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Manufacturing Processes > Additive manufacturing > Flashcards

Additive manufacturing Flashcards

1
Q

What are AM/RP technologies ?

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

Classification of AM/RP processes

A

Subtractive

Additive

Virtual

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3
Q

7 Categories of Additive Manufacturing

A

VAT Photopolymerisation

Material Jetting

Binder Jetting

Material Extrusion

Powder Bed Fusion

Sheet Lamination

Direct Energy Deposition (DED)

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4
Q

What is Direct Energy Deposition (DED)?

A

Nozzle deposits molten material (metal, polymer or ceramics) onto a build platform; molten with laser, plasma arc or electron beam

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5
Q

Process of Material Extrusion?

A

Material is drawn through a nozzle, where it is heated and is then deposited layer by layer. (FDM)

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6
Q

Process o f Binder Jetting?

A

A print head deposits a binder adhesive on a bed of powder based material; 3D Powder Printing (3DP)

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7
Q

Process of Material Jetting

?

A

Material is jetted onto a build platform where it solidifies (curing using UV); 3D Polyjet Printing

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8
Q

Process of VAT Photo polymerisation?

A

Liquid photopolymer resin is cured with a UV light source

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9
Q

What are some of the Additive technologies?

A
  • 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
  • Solid Ground Curing (SGC)
  • Laminated Object Manufacturing (LOM)
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10
Q

What are some of the characteristics of tooling?

A
  • Toughness and wear resistance
  • Complex geometries
  • Very high dimensionally accuracy (0.01 mm or better)
  • Very high surface finish
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11
Q

What are the different types of tooling?

A
  • Indirect tooling:
    Prototypes are used as patterns for making moulds and dies
  • Direct tooling:
    Production tools are cast as net shape tools directly from CAD files
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12
Q

Rapid tooling- Indirect tooling prototypes are used in a number of manufacturing processes such as..

A
  • 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 the paper shell burning out
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13
Q

What are the advantages of rapid tooling?

A

Less dependent on highly skilled patternmakers

Reduction of high labour costs

Shorter lead-times in the production of patterns and moulds using the concept of net shaped tools

Optimised mould design possible; chill- and cooling-channel placement possibly leading to reduced cycle times

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14
Q

What are the disadvantages of rapid tooling?

A

Potentially reduced tool life

Limited material range; often only specialised and proprietary materials and processes available

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15
Q

AM/RP applications

A
  • direct production of functional and saleable products
  • For short production runs
  • Products which cannot be made by subtractive processes.
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16
Q

Advantages of AM/RP

A

Natural progression to produce functional and saleable products directly from CAD data

Ideal for short production runs as no tooling is required; significant time and 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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17
Q

Limitations of AM/RP

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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18
Q

Basic steps to AM/RP models

A
  • Define what needs building either in a CAD or 3-D solid model software
  • Seperate bounding surface of the CAD model into a collection of slices (STL format)
  • Analyse each slice separately to set and compile instructions for the AM/RP machine to manufacture the part
  • Manufacture the model building one layer at a time
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19
Q

Fused Deposition Modelling (FDM)

A

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

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20
Q

FDM – Principle/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 subsequent layers upon the first; solidification by cooling

Support structures may have to be built along the way, fastened to the part

21
Q

Desired properties for FDM

A

Rigid, dimensionally stable

Good strength and toughness

High resistance (chemical, UV, abrasion)

Nontoxic (biocompatible, sterilisable

22
Q

Applications of FDM

A

Detailed models for fit & form testing using engineering plastics including patient- and food-contacting applications

Prototypes for higher-temperature applications

Trade show and marketing parts & models

Rapid manufacturing of small detailed parts

Patterns for investment casting

Fabrication of specialised manufacturing tools

23
Q

Advantages of FDM

A

Office Friendly

No Fumes

Support structures generated automatically

Prototypes can be drilled, tapped or machined

Tough and durable prototypes with no need for post curing

Wide range of plastics

24
Q

Disadvantage of FDM

A

Slow processing time compared to some AM/RP technologies

Accuracy limited by the thickness of the filament

Requires support structure

Limited to plastics

High investment cost

25
Q

Stereolithography – SLA

A

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

26
Q

SLA – Principle/Method

A
  • UV light scans the photosensitive polymer resin causing resin to cure in the shape of the part
  • Lowering the platform by the layer (slice) thickness after each new layer is formed at the surface
  • Final curing cycle in an UV oven to complete photo-polymerisation
27
Q

Advantages of SLA

A

Very accurate immediately after completion of the model

 Quick Prototyping process for visualisation and verification
purposes

 Smooth surface finish

 Support structures are generated automatically

 Can produce solid and hollow prototyp

28
Q

Disadvantages of SLA

A

Support structures need to be broken off (manually)

 Some inaccuracy in the z-direction

 Limited to photosensitive resins (typically brittle)

 Prototypes are generally difficult to machine due to being brittle

 Parts are prone to the “trapped volume” problem in which cups
in the structure that hold fluid cause inaccuracies

 Materials do not work well with “living hinges”, points, edges
and thread design

29
Q

Selective Laser Sintering – SLS

A

A moving laser beam melts and fuses (sinters) a heat-fusible powder one layer at a time to build solid 3D parts

30
Q

SLS – Principle/Method

A
  • Scanning and sintering metallic and non-metallic, thermoplastic powder using a carbon dioxide laser beam (CO2) that causes the powder to sinter (fuse or melt) and solidify in the shape of a layer of the
    prototype
  • Powder bed moves up and delivers polymer which aroller spreads across the surface of the build area, forming an even layer of powder
  • Non-sintered powder forms a ‘cake’ encapsulating and supporting the model as the build progresses
31
Q

What are the desired material properties?

