Advanced Additive Manufacturing Processes
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Questions and Answers

What is the first step in the Generalized Additive Manufacturing process chain?

  • Post-processing of part
  • Machine setup
  • Part removal and cleanup
  • Conceptualization and CAD (correct)

    • STL files are a way of describing a CAD model in terms of its color and texture.

    False

    What does STL stand for in the context of additive manufacturing?

    STereoLithography

    The process of converting a CAD model to STL is typically ______ within most CAD systems.

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

    Match the following additive manufacturing processes with their characteristics:

    <p>Photopolymer based systems = Utilize light to cure liquid resin Powder-based systems = Use powdered materials to create parts layer by layer Molten material systems = Involve melted filament that is deposited to form parts Solid sheets = Employ layers of solid sheet material fused together</p> Signup and view all the answers

    Which application area is mentioned as not involving conventional CAD modeling?

    <p>Medical modeling</p> Signup and view all the answers

    Metal additive manufacturing systems do not consider the weight and accuracy of the parts.

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

    Name one design consideration for additive manufacturing.

    <p>Part orientation</p> Signup and view all the answers

    What is the purpose of using a visualization tool before building a part?

    <p>To view and manipulate the part</p> Signup and view all the answers

    Building multiple parts at once is uncommon in additive manufacturing.

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

    What may some parts require to accommodate changes during the additive manufacturing process?

    <p>shrinkage or coating allowances</p> Signup and view all the answers

    The setup parameters for additive manufacturing machines can vary depending on whether the machine is designed for ________ materials.

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

    Match the following steps in additive manufacturing with their correct descriptions:

    <p>Verify the part = Ensure the correctness of the design before building Machine setup = Configure parameters specific to the AM machine Build = Proceed with layer-based manufacturing process Removal and Cleanup = Finish parts manually after the build</p> Signup and view all the answers

    What happens if the setup procedure is incorrect?

    <p>The part can still be built, but quality may be unacceptable</p> Signup and view all the answers

    Once the initial setup steps in additive manufacturing are complete, the process is entirely automated.

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

    What alerts the user to take action when the additive manufacturing process is complete?

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

    What is often required to support parts during the additive manufacturing process?

    <p>Support structures</p> Signup and view all the answers

    Post-processing stages in additive manufacturing commonly involve automatic processes.

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

    What can significantly impact the quality of the output during support removal?

    <p>Mishandling of parts and poor technique</p> Signup and view all the answers

    Additive Manufacturing (AM) parts may have small _______ or bubbles trapped inside them.

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

    Match the tasks with their corresponding functions in additive manufacturing:

    <p>Abrasive finishing = Improving surface quality Use of power tools = Enhancing efficiency in cleanup Application of coatings = Providing protection Careful handling = Maintaining precision</p> Signup and view all the answers

    Which of the following processes may improve the handling of supports?

    <p>Easy-to-remove supports</p> Signup and view all the answers

    The properties of parts produced by additive manufacturing are typically isotropic.

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

    What aspect influences the application of parts produced from additive manufacturing?

    <p>Part behaviour under mechanical stress</p> Signup and view all the answers

    What is the typical nominal layer thickness for most additive manufacturing machines?

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

    Thicker layers in additive manufacturing lead to more precise parts.

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

    What factor must be considered during post-processing that involves heat?

    <p>Heat resistance or melting temperature of the material</p> Signup and view all the answers

    Filaments that create parts using __________ technology typically have a layer thickness of 0.05 – 0.1 mm.

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

    Match each additive manufacturing system with its characteristic:

    <p>Photopolymer-Based Systems = Good accuracy with thin layers Powder-Based Systems = No need for supports FDM Dimension Machines = Layer thickness of 0.254 mm Binder Printing = Parts can be colored</p> Signup and view all the answers

    What is a disadvantage of photopolymer systems?

    <p>Poor mechanical properties</p> Signup and view all the answers

    Supports used in liquid vat systems can be made from any material.

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

    What improvement do newer resins offer for photopolymer systems?

