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2025 question paper

3D Printing and Design

26 questions

  1. Q1(a). Which Additive Manufacturing process utilizes a liquid photopolymer resin and a UV light source for curing and solidification? (i) Fused Deposition Modeling (FDM) (ii) Stereo Lithography (SLA) (iii) Selective Laser Sintering (SLS) (iv) Direct Energy Deposition (DED)2025?m

    Module 1: Additive Manufacturing Introduction and CAD-CAM for 3D Printing

    Which Additive Manufacturing process utilizes a liquid photopolymer resin and a UV light source for curing and solidification?

    (i) Fused Deposition Modeling (FDM)
    (ii) Stereo Lithography (SLA)
    (iii) Selective Laser Sintering (SLS)
    (iv) Direct Energy Deposition (DED)

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    Answer: (ii) Stereo Lithography (SLA)

    SLA uses a liquid photopolymer resin as the build material. A UV laser or other UV light selectively cures the resin layer by layer according to the sliced CAD model. The cured resin solidifies to form the part.

    Therefore, the correct option is SLA.

  2. Q1(b). What is the primary limitation of the STL file format in 3D printing preparation? (i) It is not compatible with all 3D printing technologies. (ii) It is a proprietary format requiring special software licenses. (iii) It cannot store color or material information. (iv) It only uses curved geometry.2025?m

    Module 1: Additive Manufacturing Introduction and CAD-CAM for 3D Printing

    What is the primary limitation of the STL file format in 3D printing preparation?

    (i) It is not compatible with all 3D printing technologies.
    (ii) It is a proprietary format requiring special software licenses.
    (iii) It cannot store color or material information.
    (iv) It only uses curved geometry.

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    Answer: (iii) It cannot store color or material information

    STL represents a 3D surface as a collection of triangular facets. The standard STL format mainly describes geometry and surface normals. It does not natively carry rich information such as color, texture, or multiple material assignments.

    This is a major limitation when a model requires multi-material or color-aware manufacturing.

  3. Q1(c). In FDM, the material is typically: (i) Liquid resin (ii) Powdered metal (iii) Thermoplastic filament (iv) Ceramic slurry2025?m

    Module 3: Solid Based 3D Printing Processes

    In FDM, the material is typically:

    (i) Liquid resin
    (ii) Powdered metal
    (iii) Thermoplastic filament
    (iv) Ceramic slurry

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    Answer: (iii) Thermoplastic filament

    FDM generally uses thermoplastic polymers supplied as a filament, such as PLA, ABS, PETG, or nylon. The filament is heated above its softening/melting temperature and extruded through a nozzle. It cools and solidifies to build the component layer by layer.

  4. Q1(d). Which of the following is an application domain of additive manufacturing? (i) Aerospace (ii) Automotive (iii) Healthcare (iv) All of the above2025?m

    Module 1: Additive Manufacturing Introduction and CAD-CAM for 3D Printing

    Which of the following is an application domain of additive manufacturing?

    (i) Aerospace
    (ii) Automotive
    (iii) Healthcare
    (iv) All of the above

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    Answer: (iv) All of the above

    Additive manufacturing is used across many industries. Aerospace uses it for lightweight and complex components, automotive uses it for prototypes and functional parts, and healthcare uses it for implants, prosthetics, surgical models, and customized devices. Hence, all listed domains are applications.

  5. Q1(e). Which Additive Manufacturing process primarily utilizes raw material in the form of a wire/filament? (i) Selective Laser Sintering (SLS) (ii) Stereo Lithography (SLA) (iii) Fused Deposition Modeling (FDM) (iv) Binder Jetting2025?m

    Module 2: 3D Printing Materials

    Which Additive Manufacturing process primarily utilizes raw material in the form of a wire/filament?

    (i) Selective Laser Sintering (SLS)
    (ii) Stereo Lithography (SLA)
    (iii) Fused Deposition Modeling (FDM)
    (iv) Binder Jetting

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    Answer: (iii) Fused Deposition Modeling (FDM)

    FDM commonly uses thermoplastic material in filament form. The filament is fed into a heated extrusion head, melted or softened, and deposited through a nozzle according to the programmed toolpath.

