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Tag: directed energy deposition

  • The Seven Additive Manufacturing Process Categories: Methods, Materials and Selection

    The Seven Additive Manufacturing Process Categories: Methods, Materials and Selection

    Additive manufacturing technologies are often described by commercial names such as FDM, SLS, SLA, DMLS, PolyJet or WAAM. These names are useful, but they can mix trademarks, historical terms and process physics. A clearer starting point is the seven process categories used by ISO/ASTM terminology.

    Choose an additive manufacturing process by how material is delivered, consolidated and supported—not by the popularity of a machine brand.

    ISO/ASTM 52900:2021 remains the current confirmed international vocabulary standard for additive manufacturing. It defines AM as creating physical 3D geometry through successive addition of material and organizes the field into standardized process categories.

    The seven standard AM process categories

    Process categoryHow the part is formedCommon feedstockTypical applications
    Vat photopolymerizationLight selectively cures liquid photopolymer in a vatPhotopolymer resin or ceramic-filled slurryDental devices, models, patterns and fine polymer parts
    Material extrusionMaterial is selectively dispensed through a nozzle or orificeThermoplastic filament, pellets, paste, concrete or bioinkPrototypes, tooling, large-format parts and construction
    Powder bed fusionThermal energy selectively fuses regions of a powder bedPolymer, metal or selected ceramic powderFunctional polymer parts, metal components and implants
    Binder jettingLiquid binder selectively joins particles in a powder bedMetal, ceramic, sand, gypsum or other particulate materialSand molds, metal parts, ceramics and visual models
    Material jettingDroplets of build material are selectively depositedPhotopolymer, wax, nanoparticle suspension or functional inkDetailed models, casting patterns and multi-material parts
    Directed energy depositionFocused energy melts material as it is depositedMetal powder or wireRepair, feature addition and large near-net metal parts
    Sheet laminationSheets are bonded and shaped layer by layerPaper, polymer, metal foil or composite sheetModels, embedded structures and selected metal components

    1. Vat photopolymerization

    Vat photopolymerization uses light to selectively solidify a liquid resin. The category includes several light-delivery and layer-separation approaches:

    • Laser SLA: a focused laser scans the layer.
    • DLP: a projector exposes a complete layer or projected region.
    • MSLA/LCD: an LCD mask shapes light from an underlying source.
    • Continuous-interface methods: reduce discrete peel interruptions through a controlled inhibition or separation zone.

    Strengths: fine detail, smooth surfaces, dental and medical material ecosystems, full-layer exposure on projection systems and broad visual-model capability.

    Constraints: uncured-resin handling, washing, drying, post-curing, support marks, long-term polymer aging and indication-specific material validation.

    Read the detailed vat photopolymerization guide.

    2. Material extrusion

    Material extrusion selectively dispenses material through a nozzle. The most familiar route melts thermoplastic filament, but the category is much broader.

    • Filament extrusion: commonly called FFF; FDM is a Stratasys-associated trademarked term.
    • Pellet extrusion: uses polymer granules for higher material flow and large-format systems.
    • Paste extrusion: deposits ceramics, food, energetic materials, silicones or other viscous formulations.
    • Concrete extrusion: deposits pumpable cementitious material for construction elements.
    • Extrusion bioprinting: deposits cell-containing or biomaterial formulations for research.

    Strengths: accessible equipment, wide material forms, low feedstock cost, large build sizes and straightforward multi-material concepts.

    Constraints: bead-scale resolution, anisotropy, voids, interlayer bonding, warpage, support needs and variable surface quality.

    3. Powder bed fusion

    Powder bed fusion spreads a layer of powder and selectively fuses regions using thermal energy. The unused powder supports surrounding geometry, although metal systems often still need supports for heat transfer, anchoring and distortion control.

    Polymer PBF

    Selective laser sintering is widely used for nylon and thermoplastic elastomer components. Other commercial platforms use alternative heating or fusing-agent strategies while remaining within powder-bed-based polymer production concepts.