    <p>Improved temperature resistance, strength, and ductility</p> Signup and view all the answers

    Which of the following methods does not require support structures in molten material systems?

    <p>Lamination methods</p> Signup and view all the answers

    Metal systems require more careful monitoring compared to polymer systems.

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

    What is a key concern when maintaining equipment that uses laser or printer technology?

    <p>It should not be used in dirty or noisy environments.</p> Signup and view all the answers

    Exposure to moisture and _____ light should be avoided in material handling.

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

    Match the application areas with their relevant technology:

    <p>Medical modeling = CT, MRI, 3D ultrasound Computerized Tomography = Imaging technology Magnetic Resonance Imaging = Non-invasive imaging method 3D ultrasound = Ultrasonic imaging</p> Signup and view all the answers

    Which of the following is NOT a consideration for design in additive manufacturing?

    <p>Color selection</p> Signup and view all the answers

    Recycling some materials from unsuccessful builds is a part of material handling.

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

    What is one of the benefits of using lamination methods?

    <p>No need for support structures.</p> Signup and view all the answers

    Which configuration of photopolymerization processes is known for irradiating entire layers at one time?

    <p>Mask projection</p> Signup and view all the answers

    Visible light is predominantly used in the microelectronic industry.

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

    What type of radiation is most commonly used in photopolymerization processes?

    <p>Ultraviolet (UV)</p> Signup and view all the answers

    Name one approach developed for photopolymerization processes that is based on high resolution point-by-point techniques.

    <p>Two-photon approaches</p> Signup and view all the answers

    Charles Hull discovered that solid polymer patterns could be produced by curing multiple layers over one another.

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

    In the vector scan and mask projection approaches, there is a need to ______, or apply a new layer of resin.

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

    What is the main application of photo-curable resins in dentistry?

    <p>Sealing teeth surfaces to prevent cavities.</p> Signup and view all the answers

    Match the following photopolymerization processes with their characteristics:

    <p>Vector scan = Requires recoating Mask projection = Irradiates entire layers Two-photon approaches = High resolution point-by-point Commercial SL machines = Typical configuration for vector scan</p> Signup and view all the answers

    Photopolymers were developed in the _____ and soon became widely used in the coating and printing industry.

    <p>1960s</p> Signup and view all the answers

    Match the following types of radiation with their use in curing photopolymers:

    <p>Gamma rays = Used in commercial photopolymers X-rays = Used for curing commercial photopolymers Ultraviolet (UV) = Most common used in photopolymerization Visible light = Some systems also utilize this radiation type</p> Signup and view all the answers

    Which of the following is a characteristic of VAT photopolymerization processes?

    <p>Involves the use of UV curable photopolymers</p> Signup and view all the answers

    Laser Scan Vat Photopolymerization utilizes a vector scan method.

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

    What is the benefit of using the two-photon vat photopolymerization process?

    <p>Higher resolution and precision in printing</p> Signup and view all the answers

    In the photopolymerization process, the formation of an interpenetrating polymer network enhances _______ properties.

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

    Match the following scan patterns with their characteristics:

    <p>WEAVE = Continuous layer deposition without gaps STAR-WEAVE = Interlaced pattern for better support ACES = Adaptive control of exposure for complex geometries Layer-based = Build process focusing on individual layers</p> Signup and view all the answers

    What is the primary advantage of vat photopolymerization technology over other AM technologies?

    <p>Accuracy and surface finish</p> Signup and view all the answers

    The maximum size of a fabrication structure in microsterolithography is 100 mm x 100 mm x 100 mm.

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

    What is the position accuracy in the x-y directions for the atypical point-wise microsterolithography process?

    <p>0.25 µm</p> Signup and view all the answers

    The trade-off during vat photopolymerization involves resolution and the size of the __________.

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

    Match the advantages and disadvantages of vat photopolymerization technology:

    <p>Accuracy = Advantage Flexibility = Advantage Degraded mechanical properties = Disadvantage Limited chemistries in photopolymers = Disadvantage</p> Signup and view all the answers

    What type of energy sources are used in processes based on photopolymerization?