  6. Q1(f). When choosing a material for a medical device that will be surgically implanted, which performance requirement is the absolute primary consideration? (i) High Shore Hardness (ii) Excellent Surface Finish (iii) Biocompatibility (iv) Low Cost2025?m

    Module 2: 3D Printing Materials

    When choosing a material for a medical device that will be surgically implanted, which performance requirement is the absolute primary consideration?

    (i) High Shore Hardness
    (ii) Excellent Surface Finish
    (iii) Biocompatibility
    (iv) Low Cost

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    Answer: (iii) Biocompatibility

    For an implantable medical device, the material must be biocompatible, meaning it should not produce an unacceptable toxic, inflammatory, allergic, or other harmful biological response. Cost, hardness, and surface finish can matter, but biological safety is the primary requirement for an implanted device.

  7. Q1(g). Which stage in the Fused Deposition Modeling (FDM) process is directly responsible for bonding a newly deposited layer to the previous layer? (i) Liquefaction (ii) Extrusion (iii) Solidification and Bonding (iv) G-Code Interpretation2025?m

    Module 3: Solid Based 3D Printing Processes

    Which stage in the Fused Deposition Modeling (FDM) process is directly responsible for bonding a newly deposited layer to the previous layer?

    (i) Liquefaction
    (ii) Extrusion
    (iii) Solidification and Bonding
    (iv) G-Code Interpretation

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    Answer: (iii) Solidification and Bonding

    In FDM, the extruded thermoplastic is deposited while hot. As the new material contacts the previous layer, heat and molecular diffusion allow interlayer adhesion. Subsequent cooling produces solidification and establishes the bond between layers. Therefore, solidification and bonding is the best answer.

  8. Q1(h). In the context of FDM 3D printing software, what is the primary function of a slicer program? (i) To create the initial 3D part geometry (CAD) (ii) To convert a 3D model (e.g., STL file) into instructions (G-code) (iii) To repair mesh errors in the 3D model (iv) To monitor and remotely control the 3D printer hardware2025?m

    Module 1: Additive Manufacturing Introduction and CAD-CAM for 3D Printing

    In the context of FDM 3D printing software, what is the primary function of a slicer program?

    (i) To create the initial 3D part geometry (CAD)
    (ii) To convert a 3D model (e.g., STL file) into instructions (G-code)
    (iii) To repair mesh errors in the 3D model
    (iv) To monitor and remotely control the 3D printer hardware

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    Answer: (ii) To convert a 3D model (e.g., STL file) into instructions (G-code)

    A slicer divides the 3D model into thin layers and generates the toolpaths needed to manufacture each layer. It then converts those toolpaths into printer instructions, commonly G-code, specifying movements, speeds, temperatures, extrusion, and other machine parameters.

  9. Q1(i). What is the primary material used in SLA 3D printing? (i) Thermoplastic filament (ii) Photopolymer resin (iii) Metal powder (iv) Ceramic slurry2025?m

    Module 4: Liquid Based 3D Printing Processes

    What is the primary material used in SLA 3D printing?

    (i) Thermoplastic filament
    (ii) Photopolymer resin
    (iii) Metal powder
    (iv) Ceramic slurry

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    Answer: (ii) Photopolymer resin

    SLA uses a liquid photopolymer resin. A UV laser or projected UV light selectively cures the resin, causing photopolymerization and transforming the liquid resin into a solid layer.

  10. Q1(j). Which of the following processes uses an electron beam for melting metal powder? (i) Laser Engineering Net Shaping (LENS) (ii) Electron Beam Melting (EBM) (iii) Binder Jetting (iv) Fused Deposition Modeling (FDM)2025?m

    Module 5: Powder Based 3D Printing Processes

    Which of the following processes uses an electron beam for melting metal powder?

