Material Extrusion Flashcards
What is material extrusion?
A material is selectively dispensed through a nozzle by an act of pressure
3 types of pressure source for material extrusion?
Forcing solid (filament feed) FFF Forcing liquid (liquid pump) paste extrusion Forcing gas (pneumatic) direct ink write
What are the stages of Fused Filament Fabrication?
Polymer filament is supplied to a heated extruder nozzle which traces the first layer.
Drive wheels force the material through the nozzle and ensure material is deposited smoothly.
Support material is added in cavities and overhanging areas to support the structure.
Layers are fused together upon touching as they are in a melted state.
Supports removed
What are the two types of extrusion drive?
Direct drive, everything on moving axis
Bowden drive, only heated nozzle on moving axis
What are the advantages of FFF?
Office friendly - non hazardous, simple operation, conventional power supply
Reliable technology - low maintenance cost
Surface finish can be mechanically and chemically smoothed
low cost build materials and widely available
More expensive machines have soluble support structures
What are the disadvantages of FFF?
Timings, denser prints take longer
accuracy - geometry and patterns can cause issues in porosity and build integrity
Stair stepping
Parts are weaker in the z axis
Requires support structures
Need to make sure layers adhere to each other and think about loading and splitting
What are FFF filaments made out of?
Thermoplastics as they can be re-melted back into viscous liquid
What are some typical materials used for FFF?
ABS - affordable, good strength and stiffness, good chemical resistance
PLA - low melting point, biodegradable, affordable
PC - very pliable, susceptible to scratching
PVA - water soluble
TPU - flexible
PPSU - high operating temp, excellent rigidity
carbon fibre filaments can be added
What kind of materials are used in liquid pump/pneumatic extrusion?
Pastes made of organic, metallic or ceramic powders in a solvent binder
What are some applications of FFF?
Medicines Organs Spare parts Prosthetics Printed circuit boards Sensors Conformal printing (on 3D surface)
What are some solidification methods for material extrusion methods?
Drying at room temp (Clay etc…)
Assistive drying /heating ( conductive pastes, dough etc…)
Photocuring, materials are cured when exposed to certain wavelengths (UV curable polymers…)
Reactive solidification, two part materials react when mixed to form solid structure (epoxies, silicones etc…)
What is the deposition system architecture of material extrusion?
Stages on 3 axis enable the movement of the print head and substrate
Material is pushed through synchronised with the coordinates of the print location
3D digital model is sliced into layers and each layer is hatched into layers
Coordinates of the lines are transferred to the printer in the form of g-code