    Laser metal PBF

    Laser powder bed fusion of metal is also described by commercial or historical names such as SLM and DMLS. The standardized process description is clearer: PBF-LB/M, powder bed fusion using a laser beam for metallic material.

    Electron-beam metal PBF

    PBF-EB/M uses an electron beam in vacuum and typically maintains an elevated powder-bed temperature. It is distinct from wire-fed electron-beam directed energy deposition.

    Strengths: complex geometry, functional polymer production, dense metal parts, strong aerospace and medical ecosystems.

    Constraints: powder safety and genealogy, thermal distortion, supports, surface condition, build size, machine qualification and post-processing.

    Related guides: LPBF terminology and electron-beam PBF.

    4. Binder jetting

    Binder jetting selectively deposits a liquid binder onto a powder bed. The printed object is usually a weak green part or mold that requires additional processing.

    • Sand binder jetting: produces molds and cores for metal casting.
    • Metal binder jetting: prints a green part followed by depowdering, debinding and sintering.
    • Ceramic binder jetting: creates green ceramic shapes requiring thermal processing or infiltration.
    • Color model printing: uses colored binder with suitable powder systems for visual models.

    Strengths: rapid area-based printing, support-free powder-bed geometry, high nesting density and useful foundry applications.

    Constraints: fragile green parts, depowdering, binder removal, furnace capacity, shrinkage, distortion and final density.

    Read the binder jetting guide.

    5. Material jetting

    Material jetting deposits droplets of build material. The deposited material can be cured by light, cooled from a molten state or processed through another consolidation step.

    • Photopolymer material jetting: produces detailed multi-material and multi-color polymer models.
    • Wax jetting: creates precision casting patterns.
    • Nanoparticle or suspension jetting: deposits material-containing droplets followed by drying, curing or sintering.
    • Functional ink deposition: overlaps with printed and additively manufactured electronics.

    Strengths: fine visual detail, color, controlled droplet placement and multi-material capability.

    Constraints: material cost, support removal, UV and thermal aging, nozzle maintenance and limited structural-material options on many platforms.

    6. Directed energy deposition

    Directed energy deposition delivers material into a focused heat source. Unlike powder bed fusion, feedstock enters only where material is being deposited.

    DED routeEnergy sourceFeedstockTypical use
    Laser DEDLaserPowder or wireRepair, coatings and feature addition
    Arc DED / WAAMElectric arcWireLarge structures and high-rate near-net deposition
    Electron-beam DEDElectron beamUsually wireLarge reactive-metal preforms under vacuum

    Strengths: repair, large build envelope, high deposition rate, hybrid manufacturing and low buy-to-fly potential.

    Constraints: coarse feature resolution, thermal distortion, bead stability, substantial machining and difficult inspection of large volumes.

    Related guides: wire arc AM and wire-fed electron-beam DED.

    7. Sheet lamination

    Sheet lamination bonds layers of sheet material and shapes them into the final geometry. Major routes include:

    • Laminated object manufacturing: cuts and bonds paper, polymer or composite sheets.
    • Ultrasonic additive manufacturing: bonds metal foils using ultrasonic energy, often with intermediate machining.
    • Composite sheet lamination: stacks and bonds reinforced sheets or tapes.

    Strengths: relatively low thermal exposure in ultrasonic metal routes, embedded sensors or channels, multi-material sheet combinations and rapid model production.

    Constraints: interlayer bonding, geometric access, removal of surrounding material, limited adoption and process-specific design rules.