    (i) Laser Engineering Net Shaping (LENS)
    (ii) Electron Beam Melting (EBM)
    (iii) Binder Jetting
    (iv) Fused Deposition Modeling (FDM)

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    Answer: (ii) Electron Beam Melting (EBM)

    EBM uses a focused electron beam to melt or fuse metal powder selectively in a vacuum environment. The beam scans the powder bed according to the sliced geometry, building the metal component layer by layer.

  12. Q2(a). Differentiate between Additive Manufacturing and Conventional Manufacturing processes based on three key parameters: material waste, geometric complexity, and tooling requirements.20257m

    Module 1: Additive Manufacturing Introduction and CAD-CAM for 3D Printing

    Differentiate between Additive Manufacturing and Conventional Manufacturing processes based on three key parameters: material waste, geometric complexity, and tooling requirements.

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    Additive Manufacturing vs Conventional Manufacturing

    Parameter Additive Manufacturing Conventional Manufacturing
    Material waste Generally low because material is deposited or fused only where required. Some waste can still arise from supports and post-processing. Often higher in subtractive processes because material is removed from a larger block; machining chips are generated.
    Geometric complexity Can produce highly complex geometries, internal channels, lattice structures and customized shapes with comparatively few manufacturing constraints. Complex shapes may require multiple operations, special machines, fixtures or assemblies and can be difficult or expensive to manufacture.
    Tooling requirements Usually requires little or no dedicated tooling; the digital model can be directly processed for production. Frequently requires dies, molds, cutting tools, jigs, fixtures or other dedicated tooling, especially for mass production.

    Conclusion

    Additive manufacturing is especially advantageous for complex, customized and low-volume parts because it reduces material waste and tooling dependence. Conventional manufacturing remains highly efficient for many standardized, high-volume products where established tooling and production methods provide low unit cost.

  13. Q2(b). Explain the working principle of Selective Laser Sintering (SLS) in detail.20257m

    Module 5: Powder Based 3D Printing Processes

    Explain the working principle of Selective Laser Sintering (SLS) in detail.

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    Working Principle of Selective Laser Sintering (SLS)

    Selective Laser Sintering is a powder-bed additive manufacturing process in which a laser selectively heats regions of a powder layer so that particles fuse together.

    Working steps

    1. A thin layer of polymer, metal or other suitable powder is spread uniformly over the build platform.
    2. A laser scans the cross-sectional areas defined by the sliced CAD model.
    3. The laser supplies sufficient energy to sinter or fuse the selected powder particles.
    4. The build platform moves downward by approximately one layer thickness.
    5. A new layer of powder is spread over the previous layer.
    6. The laser again scans the required cross-section and bonds it to the previous layer.
    7. Steps 4–6 are repeated until the complete part is produced.
    8. After printing, the part is allowed to cool and is removed from the surrounding loose powder.
    9. Excess powder is brushed, blown or otherwise removed; additional post-processing may be performed.

    Important features

    • Loose surrounding powder can provide support for many geometries, reducing the need for dedicated support structures.
    • Part quality depends on powder properties, laser power, scan speed, layer thickness, hatch spacing and bed temperature.

    Result: A three-dimensional component is obtained by selectively fusing successive powder layers according to the digital model.

  14. Q3(a). Describe the role of CAD-CAM integration in the overall Additive Manufacturing process chain.20257m

    Module 1: Additive Manufacturing Introduction and CAD-CAM for 3D Printing

    Describe the role of CAD-CAM integration in the overall Additive Manufacturing process chain.

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    Role of CAD-CAM Integration in the Additive Manufacturing Process Chain

    CAD-CAM integration connects the digital product design with the manufacturing process.

