# Laser powder bed fusion

Metal laser powder bed fusion: qualified powder and build conditions, supports, thermal effects, postprocessing, and finished-part acceptance.

Reviewed: 2026-11-01

Tags: processes, shaping, additive-manufacturing, metals

EOS lists **5.5 mm³/s (19.8 cm³/h)** for skin exposure with **MaragingSteel MS1** on an **EOS M400**, EOSPRINT v1.2 and **MS1_050_FlexM400_1.0** at **50 µm**. The worked estimate combines **20 cm³** of exposure with **1,200 layers** and an assumed **8 seconds per layer** of separate recoating to get **3.6768 h**. Add other exposure categories, thermal waits and postprocessing separately. [EOS MS1 FlexLine, June 2022, CR325](https://uk.eos.info/03_system-related-assets/material-related-contents/metal-materials-and-examples/metal-material-datasheet/werkzeugstahl_ms1_cx/ms1/ms-ms1-m400_material_data_sheet_06-22_en.pdf)

Metal LPBF (PBF-LB/M) selectively melts recoated powder under a controlled atmosphere. Define powder removal, thermal treatment, separation, machining and inspection for the delivered condition. [Renishaw, Our technology, undated](https://www.renishaw.com/en/our-technology--27362)

## Distinguish adjacent processes

| Process | Defining distinction |
| --- | --- |
| Metal laser powder bed fusion | Laser exposure selectively melts material within a prepared powder layer. |
| Electron-beam powder bed fusion, PBF-EB | An electron beam melts the powder bed in a vacuum; beam and thermal conditions differ from laser equipment. |
| Directed energy deposition, DED | Feedstock is delivered to the deposition region while an energy source melts it, rather than selectively exposing a previously spread bed. |

Fraunhofer IPK describes electron-beam bed processing under vacuum with powder preheating. NIST's DED description, updated **May 16, 2025**, describes nozzle delivery and melting onto a target. Neither process should inherit LPBF's powder, support, parameter, or acceptance assumptions solely because it also produces metal additively. [Fraunhofer IPK, SEBM, undated](https://www.ipk.fraunhofer.de/en/expertise-and-technologies/production-processes-and-facilities/what-is-additive-manufacturing/what-is-selective-electron-beam-melting-sebm.html), [NIST, Directed Energy Deposition](https://www.nist.gov/additive-manufacturing/research-areas/technologies/directed-energy-deposition)

## Qualify powder and atmosphere together

Specify the powder product and lot, chemistry, particle-size distribution, permitted contamination, handling conditions, and reuse history. Flow and packing behavior affect layer consistency; a nominal alloy designation alone does not establish equivalence between feedstocks. Renishaw identifies particle shape, flow, and close packing as important, and lists a 15–45 µm range for the systems described on its powder page. That is a manufacturer-specific range, not a definition of all LPBF powders. [Renishaw, Metal powders for AM, undated](https://www.renishaw.com/en/metal-powders-for-am--31457)

Unused powder is not automatically qualified for unlimited reuse. Establish collection, sieving, segregation, blending, sampling, and rejection rules for the actual alloy/process. EOS describes sieving and reuse of residual metal powder, while distinguishing it from polymer refresh practices; its examples do not justify transferring a polymer virgin/used blend ratio to metal. [EOS, 3D Printing Recycling: Reuse vs Recycling Explained, 2026 article](https://www.eos.info/content/blog/2026/3d-printing-recycling)

Shielding limits unwanted reactions during melting. Renishaw's atmosphere page describes vacuum evacuation followed by argon filling and oxygen control for its equipment, including the AM250. These are descriptions of that system, not universal oxygen thresholds, gas-flow settings, or authorization to substitute nitrogen for argon in another material. Record the qualified gas, purity, oxygen-monitor response, circulation/filter condition, and allowed excursions. [Renishaw, Inert atmosphere generation, undated](https://www.renishaw.com/en/inert-atmosphere-generation--31885)

## Design for heat flow, access, and orientation

Orientation changes supported area, down-facing surface quality, layer count, and access for subsequent machining. Supports also conduct heat and restrain material; loose surrounding powder does not provide the same thermal path as solid metal. Renishaw's **©2017** *Design for metal AM – a beginner's guide* discusses these functions and the tradeoff between orientation, residual stress, finish, and build economics. Its geometric examples are guidance, not a universal unsupported-overhang angle for every alloy and parameter set. [Renishaw design guide](https://www.renishaw.com/resourcecentre/download/feature-article-design-for-metal-am-a-beginners-guide--111752?userLanguage=de)

Before release to build, resolve whether internal channels can be depowdered, whether supports are reachable, and whether critical surfaces can be finished and inspected. Preserve datum features and machining stock through the planned separation and thermal sequence. A hollow CAD model is not proof of an open, clean, dimensionally correct passage.

