Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

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
Describe the properties and extrusion temperature for Nylon (Polyamide) for FDM
Tough, strong, good chemical/heat resistance, absorbs water 240-270 degrees
26
Can FDM work with composite materials? If so, how?
Yes Particulates and short fibres can be added to thermoplastic filaments Can use continuous fibre extrusion
27
How do composite materials affect the mechanical properties of a component produced with FDM?
Increased strength/stiffness Reduced ductility/toughness Increased viscosity (extrusion more difficult)
28
What challenges does using higher extrusion temperatures bring to FDM?
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
29
When might support material be necessary for FDM?
When bridging or overhangs are present
30
Certain FDM printers only print one material. How does this affect the support possible for the part?
Support must be mechanically detached or broken off Removal may be impossible, or damage final part
31
What advantages and disadvantages are offered by dual extrusion FDM printers?
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
32
What mechanical properties do most FDM components have?
Very anisotropic (strong in filament direction, weak transverse) Transverse properties depend on bonding between filaments
33
How can bonding strength between filaments be improved for FDM?
Higher extrusion/platform temperatures Slower cooling rates Negative gaps between filaments
34
What are the general advantages of FDM?
Can produce functional parts Can prototype Minimal wastage Minimal post processing Easy material changes Large build volumes possible Low cost equipment Low cost materials
35
What are the general disadvantages of FDM?
Resolution highly dependant on many factors Slow build rate Anisotropic properties
36
Briefly describe what stereolithography (SLA) is
UV laser selectively cures a liquid photopolymer in a vat
37
What are the two configuration for stereolithography?
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
What are the main constituents of a photopolymer?
Photoinitiators (absorb photos and generate free radicals) Monomers (building blocks the cross link)
39
Name some common monomers used in photopolymers
Acrylates (quick reaction, high shrinkage) Epoxies (low shrinkage, slow reaction) A blend of the two
40
What are the main difficulties for upright SLA?
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
What are the main difficulties for inverted SLA?
Part must resist peeling from the bottom of the vat
42
For inverted SLA, why is cross sectional area a limiting factor?
The larger the cross sectional area, the more difficult the surface will be to peel from the bottom of the vat
43
Why is the cross section of the polymerised material a parabola in SLA?
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
Are supports required for SLA?
Yes, non polymerised photopolymer provides no support Supports help resist peeling or wiper forces Ensure part is always connected to the build platform
45
Describe briefly the Digital Light Processing (DLP) variant of SLA
A projector illuminates a whole layer at a time, instead of scanning with a laser Polymerisation occurs at illuminated pixels
46
Describe briefly the Continuous Liquid Interface Polymerisation (CLIP) variant of SLA
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
What advantages does CLIP have over DLP
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
What are the general advantages of SLA?
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
What are the general disadvantages to SLA?
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
Briefly describe photopolymer jetting (polyjet)
Inkjet print heads jet photopolymer onto build platform UV lamps immediately cure photopolymer Multiple print heads can jet multiple materials
51
What variables need to be controlled in polyjet to achieve smooth lines?
Droplet frequency Impact speed Sweep speed (of printer head) Droplet size Contact angle
52
What are the general advantages to polyjet?
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
What are the limitations when using polyjet?
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
Briefly describe selective laser sintering (SLS)
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
Why is the powder bed heated for SLS/SLM?
Minimised thermal strains
56
What would happen if the laser energy used for SLS was too high or too low?
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
What are the three powder fusion mechanisms?
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
What benefits does solid/liquid sintering offer over full melting for SLS?
Less shrinkage, good dimensional stability, less thermal strain (warp)
59
What benefits does full melting offer over solid/liquid sintering for SLS?
Better consolidation, reduced porosity, improved mechanical properties
60
What materials are usually processed with LPS?
Amorphous polymers
61
What materials require a balance between LPS and full melting for processing?
Semi-crystalline polymers
62
What materials usually require full melting to process by SLM?
Metals
63
In terms of melting points, what is the main difference between amorphous and semi-crystalline polymers?
Semi-crystalline polymers have a very sharp melting point. Amorphous polymers melt over a longer temperature range
64
What type of polymer (amorphous or semicrystalline) is better for functional parts and why (using SLS/SLM)?
Semi-crystalline, lower porosity parts, hence stronger, improved mechanical properties
65
What type of polymer (amorphous or semicrystalline) is better for investment casting moulds and why (using SLS/SLM)?
Amorphous, produce a higher porosity part so generally weaker, but ok for investment casting
66
How can sand, metals and ceramics be processed using SLS? What are they normally used for?
Powders coated with polymer binder Sand casting moulds
67
Can unsintered powder from SLS be recycled?
Not fully, usually 1/3 of the powder can be reused.
68
How can the powder utilisation be improved for SLS?
By producing multiple parts in one build (nesting)
69
What function does unsintered powder perform in SLS?
Acts as support material for bridging/overhangs in the part
70
Why is powder spreadability important?
Allows easy flow, good coverage of previous build layer
71
Coarser, spherical powders have better spreadability. Why might the larger particles cause a problem in SLS?
Larger particles increase the minimum feature size and layer thickness
72
What problems are associated with smaller powder diameters in SLS?
Smaller particles tend to charge with static and stick together
73
What does the Hausner Number (HR) describe? How is it calculated?
Spreadability of powders HR = Powder Density / Bulk Density
74
What is the relationship between Hausner number and powder packing (and hence mechanical properties)?
Lower Hausner number means denser packing, lower porosity and fuller sintering
75
What are the general advantages to SLS?
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
What are the general limitations to using SLS?
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
Describe Selective Laser Melting (SLM)
Thin layer of metal powder selectively melted by laser
78
How does metal SLM differ from polymer SLS?
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
What three situations may occur if laser parameters are incorrect for metal SLM?
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
What are the general advantages to metal SLM?
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
What are the general limitations of metal SLM?
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
What is Electron Beam Melting (EBM)?
Electron beam melts metal powder Under high vacuum to produce electrons
83
What are the advantages of EBM?
Lower thermal strains Low risk of oxidation/contamination Fast build rate
84
What is binder jetting?
Inkjet print heads apply liquid bonding agent to powder layers
85
What are the general advantages of binder jetting?
Uses almost any powder Can print colour Unbound powder provides support Wide range of build volumes High build rate Low material/equipment cost
86
What are the general disadvantages of binder jetting?
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