Choosing the right process is one of the earliest and most consequential decisions in a project — it shapes cost, lead time, achievable tolerances and which materials are even on the table. The summaries below are deliberately honest and general: they describe what each process is and when it tends to make sense, not the equipment any one shop runs. When you want a ranked, project-specific recommendation, use the Process Selector; when you want to settle a head-to-head, use the comparisons linked under each process.
CNC Machining
CNC machining is a subtractive process: computer-controlled mills and lathes cut a solid block or bar of material down to the finished shape. It works across nearly the whole materials range — aluminum, steels, stainless, titanium, copper alloys and many engineering plastics.
When to choose it: for tight tolerances, excellent surface finish and metal parts at low-to-medium volumes, or for prototypes where you want production-grade material from the start. It avoids the upfront tooling cost of molding, so it is usually the cheapest route until volumes climb.
Injection Molding
Injection molding forces molten thermoplastic into a steel or aluminum mold under high pressure, then ejects a finished part once it cools. The mold (the tool) is expensive to make, but each subsequent part is fast and cheap.
When to choose it: for plastic parts at high volume, where amortizing the tooling cost across thousands or millions of units makes the per-part price very low. It is the wrong call for one-offs, frequent design changes, or low quantities — the tooling rarely pays off below a few thousand parts.
3D Printing / Additive
3D printing (additive manufacturing) builds parts layer by layer directly from a CAD file, with no tooling at all. Common technologies include FDM, SLA/resin and SLS, in plastics and — through metal additive — a growing range of alloys.
When to choose it: for rapid prototypes, complex geometries that are hard or impossible to machine, low quantities, and designs that are still changing. It loses to CNC and molding on surface finish, material consistency and per-part cost at volume.
Sheet Metal Fabrication
Sheet metal fabrication turns flat stock into parts through cutting (laser, punch or plasma), bending and forming, then joining by welding, riveting or fastening. It works in steel, stainless, aluminum and other formable metals.
When to choose it: for enclosures, brackets, panels, chassis and other thin-walled parts where strength-to-weight and quick turnaround matter. It is well suited to both prototypes and production, and avoids the tooling cost of casting or molding.
Die Casting
Die casting injects molten metal — typically aluminum, zinc or magnesium alloys — into a reusable steel die under high pressure. Like injection molding, it carries a significant upfront tooling cost in exchange for fast, repeatable, near-net-shape parts.
When to choose it: for high-volume metal parts with thin walls and detailed features, where the tooling investment is justified by the quantity. For lower volumes, CNC machining or sand casting is usually more economical.
Other Processes
Beyond the core five, several other processes fit specific needs. Casting (sand and investment) suits larger or complex metal parts at modest volumes without hard tooling. Extrusion produces constant-cross-section profiles efficiently. Forging delivers high strength for load-bearing parts. Urethane casting bridges the gap between 3D-printed prototypes and injection-molded production for small plastic runs. The Process Selector weighs these against the mainstream options when they're a better fit.