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Manufacturing Processes > Additive Manufacturing > Flashcards

Additive Manufacturing Flashcards

1
Q

Additive Manufacturing/ Rapid Prototyping (AM/RP) technologies

A

Referred to as:

  • Solid free-form fabrication
  • Direct Digital Manufacturing (DDM)
  • Layer(ed) manufacturing
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2
Q

What is AM/RP?

A

-Technology that quickly transforms a CAD model into a physical part directly using the computer description of the part shape (integration of CAD with CAM).

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3
Q

Method

A

-Fabrication of completely arbitrary 3-dimensional geometries without the constraints from traditional manufacturing techniques.

  • Dramatic impact to industry by helping to speed up the product development cycle:
  • Rapid evaluation of the design’s manufacturability.
  • Concept models used in design reviews to establish design effectiveness & for visualisation purposes in client presentations.
  • Working prototypes communicated to suppliers for quotes.
  • Reducing high capital costs with production tooling being one of the longest process in the manufacturing process
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4
Q

Classification AM/RP processes

A

-Subtractive:
With traditional prototyping processes material is removed from a workpiece.

-Additive:
Build up of a part by adding material incrementally.

-Virtual:
Use of adavanced computer-based visualisation.

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5
Q

7 Categories of Additive Manufacturing

A

-Standards to classify the range of AM processes by the Maerican Society for Testing Materials (ASTM) group ASTM F42 - Additive Manufacturing:

  • VAT Photopolymerisation (e.g. stereolithorgaphy)
  • Liquid photopolymer resin is cured with a UV light source.
  • Material Jetting
  • Material is jetted onto a build platform where it solidifies (curing using UV); 3D Polyjet Printing
  • Binder Jetting
  • A print head deposits a binder adhesive on a bed of powder based material; 3D Powder Printing (3DP)
  • Material Extrusion
  • Material is drawn through a nozzle, where it is heated and is then deposited layer by layer. (FDM)
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6
Q

Classification of RP processes

A

Additive technologies:

  • Fused Deposition Modelling (FDM)
  • Stereolithography (SLA - Stereolithography Apparatus; or SL, STL)
  • Selective Laser Sintering (SLS)
  • Direct Metal Laser Sintering (DMLS)
  • Electron Beam Melting (EBM)
  • 3-Dimensional Printing Technologies (3DP)
  • Laminated Object Manufacturing (LOM)
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7
Q

AM/RP Applications

A
  • Prototyping:
  • The primary use of rapid prototyping is to quickly make prototypes for communication & testing purposes.
  • Very useful for testing a design to evaluate it’s performance.
  • Allows to evaluate functionality not possible without RP, e.g. transparent prototype parts
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8
Q

AM/RP applications - Rapid Tooling

A

-Tooling is traditionally the most expensive & time consuming of all manufacturing processes. Some characteristics are:

  • Toughness & wear resistance
  • Complex geometries
  • Very high dimensionally accuracy (0.01mm or better)
  • Very high surface finish
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9
Q

Rapid Tooling - Indirect Tooling

A
  • Prototypes are used as patterns for making moulds & dies; used in a number of manufacturing processes e.g.
  • Vacuum Casting - RP pattern is cast into a silicone or other temperature vulcanised rubber (RTV) mould.
  • Sand Casting - RP pattern made by laminated Object Manufacturing resembles the traditionally used wooden pattern.
  • Investment Casting - RP pattern made by Laminated Object Manufacturing from paper are often used as they are dimensionally stable with paper shell burning out.
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10
Q

Rapid Tooling - Investment Casting

A

-Patterns made by stereolithography

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11
Q

Rapid Tooling - Direct Tooling

A
  • Hard tooling is made directly from CAD data without fabricating a pattern first
  • Selectively sintering of polymer-coated steel pellets together to produce a metal mould, burn off the polymer binder & infiltrate with copper.
  • Development of ceramic composite materials using Direct Shell Production Casting techniques
  • Construct of sand moulds directly from CAD data using sand-like material (foundry-type sand) that is sintered into moulds
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12
Q

Rapid Tooling - Facts

A
  • Advantages:
  • Less dependant on highly skilled patternmakers
  • Reduction of high labour costs
  • Shorter lead-times in the production of patterns & moulds using the concept of net shaped tools.
  • Optimised mould design possible: chill- and cooling-channel placement possibly leading to reduced cycle times.
  • Limitations:
  • Potentially reduced tool life
  • Limited material range; often only specialised and proprietary materials and processes available.
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13
Q

AM/RP Applications

A
  • Rapid Manufacturing:
  • Direct production of functional and saleable products directly from CAD data.
  • For short production runs
  • Products which cannot be made by subtractive processes
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14
Q

AM/RP Applications - Rapid Manufacturing

A
  • Advantages
  • Natural progression to produce functional and saleable products directly from CAD data.
  • Ideal for short production runs as no tooling is required; significant time & cost savings.
  • Ideal for producing custom parts tailored to customer specifications.
  • Ideal for products that cannot be made by using traditional manufacturing processes (subtractive or compressive).
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15
Q

