Overview of Manufacturing

The product cycle is the sequence of stages a product passes through from the identification of a customer need to its final disposal or recycling. Manufacturing is only one stage of it, but decisions taken in the design stage fix most of the cost of the product.

Stages of the product cycle

Market need -> Concept design -> Detail design
     ^                                |
     |                                v
 Disposal/  <- Use & service <- Manufacture <- Process
 recycling                      & assembly      planning

1. Market need and specification - customer requirement, competitors, target cost and volume.
2. Design - concept, analysis, material selection, drawings, prototype and testing (design for manufacture and assembly).
3. Process planning - choice of processes, machines, tooling, sequence of operations, inspection plan.
4. Production - fabrication of parts, assembly, quality control, packing.
5. Distribution, use and service - sales, maintenance, spare parts, warranty.
6. Disposal or recycling - reuse of materials, safe disposal.

Material flow and information flow

The material flow is the physical movement and transformation of raw material into the finished product. The information flow is the stream of data that plans, controls and records that movement.

The two flows must be synchronised: a work order (information) releases material from the store, and the completion record (information) updates the stock. Poor information flow produces idle machines, excess work-in-process and late deliveries even when the machines are good.

Manufacturing is the conversion of raw material into useful products by processes that change shape, properties or form, usually followed by assembly.

Classification of processes

Another useful grouping is primary processes (create the basic shape, e.g. casting, rolling) and secondary processes (finish or improve it, e.g. machining, heat treatment).

Evolution of manufacturing organisation

1. Craft production - skilled artisan makes the complete product to order; high cost, high variety, no interchangeability.
2. Interchangeable parts and factory system (18th-19th century) - machine tools, division of labour and gauges allowed parts to fit without hand fitting.
3. Mass production (early 20th century) - moving assembly line, standardised products, low cost per piece, low variety.
4. Scientific management and automation - work study, transfer lines, numerical control, statistical quality control.
5. Lean and flexible manufacturing - just-in-time, small batches, cellular layout, CNC, FMS, continuous improvement.
6. Integrated and digital manufacturing - CAD/CAM, CIM, ERP, robots and networked machines giving mass customisation.

The trend is from low volume and high variety by craftsmen, to high volume and low variety on lines, and then back to high variety at low cost through flexible automation.