31 Questions
What was the first commercialized PBF process developed at the University of Texas at Austin, USA?
Selective laser sintering (SLS)
What are the most common thermal sources for PBF processes?
Lasers
What were LS processes originally developed to produce?
Plastic prototypes
What do all PBF processes share in terms of characteristics?
One or more thermal sources for inducing fusion between powder particles
What is one negative effect of loose powder sintering?
Agglomeration of powder particles increases average particle size
What positive effect does loose powder sintering have on the powder bed?
Increases tensile and compressive strength
What causes a region of the powder bed to become much hotter than the surrounding loose powder during part formation?
Thermally induced fusing of the desired cross-sectional geometry
What is the primary function of the counter-rotating powder leveling roller in Powder Bed Fusion processes?
To fuse thin layers of powder
Why is an enclosed chamber filled with nitrogen gas used in Powder Bed Fusion processes?
To minimize oxidation and degradation of the powdered material
What thermal source is directed onto the powder bed to thermally fuse the material in Powder Bed Fusion processes?
Focused CO2 laser beam
Why is a cool-down period required after completing each layer in Powder Bed Fusion processes?
To allow the parts to come to a low enough temperature that they can be handled and exposed to the ambient atmosphere
Which type of materials are well-suited for powder bed processing due to their low melting temperatures, low thermal conductivities, and low tendency for balling?
Thermoplastic materials
Which type of materials are suitable for making sacrificial patterns for investment casting using pLS?
Polystyrene-based materials with low residual ash content
What aids in melting out the investment casting pattern after creating the ceramic shell?
Porosity
Which type of polymers are resistant to degradation at elevated temperatures and chemicals like gasoline and automotive coolants?
Elastomeric thermoplastic polymers with rubber-like characteristics
Which commercially available polymers for 3D printing are flame-retardant?
Polyamide and polyaryletherketone (PAEK or PEEK)
Which composite materials have been investigated for bone replacement tissue scaffolds?
PCL and ceramic particles
What type of fillers can polymers in PBF have to enhance their mechanical properties?
Glass bead filled polyamide materials
Which metals can be processed using PBF?
Stainless steels, titanium, nickel-base alloys, aluminum alloys, cobalt-chrome
What was RapidSteel developed by DTM Corp composed of?
Thermoplastic binder coated 1080 carbon steel powder with copper as the infiltrant
What did LaserForm ST-100 allow for due to its broader particle size range?
Lower temperature sintering and infiltration in a single furnace run
What proprietary powders did EOS market for direct tooling applications and parts requiring high thermal and electrical conductivities?
Nickel-based powders and Cu-based powders
Which alloys are widely available for PBF production?
Titanium alloys, steel alloys, nickel-based super alloys, and CoCrMo
What are the fusion mechanisms present in PBF processes?
Solid-state sintering, chemically induced binding, liquid-phase sintering, and full melting
What did Phenix Systems develop commercial machines for?
Ceramics
What is the primary fusion mechanism in most AM processes?
Sintering
Which materials have been processed using PBF for medical applications?
Biocompatible materials like calcium hydroxyapatite
What did advancements in mLS and EBM processes lead to?
The development of new alloys tailored for PBF production
What are ceramics composed of?
Metal oxides, carbides, and nitrides
Why are some alloys obsolete in favor of engineering-grade alloys?
Due to advancements in mLS and EBM technology
What happens to crystal structures and mechanical properties in mLS?
They differ due to high solidification rates
Study Notes
Powder Bed Fusion Processes Overview
- mLS and EBM technology have made some alloys obsolete in favor of engineering-grade alloys.
- Titanium alloys, steel alloys, nickel-based super alloys, and CoCrMo are widely available for PBF production.
- Alloys that crack under high solidification rates are not suitable for mLS.
- Crystal structures and mechanical properties differ in mLS due to high solidification rates.
- Advancements in mLS and EBM processes will lead to the development of new alloys tailored for PBF production.
- Ceramics consist of metal oxides, carbides, and nitrides, and are available commercially.
- Phenix Systems in France, acquired by 3D Systems, developed commercial machines for ceramics.
- Ceramics and metal-ceramic composites have been demonstrated in research.
- Biocompatible materials like calcium hydroxyapatite have been processed using PBF for medical applications.
- Four fusion mechanisms are present in PBF processes: solid-state sintering, chemically induced binding, liquid-phase sintering, and full melting.
- Solid-state sintering occurs at elevated temperatures without melting, driven by the minimization of total free energy of powder particles.
- Sintering is important in most thermal powder processes, but few AM processes use sintering as a primary fusion mechanism.
Test your knowledge about the mechanical properties and applications of pLS parts produced using polyamide powders and polystyrene-based materials. Explore the unique microstructures and characteristics of these materials.
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