The major additive process families
Powder bed fusion selectively melts or sinters material in a powder layer. Directed-energy deposition feeds powder or wire into a melt pool and is often evaluated for repair, cladding and larger geometry. Binder jetting deposits binder before a separate curing or sintering path. Material extrusion, vat photopolymerization and material jetting cover different polymer, tooling, pattern and end-use applications. The process name alone does not establish part capability: machine settings, feedstock, atmosphere, thermal history and post-processing all matter.
What to compare before buying
Start with qualified materials, usable build volume, layer strategy, feature resolution, thermal control, inert-gas demand, filtration, recoating method, monitoring, software workflow and the full cycle time. Then map support removal, heat treatment, hot isostatic pressing where applicable, machining, surface finishing and inspection. A low machine price can be overwhelmed by facility changes, consumables, labor, yield loss or an incomplete post-processing chain.
Metal additive is still a machine-shop decision
Many printed metal parts still need datums, bores, sealing faces, threads or critical surfaces machined after the build. Plan the additive system with CNC capacity, workholding, inspection and traceability in view. For hybrid systems, distinguish true in-process deposition and machining from separate machines connected only by workflow software.
Safety, qualification and evidence
Document the manufacturer's material and facility requirements. Metal powder programs can involve combustible-dust, respiratory, housekeeping, grounding, fire-protection and inert-gas controls. Polymer processes may introduce resin, solvent, ventilation or thermal hazards. Qualification should be based on the actual machine, material, parameter set, orientation, post-processing route and inspection plan—not a generic sample part.
Questions manufacturers ask
Is every 3D printer an additive-manufacturing production system?
No. The term covers desktop prototyping through qualified industrial production. Evaluate the process, material, repeatability, workflow and required evidence.
Can additive replace CNC machining?
Sometimes it replaces steps or enables geometry that machining cannot create economically, but many production parts still require CNC finishing and inspection.
What is the hidden cost?
Post-processing, material handling, facility controls, software, qualification, labor and yield are frequently more important than the printer sticker price.
Primary sources and further reading
MBB uses these sources for general process and safety context. A link is not an endorsement, affiliation or substitute for current manufacturer documentation.