The same Renishaw guide discusses redesigning lateral holes or machining them afterward, and adding machining stock where appropriate. Evaluate the complete production route instead of optimizing only the printed shape. [Renishaw design guide, lateral holes and optimization](https://www.renishaw.com/resourcecentre/download/feature-article-design-for-metal-am-a-beginners-guide--111752?userLanguage=de)

## Control the process without assuming density proves performance

Laser power, scan speed, hatch spacing, layer thickness, scan strategy, powder spreading, and local thermal history interact. A parameter set must be associated with its machine configuration, material, software, and build conditions; matching one energy-density number does not demonstrate that two routes produce equivalent parts.

ASTM E3353-22, listed active with a **September 16, 2022** update, distinguishes lack-of-fusion, keyhole-related porosity, gas pores, and cracking. It explains that optical/thermal monitoring observes process signatures whose relationship to flaws and properties requires correlation. A normal monitoring trace is therefore not, by itself, a finished-part acceptance test. [ASTM E3353-22, monitoring and flaw interpretation](https://store.astm.org/e3353-22.html)

ISO/ASTM 52948:2026, **edition 1, January 2026**, classifies imperfections in metal laser- and electron-beam powder bed fusion and identifies probable causes. Its public scope is a classification framework, not a universal acceptable pore size or fatigue guarantee. [ISO/ASTM 52948 official scope](https://www.iso.org/standard/84919.html)

## Bounded material and time example

EOS's **June 2022, CR325** MS1 FlexLine sheet applies to **EOS M400, EOSPRINT v1.2, parameter set MS1_050_FlexM400_1.0**, using the identified MaragingSteel MS1 powder. It lists a **50 µm** layer thickness and **5.5 mm³/s, or 19.8 cm³/h**, volume rate. Its footnote restricts that rate to skin-area laser exposure and states that contours, supports, down/upskin, recoating, and machine settings affect total speed. [EOS MS1 material sheet, pages 1–3](https://uk.eos.info/03_system-related-assets/material-related-contents/metal-materials-and-examples/metal-material-datasheet/werkzeugstahl_ms1_cx/ms1/ms-ms1-m400_material_data_sheet_06-22_en.pdf)

For an **original hypothetical estimate**, assume 20 cm³ is exposed at that rate, a 60 mm build height at 0.050 mm/layer, and 8 seconds of non-overlapping recoating overhead per layer:

- Exposure contribution: 20 / 19.8 = **1.0101 h**.
- Layers: 60 / 0.050 = **1,200**.
- Assumed recoating contribution: 1,200 × 8 / 3,600 = **2.6667 h**.
- Subtotal: **3.6768 h**, approximately **3 h 41 min**.

This excludes other exposure categories, preparation, thermal waits, and postprocessing. The assumed eight seconds is not EOS performance data. The exercise shows why dividing part volume by a headline rate understates a complete manufacturing cycle.

## Postprocess and accept the finished part

Define the sequence for depowdering, stress relief or other alloy-specific heat treatment, removal from the plate, support removal, machining, surface finishing, cleaning, and inspection. Resolve when restraints are removed and which dimensions require reinspection afterward. Do not assume heat treatment, hot isostatic pressing, and surface finishing perform interchangeable functions.

The MS1 sheet separately reports as-built and heat-treated properties and cautions that its informational part data do not guarantee the user's achieved properties or establish a sufficient design basis. Its values apply to the stated system and test conditions, not all printed maraging steels. [EOS MS1 material sheet, pages 4–5](https://uk.eos.info/03_system-related-assets/material-related-contents/metal-materials-and-examples/metal-material-datasheet/werkzeugstahl_ms1_cx/ms1/ms-ms1-m400_material_data_sheet_06-22_en.pdf)

Agree on dimensional and surface criteria, material condition, internal-feature cleanliness, relevant mechanical tests, and inspection coverage and detection limits. Record specimen orientation, location, and processing history when coupons are used; a coupon is evidence for its represented conditions, not direct inspection of every internal feature.

As a bounded qualification example, NASA's **MSFC-SPEC-3717 baseline, October 18, 2017**, addresses LPBF metallurgical process definition/qualification, equipment and facility control, and personnel training within its stated MSFC framework. It illustrates that qualification covers an organized process, not merely a machine brand; it is not an automatic requirement for every commercial LPBF order. [NASA official standard record](https://standards.nasa.gov/standard/MSFC/MSFC-SPEC-3717)

## Related reference

[Manufacturing processes](../index.md)