Choosing the right metal-forming process early in a design controls strength, cost, and lead time more than almost any decision made later. Here is a practical way to weigh three of the most common options for metal parts: extrusion, casting, and forging.
Extrusion
A metal billet is forced through a die to form a constant cross-section. Extrusion produces a wide range of profiles with good mechanical strength from an elongated grain structure, at relatively low tooling cost.
- Strengths: wide range of profile shapes, strong grain flow, low tooling cost, efficient at higher volumes.
- Trade-offs: limited to constant 2D cross-sections; possible surface defects; lower stiffness than forging.
- Best for: simpler profiles and higher-volume parts where maximum strength is not the priority.
Casting
Molten metal is poured into a mould to form complex shapes. Casting excels at intricate geometries and large parts, and can be very cost-effective for the right application.
- Strengths: intricate geometries, large parts (sand casting has effectively no size limit), economical for complex shapes.
- Trade-offs: lower strength than forged parts; risk of porosity or internal voids; often needs secondary machining for a quality finish.
- Best for: large or complex parts where cost matters more than maximum strength.
Forging
Solid metal is compressed under extreme force into high-strength parts. The refined grain structure gives forged parts superior strength and structural integrity, and closed-die forging can hold complex 3D geometries to tight tolerances.
- Strengths: highest strength and fatigue resistance, refined grain flow, tight tolerances with closed-die forging, minimal porosity.
- Trade-offs: higher cost, especially for intricate designs or smaller production runs.
- Best for: high-performance, stress- and shock-bearing parts such as pistons and gears.
How to decide
Start from load case, tolerance, geometry, and volume, and let those drive the process rather than the other way around. Need strength and 3D complexity? Forging — particularly closed-die forging — leads on durability and precision. Prioritising cost at volume? Extrusion suits simpler profiles. Complex but less safety-critical parts? Casting handles large or intricate shapes economically. For a related comparison of three different options, see our guide on die casting, extrusion, or CNC machining.
PA International works across a vetted partner network to engineer and source the right process for each part — from prototype through to volume production. Talk to an engineer about your part and we will help match it to the most cost-effective option.