Metal 3D Printing: DMLS, EBM, and Binder Jetting Explained

Metal additive manufacturing has moved from laboratory curiosity to production reality. GE prints cobalt-chrome fuel nozzles in volume. Stryker prints titanium spinal implants with bone-ingrowth surface textures impossible to machine. Racing teams print optimised aluminium suspension components overnight. The technology is mature, the materials are certified, and the applications are expanding rapidly. Here's what you need to understand about the three dominant metal 3D printing processes.

DMLS and SLM: Powder Bed Laser Fusion

Direct Metal Laser Sintering (DMLS) and Selective Laser Melting (SLM) are functionally very similar processes, the terminology distinction largely reflecting different machine manufacturers' branding (EOS uses DMLS; SLM Solutions uses SLM). Both use a high-powered fibre laser to melt fine metal powder — layer by layer — in an inert atmosphere to prevent oxidation. The key distinction between sintering (DMLS) and melting (SLM) is that SLM achieves full melting of powder particles, producing denser, homogeneous parts, whereas DMLS can operate below full melting point. In practice, modern DMLS systems also achieve near-full density, and the terms are used interchangeably in most industry contexts.

Parts produced by DMLS/SLM achieve densities above 99.5%, with mechanical properties that meet or exceed those of wrought equivalents in many alloys. The process requires support structures for overhanging geometry — unlike polymer SLS, metal powder cannot support itself during the build, and supports also conduct heat to prevent thermal distortion. Support removal in metal requires EDM, grinding, or machining, adding post-processing steps.

Materials Available in DMLS/SLM

Titanium alloys (Ti-6Al-4V) are the dominant aerospace and medical material — high specific strength, excellent corrosion resistance, and biocompatibility. Nickel superalloys (Inconel 625, 718; Hastelloy X) survive extreme temperatures in gas turbine hot sections. Stainless steels (316L, 17-4PH, 15-5PH) are widely used in industrial, oil and gas, and tooling applications. Aluminium alloys (AlSi10Mg, Scalmalloy) deliver good strength-to-weight for structural components. Cobalt-chrome is the material behind GE's LEAP nozzle and is used extensively in dental and orthopaedic applications.

Electron Beam Melting (EBM)

EBM, developed by Arcam (now a GE Additive company), uses an electron beam rather than a laser to melt powder. The process occurs in a high vacuum, and the entire powder bed is maintained at elevated temperature (700–900°C for titanium) throughout the build. This hot-bed approach has important consequences: parts are largely stress-free when removed, requiring minimal post-process stress relief, and support requirements are significantly reduced compared to DMLS.

EBM's primary application is titanium medical implants. The elevated build temperature promotes the alpha-phase microstructure preferred for orthopaedic implants, and the ability to print highly porous lattice structures enables bone-ingrowth surfaces on acetabular cups, tibial trays, and spinal cages. Stryker's Tritanium product line, printed in EBM titanium, has been implanted in millions of patients. EBM is also used for aerospace titanium structural components and nickel superalloy turbine blades by several primes.

Binder Jetting: High-Volume Metal Printing

Binder Jetting takes a fundamentally different approach: instead of melting powder with energy, a print head jets a liquid binder onto a powder bed to hold particles together layer by layer. The result is a 'green' part — held together by the binder but not yet dense metal. The green part is then sintered in a furnace, where the binder burns off and powder particles fuse. Shrinkage of 15–20% occurs during sintering, which must be compensated in the digital model.

Binder Jetting's key advantage is speed and cost. Because no laser melting occurs during the build, print speeds are 10–50 times faster than DMLS. Multiple parts can be printed simultaneously in dense nests without supports (powder supports the green parts as it does in polymer SLS). Desktop Metal, ExOne, and HP Metal Jet have all commercialised binder jetting for production. The technology is most compelling for high-volume, small-to-medium parts in stainless steel, Inconel, and tungsten carbide.

Post-Processing Metal 3D Printed Parts

All metal additive processes require post-processing. DMLS/SLM parts require stress relief heat treatment before support removal to prevent distortion. Hot Isostatic Pressing (HIP) is often applied to close internal porosity for fatigue-critical applications. Support structures are removed by machining, grinding, or EDM wire cutting. Surfaces can be machined to tolerance, shot-peened for compressive residual stress, or abrasive flow machined for internal channel finishing. Certification-grade parts require full dimensional inspection and often NDT (non-destructive testing) including CT scanning to verify internal integrity.

When Does Metal Additive Manufacturing Make Sense?

Metal additive is not yet competitive with machining for simple geometries at volume. Its compelling use cases are: geometrically complex parts with internal features, channels, or topology-optimised forms impossible to machine; low-to-medium volume production where tooling costs for casting or forging are prohibitive; consolidated assemblies where multiple machined parts can be replaced by a single printed component; rapid prototyping of metal components for fit, form, and early function testing; and on-demand production of legacy or custom parts.

The cost inflection point varies by application, but as a rough guide: DMLS parts costing under £500 per part are rare unless they're very small and simple; most production metal AM parts cost £500–10,000+ depending on volume and complexity. The business case is not unit cost — it's total value delivered: weight savings over a product lifetime, consolidation of supply chain, elimination of tooling, and performance benefits from geometry optimisation that conventional manufacturing simply cannot achieve.