    Process chain

    1. CAD modeling: The component is created using solid or surface modeling software.
    2. File export: The model is exported into a manufacturing-compatible format such as STL or another modern 3D-printing interface.
    3. Model checking: The geometry is inspected and repaired for gaps, inverted normals, non-manifold edges and other mesh problems.
    4. Part orientation: The model is oriented to balance surface quality, build time, strength and support requirements.
    5. Slicing: The model is divided into thin cross-sectional layers.
    6. Tool-path generation: CAM software determines the path of the print head, laser, nozzle or other energy source.
    7. Machine instructions: The toolpath is converted into machine-specific instructions.
    8. Manufacturing: The 3D printer builds the component layer by layer.
    9. Post-processing and inspection: The printed part is cleaned, finished and inspected against the design requirements.

    Importance

    CAD-CAM integration reduces manual data conversion, improves dimensional consistency, speeds up design-to-production, enables rapid prototyping and makes it possible to manufacture complex geometries directly from digital models.

  15. Q3(b). Identify at least three distinct factors affecting part orientation. Explain the critical need for part orientation determination in 3D printing.20257m

    Module 1: Additive Manufacturing Introduction and CAD-CAM for 3D Printing

    Identify at least three distinct factors affecting part orientation. Explain the critical need for part orientation determination in 3D printing.

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    Factors Affecting Part Orientation and Its Importance

    Part orientation is the choice of how a 3D model is positioned relative to the build direction.

    Factors affecting orientation

    1. Surface quality: Surfaces facing the build direction can show layer-stepping; orientation affects the visibility and severity of this effect.
    2. Support requirement: Orientation determines which overhangs need supports. Fewer supports can reduce material use and post-processing.
    3. Mechanical strength: Layer bonding can make properties direction-dependent. Orientation should place critical loads in favorable directions.
    4. Build time: Orientation affects the number of layers and therefore build duration.
    5. Dimensional accuracy: Different surfaces and features may have different accuracy depending on their angle relative to the layers.
    6. Thermal behavior: In processes involving heating, orientation can influence heat flow, distortion and residual stresses.

    Need for orientation determination

    Correct orientation can minimize supports, improve surface finish and dimensional accuracy, reduce build time and material consumption, and improve the functional strength of the final part.

    Thus, part orientation is an important process-planning decision rather than merely a positioning step.

  16. Q4(a). Describe the process of Model Slicing and Contour Data organization in the context of 3D printing preparation.20257m

    Module 1: Additive Manufacturing Introduction and CAD-CAM for 3D Printing

    Describe the process of Model Slicing and Contour Data organization in the context of 3D printing preparation.

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    Model Slicing and Contour Data Organization

    Slicing is the process of converting a three-dimensional CAD model into a sequence of two-dimensional cross-sectional layers that a 3D printer can manufacture.

    Steps

    1. Import the repaired 3D model into slicing software.
    2. Select the required part orientation and layer thickness.
    3. Intersect the model with a series of horizontal planes at successive Z-heights.
    4. Calculate the closed contours produced by each intersection.
    5. Organize the contours into outer boundaries, inner boundaries, holes and internal regions.
    6. Generate toolpaths such as perimeter paths, infill paths or scan paths from the contour information.
    7. Add process parameters such as layer height, speed, extrusion or laser settings.
    8. Convert the resulting toolpaths into machine instructions.

    Contour data organization

    Contour data defines the boundaries of each layer. The software must distinguish external profiles from internal holes and determine a suitable order for processing them. Proper organization prevents missing regions, incorrect paths and unwanted intersections.

    Importance

    Accurate slicing determines layer geometry and directly affects dimensional accuracy, surface finish, build time and final part quality.

  17. Q4(b). Describe the working principle of Fused Deposition Modeling (FDM) and Stereo Lithography (SLA) with suitable diagrams.20257m

    Module 3: Solid Based 3D Printing Processes

    Describe the working principle of Fused Deposition Modeling (FDM) and Stereo Lithography (SLA) with suitable diagrams.

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    FDM and SLA: Working Principles

    1. Fused Deposition Modeling (FDM)

    FDM is a material-extrusion process that normally uses thermoplastic filament.