    Processes often confused with the seven categories

    TermHow to classify it
    Hybrid manufacturingA production system combining AM with machining or another process; the AM step still belongs to one of the seven categories
    BioprintingAn application domain using extrusion, material jetting, vat or other deposition principles
    Construction 3D printingUsually material extrusion, although printed formwork and metal routes can use other categories
    Additively manufactured electronicsAn application field using material jetting, extrusion, aerosol deposition and hybrid methods
    Cold spray additive manufacturingCommonly treated within directed-energy-deposition-related industrial frameworks, although consolidation occurs through high-velocity solid-state impact rather than melting
    Voxel printingA design and material-control concept rather than a separate fundamental process category
    4D printingPrinted objects designed to change over time under a stimulus; not a separate AM process category

    How to select the right process

    1. Define the application. Prototype, tool, implant, flight part and visual model require different evidence.
    2. Start with the material. Confirm that a qualified feedstock and post-processing route exist.
    3. Set the geometry envelope. Include build size, minimum walls, channels, overhangs and machining access.
    4. Define property requirements. Strength, fatigue, temperature, chemical resistance and aging may eliminate processes early.
    5. Map post-processing. Supports, cleaning, heat treatment, HIP, debinding, sintering and finishing can determine feasibility.
    6. Plan inspection. Complex internal features need credible measurement and defect-detection methods.
    7. Calculate accepted-part economics. Include yield, labor, furnaces, machining and quality—not only print time.
    8. Evaluate scale. Determine whether takt time and downstream capacity meet demand.
    9. Check qualification maturity. Standards, supplier capability and material data vary by process.
    10. Compare hybrid alternatives. The best solution may print only the difficult feature and use conventional processes elsewhere.

    Quick process-selection matrix

    RequirementProcesses commonly considered first
    Fine polymer detailVat photopolymerization or material jetting
    Durable support-free polymer productionPolymer powder bed fusion
    Complex dense metal partsMetal powder bed fusion
    Large metal near-net shapesDirected energy deposition
    High-density metal batch productionMetal binder jetting where sintering and economics are proven
    Low-cost desktop prototypesMaterial extrusion
    Sand molds and coresBinder jetting
    Multi-color visual modelsMaterial jetting or selected binder-jet systems
    Embedded materials or sensors in metal foilUltrasonic sheet lamination
    Repair or local feature additionDirected energy deposition

    Conclusion

    The additive manufacturing universe is easier to understand when commercial names are mapped to seven standardized process categories. Each category solves a different material-delivery and consolidation problem. Process selection should begin with application requirements and include the complete downstream route, qualification burden and cost per accepted part.

    Related Addithive resources: Introduction to Additive Manufacturing · Metal AM Process Selection · History of Additive Manufacturing

    Reference

  • Metal Additive Manufacturing Process Selection: A Practical Guide

    Metal Additive Manufacturing Process Selection: A Practical Guide

    Metal additive manufacturing process selection means choosing among laser powder bed fusion (LPBF), electron-beam PBF, powder and wire directed energy deposition (DED/WAAM), binder jetting and bound-metal extrusion. The useful question is not which process is best overall, but which production route best matches part size, geometry, alloy maturity, production volume, post-processing, inspection and qualification requirements.

    Process selection should begin with the component requirement and the complete production route — not with the machine already available.

    The first decision: what problem is AM solving?

    A strong metal AM application normally has at least one clear value driver: complex internal geometry, part consolidation, expensive material savings, low-volume tooling avoidance, rapid iteration, repair, feature addition, digital inventory or a significant performance improvement.

    If the only argument is that the part can be printed, the business case is incomplete. Conventional machining, casting, forging, sheet fabrication or a hybrid route may remain more robust and economical.

