Metal 3D Printing: Processes, Costs and When It Beats Machining

Metal 3D printing is now a production process, not a curiosity. Aerospace brackets, hydraulic manifolds, surgical instruments and conformally cooled mold inserts are printed in volume every day. The engineering question is no longer can it be printed but which process, at what tolerance, and at what cost per part compared with machining or casting.

Powder bed fusion (DMLS/SLM) dominates because it holds the tightest tolerances and prints fully dense parts in aerospace alloys. Binder jetting trades tolerance for throughput and is the only additive route that competes with casting on unit cost at volume. Directed energy deposition (DED) builds and repairs large parts. Bound metal deposition is the office-friendly option for jigs, fixtures and low-volume tooling.

Cost is driven by build volume consumed, not by part complexity. A laser powder bed machine bills roughly $80-$180 per build hour, and a build plate is amortized across every part that fits on it. That is why nesting matters more than geometry: printing one bracket costs the same machine time as printing eight nested brackets, so the per-part price falls by nearly a factor of eight. Expect $150-$800 for a fist-sized stainless part in low quantity, plus post-processing that is routinely 30-50% of the total: stress relief, wire EDM removal from the plate, support removal, HIP if fatigue matters, and machining of critical features.

Printing loses badly on simple geometry. If the part is a prismatic block with a few bores, a 3-axis mill will produce it faster and cheaper at almost any quantity. Additive wins when the geometry buys you something: internal conformal channels, topology-optimized mass reduction, consolidation of an eight-piece weldment into one part, or a lead time measured in days instead of the ten weeks a casting tool takes. As a rule of thumb, below roughly 50-100 units of a complex, consolidated part, additive is cost-competitive; above that, casting plus machining usually takes over unless the design cannot be made any other way.

The reliable production alloys are 316L and 17-4PH stainless, AlSi10Mg and A6061-RAM2 aluminum, Ti-6Al-4V titanium, Inconel 625 and 718, maraging steel 1.2709 for tooling, and cobalt chrome for dental and medical parts. Copper and tungsten are printable but need green lasers or binder jetting. If a program depends on an unusual alloy, qualify the powder lot and the machine parameter set before the design freezes - parameter development alone can take months.

Additive parts fail audits for process control, not for strength. A production program needs a frozen build file, a documented powder lot and reuse policy, a fixed post-processing recipe, and first-article inspection against the same drawing you would give a machine shop. Our engineering team builds that documentation package alongside the part so a second supplier can reproduce the first supplier's results.