    <p>Lasers and X-rays</p> Signup and view all the answers

    Current SL materials possess high impact strength and durability similar to good quality injection molded thermoplastics.

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

    What is the minimum size of the unit of hardened polymer in atypical microsterolithography?

    <p>5 µm x 5 µm x 3 µm</p> Signup and view all the answers

    Which type of polymerization is primarily used for acrylates in UV curable photopolymers?

    <p>Free radical polymerization</p> Signup and view all the answers

    UV and electron beam are the most prevalent radiation sources used to cure commercial photopolymers.

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

    What is the primary role of a photoinitiator in photopolymerization?

    <p>To convert physical energy of light into chemical energy.</p> Signup and view all the answers

    During the laser scan vat photopolymerization process, the operator must perform _____ after building the part.

    <p>cleaning, post-curing, and finishing</p> Signup and view all the answers

    Match the following photopolymerization types with their corresponding materials:

    <p>Acrylate = Free radical polymerization Epoxy = Cationic polymerization Vinylether = Cationic polymerization Polyols = Monomer formulation</p> Signup and view all the answers

    What happens during the recoating process in vector scan VP machines?

    <p>The recoater blade deposits a new layer of resin.</p> Signup and view all the answers

    The parts produced by laser scan vat photopolymerization do not require support structures.

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

    Name one of the main subsystems involved in vector scan VP machines.

    <p>Recoating system, platform system, vat system, laser and optics systems, or control system.</p> Signup and view all the answers

    Study Notes

    Generalized Additive Manufacturing Process Chain

    • Key steps in the AM process:
      • Conceptualization and CAD
      • Conversion to STL
      • Transfer and manipulation of STL file
      • Machine setup
      • Build
      • Part removal and cleanup
      • Post-processing
      • Application

    Variations from One AM Machine to Another

    • Typically uses 0.1 mm layer thickness.
    • FDM Dimension Machines use 0.254 mm.
    • SL uses 0.05 mm to 0.1 mm.
    • Thicker layers build faster but are less precise.
    • Fine details can be problematic with low layer thickness.
    • Material variation impacts time, resources, and skills needed.
    • Post-processing with heat requires material heat resistance.
    • Material properties impact abrasive and machining-based post-processing.
    • Processing variations: Powder, molten, solid sheet, vat of liquid photopolymer, or in-jet deposited photopolymer.

    Photopolymer-Based Systems

    • Easy setup.
    • Liquid vat systems use material as support.
    • Droplet deposition offers flexible material support.
    • Generally accurate with thin layers.
    • Compared to other materials, mechanical properties are poor.
    • Newer resins improve temperature resistance, strength and ductility.
    • Degradation can occur rapidly if UV protected coatings are not applied.

    Powder-Based Systems

    • No need for supports due to layering of powder.
    • Easiest setup for simple builds.
    • Zcorp systems use colored binder material to make colored parts.

    Molten Material Systems

    • Requires support structures.
    • Droplet-based systems ( Thermojet) automatically generate supports.
    • Extrusion processes (FDM) offers either automatic or user-generated supports.

    Solid Sheets

    • Lamination methods do not require supports.
    • Waste material needs to be removable.
    • Cleaning up is labor-intensive.
    • The paper-based systems experienced handling issues.
    • Polymer sheet bonding (Solido) seems less problematical.

    Metal Systems

    • Similar to polymer systems.
    • Consider:
      • Substrates
      • Energy density
      • Weight
      • Accuracy
      • Speed

    Maintenance of Equipment

    • Fragile laser or printer technology needs careful monitoring.
    • Avoid dirty and noisy environments.

    Material Handling Issues

    • Avoid exposure to moisture and excess light.
    • Loading material offline using software.
    • Recycle some or all material from unused builds.