    The main metal AM process families

    ProcessBest suited toTypical strengthsPrimary constraints
    Laser powder bed fusion (PBF-LB/M or LPBF)Small-to-medium complex parts requiring fine features and strong material performanceHigh geometric detail, mature alloy routes, complex internal channelsHigh equipment and powder cost, supports, residual stress, limited build rate, extensive post-processing
    Electron-beam powder bed fusion (PBF-EB/M)Reactive alloys and production parts that benefit from elevated build temperatureLower residual stress for suitable alloys, no laser optics, effective for some titanium applicationsCoarser surface/detail, narrower supplier ecosystem, vacuum and material limitations
    Powder directed energy deposition (DED)Repair, feature addition, multi-axis deposition and medium-to-large near-net shapesLocal material addition, repair capability, multi-material potentialLower resolution, machining required, powder efficiency and shielding complexity
    Wire DED / DED-Arc / WAAMLarge metal structures and high-deposition-rate near-net shapesHigh deposition rate, low-cost wire feedstock, large scaleHigh heat input, distortion, coarse finish, substantial machining and process control
    Metal binder jettingBatch production of smaller sinter-based parts and geometries compatible with debinding/sinteringNo attached thermal supports during printing, high nesting potential, broad powder routesGreen-part fragility, shrinkage, distortion, furnace capacity and sintering qualification
    Bound-metal material extrusionPrototypes, tooling and low-volume parts where accessibility matters more than speed or propertiesLower entry barrier, simpler material handling, office/workshop workflowsDebinding and sintering, shrinkage, limited feature/property envelope, lower throughput
    Sheet lamination / ultrasonic additive routesSpecialized laminates, embedded features and selected multi-material structuresLow bulk thermal load, unique material combinationsNiche equipment, interface control, limited general-purpose adoption

    A practical selection framework

    1. Part envelope and local feature size

    Start with the complete bounding box, but do not stop there. Minimum wall, hole, channel, lattice and edge requirements may eliminate a process even when the part fits inside the machine. LPBF offers finer feature control than DED, while large wire or powder DED systems can exceed conventional powder-bed envelopes.

    2. Material and property maturity

    Ask whether the required alloy has a controlled feedstock specification, validated parameter set, heat-treatment route and relevant property data. A process may technically deposit an alloy without being suitable for a production or safety-critical program.

    The most mature route is often better than the most novel one. Qualification evidence, powder or wire availability, thermal-processing capacity and supplier experience materially change program risk.

    3. Geometry and design intent

    • Internal channels and compact complexity: favor LPBF when dimensions, powder removal and inspection are manageable.
    • Large near-net structures: favor wire or powder DED when machining can create final interfaces.
    • Repair or local feature addition: favor DED, particularly with multi-axis access and a controlled substrate.
    • High part count per batch: may favor binder jetting if the sintering route is stable.
    • Simple prismatic geometry: is often better machined, forged, cast or fabricated.

    4. Surface condition and tolerance

    As-built capability should be separated from final part capability. LPBF can produce finer surfaces and features than DED, but critical interfaces commonly require machining. WAAM and other high-deposition-rate processes are generally near-net-shape methods. Binder-jetted metal parts may achieve useful detail, yet sintering shrinkage and distortion must be included in the dimensional strategy.

    Create a surface-by-surface plan: as-built, machined, polished, coated or otherwise finished. Then evaluate whether the geometry provides access for the required operation.

    5. Production rate and batch economics

    Deposition rate alone is not production rate. Total lead time includes setup, printing, cooling, depowdering, debinding, sintering, heat treatment, cut-off, support removal, machining, cleaning, inspection and queue time.

    Binder jetting can place many parts in a build, but furnace capacity and sintering cycle time can become the bottleneck. Multi-laser LPBF can raise output, but build preparation, qualification and downstream operations still determine effective capacity. DED can deposit quickly, but heavy machining may reduce the net advantage.

    6. Material utilization

    Processes using wire typically offer high feedstock utilization. LPBF reuses a large fraction of unmelted powder, but powder conditioning, contamination control, sieving and refresh rules affect true yield. Binder jetting can pack many parts efficiently, but handling loss and sintering scrap matter. Compare the full buy-to-use ratio rather than quoting only printer waste.

    7. Post-processing and facility capability

    Process selection must include the equipment and expertise surrounding the printer. Consider:

    • Stress-relief and heat-treatment furnaces
    • Hot isostatic pressing where required
    • Depowdering and powder-safe handling
    • Debinding and sintering capacity
    • Build-plate removal and support removal
    • Five-axis machining, EDM, grinding and finishing
    • Cleaning and contamination controls
    • Dimensional metrology, material testing and NDT

    A theoretically attractive print route can fail commercially when the local post-processing chain is immature or overloaded.

