Additive Manufacturing

What best describes additive manufacturing (AM)? Building a part by joining material from 3D model data, typically layer by layer
Which manufacturing process is subtractive rather than additive? CNC milling
Which is an example of formative manufacturing? Injection molding
What is the primary purpose of a prototype during product development? To evaluate and communicate aspects of a proposed design
In prototyping, what does degree of approximation describe? How closely a prototype represents the intended product in relevant characteristics
Which is an example of a virtual prototype? A digital CAD assembly evaluated on a computer
Which is an example of a physical prototype? A 3D-printed enclosure used for fit testing
Which statement about prototype fidelity is most accurate? prototype may closely represent some product characteristics while simplifying others
What is a common first step in a digital AM workflow? Create or obtain a three-dimensional digital model
What does slicing software generally produce? Layer-by-layer toolpath or build instructions for the printer
What is tessellation in the context of STL data? Approximating surfaces using interconnected triangles
A key limitation of the STL file format is that it typically does not directly store what information? Full material and color properties of a part
Why might support structures be necessary in some AM processes? To stabilize overhangs or anchor features during building
Which activity is typically considered AM postprocessing? Removing supports and finishing surfaces
Which of the following is one of the seven ISO/ASTM AM process categories? Material extrusion
Which AM category selectively cures liquid photopolymer in a vat? Vat photopolymerization
Which category deposits material through a nozzle or orifice? Material extrusion
Which category uses thermal energy to fuse selected regions of a powder bed? Powder bed fusion
Which category joins sheet materials to form a part? Sheet lamination
What distinguishes binder jetting from powder bed fusion? Binder jetting selectively deposits a liquid bonding agent
Which AM process category feeds material into a focused thermal energy source as it is deposited? Directed energy deposition
Which process selectively deposits droplets of build material? Material jetting
Which is a widely recognized design advantage of AM? Ability to fabricate complex geometries that can be difficult to machine
What is part consolidation? Combining multiple components into fewer printed components
Why can AM be useful for customized medical devices? Geometry can be tailored to patient-specific requirements
Which scenario is most likely to favor AM over dedicated high-volume tooling? Low-volume production of a complex customized component
What is a conformal cooling channel in AM tooling? A cooling passage shaped to follow the contours of a tool surface
Which is a realistic limitation of AM? Build speed, material choices, and postprocessing can constrain its use
What is the role of AM standards such as those developed through ASTM and ISO? Establish consistent terminology, testing methods, and technical practices
What does point-of-need manufacturing emphasize? Producing needed items near their place or time of use
T/F AM processes generally create parts directly from three-dimensional model data. True
T/F A prototype must always have the same material and functional performance as the final product. False
T/F A virtual prototype can be assessed without first producing a physical part. True
T/F STL files represent curved surfaces with a triangular mesh. True
T/F All AM technologies use a liquid feedstock. False
T/F Material extrusion is one of the standardized AM process categories. True
T/F Binder jetting and powder bed fusion are identical processes. False
T/F AM automatically eliminates all requirements for finishing and inspection. False
T/F Part consolidation can reduce the number of individual components in an assembly. True
T/F AM is always the least expensive approach for mass-producing simple identical parts. False
Match each additive manufacturing term with its correct definition. Producing prototypes quickly for design evaluation Rapid Prototyping
Producing parts by joining material from 3D model data 3D Printing
Designing specifically for AM capabilities and constraints Design for Additive Manufacturing
Commonly used term for AM Additive Manufacturing
Using digital data to manufacture functional products Direct Digital Manufacturing
Using AM to produce tooling or tooling components Rapid Tooling
Material used to support features during fabrication Support Structure
Position of a component within the build volume Build Orientation
Operations performed after fabrication to achieve required properties or finish Post-Processing
Nominal height of each manufactured layer Layer Thickness
Variation in material properties with direction Anisotropy
Available manufacturing space within the equipment Build Volume
Which fabrication process removes material from an initial workpiece? Subtractive manufacturing
Which operation is primarily a formative process? Forging
Which process builds a component by successively adding material? Additive manufacturing
Which is an example of material extrusion AM? Fused filament fabrication (FFF)
Which AM category includes stereolithography (SLA)? Vat photopolymerization
Which AM process uses energy to fuse selected regions of a powder bed? Powder bed fusion
What best describes a hybrid additive-subtractive machine? It builds material and machines features within an integrated system
What is the first stage of the five-step AM process chain presented in Chapter 2? 3D modeling
During which process-chain stage is a CAD design exported into a printable file format? Data conversion and transmission
Which activity belongs primarily to checking and preparing? Repairing mesh errors and choosing build orientation
What is the primary activity during the building stage? Fabricating the part layer by layer
Which action is an example of post-processing? Removing supports and cleaning the finished build
A printed bracket warps during fabrication. What is the best next action? Review orientation, supports, and settings before rebuilding
What does a watertight solid mesh represent? A closed surface that encloses the intended volume