A
  • Sterilisable, biocompatible, flame-retardant
  • High stiffness, toughness, elevated temperature resistance
  • Anisotropic mechanical properties (fibre-filled)
32
Q

What are the two types of 3D Printing technologies?

A
  • Binder Jetting

- Material Jetting

33
Q

Powder 3DP technology

A

Ink-jet printing heads move across a powdered material in a scanning pattern, distributing (printing) a liquid inorganic binder to “glue” (fuse) the powder in the shape of each layer

34
Q

Applications of 3D Printing?

A
  • Concept models
  • Parts for limited functional testing
  • Colour models for FEA and other engineering related applications
  • Architectural & landscape models
  • Colour industrial design models, especially consumer goods & packaging
  • Castings
35
Q

3D-Jetted Photopolymer – Principle

A

Ink-jet printing heads ejects micro-droplets of molten plastic or wax material onto a stationary platform which is cured by UV light(polymer phase change inkjet or jetted photopolymer technology)

36
Q

3D-Jetted Photopolymer – Applications

A
  • Concept development
  • Design validation
  • Form and fit analysis
  • Moulding and foundry casting patterns
  • Pattern for investment casting
37
Q

Laminated Object Manufacturing – LOM

A

Solid models are generated by laminating layers of sheet material on top of each other and laser-trim the cross-sectional shape of each layer

38
Q

LOM – Principle/Method

A
  • Paper or plastic sheet material with a heat-activated glue on one side is bonded to the build platform by applying pressure using a heated roller
  • A focused CO2 laser burns the outline of the first layer into the paper and then criss-crosses the excess area
  • The platform lowers and a feeder/collector mechanism advances new sheet material onto the build platform
  • The platform raises to a height consistent with the sheet/stock thickness ready for laminating the next layer
39
Q

Solid Ground Curing – SGC

A

A solid model is created by selectively exposing and curing an entire layer of photosensitive polymer when shining a UV light source through a photo mask that is positioned above the surface of the liquid polymer

40
Q

SGC – Principle/Method

A
  • A photo mask is printed on a glass plate using an electrostatic process (similar to photocopying and laser printing) charging a negative image of the layer onto the surface
  • Thin layer of liquid photopolymer is distributed over the surface of the work platform
  • Photo mask is positioned above the polymer surface, exposed to a high powered UV light source which cures the desired cross section of the photopolymer layer
41
Q

Additive Manufacturing : Limitations

A

Materials – growing range but will remain limited range with high costs

Accuracy and surface roughness – often tolerance limit +/- 0.01mm

Equipment cost – expensive often with poor output per £ investment

42
Q

Which of the following are typical problems with the various additive manufacturing technologies? (three best answers)

a) Inability of the designer to design the part
b) Inability to convert a solid part into layers
c) Limited material variety
d) Part accuracy
e) Poor machinability of the starting material
f) Part shrinkage

A

c) Limited material variety
d) Part accuracy
e) Poor machinability of the starting material

43
Q

Direct Metal Laser Sintering - Principle/Method

A

Scanning and sintering metallic powder using a focusedlaser beam (fibre laser) that causes the powder to sinter (fuse or melt) and solidify in the shape of a layer of the prototype

44
Q

DMLS – Applications

A

Functional Prototypes

Series-production parts

Tooling

Aerospace, Motorsport, Medical (dental, implants etc.)

45
Q

DMLS – Advantages

A

 All metals are recyclable; use only what you sinter!

 Near net-shape process, producing parts with high accuracy
and detail resolution

 Good surface quality and excellent mechanical properties

 Constant development and release of new materials onto the
market

46
Q

DMLS – Limitations

A

 Much more complex process than Selective Laser Sintering
with regards to designing support structure and orientation

 Parts need to be cut from the steel plate (usually using WireEDM);
increase to cycle time and labour costs

47
Q

3D-Jetted Photopolymer – Advantages

A

 Small layer thickness eliminating the stair effect common to
complicated curved surfaces

 Quick processing time; adjustable resolution

 Coloured printing

 Multi-material printing

 End-use parts

 Office friendly (quiet, safe, odour-free, easy to use)

 Living hinges and joints
Plymouth University - School of Marine Science and Engineer

48
Q

3D-Jetted Photopolymer – Limitations

A

 Limited choice of materials – only polymer and waxes can be
used

 Limited opportunity to enhance properties during post
processing – functional and aesthetic qualities of parts are
largely determined during the printing stage

 Support structure needed for overhangs, undercuts and fragile
elements

Manufacturing Processes (11 decks)

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