AM/RP Applications - Rapid Manufacturing - Limitations

A
  • Economic reasons due to high raw material costs.
  • Time issue to produce parts quickly for high volume manufacture.
  • Long-term performance characteristics with regards to wear and life cycle compared to well established traditional methods of manufacturing.
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16
Q

Basic Steps in create AM/RP models

A
  • Define the part to be built a CAD environment as a surface or 3D solid model
  • Separate bounding surfaces of the CAD model into a collection of slices (triangle facets) and write on a file using STL-format (STL - Stereolithography Tessellation Language).
  • Analyse each slice separately to set & compile instructions for the AM/RP machine to manufacture the part.
  • Manufacture the model building up one layer at a time driving a laser or modelling head (depending on the type of process) along a path.
17
Q

Basic Steps in creating AM/RP models

A
  • Three-dimensional description of each part.
  • The part is divided into slices
  • Support material is planned.
  • A set of tool directions is determined to manufacture each slice
  • Extruder path at section A-A for a Fused Deposition Modelling operation.
18
Q

STL File

A
  • Link between 3-D CAD design & the 3-D printer hardware
  • File format contains design data.
  • Modern CAD systems include STL output feature:
  • files suitable for rapid prototyping
  • requires solid-modellers rather than surface modellers.
19
Q

STL Format

A
  • CAD system settings with regards to STL mesh:
  • Triangles that are too large, small file size, prototyping with visible facets often calling “facets.”
  • Very small triangle mesh, big file size, long processing time, prototype accuracy or resolution not necessarily better.
  • For best fidelity a mesh approximately the size of the layers is used by the Additive Manufacturing / Rapid Prototyping system.
20
Q

Fused Deposition Modelling -FDM

A

-Thermoplastic is spool-fed & extruded through a heated die constructing the part layer by layer.

21
Q

FDM - Method

A
  • Filaments of heated thermoplastic or wax are extruded from the tip of an extruder-die that moves in the x-y plane.
  • Lowering the platform which is kept at a lower temperature to apply to subsequent layers upon the first; solidification by cooling.
  • Support structures may have to be built along the way, fastened to the part.
22
Q

FDM - Process Characteristics

A
  • Layer thickness is determined by extruder-die diameter (0.13mm - 0.33mm)
  • Extrusion detail of material (flat ribbon 0.08mm - 0.97mm)
  • Stepped surface finish on oblique surfaces.
  • Surface finish & accuracy:
  • Dimensional accuracy in x-y plane between 0.13mm-0.241mm
  • Fair to good surface finish
23
Q

FDM - Materials

A
  • Polymers - production-grad thermoplastics
  • Wax
  • Desired properties:
  • Rigid, dimensionally stable
  • Good strength & toughness
  • High resistance (chemical, UV, abrasion).
  • Nontoxic (biocompatible, sterilisable).
24
Q

FDM - Applications

A
  • Detailed models for fit form testing using engineering plastics including patient - and food - contacting applications.
  • Prototypes for higher-temperature applications
  • Trade show & marketing parts & models.
  • Rapid manufacturing of small detailed parts.
  • Patterns for investment casting
  • fabrication of specialised manufacturing tools.
25
Q

Stereolithography - SLA

A

-Fabricating a solid plastic part out of a photsensistive liquid polymer using a UV laser beam to solidify the polymer.

26
Q

SLA - Method

A
  • Scanning the liquid surface of a bath of phot-sensitive polymer resin with a ultraviolet (UV) laser beam that causes the resin to cure in the shape of a layer of the part.
  • Lowering the platform by the slice of thickness after each new layer is formed at the surface.
  • Final curing cycle in a UV oven to complete photo-polymerisation
27
Q

SLA - Process characteristics

A
  • Layer thickness 0.05mm -0.5mm
  • Capable of producing hollow & solid prototypes.
  • Prototype must start to be built on the tray for support structure
  • Surface finish & accuracy:
  • Smooth surface finish
  • Stair stepping & faceting depending on layer thickness
  • 0.025mm-0.05mm per 25.4mm of part dimension.
28
Q

SLA - Materials

A
  • Photo-sensitive polymers (resins)
  • Versatile in allowing to mimic a wide variety of engineering plastics.
  • Material spectrum to address requirements such as accuracy, durability, rigidity, flexibility, transparency, colour, temperature or moisture resistance, etc.
29
Q

Special applications resins

A

-Resins filled with non-crystalline nano-particles for improved strength or detail resolution.

30
Q

SLA - Applications

A
  • Functional prototypes - mimic production parts, used for functional testing & evaluation.
  • Presentation models - for design reviews, presentation, sales or marketing purposes.
  • Casting pattern for investment casting of a metal part, also used for sand or plaster casting.
  • End use production parts, even assemblies.
  • Rapid Tooling used to create limited-run tooling.
  • Architectural
  • Packaging
  • Electronics Applications
  • Automotive Applications
31
Q

SLA - Variation

A
  • Micro-stereolithography:
  • More highly focused laser (as small as 1micrometer)
  • Layer thickness ~ 10 micrometers
  • Photopolymers with much lower viscosity to ensure uniform layers.

Manufacturing Processes (12 decks)

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