    Working:

    1. Filament is fed from the spool into a heated extrusion head.
    2. The filament is heated until it becomes sufficiently soft or molten.
    3. The nozzle deposits the material along the programmed path of the current layer.
    4. The deposited material cools and bonds with the previous layer.
    5. The build platform or print head moves by one layer height.
    6. The process repeats until the complete part is formed.

    Advantages: relatively simple equipment, low material cost for common polymers, and easy prototyping.

    2. Stereo Lithography (SLA)

    SLA is a vat photopolymerization process that uses liquid photosensitive resin.

    Working:

    1. A build platform is positioned in a vat of photopolymer resin.
    2. A UV laser or projected UV light selectively exposes the resin according to the current layer.
    3. The exposed resin polymerizes and becomes solid.
    4. The platform moves by the layer thickness and fresh resin covers the next layer region.
    5. Exposure is repeated until the part is complete.
    6. The printed part is removed, washed and normally post-cured.

    Comparison: FDM deposits melted/softened filament, whereas SLA selectively cures liquid resin using light. SLA generally provides finer details and smoother surfaces, while FDM is often simpler and economical for many prototype applications.

  18. Q5(a). Discuss the four primary forms of 3D printing raw material.20257m

    Module 2: 3D Printing Materials

    Discuss the four primary forms of 3D printing raw material.

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    Four Primary Forms of 3D Printing Raw Material

    The major forms of raw material used in additive manufacturing are:

    1. Liquid: Used mainly in vat photopolymerization processes such as SLA. The liquid photopolymer is selectively cured by light.
    2. Solid: Includes thermoplastic filaments, pellets and sheets. FDM commonly uses filament, while some extrusion systems use pellets.
    3. Wire: Metal wire is used as feedstock in wire-based additive manufacturing and some directed-energy-deposition systems. The wire is melted by a heat source and deposited layer by layer.
    4. Powder: Powder is used in processes such as SLS, selective laser melting and binder jetting. Particle size, distribution, flowability and other powder properties strongly influence the process.

    Selection

    The appropriate feedstock depends on the manufacturing process, required mechanical properties, accuracy, surface finish, production rate and cost.

  19. Q5(b). Explain the properties of polymers used in FDM and SLA processes. How do these properties affect the final product performance?20257m

    Module 2: 3D Printing Materials

    Explain the properties of polymers used in FDM and SLA processes. How do these properties affect the final product performance?

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    Properties of Polymers Used in FDM and SLA

    Polymers in FDM

    FDM uses thermoplastics such as PLA, ABS, PETG and nylon. Important properties include:

    • Melting/softening behavior: determines extrusion temperature and processing window.
    • Viscosity in the molten state: affects flow through the nozzle and layer deposition.
    • Interlayer adhesion: strongly affects strength in the build direction.
    • Shrinkage and thermal expansion: influence warping and dimensional accuracy.
    • Toughness and strength: determine functional performance.
    • Moisture sensitivity: some polymers absorb moisture, which can degrade print quality.

    Polymers in SLA

    SLA uses photosensitive liquid resins. Important properties include:

    • Photosensitivity: determines how effectively the resin cures under the selected wavelength.
    • Viscosity: affects resin recoating and flow between layers.
    • Cure depth and conversion: influence dimensional accuracy and mechanical properties.
    • Shrinkage: can affect dimensions during and after curing.
    • Mechanical properties: determine stiffness, strength, toughness and durability of the finished part.

    Effect on final performance

    Material properties influence dimensional accuracy, surface quality, layer adhesion, strength, flexibility, heat resistance and durability. Therefore, polymer selection must match the functional requirements of the component.

  20. Q6(a). What are the steps involved in cost estimation of an FDM 3D printed component? Mention the key factors affecting cost.20257m

    Module 3: Solid Based 3D Printing Processes

    What are the steps involved in cost estimation of an FDM 3D printed component? Mention the key factors affecting cost.

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    Cost Estimation of an FDM 3D Printed Component

    A practical FDM cost estimate can be divided into material, machine, labor, energy and post-processing costs.

