Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Manufacturing And Materials > Additive Manufacturing > Flashcards

Additive Manufacturing Flashcards

1
Q

What disadvantages of traditional manufacture does additive manufacturing aim to counteract?

A

Restricted geometric complexity

Long lead times

Expensive tooling

Material wastage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is additive manufacturing?

A

Building of a shape by adding material using point or line addition

“A process of joining materials to make objects from 3D model data, usually layer upon layer.”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the 7 categories of AM?

A

Material Extrusion

Vat Polymerisation

Material Jetting

Binder Jetting

Powder Bed Fusion

Direct Energy Deposition

Sheet Lamination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the general advantages of AM?

A

Greater design freedom (allows for more complex geometry

Reduced lead times (no production lines, minimal set up)

Efficient material usage

Tool-less process

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the general disadvantages to AM?

A

Slower production rates

Higher material costs

Limited component sizes

Limited material selection

Potentially lower mechanical properties (in some processes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Briefly describe the generalised AM workflow

A

1) Design part using CAD
2) Convert 3D model into 2D slices
3) Set up printing technique
4) Print part
5) Remove and clean up part

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What information does the STL file contain?

A

XYZ coordinates of the vertices of each triangle element in the mesh and the surface normal vector

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What resolution should the CAD model be for AM?

A

1/10 of the printer resolution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where is support material needed?

A

Where features are disconnected

Where overhangs are present at angles greater than 45 degrees

Where features bridge previous layers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the key considerations when designing a part with AM?

A

STL Resolution

STL Errors

Slice thickness

Support material

Part orientation (minimal support/build time, anisotropic properties, mechanical behaviour, surface roughness)

Wall thickness/infill

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why is infill a key consideration for AM component design?

A

Infill affects the build time and final strength of the part

Infill density and geometry needs to be determined

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Briefly describe Fused Deposition Modelling (FDM)

A

Thermoplastic filament melted and extruded through nozzle

Filament deposited layer by layer and solidifies

Print head moves in XY plane. Once a layer is completed, it moves in Z direction for new layer

Depending on geometry, support material may be required

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What factors determine the print resolution for FDM?

A

Nozzle diameter (determines min feature size)

Layer height

‘Road width’, depends on flow rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

In FDM, why is a gap left intentionally between printed roads? And why may this cause problems?

A

Avoids distortion

Leads to porosity and reduced mechanical properties

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How are distortion and print velocity related for FDM?

A

Changing print velocity without changing material flow rate causes distortion

Generally, higher print velocities cause higher distortion at corners

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What surface finish does FDM produce?

A

Rough, due to stacking layers of filament

Stair-stepping occurs at angled surfaces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How is surface roughness defined for FDM?

A

Roughness, Rt, is the distance from peak to valley

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the two main factors that affect rate of deposition for FDM?

A

Print velocity

Layer height (h)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What affect would increasing the layer height, h, have for FDM?

A

Increase build rate

Decrease resolution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What affect would increasing the print velocity have for FDM?

A

Increase build rate

Decrease resolution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What factors limit the flow rate and nozzle diameter for FDM?

A

Force that can be applied to the filament (depends on motor, polymer stiffness)

Polymer melt viscosity

Heat transfer possible to melt the filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does the Poisuelle equation determine?

A

Approximate force required for extrusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe the properties and extrusion temperature for PLA (Polylactic Acid) for FDM

A

Biodegradable, stuff, hard, brittle

180-230 degrees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Describe the properties and extrusion temperature for PEEK (Polyether Ether Ketone) for FDM

A

Tough, very strong, high temperature and chemical resistance

360-400 degrees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Describe the properties and extrusion temperature for Nylon (Polyamide) for FDM

A

Tough, strong, good chemical/heat resistance, absorbs water

240-270 degrees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Can FDM work with composite materials? If so, how?

A

Yes

Particulates and short fibres can be added to thermoplastic filaments

Can use continuous fibre extrusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How do composite materials affect the mechanical properties of a component produced with FDM?

A

Increased strength/stiffness

Reduced ductility/toughness

Increased viscosity (extrusion more difficult)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What challenges does using higher extrusion temperatures bring to FDM?

A

Printers must be able to withstand the higher temperature

Large difference in temperature between extruded and build platform induces mechanical strains (warp)

Secondary support materials also need to support the higher temperature

Longer cooling times increase reliance on support material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

When might support material be necessary for FDM?

A

When bridging or overhangs are present

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Certain FDM printers only print one material. How does this affect the support possible for the part?

A

Support must be mechanically detached or broken off

Removal may be impossible, or damage final part

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What advantages and disadvantages are offered by dual extrusion FDM printers?

A

Support material is a different material to primary build material

Can be a dissolvable material, allowing for easier removal from complex geometry or internal structures

Leave little or no surface defects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What mechanical properties do most FDM components have?

A

Very anisotropic (strong in filament direction, weak transverse)

Transverse properties depend on bonding between filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

How can bonding strength between filaments be improved for FDM?

