method Study and Time Study

Work study encompasses two complementary techniques used to improve productivity: method study, which systematically records, analyses, and critically examines existing methods of doing work, in order to develop and implement easier, more effective methods and reduce costs; and time study, which is used to establish the standard time required for a qualified worker to carry out a specified task at a defined level of performance, used for production planning, costing, and incentive scheme design.

Common method study tools include process charts (recording the sequence of operations, inspections, transports, delays, and storages involved in a process) and motion study (analysing the detailed body/hand motions involved in a task, aiming to eliminate unnecessary or wasteful motions, closely associated with the pioneering work of Frank and Lillian Gilbreth).

Automobile Engineering Basics

Automobile engines are predominantly internal combustion reciprocating engines, most commonly operating on either the petrol (spark-ignition, Otto cycle) principle, in which an air-fuel mixture is compressed and ignited by a spark plug, or the diesel (compression-ignition) principle, in which air alone is compressed to a high temperature, and fuel is then injected and self-ignites due to the high compression temperature, without a spark plug.

The transmission system of a vehicle transfers power from the engine to the wheels, adapting torque and speed to suit varying driving conditions. A clutch allows the engine to be smoothly connected to or disconnected from the transmission (essential for gear changes and starting from rest), commonly using a friction disc pressed between a flywheel and a pressure plate. The gearbox (transmission) provides a range of gear ratios, allowing the engine to operate efficiently across a range of vehicle speeds and load conditions; a manual transmission requires the driver to select gears, while an automatic transmission selects gears automatically, commonly using a torque converter and planetary gear sets (or, in modern designs, a continuously variable transmission or dual-clutch system).

The differential in a vehicle's final drive allows the two driven wheels to rotate at different speeds when the vehicle turns a corner (the outer wheel travels a longer path than the inner wheel), while still delivering power to both wheels from a single input.

A vehicle's suspension system supports the vehicle's weight, absorbs shocks from road irregularities, and maintains tyre contact with the road for stability and control, typically comprising springs (coil springs, leaf springs, or torsion bars) to absorb impact energy, and dampers (shock absorbers) to dissipate that energy and prevent excessive oscillation. The braking system decelerates or stops the vehicle by converting its kinetic energy into heat through friction, using either drum brakes (friction shoes pressing outward against the inside of a rotating drum) or disc brakes (friction pads clamping onto a rotating disc/rotor), with disc brakes generally offering better heat dissipation and more consistent performance, especially under repeated/severe braking.

Practice Questions — Industrial and Automobile Engineering

1. In PERT/CPM terminology, the critical path is the:
   (a) Longest path through the network, determining minimum project duration (b) Shortest path through the network (c) Path with the fewest number of activities only (d) Path with zero duration
2. Float (slack) in a project network represents the:
   (a) Amount an activity can be delayed without affecting overall project completion (b) Total project cost (c) Number of resources assigned to an activity (d) Exact duration of the critical path itself
3. The Economic Order Quantity (EOQ) balances ordering costs against:
   (a) Carrying (holding) costs (b) Labour wages exclusively (c) Transportation costs exclusively, with no other cost considered (d) Marketing costs exclusively
4. In ABC inventory analysis, "A" items are characterised by:
   (a) A small percentage of items accounting for a large percentage of total value (b) A large percentage of items accounting for a small percentage of total value (c) Items requiring no control whatsoever (d) Items with zero consumption
5. Control charts in statistical quality control are used to:
   (a) Monitor a process characteristic over time against statistically calculated control limits (b) Replace the need for any inspection entirely (c) Measure only the final selling price of a product (d) Serve only a decorative record-keeping function
6. Acceptance sampling involves inspecting:
   (a) A random sample from a lot, accepting/rejecting the entire lot based on results (b) Every single item in the lot without exception (c) No items at all from any lot (d) Only items already known to be defective
7. Time study is primarily used to establish:
   (a) The standard time for a qualified worker to perform a specified task (b) The total floor space required for a factory (c) The exact market price of a finished product (d) The chemical composition of raw materials
8. A diesel engine, unlike a petrol engine, achieves ignition through:
   (a) Self-ignition of fuel injected into highly compressed, heated air (b) A spark plug igniting a pre-mixed air-fuel charge (c) Electrical resistance heating of the fuel (d) External flame ignition applied manually
9. A vehicle's differential allows the two driven wheels to:
   (a) Rotate at different speeds while cornering (b) Always rotate at exactly the same speed under all conditions (c) Never rotate at all (d) Rotate only when the vehicle is stationary
10. Disc brakes, compared to drum brakes, generally offer:
    (a) Better heat dissipation and more consistent performance (b) Poorer heat dissipation under all conditions (c) No difference in performance under any condition (d) Function only at very low vehicle speeds

Answer Key: 1.(a) The critical path is the longest path, setting minimum project duration. 2.(a) Float is the allowable delay without affecting project completion. 3.(a) EOQ balances ordering costs against carrying costs. 4.(a) A-items are few in number but high in value. 5.(a) Control charts monitor a process against statistical control limits. 6.(a) Acceptance sampling inspects a random sample to judge the whole lot. 7.(a) Time study establishes standard time for a qualified worker's task. 8.(a) Diesel engines rely on self-ignition of injected fuel in compressed, heated air. 9.(a) A differential lets driven wheels rotate at different speeds while cornering. 10.(a) Disc brakes generally give better heat dissipation and more consistent performance.