Why can an open gap in a mesh create problems? It can prevent the slicer from defining closed cross-sections
A non-manifold edge may occur when: More than two faces share the same edge
What are inverted normals in a polygon mesh? Faces whose normal directions point incorrectly
What problem may result from overlapping bodies that are not properly joined? Unpredictable slicing or build geometry
What is a potential disadvantage of using an unnecessarily dense triangle mesh? Larger files and increased processing requirements
What is the most appropriate response to an STL file with holes and inverted normals? Repair and verify the mesh before slicing
What is the primary function of a support structure? Stabilize features that may deform or fail during fabrication
Under the Y-H-T guideline, which feature often builds more easily without supports? A sloped Y-shaped feature within process limits
For an H-shaped feature, what is an important support consideration? The unsupported bridge span length
Why might a T-shaped overhang need supports? Its horizontal arm may sag or fail without underlying material
Which statement about support material is accurate? Some powder-based processes allow recovery of unfused surrounding powder
What trade-off should guide support placement? Build reliability, material consumption, surface marks, and removal access
Which statement best describes STL? A widely supported format representing surfaces with triangles
What is an advantage of 3MF over basic STL when supported by the software? It can carry geometry plus additional manufacturing information
Which information should be checked before transferring a model to a printer? Units, scale, revision, and software compatibility
What does slicing software generate from a prepared model? Layer cross-sections and process instructions for the selected machine
What is infill in a material-extrusion print? The internal structure defined within the part
Why review the sliced preview before starting a build? To check layers, supports, placement, and estimated resource use
Which change could improve build-plate productivity? Arrange multiple compatible parts while maintaining adequate spacing
Which factor can increase risk of damage during post-processing? Aggressive support removal from delicate features
What is the purpose of inspection and acceptance? Determine whether the part meets requirements and should be accepted, reworked, or rebuilt
T/F Milling and turning are examples of subtractive manufacturing. True
T/F The AM process chain must always proceed without returning to an earlier stage. False
T/F A watertight mesh fully encloses the intended build volume. True
T/F Increasing the number of mesh triangles always guarantees a better printed part. False
T/F A short bridge may print without supports depending on the process and settings. True
T/F All AM processes require identical support geometry and removal procedures. False
T/F An STL file can contain geometry defects even when the CAD model looks correct on screen. True
T/F Slicing preview should be skipped if a file opens without an error message. False
T/F Some AM builds can be monitored with cameras or automated notifications. True
T/F A completed build automatically satisfies all dimensional and functional requirements. False
Match each additive manufacturing process-chain activity or concept to its correct description. Cleaning, curing, support removal, and finishing as required Post-processing
Automated layer-by-layer fabrication of the part Building
Mesh repair, orientation, support generation, and slicing setup Checking and preparing
Creation of the intended part geometry in CAD 3D Modeling
Exporting and transferring compatible model data to the AM system Data conversion and transmission
Verification of dimensions, fit, function, and acceptance criteria Inspection and acceptance
What is the primary build material used in conventional vat photopolymerization? Liquid photocurable resin
What causes liquid photopolymer resin to solidify during a typical light-based AM process? Exposure to light initiates a chemical polymerization reaction
In stereolithography (SLA), how is a cross section typically formed? A focused laser beam scans the desired pattern on the resin
In the top-down SLA configuration presented in Chapter 3, what happens after a layer is cured? The platform lowers so fresh liquid resin can cover the layer
What does slicing a CAD model provide to a layer-based liquid-resin printer? A sequence of cross-sectional patterns to form
Which statement best describes photopolymerization? Light initiates the linking and cross-linking of molecules to form a solid polymer
Why must the delivered exposure exceed a resin-specific threshold? Insufficient energy may fail to cure the resin into a solid
Which factor helps determine how deeply an SLA resin cures? Light exposure intensity and duration
What is a function of galvanometer-driven mirrors in laser-based SLA? Direct the focused laser spot across the resin in X-Y patterns
Why can cure depth limit the effective vertical resolution of a photopolymer process? The light can harden material deeper than the nominal mechanical layer increment
What is a common reason SLA parts need support structures? To stabilize overhangs and complex features during fabrication
Which post-processing sequence is commonly necessary for SLA parts? Remove uncured resin, remove supports as needed, and post-cure
Why is post-curing commonly performed on an SLA part? To further develop the cured polymer and its intended properties
Which combination is a typical strength of SLA? Fine detail and good surface finish
What distinguishes material jetting such as PolyJet from vat-based SLA? Tiny droplets of photopolymer are deposited onto the build surface and UV cured
What allows a photopolymer material-jetting process to produce multimaterial prototypes? Different jetting channels can deposit different build materials in one part
What is a common post-processing task for photopolymer material-jetting parts? Removing gel-like or other sacrificial support material
Which statement best describes the curing approach in the PolyJet process presented? UV light cures deposited photopolymer droplets during the build
Which limitation can make intricate material-jetted models labor-intensive to finish?