A

Higher extrusion/platform temperatures

Slower cooling rates

Negative gaps between filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What are the general advantages of FDM?

A

Can produce functional parts

Can prototype

Minimal wastage

Minimal post processing

Easy material changes

Large build volumes possible

Low cost equipment

Low cost materials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What are the general disadvantages of FDM?

A

Resolution highly dependant on many factors

Slow build rate

Anisotropic properties

36
Q

Briefly describe what stereolithography (SLA) is

A

UV laser selectively cures a liquid photopolymer in a vat

37
Q

What are the two configuration for stereolithography?

A

Upright (laser above, surface of liquid cures, build platform lowers into vat)

Inverted (laser underneath, laser at bottom of vat cures, build platform raises)

38
Q

What are the main constituents of a photopolymer?

A

Photoinitiators (absorb photos and generate free radicals)

Monomers (building blocks the cross link)

39
Q

Name some common monomers used in photopolymers

A

Acrylates (quick reaction, high shrinkage)

Epoxies (low shrinkage, slow reaction)

A blend of the two

40
Q

What are the main difficulties for upright SLA?

A

The surface of the polymer must be completely level and ripple-free

The part must be able to resist the wiper blade brushing over

41
Q

What are the main difficulties for inverted SLA?

A

Part must resist peeling from the bottom of the vat

42
Q

For inverted SLA, why is cross sectional area a limiting factor?

A

The larger the cross sectional area, the more difficult the surface will be to peel from the bottom of the vat

43
Q

Why is the cross section of the polymerised material a parabola in SLA?

A

Caused by the Gaussian Intensity profile of the UV laser (most intense in the centre and lowers towards the edges so more penetration in centre)

44
Q

Are supports required for SLA?

A

Yes, non polymerised photopolymer provides no support

Supports help resist peeling or wiper forces

Ensure part is always connected to the build platform

45
Q

Describe briefly the Digital Light Processing (DLP) variant of SLA

A

A projector illuminates a whole layer at a time, instead of scanning with a laser

Polymerisation occurs at illuminated pixels

46
Q

Describe briefly the Continuous Liquid Interface Polymerisation (CLIP) variant of SLA

A

Similar to DLP, but has an oxygen permeable bottom plate. The oxygen inhibits polymerisation, creating a dead zone of liquid photopolymer.

Photopolymer just above dead zone is cured and raised from the vat.

Projector image continuously changes and projects the required cross section as the part is drawn out

47
Q

What advantages does CLIP have over DLP

A

CLIP can raise the platform continuously so build times are faster

No peeling damage due to the liquid dead zone

No stair stepping due to continuous nature

48
Q

What are the general advantages of SLA?

A

High resolution (even applicable to micro scale with beam focusing)

Excellent surface finish

Large range of build volumes

Range of material properties

Isotropic

Fast build rates possible (with CLIP and DLP)

49
Q

What are the general disadvantages to SLA?

A

Only one material can be printed at a time

Products tend to be brittle, lack durability

Products degrade over time due to extended UV exposure

Limited material choice (needs to be photopolymerisable)

SLA has low build rate

Stair stepping (for SLA and DLP)

Support needed

Multiple processing steps

High equipment/material cost

Difficult to change material

50
Q

Briefly describe photopolymer jetting (polyjet)

A

Inkjet print heads jet photopolymer onto build platform

UV lamps immediately cure photopolymer

Multiple print heads can jet multiple materials

51
Q

What variables need to be controlled in polyjet to achieve smooth lines?

A

Droplet frequency

Impact speed

Sweep speed (of printer head)

Droplet size

Contact angle

52
Q

What are the general advantages to polyjet?

A

Multiple build materials at once/easily change material

High resolution

Fast build rate

Good surface finish

Wide range of build volumes

Range of material properties

Isotropic component

Low cost equipment

53
Q

What are the limitations when using polyjet?

A

Limited selection of materials (need low viscosity and to be photopolymerisable)

Brittle

Some surface roughness from stair stepping

Need extensive support material

Difficult post processing

High wastage (support)

High material cost

54
Q

Briefly describe selective laser sintering (SLS)

A

Thin layer of plastic power selectively sintered (partially melted) by a laser

Inert (N2) atmosphere prevents powder oxidation

After each layer is sintered, build platform lowers into powder bed and new powder is spread on top

Powder bed heated

55
Q

Why is the powder bed heated for SLS/SLM?

A

Minimised thermal strains

56
Q

What would happen if the laser energy used for SLS was too high or too low?

A

If too high, the powder is severely degraded, dimensions are enlarged

If too low, the powder doesn’t fully sinter. Product is highly porous and weak

57
Q

What are the three powder fusion mechanisms?

