Processes overview Flashcards
Describe Material Extrusion.
A material is selectively dispensed through a nozzle or orifice.
Fused Deposition Modeling (FDM)
What materials are used for MEAM?
Polymers: ABS, PLA, PETG
What are the advantages of MEAM?
cheapest and most common AM tech
Describe Vat Photopolymerisation.
Liquid photopolymer in a vat is selectively cured by light-activated polymerization.
Top down or bottom up.
Laser or projector used.
What materials are used in VAT polymerisation?
Liquid photopolymers: epoxy/acrylic non polymerised liquid.
Compare projector to laser image projection in VAT polymerisation.
Projector:
- Faster (laser moves around whole shape)
- Less moving parts
Laser:
- More detailed
- can change resolution
- Larger range light spectrum.
Compare top down to bottom up image projection in VAT polymerisation.
Bottom up:
Advantages:
- Accurate layer thickness control
- No sweeper
- part height not limited
- smaller vats used
Disadvantages:
- sticking
- Peeling process
Top down:
Advantages:
- Higher resolution
- No peeling process required
Disadvantages:
- Resin surface charecteristics can affect the quality of the part.
- Slower due to recoating process
- part thickness determined by the viscocity of the resin.
What are the advantages of VAT polymerisation?
Accurate, good surface finish, large build sizes available, low thermal energy input.
What are the disadvantages of Vat polymerisation?
Curling of large flat surfaces - prevents sweeper from sweeping.
Toxic materials
UV light ages parts
Parts need cleaning and the post curing.
Describe Powder Bed Fusion
Thermal energy selectively fuses regions of a powder bed.
Selective Laser Sintering (SLS) or Selective Laser Melting (SLM)
What materials are used for SLS and SLM?
SLS - Polymer powder (nylon, polystyrene, PEEK)
SLM - Metal powder ( stainless steel, aluminium, Ti alloy)
What are the pros of SLS?
Similar properties to injection moulded parts
Supports not needed
minimal post processing required
tough parts
What are the pros of SLM?
- materials used are common
- bespoke geometries possible
- dense metallic components
- any unfused powder can be reused
What are the cons of SLS?
Distortion in parts
High thermal energy input
dust and particle control
rough surface finish
What are the cons of SLM?
Distortion in parts
High thermal energy input
dust and particle control
rough surface finish
Supports to allow heat escape required
Describe Material Jetting
Droplets of build material are selectively deposited.
- Ink Jet Printing.
What actuation methods are used for material jetting? compare them
thermal:
pros
- Cheaper print heads
cons
- material gets burnt on print head reducing performance and lifetime
- Thermal cycling of print material can affect its properties
piezoelectric:
pros
- wider range of materials can be printed
- More viscous materials can be printed.
What materials are used in material jetting?
Polymers and waxes, Metals and Ceramics, UV cured materials.
What are the pros of material jetting?
dissolvable supports
multi material parts
smooth surfaces
fast process
What are the cons of material jetting?
Material properties are limiting, sometimes too weak
Describe Binder Jetting
A liquid bonding agent is selectively deposited to join powder materials. Similar to powder bed fusion.
2 types: visual and large scale visual/ mechanical
What materials are used in the two types of binder jetting?
Visual = Cornstarch or plaster powder
Large scale/mechanical = polymer metal or ceramic powder
What are the pros of binder jetting?
visual and mech properties:
Fast
low cost
low waste
mech properties only:
low temp - less energy
better mech properties than pbf
New process so less old systems.
What are the cons of binder jetting?
visual models:
- not functional parts
- limited materials
- low strength and poor surface quality
Mech properties:
quite a few post processing steps required
