Podcast
Questions and Answers
Which material is most commonly used in PBF processing?
Which material is most commonly used in PBF processing?
- Nylon Polyamide (correct)
- Titanium
- Stainless Steel
- Cemented Carbide
LPS involves the complete melting of all powder particles in the processing method.
LPS involves the complete melting of all powder particles in the processing method.
False (B)
What role does Co (cobalt) play in traditional powder metallurgy?
What role does Co (cobalt) play in traditional powder metallurgy?
It acts as a lower-melting-point constituent that glues together particles of WC.
In full melting processes, thermal energy from subsequent scans can re-melt portions of the previously __________ solid structure.
In full melting processes, thermal energy from subsequent scans can re-melt portions of the previously __________ solid structure.
Match the following properties with their corresponding concepts:
Match the following properties with their corresponding concepts:
Which factor leads to an increase in the rate constant according to the Arrhenius equation?
Which factor leads to an increase in the rate constant according to the Arrhenius equation?
The activation energy of a catalyzed reaction is higher than that of an un-catalyzed reaction.
The activation energy of a catalyzed reaction is higher than that of an un-catalyzed reaction.
What is the rate constant when the temperature is 289K, the activation energy is 200kJ/mol, and the pre-exponential factor is 9 M-1s-1?
What is the rate constant when the temperature is 289K, the activation energy is 200kJ/mol, and the pre-exponential factor is 9 M-1s-1?
In chemically-induced sintering, a by-product is formed which binds the powder together during _______ reactions.
In chemically-induced sintering, a by-product is formed which binds the powder together during _______ reactions.
What is a common characteristic of chemically-induced sintering that often necessitates additional processing?
What is a common characteristic of chemically-induced sintering that often necessitates additional processing?
Match the following reactions with their products formed during laser processing:
Match the following reactions with their products formed during laser processing:
Liquid-Phase Sintering is considered the least versatile mechanism for Powder Bed Fusion.
Liquid-Phase Sintering is considered the least versatile mechanism for Powder Bed Fusion.
The equation used to find the new temperature in the Arrhenius equation is ln(k1/k2) = -[Ea/R](1/T1 - 1/T2). Fill in the blank: Ea in this equation represents _______.
The equation used to find the new temperature in the Arrhenius equation is ln(k1/k2) = -[Ea/R](1/T1 - 1/T2). Fill in the blank: Ea in this equation represents _______.
Which mode of scanning is focused on scanning the outline of the part cross-section?
Which mode of scanning is focused on scanning the outline of the part cross-section?
In fill mode, there is a preferential direction for the residual stresses induced by scanning.
In fill mode, there is a preferential direction for the residual stresses induced by scanning.
What must any powder delivery system for PBF be capable of transporting?
What must any powder delivery system for PBF be capable of transporting?
A powder delivery system must have a powder reservoir of sufficient _____ to build to the maximum build height.
A powder delivery system must have a powder reservoir of sufficient _____ to build to the maximum build height.
Match the characteristics of powder handling with their implications:
Match the characteristics of powder handling with their implications:
Which of the following is NOT a characteristic for powder feeding systems?
Which of the following is NOT a characteristic for powder feeding systems?
Randomized scanning patterns are sometimes used to achieve a uniform layer.
Randomized scanning patterns are sometimes used to achieve a uniform layer.
What is one outcome of using smaller powder particle sizes in PBF?
What is one outcome of using smaller powder particle sizes in PBF?
Which of the following thermal sources is NOT used in Powder Bed Fusion processes?
Which of the following thermal sources is NOT used in Powder Bed Fusion processes?
Thermoset polymers can effectively be processed using Powder Bed Fusion technology.
Thermoset polymers can effectively be processed using Powder Bed Fusion technology.
What is the main purpose of using nitrogen gas in the PLS process?
What is the main purpose of using nitrogen gas in the PLS process?
The pLS process typically fuses layers of powder that are __________ thick.
The pLS process typically fuses layers of powder that are __________ thick.
Match the material types with their descriptions:
Match the material types with their descriptions:
Which material is commonly processed in PBF and is known as nylon?
Which material is commonly processed in PBF and is known as nylon?
The build platform in the PLS process is often cooled down after part formation.
The build platform in the PLS process is often cooled down after part formation.
Name one type of metal that has been processed and is commercially available through PBF.
Name one type of metal that has been processed and is commercially available through PBF.
The process of adding and smoothing powder layers in PBF is facilitated by a __________ roller.
The process of adding and smoothing powder layers in PBF is facilitated by a __________ roller.
Which of the following is NOT a characteristic of Powder Bed Fusion processes?
Which of the following is NOT a characteristic of Powder Bed Fusion processes?
What materials are commonly used in polymer laser sintering (pLS) machines?
What materials are commonly used in polymer laser sintering (pLS) machines?
Electron Beam Melting (EBM) uses laser technology to melt metal powder particles.
Electron Beam Melting (EBM) uses laser technology to melt metal powder particles.
Name one advantage of using Nd-YAG lasers in polymer laser sintering.
Name one advantage of using Nd-YAG lasers in polymer laser sintering.