    Steps

    1. Determine material consumption: Obtain filament mass or volume from the slicer, including model material and support material.
    2. Calculate material cost: Multiply consumed mass by the material cost per unit mass.
    3. Determine machine time: Estimate printing time from the slicer.
    4. Calculate machine cost: Multiply machine operating time by the machine hourly rate, including depreciation, maintenance and overhead.
    5. Calculate electricity cost: Estimate energy consumption and multiply by the electricity tariff.
    6. Add labor cost: Include setup, bed preparation, filament loading, monitoring and part removal where applicable.
    7. Add post-processing: Include support removal, sanding, finishing, washing or other required operations.
    8. Add overhead and profit: For commercial production, include facility overhead, reject allowance and desired profit margin.

    Simplified formula

    Total cost = Material + Machine time + Electricity + Labor + Post-processing + Overhead

    Key cost factors

    Material type and quantity, infill percentage, layer height, support volume, print duration, machine depreciation, electricity, labor, failure rate and finishing requirements all influence the final cost.

  21. Q6(b). Explain the principle and working of the Stereo Lithography Apparatus (SLA) process. Include the role of photopolymerization.20257m

    Module 4: Liquid Based 3D Printing Processes

    Explain the principle and working of the Stereo Lithography Apparatus (SLA) process. Include the role of photopolymerization.

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    Principle and Working of Stereo Lithography Apparatus (SLA)

    SLA is based on photopolymerization, in which liquid photosensitive resin is converted into a solid polymer when exposed to suitable light.

    Working

    1. A CAD model is converted into layers by slicing software.
    2. The build platform is positioned in a vat containing photopolymer resin.
    3. A UV laser or projected UV light selectively exposes the resin according to the first layer.
    4. Photoinitiators in the resin absorb light and initiate polymerization, causing the exposed resin to solidify.
    5. The platform moves by one layer thickness.
    6. Fresh liquid resin flows or recoats the build area.
    7. The next layer is exposed and bonded to the previous layer.
    8. The cycle continues until the complete component is built.
    9. The part is removed, washed to remove uncured resin and usually post-cured to achieve the required properties.

    Role of photopolymerization

    Light initiates chemical reactions that link monomer molecules into polymer chains. The exposure dose, wavelength, resin formulation and curing conditions affect cure depth, dimensional accuracy, surface quality and final mechanical properties.

    Conclusion: SLA provides high resolution and fine surface detail because the part is formed by controlled optical curing of liquid resin.

  23. Q7(a). Discuss the scanning techniques and curing processes involved in SLA-based 3D printing. Why are these steps critical for part accuracy?20257m

    Module 4: Liquid Based 3D Printing Processes

    Discuss the scanning techniques and curing processes involved in SLA-based 3D printing. Why are these steps critical for part accuracy?

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    Scanning Techniques and Curing in SLA

    Scanning techniques

    SLA selectively exposes resin to create each layer. Common approaches include:

    • Laser scanning: A focused UV laser is directed by mirrors/galvanometers and traces the contours and required interior regions of the layer.
    • Vector scanning: The laser follows calculated paths corresponding to boundaries and internal hatch patterns.
    • Projection-based exposure: A projector or imaging system exposes an entire layer pattern, reducing the need for point-by-point laser movement.

    Curing process

    The light activates photoinitiators in the resin and starts polymerization. Exposure must provide sufficient energy to cure the required depth while avoiding excessive curing beyond the intended boundary.

    After printing, the part is normally washed and post-cured under controlled light conditions to improve conversion and mechanical properties.

    Why scanning and curing affect accuracy

    1. Incorrect laser power or exposure can cause under-cure or over-cure.
    2. Over-cure can enlarge features and close small gaps.
    3. Under-cure can produce weak layers and incomplete features.
    4. Scan speed, spot size and path spacing affect dimensional accuracy and surface quality.
    5. Layer thickness influences stair-stepping and detail resolution.

    Therefore, controlled scanning and curing are essential for obtaining accurate dimensions, good surface finish and adequate interlayer bonding.

