Additive Manufacturing: Powder Bed Fusion Quiz
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Questions and Answers

Which of the following materials is commonly used in PBF processing for producing high density structures?

  • Wood
  • Nylon Polyamide (correct)
  • Aluminum
  • Glass

    • LPS involves the complete melting of all powder constituents during processing.

    False

    What role does Co (cobalt) play in LPS used for forming cemented carbide cutting tools?

    It acts as a lower-melting-point constituent to glue together WC particles.

    In PBF processing, the thermal energy is generally sufficient to _____ a portion of the previously solidified solid-structure.

    <p>re-melt</p> Signup and view all the answers

    Match the materials with their corresponding types used in powder processing:

    <p>Ti = Engineering alloy Co Cr = Engineering alloy Nylon Polyamide = Semi-crystalline polymer WC = Cutting tool material</p> Signup and view all the answers

    Which binding mechanism involves fully melting metallic powder?

    <p>Full melting</p> Signup and view all the answers

    Indirect processing uses solely metallic powder for part construction.

    <p>False</p> Signup and view all the answers

    Name one process utilized for creating ceramic parts.

    <p>Direct sintering</p> Signup and view all the answers

    The required laser power typically increases with the melting point of the material and lower powder bed temperature, influenced by the material's __________ characteristics.

    <p>absorptivity</p> Signup and view all the answers

    Match each process with its description:

    <p>Full melting = A process that uses high-power lasers or electron beams to melt powder. Liquid-phase sintering = A method utilizing a mixture of metal powders with different melting points. Direct sintering = A method for fabricating solid ceramic parts. Indirect processing = Uses polymer-coated metallic powders for part construction.</p> Signup and view all the answers

    Which parameter influences both the required laser power and the powder bed temperature?

    <p>Material type</p> Signup and view all the answers

    Scan related parameters include laser power and pulse duration.

    <p>False</p> Signup and view all the answers

    How many galvanometers are typically included in a PBF machine?

    <p>Two</p> Signup and view all the answers

    Which mode involves scanning the outline of the part cross-section for accuracy and surface finish reasons?

    <p>Contour mode</p> Signup and view all the answers

    In fill mode, the entire cross-section is scanned with a specific direction for residual stresses.

    <p>False</p> Signup and view all the answers

    What are two challenges in powder handling for PBF?

    <p>Transporting the correct volume of powder and creating a smooth layer of powder.</p> Signup and view all the answers

    The lack of a single solution for powder delivery includes the use of the __________ roller in PBF.

    <p>counter-rotating</p> Signup and view all the answers

    Match the characteristics of powder feeding systems with their descriptions:

    <p>Decreased particle size = Increases interparticle friction and electrostatic forces Higher surface area to volume ratio = Increases surface energy and reactivity Small particles = Tend to become airborne and float as a cloud Thinner layers = Enable better surface finish and higher accuracy</p> Signup and view all the answers

    What is one of the universal characteristics of powder feeding?

    <p>Smaller particles have a tendency to become airborne</p> Signup and view all the answers

    Powder delivery systems must create excessive shear forces to ensure previously processed layers are not disturbed.

    <p>False</p> Signup and view all the answers

    Name one type of scan pattern used in the applied energy calculations.

    <p>Balling tendency tracks</p> Signup and view all the answers

    Which type of laser is primarily used in the Polymer Laser Sintering (pLS) process?

    <p>CO2 laser</p> Signup and view all the answers

    Thermoset polymers are typically processed using Powder Bed Fusion (PBF).

    <p>False</p> Signup and view all the answers

    What is the typical thickness of the powder layers in the pLS process?

    <p>0.075 - 0.1 mm</p> Signup and view all the answers

    The Powder Bed Fusion process uses _____ to induce fusion between powder particles.

    <p>thermal sources</p> Signup and view all the answers

    Match the following materials with their properties:

    <p>Polymers = Thermoplastic and thermoset Metals = Stainless steels and titanium alloys Ceramics = Compounds of metal oxides and nitrides Composites = Combination of materials to enhance properties</p> Signup and view all the answers

    Which of the following materials is NOT commonly processed using Powder Bed Fusion?

    <p>Thermoset polymers</p> Signup and view all the answers

    In the pLS process, the part building occurs in an environment filled with oxygen.

    <p>False</p> Signup and view all the answers

    What happens to the build platform after completing a layer in the pLS process?

    <p>It is lowered by one layer thickness.</p> Signup and view all the answers

    The SLS process originally developed for producing _____ prototypes.

    <p>plastic</p> Signup and view all the answers

    Which characteristic is common among all Powder Bed Fusion processes?

    <p>A method for controlling powder fusion</p> Signup and view all the answers

    What is true about the interaction between an electron beam and gas?

    <p>Electrons are deflected when passing through the gas.</p> Signup and view all the answers

    Laser beams are unaffected when passing through transparent gases at their wavelength.

    <p>True</p> Signup and view all the answers

    What type of environment is EBM typically practiced in?

    <p>low-partial-pressure vacuum environment</p> Signup and view all the answers

    During part building in polymer PBF, loose powder acts as a sufficient support material, saving ___ during part building and post-processing.

    <p>time</p> Signup and view all the answers

    Match the following PBF process benefits and drawbacks:

    <p>Wide variety of materials = Benefit Inferior accuracy and surface finish = Drawback Finer particle sizes = Benefit Long total construction time = Drawback</p> Signup and view all the answers

    What is a common outcome of using larger powder particle sizes in PBF?

    <p>Easier powder processing and delivery.</p> Signup and view all the answers

    The future of PBF technology does not look promising for additive manufacturing.

    <p>False</p> Signup and view all the answers

    The presence of beam traces in the final microstructure is dependent on process parameters and ___ material.

    <p>material</p> Signup and view all the answers

    Which material is the most popular for Polymer Laser Sintering (pLS)?

    <p>Nylon polyamide</p> Signup and view all the answers

    Electron Beam Melting (EBM) uses lasers to fuse metal powder particles.

    <p>False</p> Signup and view all the answers

    What is one of the limitations of Polymer Laser Sintering (pLS) machines?

    <p>Incapable of directly processing pure metals or ceramics</p> Signup and view all the answers

    The machines designed for Polymer Laser Sintering (pLS) are commonly called ___ or ___.

    <p>Selective Laser Sintering, Laser Sintering</p> Signup and view all the answers

    Match the following PBF processes with their primary characteristics:

    <p>Polymer Laser Sintering = Uses CO2 lasers to process polymers Electron Beam Melting = Uses high-energy electron beams for fusion Selective Laser Sintering = A method of direct polymer processing Additive Manufacturing = Builds objects layer by layer</p> Signup and view all the answers

    What differentiates Electron Beam Melting (EBM) from laser-based systems?

    <p>EBM employs high-energy electron beams</p> Signup and view all the answers

    3D Systems' low-temperature machines can only process nylon materials in Polymer Laser Sintering (pLS).

    <p>False</p> Signup and view all the answers

    In Electron Beam Melting, the electron beams move at a speed close to the ___ of light.

    <p>speed</p> Signup and view all the answers

    Study Notes

    Chapter 5: Powder Bed Fusion Processes

    • Powder bed fusion (PBF) is a 3D printing process
    • Focuses on the fusion of powder particles
    • SLS is a type of PBF
    • First commercialized PBF process: Selective Laser Sintering (SLS)
    • Developed at the University of Texas at Austin
    • Other PBF processes use different techniques to enhance machine productivity or avoid specific patented features
    • All PBF processes share basic characteristics:
      • One or more thermal sources to fuse powder particles
      • A method to control powder fusion to a specific layer
      • Mechanisms to add and smooth powder layers

    Objectives

    • Discuss powder bed fusion processes
    • Describe the Selective Laser Sintering (SLS) process
    • Examine the different materials used
    • Explore powder fusion mechanisms
    • Investigate process parameters and modeling
    • Analyze powder handling
    • Discuss PBF process variants
    • Look at different types of commercial machines

    Materials

    • Polymers and composites
      • Thermoset polymers are typically not processed into parts using PBF due to degradation
      • Thermoplastics are used because they do not degrade
        • Amorphous polymers have random molecular structures
        • Crystalline polymers have a regular molecular structure
    • Metals and composites: Steel, stainless steel, tool steels, titanium, nickel, some aluminum alloys, and cobalt-chromium are all used in PBF
    • Ceramics and ceramic composites: Metal oxides, carbides, and nitrides are commonly used

    Powder Fusion Mechanisms

    • Four types of fusion mechanisms:
      • Solid-state sintering: Powder fusion without melting at elevated temperatures
      • Chemically induced binding: Powder fusion via chemical reactions between powders and atmospheric gases
      • Liquid-phase sintering and partial melting: A portion of the powder melts, acting as a glue to bind other particles
      • Full melting: The material is fully melted using a high energy laser or electron beam

    Process Parameters and Modeling

    • Laser processing parameters: Laser power, spot size, pulse duration, pulse frequency, and others
    • Powder-related parameters: Particle shape, size, distribution, powder bed density, layer thickness, and material properties
    • Temperature-related parameters: Powder bed temperature, powder feeder temperature, temperature uniformity, etc

    Powder Handling

    • Powder handling challenges: Powder delivery systems, powder recycling, and maintaining powder quality
    • Any powder delivery system must meet certain characteristics, including having sufficient reservoir volume and being capable of accurately transporting and spreading powder thinly

    PBF Process Variants and Commercial Machines

    • Polymer laser sintering (SLS or LS): Using CO2 lasers and low temperatures
    • Laser-based systems for metals and ceramics: Using different lasers and more sophisticated systems such as Nd-YAG lasers
    • Electron beam melting (EBM): High-energy electron beam, low pressure environments
    • Line-wise and layer-wise PBF processing methods: Specific approaches for processing different materials or improving accuracy

    Process Benefits and Drawbacks

    • PBF can process a wide variety of materials
    • Saves time during part building and post-processing, which is particularly true in polymer processing
    • Accuracies are generally lower than liquid-based processes; Materials with low thermal conductivity provide more accurate parts and lower shrinkage amounts

    Exercises

    • Examples of Arrhenius equation applications to solid-state sintering
    • Energy driving force differences in different powder beds
    • Advantages and disadvantages of binder and structural material alternatives for bone tissue scaffold application in Liquid-Phase Sintering (LPS) for bone-tissue scaffolds
    • Examination of powder characteristics and handling using standard kitchen ingredients
    • Examination of parameter limitations for nylon polyamide in laser sintering
    • Estimating the minimum laser dwell time for maintaining a type B scan track in applied energy calculations

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    Related Documents

    Powder Bed Fusion Processes Chapter 5 PDF

    Description

    Test your knowledge on Powder Bed Fusion (PBF) processing and its various aspects, such as material types, binding mechanisms, and parameters affecting laser power. This quiz covers information relevant to the production of high-density structures and cemented carbide cutting tools. Dive deep into the world of additive manufacturing!

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