Question Support material can be difficult to remove from fine or internal features
In MultiJet Printing (MJP), what deposits the build material? A print head containing many small jets
According to the chapter, how is a deposited MJP layer typically solidified? The layer is exposed to UV light
What is a typical application of high-precision material-jetting processes? Patterns for casting and detailed design validation
How does digital light processing (DLP) form a resin layer? A projected pattern exposes a full layer region
In the bottom-up DLP arrangement described, why is the cured layer peeled away from a transparent window? To allow fresh resin to flow into the layer-forming gap
What does a bitmap or mask represent in the DLP process? The spatial pattern of light exposure for a layer
What is a potential weakness associated with bottom-up DLP fabrication? Peel and separation forces acting on the newly cured part
What is a bioink in 3D bioprinting? A printable biomaterial formulation that may contain living cells
Why are hydrogels commonly used in bioink formulations? They can provide a supportive, extracellular-matrix-like environment for cells
What is the primary intended application of an osteoink? Fabrication of constructs for bone tissue engineering
Why is a sterile environment important for many bioprinting operations? To reduce contamination of living cells and biological constructs
What is the fundamental solidification mechanism in rapid freeze prototyping (RFP)? Deposited water droplets freeze to build an ice part
Why is temperature control essential to rapid freeze prototyping? The deposited material must freeze and remain stable during fabrication
What is the core deposition principle of aerosol jet printing? Atomize a liquid ink into fine droplets, focus the aerosol, and deposit a pattern
Which application particularly benefits from aerosol jet deposition onto nonplanar surfaces? Printing electronic traces or components onto three-dimensional substrates
What makes two-photon polymerization (TPP) distinct from conventional layer-by-layer photopolymer printing? Femtosecond-scale focused light exposure can polymerize tiny volumes within a photosensitive material
T /F In SLA, a focused light source can selectively solidify liquid photopolymer resin.
T /F In SLA, a focused light source can selectively solidify liquid photopolymer resin. True
T /F Photopolymerization is fundamentally a chemical curing reaction initiated by radiation. True
T /F If resin exposure remains below the curing threshold, a solid feature may not form. True
T /F SLA parts never require support removal or cleaning after fabrication. False
T /F Photopolymer material jetting can deposit different materials within a single build. True
T /F In DLP, the projection image is used to control which regions of liquid resin cure. True
T /F In the bottom-up DLP setup discussed, the printed layer must separate from the transparent window before new resin enters. True
T /F Bioinks are always composed exclusively of molten metal and contain no biomaterials. False
T /F Rapid freeze prototyping builds ice-based parts by freezing deposited water. True
T/F Two-photon polymerization is limited to making only large flat sheets using a cutting blade. False
Match each liquid-based additive manufacturing process with its operating principle. Bioinks are deposited to create cell-containing or tissue-like constructs. 3D bioprinting
Deposited water freezes into successive layers of an ice model. Rapid freeze prototyping (RFP)
A projected light pattern cures selected areas of a resin layer. Digital light processing (DLP)
Focused aerosolized ink is deposited as fine patterns on a substrate. Aerosol jet printing
A scanned laser selectively cures resin in a vat. Stereolithography (SLA)
Print heads deposit photopolymer droplets that are cured by UV light. Photopolymer material jetting
Which feedstock is used in fused deposition modeling (FDM)? Solid thermoplastic filament
What happens to the filament inside an FDM extrusion head? It is heated until it can flow through a nozzle
How does an FDM printer typically create each horizontal layer? It deposits heated material along programmed toolpaths
After an FDM layer is completed, what adjustment enables the next layer? The relative nozzle-to-part position changes along the Z axis
Which characteristic makes FDM useful for functional prototypes? Its ability to produce thermoplastic components for form and function testing
Which common FDM limitation can affect dimensional accuracy? Cooling shrinkage and warping
What is a common surface-quality issue with FDM parts? Visible deposition layer lines
What is a benefit of soluble support material in some FDM systems? Supports can be dissolved to simplify removal
Which task is an appropriate application of FDM? Producing a customized jig or fixture