    8. Qualification and change control

    For aerospace, medical, energy and defense applications, qualification may dominate the decision. Define who owns process approval, what evidence is required, how machine equivalency is handled and which changes trigger revalidation.

    The cheapest prototype route may not be the lowest-risk production route. A qualified supply chain, stable machine platform and experienced service provider can outweigh a small difference in print cost.

    Process comparison matrix

    CriterionLPBFEB-PBFPowder DEDWire DED / WAAMBinder jettingBound-metal extrusion
    Feature resolutionHighMediumLow–mediumLowMediumMedium
    Typical part scaleSmall–medium; increasingly large systems existSmall–mediumMedium–largeLarge–very largeSmall–medium batch partsSmall–medium
    Deposition/build rateLow–mediumMediumMedium–highHighHigh print throughput; sintering dependentLow
    Attached supportsOften requiredLimited/process-dependentNot conventional supports; fixturing/substrate strategy requiredNot conventional supports; fixturing/substrate strategy requiredNot during printingProcess-dependent
    Final machining needCommonCommonUsually extensiveUsually extensiveApplication-dependentCommon for precision interfaces
    Thermal distortion riskMedium–highLower for suitable preheated routes but still design-dependentHighHighPrimarily during sinteringPrimarily during sintering
    Repair capabilityLimitedLimitedStrongStrong for suitable geometryNoNo
    Qualification maturityHigh for selected alloys and industriesEstablished in selected nichesEstablished for repair and selected buildsGrowing, with aerospace standards emergingGrowing; highly route-dependentLimited for critical applications

    Application-driven recommendations

    Choose LPBF when

    • The part requires fine metal features, internal channels or compact geometric complexity.
    • Production volume is modest and part value is high.
    • A qualified alloy and post-processing route exists.
    • Support removal, powder removal and inspection are feasible.

    Choose electron-beam PBF when

    • The alloy and application benefit from a hot, vacuum-based powder-bed process.
    • Residual-stress reduction and productivity for suitable geometries outweigh surface/detail limitations.
    • The supplier ecosystem and material route are available.

    Choose powder DED when

    • The requirement is repair, cladding, feature addition or a medium-to-large near-net shape.
    • Multi-axis deposition and local material placement provide value.
    • Machining and inspection are planned from the beginning.

    Choose wire DED or WAAM when

    • The component is large and deposition rate matters more than fine resolution.
    • Wire feedstock is available and the geometry can tolerate substantial machining.
    • Heat input, distortion, interpass control and toolpath planning can be managed.

    Choose binder jetting when

    • Many parts can be nested in a batch and the geometry is compatible with depowdering and sintering.
    • The organization has powder-metallurgy or metal-injection-molding expertise.
    • Shrinkage compensation, furnace loading and dimensional control have been demonstrated.

    Choose bound-metal extrusion when

    • The objective is accessible prototyping, tooling or low-volume metal parts.
    • The required properties and tolerance can be achieved after debinding, sintering and machining.
    • Low capital complexity matters more than high throughput.

    Questions to ask a machine supplier or service bureau

    1. What exact machine–material–parameter–post-process route supports the quoted properties?
    2. Which dimensions are as-built and which assume machining?
    3. What are the demonstrated minimum walls, holes and channels for this alloy and orientation?
    4. How are powder or wire batches controlled and traced?
    5. What is the historical first-pass yield for comparable parts?
    6. Which operations are performed internally and which are subcontracted?
    7. What are the largest recurring causes of nonconformance?
    8. How are machine maintenance, calibration and parameter changes controlled?
    9. What inspection methods are validated for the critical defect modes?
    10. What capacity constraint will dominate at the target annual volume?

    Conclusion

    Metal AM process selection is a systems-engineering decision. Part size, geometry, material maturity, final tolerances, post-processing, inspection, production rate and qualification must be evaluated together. The best process is the one that delivers accepted parts reliably at the required scale — not the one with the most impressive printer specification.

    Related Addithive research: Metal AM Supply Chain Map · Aerospace AM Qualification Guide

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