  24. Q7(b). Describe the steps for cost estimation of an SLA 3D printed component. What factors influence the overall cost?20257m

    Module 4: Liquid Based 3D Printing Processes

    Describe the steps for cost estimation of an SLA 3D printed component. What factors influence the overall cost?

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    Cost Estimation of an SLA 3D Printed Component

    Steps

    1. Estimate resin consumption: Determine the volume or mass of model resin and support structures from the slicer.
    2. Calculate resin cost: Multiply the consumed resin quantity by the resin price per unit quantity.
    3. Estimate machine time: Obtain build time from the printer software.
    4. Calculate machine cost: Apply the printer's hourly operating/depreciation and maintenance rate.
    5. Add electricity cost: Estimate energy used during printing and multiply by the applicable tariff.
    6. Add labor: Include setup, resin preparation, platform handling, washing and part removal.
    7. Add post-processing: Include washing, support removal, UV post-curing, sanding and other finishing.
    8. Add overhead/reject allowance: Include facility overhead, consumables and possible failed prints.

    Cost factors

    Major factors are resin price and volume, support volume, print time, layer height, model orientation, printer depreciation, electricity, labor, cleaning supplies, post-curing and finishing requirements.

    Approximate formula:

    Total SLA cost = Resin + Machine + Electricity + Labor + Post-processing + Overhead + Reject allowance.

  25. Q8(a). Explain the need for post-processing in 3D printing. Discuss both functional and aesthetic reasons with examples.20257m

    Module 6: Post Processing and Quality

    Explain the need for post-processing in 3D printing. Discuss both functional and aesthetic reasons with examples.

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    Need for Post-Processing in 3D Printing

    Post-processing consists of operations performed after printing to obtain the required functional and aesthetic properties.

    Functional reasons

    • Remove supports: Makes the part usable and exposes required features.
    • Improve dimensional accuracy: Finishing operations can remove small unwanted material.
    • Increase surface quality: Smoothing can reduce roughness and friction.
    • Improve mechanical properties: Curing, heat treatment, coating or other processes can improve strength, hardness or durability depending on the material.
    • Improve chemical/environmental resistance: Coatings can protect surfaces.
    • Prepare for assembly: Holes, interfaces and mating surfaces may need cleaning or finishing.

    Aesthetic reasons

    • Remove visible layer lines and print marks.
    • Produce a smoother and more uniform appearance.
    • Apply primer, paint, colour or protective coating.
    • Improve gloss, texture or surface uniformity.

    Examples

    FDM parts may require support removal, sanding, polishing or acetone vapour smoothing for suitable materials. SLA parts generally require washing and UV post-curing. SLS parts require powder removal and may be polished, dyed or coated.

    Thus, post-processing converts a freshly printed part into a component that meets its required functional and visual specifications.

  26. Q8(b). Describe the steps involved in post-processing of 3D printed parts. Include cleaning, fixing, curing, surface finishing, and colouring techniques.20257m

    Module 6: Post Processing and Quality

    Describe the steps involved in post-processing of 3D printed parts. Include cleaning, fixing, curing, surface finishing, and colouring techniques.

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    Steps in Post-Processing of 3D Printed Parts

    1. Cleaning and support/powder removal

    • FDM: Remove support structures mechanically or with suitable soluble-support methods.
    • Material Jetting: Remove support material according to the material system.
    • SLS/Powder-bed processes: Remove loose powder using brushing, air or appropriate powder-removal equipment.
    • SLA: Wash the part to remove uncured resin.

    2. Fixing and repair

    Defects or surface gaps may be corrected using filling, gluing, welding or other material-compatible repair techniques.

    3. Curing or hardening

    SLA and some other resin-based parts are post-cured under controlled UV exposure to increase polymer conversion and achieve the intended properties.

    4. Surface finishing

    Common methods include:

    • Sanding
    • Polishing
    • Tumbling
    • Hydro dipping
    • Epoxy coating
    • Electroplating
    • Vapour smoothing, such as acetone treatment for suitable thermoplastics

    5. Colouring and coating

    The surface may be primed and painted or treated with dyes/coatings to obtain the required colour, appearance and protection.

