Fundamentals of Additive

Manufacturing

Lesson 1:

Powder Bed Fusion & Directed Energy Deposition

Finished Parts from Metals

• Both Powder Bed Fusion (PBF) & Directed

Energy Deposition (DED) are used to

produce finished parts from metal.

• PBF is most often used to build new parts.

• DED can also repair worn parts or add

features to new parts.

Terminology

• ASTM identifies these process classes as

PBF and DED

– Alternate names for PBF:

• Direct metal laser sintering (DMLS)

• Selective laser melting (SLM)

– Alternate DED terms:

• Laser engineered net shaping (LENSTM)

• Laser cladding (part repair or feature addition)

Heat Sources

• Laser

– Most widely used heat source for both PBF

& DED

– Requires inert gas shielding

• Flooding of work chamber or nozzle-directed to

work zone

• Electron Beam

– Requires a vacuum chamber to sustain

beam

PBF Pre-Processing

• Import & prepare solid model

– Check file continuity

– Orient part to build direction

– Add supporting structures if needed

• Prepare machine

– Load with correct powder

– Verify dimensional accuracy of X,Y,Z axes

– Check build chamber for leaks

PBF Process

1. Powder coater deposits thin layer of metal powder.

2. Laser selectively melts desired area, forming new part layer.

3. Work table moves down.4. Steps 1 & 2 repeat.

Powder coater

Loose powder

Work table

(Click to start)

PBF Post-Processing

• Powder removal & part cleaning

• Removal of any support structures

• Heat treatment or hot isostatic pressing, if

needed

• Non-destructive testing, if required

PBF Applications

• Parts with complex geometries, thin walls,

voids, channels

Source: 3dvisdesign.com

Source: Andrew Coyne

PBF/DED Comparison

Source: Roland Berger Strategy Consultants

November, 2013

DED Process

Source: Roland Berger Strategy Consultants

November, 2013

1. Laser forms melt pool on substrate.

2. Powder deposited in melt pool.

3. Powder melts, forming fusion bond with substrate.

DED Post-Processing

• Machining required to achieve final

tolerance

• Removal of any support structures

• Heat treatment or hot isostatic pressing, if

needed

• Non-destructive testing, if required

DED Applications

• Parts with complex geometries, thin walls,

voids, channels

• Part repair or adding features to parts

produced by other processes

• Large parts possible

– Not limited by

chamber size

Source: Sandia National Labs

PBF/DED Comparison

Source: Roland Berger Strategy Consultants

November, 2013

Compared to Traditional Processes

• PBF/DED vs. casting, machining, forming,

welding:

– PBF/DED Strengths

• Can produce complex geometries

– thin walls, voids, channels

– new shapes not currently producible

• Added complexity does not add cost

• May consolidate assemblies into single part

• Tooling cost reduction

– Support structures added during build process

Compared to Traditional Processes

• PBF/DED vs. casting, machining, forming,

welding:

– PBF/DED Challenges

• Slow build rates

• High cost

• Complex design and process parameters

• Post-processing required for close tolerances

Resources

Northern Illinois University (NIU)

Additive Manufacturing Lab

Federico Sciammarella, Director

sciammarella@niu.edu

Northwestern University

Mechanical Engineering Department

McCormick School of EngineeringJian Cao

jcao@northwestern.edu

National Institute of Standards and Technology (NIST)

Engineering Laboratory

Kevin Jurrens, Deputy Division Chief

kevin.jurrens@nist.gov

This work was performed under the following financial assistance award 70NANB13H194 from the U.S. Department of Commerce, National Institute of Standards and Technology. The views expressed do not necessarily reflect the official policies of NIST; nor does mention by

trade names, commercial practices, or organizations imply endorsement of the U.S. Government.