The primary difference between EBM and SLM lies in their respective energy sources: EBM uses ________ while SLM utilizes ________.
The primary difference between EBM and SLM lies in their respective energy sources: EBM uses ________ while SLM utilizes ________.
Match the following terms with their correct descriptions:
Match the following terms with their correct descriptions:
What type of environment do polymer laser sintering machines work in?
What type of environment do polymer laser sintering machines work in?
Laser-based systems can directly process pure metals and ceramics.
Laser-based systems can directly process pure metals and ceramics.
What is one common use of aluminum oxide powders in machining?
What is one common use of aluminum oxide powders in machining?
What is a key requirement for EBM to function effectively?
What is a key requirement for EBM to function effectively?
A laser beam is affected by the presence of gas in the same way as an electron beam.
A laser beam is affected by the presence of gas in the same way as an electron beam.
What is one drawback of powder-based additive manufacturing compared to liquid-based processes?
What is one drawback of powder-based additive manufacturing compared to liquid-based processes?
The build materials in PBF typically exhibit _____ shrinkage, which can lead to part distortion.
The build materials in PBF typically exhibit _____ shrinkage, which can lead to part distortion.
Match the following approaches to line- and layer-wise PBF processing with their descriptions:
Match the following approaches to line- and layer-wise PBF processing with their descriptions:
Which factor contributes to better accuracy in PBF materials?
Which factor contributes to better accuracy in PBF materials?
The accuracy of powder-based additive manufacturing is influenced only by the operating conditions.
The accuracy of powder-based additive manufacturing is influenced only by the operating conditions.
What makes the future of PBF processes promising?
What makes the future of PBF processes promising?
What is one of the primary approaches to controlling material state in extrusion-based systems?
What is one of the primary approaches to controlling material state in extrusion-based systems?
Using a chemical change to cause solidification does not apply to biomedical applications.
Using a chemical change to cause solidification does not apply to biomedical applications.
Name one method of solidification that can occur in an extrusion-based system.
Name one method of solidification that can occur in an extrusion-based system.
In Fused Deposition Modeling (FDM), materials are extruded in a __________ state before solidification.
In Fused Deposition Modeling (FDM), materials are extruded in a __________ state before solidification.
Which of the following is a limitation of FDM?
Which of the following is a limitation of FDM?
Match the extrusion processes with their specific characteristics.
Match the extrusion processes with their specific characteristics.
Contouring crafting is primarily used for small-scale applications.
Contouring crafting is primarily used for small-scale applications.
What is a significant requirement for materials used in bioextrusion?
What is a significant requirement for materials used in bioextrusion?
Flashcards
Powder Bed Fusion (PBF)
Powder Bed Fusion (PBF)
A 3D printing process where powdered material is fused layer by layer using a thermal source, like a laser or electron beam.
Key PBF Characteristics
Key PBF Characteristics
PBF processes share common features: thermal sources for fusion, controlled fusion region per layer, powder layer addition and smoothing mechanisms.
Laser Sintering (LS)
Laser Sintering (LS)
A PBF technique where a laser is used to fuse powder layers, originally developed for plastic prototypes.
pLS (Polymer Laser Sintering)
pLS (Polymer Laser Sintering)
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pLS Process Overview
pLS Process Overview
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pLS Process Environment
pLS Process Environment
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pLS Process Temperature Control
pLS Process Temperature Control
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pLS Materials
pLS Materials
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Metals and Composites in PBF
Metals and Composites in PBF
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Ceramics in PBF
Ceramics in PBF
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Arrhenius Equation
Arrhenius Equation
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Activation Energy
Activation Energy
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Rate Constant
Rate Constant
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Temperature Impact on Rate Constant
Temperature Impact on Rate Constant
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Chemically-induced Sintering
Chemically-induced Sintering
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Liquid-Phase Sintering (LPS)
Liquid-Phase Sintering (LPS)
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Post-process Infiltration
Post-process Infiltration
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Catalyzed vs. Uncatalyzed Reactions
Catalyzed vs. Uncatalyzed Reactions
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LPS in Powder Metallurgy
LPS in Powder Metallurgy
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LPS in Additive Manufacturing (AM)
LPS in Additive Manufacturing (AM)
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Full Melting in PBF
Full Melting in PBF
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Materials Used in Full Melting PBF
Materials Used in Full Melting PBF
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Contour Mode Scanning
Contour Mode Scanning
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Fill Mode Scanning
Fill Mode Scanning
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Balling Tendency
Balling Tendency
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Powder Delivery Systems in PBF
Powder Delivery Systems in PBF
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Key Challenges with Powder Delivery
Key Challenges with Powder Delivery
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Powder Particle Size and PBF
Powder Particle Size and PBF
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Interparticle Friction
Interparticle Friction
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Surface Energy of Powder
Surface Energy of Powder
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What is pLS?
What is pLS?
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Why can't pLS directly process metals?
Why can't pLS directly process metals?
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What are the most popular materials in pLS?
What are the most popular materials in pLS?
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How does EBM work?
How does EBM work?
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What's the key difference between EBM and SLM?
What's the key difference between EBM and SLM?
