©EVERLY 2024/2025 ALL RIGHTS RESERVED.
Additive Manufacturing Exam Study Guide.
Formative Manufacturing - Answer✔Manufacturing method that fills a negative void in the
shape of the desired part.
Subtractive Manufacturing - Answer✔Manufacturing processes based on controlled removal of
undesired materials through cutting, drilling or milling to achieve the desired forms.
Additive Manufacturing - Answer✔;the production of physical items by adding layer upon layer,
much in the same way an inkjet printer lays down ink
VAT Photopolymerization (SLA) - Answer✔Liquid photopolymer in a vat is selectively cured
by light. Stereolithography is a form of it
1. adhesion layer and substrate stacked on top of eachother
2. wafer is prebaked removing excess liquid
3. chrome mask is placed over sample and exposed to uv light
4. revealed regions leave a mould
Typically used to produce highly accurate moulds/models, e.g. F1 & invisalign
Original stereolithography (SLA) - Answer✔laser scans the liquid surface causing it to
polymerise, platform drops and once it has been recoated it is scanned again.
Projection based SLA - Answer✔Uses a digital light projector to project an image across the
surface through a transparent bottom of the vat, scans region before moving up and coating the
bottom and repeating.
Top down advantage - Answer✔- Highest resolution of parts
- Layer only adheres to previous layer
- Easy access to retrofit
Top down disadvantage - Answer✔- Surface characteristics of resin can affect quality of part
- Recoating step slows process
- Viscosity of resin determines thickness of part
Bottom up advantage - Answer✔- No recoating step
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, ©EVERLY 2024/2025 ALL RIGHTS RESERVED.
- Ultrathin layers are possible
- Less wasted material
Bottom up disadvantage - Answer✔- Light has to pass through more surfaces, reducing intensity
- Current layer adhering to vat can damage part
- Hard to retrofit
Light curable resins - Answer✔Consist of a monomer, photoinitiator and an inhibator. The
photoinitiator is excited by UV producing free radicals, this causes the monomers to link into
polymers.
Post curing - Answer✔UV Curing to ensure complete polymerisation and cross linking of
polymer bonds, if not complete mechanical integrity is at risk. Dependent on the mass and
material of the part, requires moving in the chamber.
Vat Photopolymerization Advantages - Answer✔- Accurate, small feature size and small layer
thickness
- Good surface finish
- Parts can be treated
- Large volumes possible
- Easy to remove support structures before final curing
- Lower density infill can be used for investment casting
- Low input energy
VAT Photopolymerization Disadvantages - Answer✔- Expensive machines
- Expensive materials to run (full vat of resin)
- Support structures are required
- Resins are toxic and require h&s
- Hygroscopic, parts not stable over time and age in sunlight
- Thorough cleaning needed to swap materials in machine
- Part orientation worse on bottom than top
Material Extrusion - Answer✔Material is selectively dispensed through a nozzle by an act of
pressure.
Fused Filament Fabrication (FFF) - Answer✔Thermoplastic filament is pushed through a hot
nozzle which liquifies the filament through the nozzle. Requires support materials for overhangs,
can be removed mechanically or sometimes chemically. Poor surface finish requires acetone
vapour baths.
2|Page
Additive Manufacturing Exam Study Guide.
Formative Manufacturing - Answer✔Manufacturing method that fills a negative void in the
shape of the desired part.
Subtractive Manufacturing - Answer✔Manufacturing processes based on controlled removal of
undesired materials through cutting, drilling or milling to achieve the desired forms.
Additive Manufacturing - Answer✔;the production of physical items by adding layer upon layer,
much in the same way an inkjet printer lays down ink
VAT Photopolymerization (SLA) - Answer✔Liquid photopolymer in a vat is selectively cured
by light. Stereolithography is a form of it
1. adhesion layer and substrate stacked on top of eachother
2. wafer is prebaked removing excess liquid
3. chrome mask is placed over sample and exposed to uv light
4. revealed regions leave a mould
Typically used to produce highly accurate moulds/models, e.g. F1 & invisalign
Original stereolithography (SLA) - Answer✔laser scans the liquid surface causing it to
polymerise, platform drops and once it has been recoated it is scanned again.
Projection based SLA - Answer✔Uses a digital light projector to project an image across the
surface through a transparent bottom of the vat, scans region before moving up and coating the
bottom and repeating.
Top down advantage - Answer✔- Highest resolution of parts
- Layer only adheres to previous layer
- Easy access to retrofit
Top down disadvantage - Answer✔- Surface characteristics of resin can affect quality of part
- Recoating step slows process
- Viscosity of resin determines thickness of part
Bottom up advantage - Answer✔- No recoating step
1|Page
, ©EVERLY 2024/2025 ALL RIGHTS RESERVED.
- Ultrathin layers are possible
- Less wasted material
Bottom up disadvantage - Answer✔- Light has to pass through more surfaces, reducing intensity
- Current layer adhering to vat can damage part
- Hard to retrofit
Light curable resins - Answer✔Consist of a monomer, photoinitiator and an inhibator. The
photoinitiator is excited by UV producing free radicals, this causes the monomers to link into
polymers.
Post curing - Answer✔UV Curing to ensure complete polymerisation and cross linking of
polymer bonds, if not complete mechanical integrity is at risk. Dependent on the mass and
material of the part, requires moving in the chamber.
Vat Photopolymerization Advantages - Answer✔- Accurate, small feature size and small layer
thickness
- Good surface finish
- Parts can be treated
- Large volumes possible
- Easy to remove support structures before final curing
- Lower density infill can be used for investment casting
- Low input energy
VAT Photopolymerization Disadvantages - Answer✔- Expensive machines
- Expensive materials to run (full vat of resin)
- Support structures are required
- Resins are toxic and require h&s
- Hygroscopic, parts not stable over time and age in sunlight
- Thorough cleaning needed to swap materials in machine
- Part orientation worse on bottom than top
Material Extrusion - Answer✔Material is selectively dispensed through a nozzle by an act of
pressure.
Fused Filament Fabrication (FFF) - Answer✔Thermoplastic filament is pushed through a hot
nozzle which liquifies the filament through the nozzle. Requires support materials for overhangs,
can be removed mechanically or sometimes chemically. Poor surface finish requires acetone
vapour baths.
2|Page