    Final result

    The sequence is generally clean/remove supports or powder → repair/fix → cure/harden where required → surface finish → prime/paint/coat. The exact sequence depends on the printing material and intended application.

  27. Q9(a). Explain various inspection and testing methods (digital, visual, physical) used in 3D printing. What are common defects and their causes?20257m

    Module 6: Post Processing and Quality

    Explain various inspection and testing methods (digital, visual, physical) used in 3D printing. What are common defects and their causes?

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    Inspection, Testing, Defects and Their Causes

    Inspection and testing verify that a printed component satisfies dimensional, visual and functional requirements.

    1. Digital inspection

    The manufactured part can be measured or scanned digitally and compared with the CAD model. Methods include 3D scanning, dimensional metrology and digital deviation maps. These methods help identify dimensional errors and geometric deviations.

    2. Visual inspection

    The surface is examined for visible defects such as cracks, warping, layer separation, roughness, incomplete features, discoloration and poor support removal.

    3. Physical inspection/testing

    Depending on the application, tests can include dimensional measurement, hardness, tensile testing, compression testing, density/porosity measurement and functional fit tests.

    Common defects and causes

    Defect Typical causes
    Warping Thermal contraction, poor bed adhesion, unsuitable temperature or cooling
    Layer separation/delamination Poor interlayer bonding, low temperature, contamination or excessive cooling
    Stringing Incorrect retraction or temperature settings in FDM
    Under-extrusion Poor filament feed, clogged nozzle or incorrect extrusion settings
    Stair-stepping Excessive layer thickness or unfavorable orientation
    Voids/porosity Insufficient fusion, poor powder quality or incorrect process parameters
    Surface roughness Layer height, powder characteristics, scanning/extrusion conditions or inadequate finishing

    Conclusion

    A combination of digital, visual and physical inspection gives a more reliable assessment because no single method detects every possible defect.

  28. Q9(b). Discuss the materials and process parameters that influence the quality of SLS-based 3D printed parts. Provide examples.20257m

    Module 5: Powder Based 3D Printing Processes

    Discuss the materials and process parameters that influence the quality of SLS-based 3D printed parts. Provide examples.

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    Materials and Process Parameters Affecting SLS Part Quality

    Material-related factors

    1. Particle size and distribution: Fine, consistently distributed powder can improve layer uniformity and resolution, while unsuitable distributions can reduce packing quality.
    2. Flowability: Powder must spread evenly to form consistent layers.
    3. Powder morphology: Particle shape affects packing density and spreading behavior.
    4. Moisture/contamination: Moisture and contamination can affect flow, bonding and final properties.
    5. Recyclability/refresh ratio: Reused powder may experience changes in properties, so the allowable reuse and fresh-powder ratio must be controlled.
    6. Material melting/sintering behavior: Thermal properties determine the energy required for consolidation.

    Process parameters

    • Laser power: Too little energy may cause incomplete fusion; excessive energy can cause overheating and distortion.
    • Scan speed: Affects energy delivered per unit area. Excessive speed can reduce fusion.
    • Layer thickness: Smaller layers can improve detail and surface quality but may increase build time.
    • Hatch spacing: Controls overlap between adjacent scan tracks and therefore affects consolidation.
    • Bed/chamber temperature: Helps control thermal gradients and dimensional stability.
    • Scan strategy: Influences heat distribution, residual stress and part properties.

    Examples

    For polymer SLS using materials such as nylon, unsuitable powder flowability or excessive laser energy can produce poor surface quality or dimensional defects. For metal powder-bed systems, carefully controlled laser energy, scan speed and layer thickness are essential for adequate fusion and low porosity.

    Conclusion

    High-quality SLS parts require the correct combination of powder characteristics and process parameters. These variables directly influence density, strength, dimensional accuracy, surface finish and defect formation.