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What are the benefits of EBM?
What are the benefits of EBM?
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How are the electron beams used in EBM different from laser beams?
How are the electron beams used in EBM different from laser beams?
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What are the advantages of EBM over pLS for metal parts?
What are the advantages of EBM over pLS for metal parts?
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Electron Beam Melting (EBM)
Electron Beam Melting (EBM)
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PBF Vacuum Environment
PBF Vacuum Environment
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PBF Material Dependence
PBF Material Dependence
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Mask-Based Sintering
Mask-Based Sintering
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PBF Drawbacks
PBF Drawbacks
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PBF Accuracy Factors
PBF Accuracy Factors
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PBF Future
PBF Future
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Extrusion-based Systems
Extrusion-based Systems
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Material Loading
Material Loading
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Liquification
Liquification
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Bonding in Extrusion
Bonding in Extrusion
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Fused Deposition Modeling (FDM)
Fused Deposition Modeling (FDM)
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Melt Extrusion
Melt Extrusion
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Contour Crafting
Contour Crafting
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Bioextrusion
Bioextrusion
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Study Notes
Chapter 6: Extrusion-Based Systems
- Extrusion-based systems are a type of additive manufacturing (AM) technique.
- Extrusion-based systems use temperature or chemical changes to control the material state, producing material by forcing a liquefied material through a nozzle.
- Some methods rely on a continuous supply of material, while others use pellets or powders.
Objectives
- Discuss extrusion-based systems
- Describe basic principles (material loading, liquefaction, extrusion, solidification, bonding, and support generation).
- Analyze plotting and path control.
- Explain Fused Deposition Modeling (FDM) from Stratasys, including machine types.
- Identify materials used in extrusion.
- Discuss the limitations of FDM.
- Describe bioextrusion techniques (gel formation, melt extrusion, scaffold architectures).
- Explore other extrusion-based systems (contour crafting, nonplanar systems, FDM of ceramics, Reprap).
Materials
- Materials suitable for extrusion-based AM are varied, including polymers (thermoplastics and some thermosets), metals, and ceramics.
- Biocompatible materials are well-suited to medical applications in extrusion.
- Specific material properties (viscosity, melting point, thermal stability) influence the selection of appropriate processes and equipment for extrusion.
Basic Principles
- Material loading: Materials can be loaded using methods such as pellet feeding, powder feeding, or continuous filament input.
- Liquefaction: Temperature or chemical reactions are used to liquefy the material to make possible bonding and printing.
- Extrusion: The liquefied material is forced through a nozzle under pressure.
- Solidification: Depending on the material, solidification can be due to cooling, curing, reacting with air, or drying.
- Bonding: During extrusion, bonding between the deposited material and the preceding layers determines the overall strength and structural integrity.
- Support generation: This involves creating supportive structures within the 3D print to maintain part integrity, which are fabricated or designed to be removed later.
- Plotting and path control: This involves defining the deposition path and shape of the final part, which can have an impact on the structural strength of the material.
Fused Deposition Modeling (FDM)
- FDM is a widely used extrusion-based technique, commonly used in polymer 3D printing processes.
- FDM machines use a heating chamber to liquefy the filament.
- A variety of FDM machines from Stratasys and other manufacturers are available and vary in build volume and other features. Some are aimed at the general engineering market and some at niche applications.
Extrusion Principles
- Some extrusion methods employ the extrusion of a heated, molten material, whereas others use a solidified or gel structure.
- Extruders are equipped with a nozzle to direct the flow of extruded material.
- Pressure is exerted by a screw or other mechanisms to move the material through the nozzle.
Limitations of FDM
- Depending on the size and shape of the part, some distortion, shrinkage, and other manufacturing defects can occur.
- Build speed can impact accuracy in some cases.
Scaffold Architectures
- Proper spacing between extruded structures is important for tissue engineering scaffolds to allow cell growth.
- Porosity or the proportion of space between scaffold struts is critical for the amount of material transport possible and the success of biological implantation.
- Specific geometric patterns can be used to create scaffolds with different structures that may create different amounts and spaces, and thereby may help with the process of cell or tissue growth.
Other Extrusion-based Systems
- Contour crafting: Technology is related to the contour or shape being sculpted.
- Other systems use particular technologies or principles, including particular machines, like the Reprap and Fab@home projects.These systems use simple, low-cost 3D printing technology concepts.
- FDM of Ceramics: This technique is used to fire and fuse similar to the FDM process.
- Nonplanar systems: This design permits building materials at odd angles.
Process Benefits and Drawbacks
- Extrusion-based methods are versatile.
- Wide range of polymer or other material choices and application possibilities.
- Relatively low cost for entry level systems.
- Some drawbacks could include: less precise details in the design (though it depends on the complexity).
- Design and accuracy (including support removal) and processing times can vary significantly across these systems.
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Description
Test your knowledge on powder metallurgy, focusing on PBF processing, the role of cobalt, and key concepts in chemically-induced sintering. Additionally, explore factors that influence reaction rates and the Arrhenius equation. This quiz covers essential topics that are fundamental to understanding the field of materials science.