    Design for AM

    • Part orientation
    • Removal of supports
    • Hollowing out parts
    • Inclusion of undercuts and manufacturing constraining features
    • Interlocking features
    • Reducing part count in an assembly
    • Identification marking/numbering

    Application Areas

    • Medical modeling
    • Reverse engineering data
    • Architecture modeling
      • CT scans
      • MRI imaging
      • 3D ultrasound scans

    Vat Photopolymerization Processes

    • Vat photopolymerization processes utilize liquid, radiation curable resins, or photopolymers.
    • Most photopolymers react to radiation in the ultraviolet (UV) range.
    • Photopolymers, developed in the 1960s, have become widely used in the coating and printing industries.
    • Charles Hull, in the mid-1980s, discovered that solid polymer patterns could be produced by exposing UV curable materials to a scanning laser. This discovery led to the development of stereolithography technology.
    • There are three primary configurations for photopolymerization processes: Vector scan, mask projection, and two-photon.

    Vector Scan Vat Photopolymerization

    • Uses a UV laser to selectively solidify a liquid photopolymer resin.
    • Creates solid parts by fabricating cross-sectional contours, or slices, one on top of the other.
    • Requires cleaning, post-curing, and finishing after the part is built.

    Mask Projection Vat Photopolymerization

    • Utilizes a large radiation beam patterned by another device, like a Digital Micromirror Device.
    • Offers speed advantages over laser scanning SL, but there is a trade-off between resolution and pattern size.

    Two-Photon Vat Photopolymerization

    • Uses the intersection of two scanning laser beams to initiate photopolymerization.
    • Offers high resolution and avoids recoating, making it faster and simpler.

    UV Curable Photopolymers

    • Used as photoresists in the microelectronic industry.
    • Commonly cured with UV or electron beams, though other radiation types can be employed.

    Photopolymer Chemistry

    • Two primary types of polymerization: Free radical polymerization (for acrylates) and Cationic polymerization (for epoxies and vinylethers)

    Resin Formulation and Reaction Mechanisms

    • Formulated using raw materials like polyols, expoides, (meth) acrylic acids, and their esters.
    • Most monomers are multifunctional monomers.
    • Photoinitiators convert incident light energy into chemical energy, facilitating polymerization.

    Photopolymerization Process Modeling

    • Important factors include irradiance and exposure, laser-resin interaction, photospeed, and time scales.

    Vector Scan VP Machines

    • Main subsystems include recoating system, platform system, vat system, laser and optics systems, and control system.
    • The process involves depositing a new layer of resin, smoothing the surface of the vat, and dipping the platform down by a layer thickness after each cured layer.

    SL Scan Patterns

    • Layer-based build phenomena can lead to errors like discretization, which causes "stair steps" on the part's surface.
    • Various scan patterns are employed to mitigate these errors, including WEAVE, STAR-WEAVE, and ACES patterns.

    Vector Scan Micro-Vat Photopolymerization

    • Developed for microfabrication applications, utilizing lasers and X-rays as energy sources.
    • Typical specifications include 5-µm spot size, position accuracy of 0.25 µm in the x-y directions and 1 µm in the z-direction, and a minimum hardened polymer unit size of 5 µm x 5 µm x 3 µm.

    Mask Projection VP Technologies and Processes

    • Consists of a liquid photopolymer resin cured layer-by-layer through a patterned mask.
    • Several commercial MPSL (Mask Projection Stereolithography) systems are available.
    • MPSL models account for factors like mask dimensions, light intensity, and resin properties.

    Two-Photon VP

    • A high-resolution method that uses the intersection of two focused laser beams to initiate polymerization.

    Process Benefits and Drawbacks

    • Advantages: High accuracy and surface finish, flexibility in machine configurations and scales, speed advantage for mask projection VP.
    • Drawbacks: Limited material choices (acrylates and epoxies), lower impact strength and durability compared to injection molded thermoplastics, material aging degrades properties over time.

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    Related Documents

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    Vat Photopolymerization Processes PDF

    Description

    Explore the key steps and variations in additive manufacturing (AM) processes, focusing on conceptualization, machine setup, and post-processing. Understand how different AM technologies affect build precision and material usage. This quiz covers photopolymer-based systems and their operational characteristics.

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