36 Questions
What was the first commercialized PBF process developed at the University of Texas at Austin?
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 using a point-wise laser scanning technique
Which PBF processes utilize significantly different machine architectures than laser sintering machines?
Non-laser thermal sources
What is one negative effect of loose powder sintering in a build platform?
Agglomeration of powder particles, leading to increased average particle size upon recycling
What is one positive effect of loose powder sintering in a build platform?
The powder bed gains a degree of tensile and compressive strength, minimizing part curling
What causes a region of the powder bed to become much hotter than the surrounding loose powder during part formation in a build platform?
Thermally induced fusing of the desired cross-sectional geometry
Which type of material is 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 in the investment casting pattern
Which type of polymers are resistant to degradation at elevated temperatures and chemicals like gasoline and automotive coolants?
Elastomeric thermoplastic polymers
Which commercially available polymers for 3D printing are flame-retardant?
Polyamide and polyaryletherketone (PAEK or PEEK)
Which polymers processed using pLS include biocompatible and biodegradable options?
Polycaprolactone (PCL), polylactide (PLA), and poly-Llactide (PLLA)
What type of materials have been investigated for bone replacement tissue scaffolds?
PCL and ceramic particles composite materials
What type of fillers can enhance the mechanical properties of polymers in PBF?
Ceramic fillers
What metals can be processed using PBF?
Titanium alloy
Which materials are widely available for PBF production?
Titanium alloys, steel alloys, nickel-based super alloys, and CoCrMo
What are some examples of ceramics mentioned in the text?
Metal oxides, carbides, and nitrides
Which company developed commercial machines for ceramics?
Phenix Systems in France (acquired by 3D Systems)
What are some biocompatible materials processed using PBF for medical applications?
Calcium hydroxyapatite
How many fusion mechanisms are present in PBF processes?
Four: solid-state sintering, chemically induced binding, liquid-phase sintering, and full melting
What drives solid-state sintering?
Minimization of total free energy of powder particles
What is the primary fusion mechanism used in most AM processes?
Full melting
Which technology has made some alloys obsolete in favor of engineering-grade alloys?
mLS and EBM technology
What differs in crystal structures and mechanical properties due to high solidification rates in mLS?
Crystal structures and mechanical properties differ
Which type of alloys are not suitable for mLS due to cracking under high solidification rates?
Alloys that crack under high solidification rates are not suitable for mLS.
What is the primary purpose of using an enclosed chamber filled with nitrogen gas in Powder Bed Fusion processes?
To minimize oxidation and degradation of the powdered material
What thermal source is commonly used in Powder Bed Fusion processes to maintain an elevated temperature around the part being formed?
Infrared heaters
What is the purpose of using a counter-rotating powder leveling roller in Powder Bed Fusion processes?
To evenly distribute and level the thin layers of powder
Which material is commonly used in Powder Bed Fusion processes due to its distinct melting points enabling reliable processing?
Polyamide (nylon)
What is required after each layer is completed in a Powder Bed Fusion process?
$\text{Build platform} \text{ lowering by one layer thickness and laying a new layer of powder}$
What 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
What is used to thermally fuse the material to form the slice cross-section in Powder Bed Fusion processes?
Focused CO2 laser beam
What is required to minimize oxidation and degradation of powdered material during Powder Bed Fusion processes?
An enclosed chamber filled with nitrogen gas
What type of heating source is used above the feed cartridges to preheat the powder in Powder Bed Fusion processes?
Infrared heaters
What process involves thin layers of powder being fused using a counter-rotating powder leveling roller?
Powder Bed Fusion processes
What is used to lower the build platform by one layer thickness after each layer is completed in Powder Bed Fusion processes?
Screw mechanism
Study Notes
Powder Bed Fusion Processes in Additive Manufacturing
- Powder Bed Fusion (PBF) processes have been extended to metal and ceramic powders, with various thermal sources being utilized.
- PBF processes are widely used globally and can be used with a broad range of materials, including polymers, metals, ceramics, and composites.
- The process is increasingly used for the direct manufacturing of end-use products due to comparable material properties to engineering-grade polymers, metals, and ceramics.
- Powder Bed Fusion processes involve thin layers of powder being fused using a counter-rotating powder leveling roller.
- The part building process takes place in an enclosed chamber filled with nitrogen gas to minimize oxidation and degradation of the powdered material.
- Infrared heaters are used to maintain an elevated temperature around the part being formed and above the feed cartridges to preheat the powder.
- A focused CO2 laser beam is directed onto the powder bed to thermally fuse the material to form the slice cross-section.
- After each layer is completed, the build platform is lowered by one layer thickness and a new layer of powder is laid and leveled using the roller.
- A cool-down period is required to allow the parts to come to a low enough temperature that they can be handled and exposed to the ambient atmosphere.
- PBF processes can be used with all materials that can be melted and resolidified.
- Thermoplastic materials are well-suited for powder bed processing due to their low melting temperatures, low thermal conductivities, and low tendency for balling.
- The most common material used in PBF is polyamide, a thermoplastic polymer, commonly known as nylon, which has distinct melting points enabling reliable processing.
Test your knowledge on the mechanical properties of pLS parts and their use in investment casting. Learn about how polyamide powders and polystyrene-based materials are used in manufacturing processes.
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