A

1) Solid State Sintering (SSS): particle diffusion occurs at elevated temperatures, driven by reduction in surface area and surface energy (slow)
2) Liquid Phase Sintering (LPS): melted portion acts as binder for solid portion (faster)
3) Full melting: solid particles melt together (fastest)

58
Q

What benefits does solid/liquid sintering offer over full melting for SLS?

A

Less shrinkage, good dimensional stability, less thermal strain (warp)

59
Q

What benefits does full melting offer over solid/liquid sintering for SLS?

A

Better consolidation, reduced porosity, improved mechanical properties

60
Q

What materials are usually processed with LPS?

A

Amorphous polymers

61
Q

What materials require a balance between LPS and full melting for processing?

A

Semi-crystalline polymers

62
Q

What materials usually require full melting to process by SLM?

A

Metals

63
Q

In terms of melting points, what is the main difference between amorphous and semi-crystalline polymers?

A

Semi-crystalline polymers have a very sharp melting point.

Amorphous polymers melt over a longer temperature range

64
Q

What type of polymer (amorphous or semicrystalline) is better for functional parts and why (using SLS/SLM)?

A

Semi-crystalline, lower porosity parts, hence stronger, improved mechanical properties

65
Q

What type of polymer (amorphous or semicrystalline) is better for investment casting moulds and why (using SLS/SLM)?

A

Amorphous, produce a higher porosity part so generally weaker, but ok for investment casting

66
Q

How can sand, metals and ceramics be processed using SLS? What are they normally used for?

A

Powders coated with polymer binder

Sand casting moulds

67
Q

Can unsintered powder from SLS be recycled?

A

Not fully, usually 1/3 of the powder can be reused.

68
Q

How can the powder utilisation be improved for SLS?

A

By producing multiple parts in one build (nesting)

69
Q

What function does unsintered powder perform in SLS?

A

Acts as support material for bridging/overhangs in the part

70
Q

Why is powder spreadability important?

A

Allows easy flow, good coverage of previous build layer

71
Q

Coarser, spherical powders have better spreadability. Why might the larger particles cause a problem in SLS?

A

Larger particles increase the minimum feature size and layer thickness

72
Q

What problems are associated with smaller powder diameters in SLS?

A

Smaller particles tend to charge with static and stick together

73
Q

What does the Hausner Number (HR) describe? How is it calculated?

A

Spreadability of powders

HR = Powder Density / Bulk Density

74
Q

What is the relationship between Hausner number and powder packing (and hence mechanical properties)?

A

Lower Hausner number means denser packing, lower porosity and fuller sintering

75
Q

What are the general advantages to SLS?

A

Can produce functional parts

Almost isotropic properties

Wide range of materials

Good resolution

Geometric freedom

Support from unsintered powder

Wide range of build volumes

High build rate

76
Q

What are the general limitations to using SLS?

A

Only one build material at a time

Sintering produces porosity (limited functionality of amorphous polymers)

Moderate surface roughness

Stair stepping

Powder handling is difficult, potentially explosive

High wastage

77
Q

Describe Selective Laser Melting (SLM)

A

Thin layer of metal powder selectively melted by laser

78
Q

How does metal SLM differ from polymer SLS?

A

Full melting occurs

Higher laser power needed

Need inert atmosphere for reactive metals

Anti-spark precautions are very important

Metal powders are finer, produce higher density part

Layer thickness is smaller

Support structures are needed

May use cross hatch scanning patterns to reduce thermal strains

79
Q

What three situations may occur if laser parameters are incorrect for metal SLM?

A

Keyhole formation: when laser velocity is too low, laser power is too high. Results in high porosity

Balling (melt pool separation): laser velocity too high

Incomplete melting: laser velocity too high, laser power too low

80
Q

What are the general advantages to metal SLM?

A

Can make functional parts

Full melting results in low porosity and good mechanical properties

Rapid heating/cooling gives fine-grained microstructure

Nearly isotropic properties

Wide range of engineering metals

Good resolution

Geometric freedom

Wide range of build volumes

Low wastage

81
Q

What are the general limitations of metal SLM?

A

Only one material at a time

Moderate surface roughness

Stair stepping

Metal powders are hazardous/explosive

Difficult post-processing

Low build rate

High equipment cost

82
Q

What is Electron Beam Melting (EBM)?

A

Electron beam melts metal powder

Under high vacuum to produce electrons

83
Q

What are the advantages of EBM?

A

Lower thermal strains

Low risk of oxidation/contamination

Fast build rate

84
Q

What is binder jetting?

A

Inkjet print heads apply liquid bonding agent to powder layers

85
Q

What are the general advantages of binder jetting?

A

Uses almost any powder

Can print colour

Unbound powder provides support

Wide range of build volumes

High build rate

Low material/equipment cost

86
Q

What are the general disadvantages of binder jetting?

A

Limited resolution

Only one powder at a time

High porosity, low mechanical strength

Post-processing required for metals/ceramics

Moderate surface roughness

Stair stepping

Difficult powder handling

Manufacturing And Materials (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions