Lecture 7 Flashcards
4 main print methods
- Photocuring
- Jetting based
- Extrusion based
- Sinter based
4 key steps of photpolymerization
Exposure
initiation
Chain growth
Temination
Exposure
Initiation
Chain growth
Termination
What is oxygen inhibitation?
When oxygen is present in the photopolymerisation process
What is the core process of photpolymerisation?
layer-by-layer hardening through light source (typically UV)
Once a layer is hardened, teh build platform (or the light source moves to expose a new layer of liquid resin
What is top-down printing? Pros & Cons?
- Light source shines form above onto resin
- Build platform lowers as each layer is built
- Pros: Larger print area, ideal for thicker layers, less stress on part
- Cons: Hihg resin volume requiredd, gravity can affect layer consistency
What is bottom-up prinitng? Pros & Cons?
- Light source shines from below, through transparent surface
- Build platform lifts with each layer
- Pros: Lower resin usage; better for thinner layers, higher resolution layers
- Cons: May require strong adhesion to counteract peeling forces during lifting (weight of the part hanging upside down)
Bottom-up printing process (general)
- Positioning (to determine the layer height)
- Exposure (UV curing of the resin to create layer)
- Peeling (cured layer is seperated from the bottom of the Vat)
- Lifting (and reflow of resin)
- Pause (Time for resin to cool and stabilise)
Repeat
Which 3D printing methods use vat polymerisation?
- Stereolithography (SLA)
- Digital Light Processing (DLP)
- Liquid Crystal Display (LCD)
How does SLA work?
A laser beam selectively cures teh liquid resin spot-by-spot
How does DLP work?
A projector casts light over the entire layer to cure it all at once
How does LCD work?
An LCD screen masks a projector’s light and cures entire layers at a time
Pros of SLA
- Smoth surface finish
- High resolution
- Controlled heat dissipation (time for heat to dissipate as teh laser moves, reducing heat buildup)
- Consistent quality across the paint bed
- Wide range of material compatibility
Cons of SLA
- Slower print speeds
- Higher costs
- Complex electromechanical system (high maintenance and susceptibility to failure)
- Limited build volume
Pros of DLP
- Speed (cures whole layer at a time)
- No light bleed (unused light directed away)
- Quick layer times
- Low complexity
- Wide range of material compatibility
- Continous layer manufacturing possible
Cons of DLP
- Higher costs
- Build soze constraints
- Heat generation (wastes energy and heats up work area)
- Pixalation
Pros of LCD printing
- Cheap
- No moving parts
- Very compact (LED can be placed directly below the bed)
- High resolution
Cons of LCD printing
- Lightbleed (LCD pixels are never truly opaque)
- Low light energy (longer layer times)
- Exposure uniformity
- Pixalation (due to resolution of the display)
- Specialised resins needed
Photopolymer jetting
What is thermoplastic?
Type of polymer that becomes moldable upon heating and solidifies upon cooling.
Process can be repeated multiple times, allowing thermoplastics to be reshaped and reprocessed without significantly altering their chemical structure
Thermoplast:
Material that conists of linear pr branched polymer chains that are not chemically bonded to each other
This allows them to be remelted and reshaped
