The selection of a manufacturing process is an important part of engineering design. The process must be capable of producing the required material, component geometry, dimensions, section thickness, surface finish and tolerances at an appropriate production quantity and cost.
Primary manufacturing processes create the basic shape of a component from raw or semi-finished material. Common processes include casting, forging, extrusion, drawing, powder metallurgy and sheet or bulk metal forming. Secondary operations such as machining, joining and surface finishing may then be used to achieve the final component requirements.
Manufacturing components by pouring molten material into a mould and allowing it to solidify.
CastingShaping metal using compressive forces, commonly by hammering, pressing or forming between dies.
ForgingReducing and controlling wire, rod or tube cross-section by drawing material through a die.
Wire & Tube DrawingProducing components from metal powders by compaction and controlled heating below the principal melting temperature.
SinteringBending, deep drawing, spinning and related processes used to form sheet material into engineering components.
Sheet Metal FormingManufacturing processes should not normally be selected from a single capability value. Material, component geometry, size, section thickness, required properties, dimensional accuracy, surface finish and production quantity all influence the most appropriate manufacturing route.
The following table provides a broad engineering comparison. It is intended as a process-selection guide rather than a statement of absolute process limits.
| Process | Typical Geometry / Application | Production Considerations | Engineering Characteristics |
|---|---|---|---|
| Casting | Complex three-dimensional shapes, internal cavities and components ranging from relatively small parts to very large structures. | Choice of casting process is strongly influenced by quantity, component size, material, tooling and required finish. | Can produce complex near-net shapes. Properties, tolerance and surface finish depend strongly on the particular casting process. |
| Forging | Structural components requiring good mechanical properties, including shafts, connecting components, gears and other highly loaded parts. | Open-die forging can suit low quantities and large components. Closed-die forging normally requires greater tooling investment and is more attractive for repeat production. | Controlled deformation can produce favourable grain flow and mechanical properties. Geometry is constrained by material flow and tooling. |
| Extrusion | Long products having a substantially constant cross-section, including solid and hollow profiles. | Requires an extrusion die and suitable press capacity. Particularly effective where significant lengths of a common profile are required. | Can produce complex constant cross-sections and reduce subsequent machining. Material, section geometry and extrusion conditions affect practical limits. |
| Wire and Tube Drawing | Wire, rod and tube requiring reduced cross-section, controlled dimensions or improved surface condition. | Large reductions may require several drawing stages and, depending on the material, intermediate thermal treatment. | Good dimensional control and surface finish can be achieved. Cold drawing also changes material properties through work hardening. |
| Powder Metallurgy | Near-net-shape components, controlled-porosity products and components made from specialised powder-based material systems. | Compaction tooling can be significant, making conventional die-compacted parts particularly attractive for repeat production. | High material utilisation and controlled porosity are possible. Component geometry must suit powder filling, compaction and ejection. |
| Sheet Metal Forming | Thin-walled sheet components including bends, cups, shells and axisymmetric spun components. | Tooling requirements vary considerably from relatively simple spinning tooling to dedicated high-production press tools. | Efficient use of sheet material. Formability, springback, thinning, wrinkling and work hardening must be considered. |
A useful process-selection sequence is to consider the component requirements in stages rather than starting with a preferred manufacturing method.
The primary process establishes most of the component's basic geometry, but it is rarely the only manufacturing operation which needs to be considered.
Machining may provide precision interfaces and holes, heat treatment may develop the required material properties, joining may create a larger assembly, and surface engineering or protective coatings may provide the required wear or corrosion performance.
For this reason, process selection should be considered alongside the other RoyMech manufacturing sections below.
The following external resources were included on the original RoyMech page and provide additional information relating to forging and manufacturing process selection.