For a tall and complex FDM print, which tradeoff is most likely? Longer build time and potentially greater support demand
Why may an FDM prototype require finishing operations? To improve surface appearance or meet fit requirements
Which statement best describes material efficiency in FDM? Material is deposited where needed, though supports and failed builds still create waste
What is the primary build material in selective deposition lamination (SDL) as covered in Chapter 4? Sheets of paper
Which sequence best characterizes SDL? Color or print, apply adhesive selectively, press and cut a sheet
What is the purpose of selectively applying adhesive in SDL? To bond only the paper regions intended to form the model
What tool creates the profile of each paper layer in SDL? A cutting blade
What makes SDL particularly effective for presentation and architectural models? Its capability to reproduce detailed colors and visual features
Which limitation should be considered for a paper-based SDL model used outdoors? Susceptibility to moisture or humidity
Why is SDL generally a poor selection for a load-bearing mechanical bracket? Paper-based models typically have limited mechanical strength
Which feedstock and energy source are used in wire-fed electron beam additive manufacturing (EBAM)? Metal wire and a focused electron beam
Why is a vacuum environment used in electron-beam wire deposition? To support electron-beam operation and limit oxidation or contamination
What happens where the electron beam meets the deposited metal wire? A molten pool forms and solidifies into deposited material
Which type of component is especially well suited to wire-fed EBAM? A large near-net-shape metal structural component
What does near-net-shape mean in the context of EBAM? The deposited part approximates final geometry but often needs machining
What is a common limitation of wire-fed EBAM parts? Rough surfaces and a need for finish machining
How can a dual-wire EBAM system expand material possibilities? By varying the feed rates to form tailored compositions or graded regions
Why can wire-fed EBAM have difficulty with very fine details? Its deposition scale favors larger metal features
Which feature can make wire-fed EBAM material-efficient for large components? Depositing metal near the required shape instead of machining an entire billet
What is the joining mechanism in ultrasonic additive manufacturing (UAM)? Ultrasonic vibration and pressure bond metal foils in the solid state
What is the function of the sonotrode in UAM? To apply high-frequency vibration and pressure to bond foil layers
What does solid-state bonding mean in UAM? Metal layers are bonded without melting the bulk feedstock
Why can UAM be advantageous for embedding sensors in metal parts? Bonding occurs without fully melting the surrounding metal, helping protect embedded components
Why might CNC milling be integrated into a UAM machine? To machine contours or internal features between foil-bonding stages
Which capability is a distinctive advantage of UAM? Joining certain dissimilar metal foils within one part
Which factor can limit UAM production throughput? Repeated foil bonding and intermediate machining operations
T/F FDM builds parts by depositing heated thermoplastic material along programmed paths. True
T/F FDM parts are always free from warping because the deposited material never cools. False
T/F Some FDM systems use dissolvable support materials to simplify support removal. True
T/F SDL forms parts by selectively bonding and cutting sheets of paper. True
T/F Paper-based SDL models are generally ideal for high-load structural parts without reinforcement. False
T/F Wire-fed EBAM uses an electron beam to melt metal wire during deposition. True
T/F The vacuum environment used in electron-beam deposition helps reduce oxidation. True
T/F A wire-fed EBAM part always leaves the machine at final surface finish and tolerance without machining. False
T/F UAM bonds metal foils by using ultrasonic vibration and pressure without melting the bulk material. True
T/F UAM cannot combine foil bonding with CNC machining operations. False
Match each solid-based additive manufacturing process or term with its correct description.
Bonds metal foils through ultrasonic vibration and pressure without bulk melting. Ultrasonic additive manufacturing (UAM)
Uses a focused electron beam to melt and deposit metal wire in a vacuum. Wire-fed electron beam AM (EBAM)
Produces a geometry close to its final form but may still require finishing. Near-net-shape manufacturing
Tool that applies high-frequency vibration and pressure during foil bonding. Sonotrode
Selectively bonds and cuts successive paper sheets to form a model. Selective deposition lamination (SDL)
Deposits heated thermoplastic filament through a nozzle along programmed paths. Fused deposition modeling (FDM)