W4 Additive Manufacturing Technologies Flashcards
Additive manufacturing
“Additive manufacturing, also known as 3D printing,
uses computer-aided design to build objects layer by
layer. This contrasts with traditional manufacturing,
which cuts, drills, and grinds away unwanted excess
from a solid piece of material, often metal.”
When traditional manufacturing is difficult
Internal/ Difficult to reach features
Thin structures
Sharp corners
Difficult to hold
Material Waste
Why AM
- Fast prototyping
- No tooling! * Complex/optimized/lighter structures
- Material savings
- Multiple materials
- Customization/Personalization
- Improved supply chain/On demand manufacturing* Simultaneous production of diverse parts
AM Processes
- Fused Filament Fabrication
- Stereolithography
- Selective Laser Sintering
- Electron Beam Melting
- Binder jetting
- Laminated Object Manufacturing
FFF Challenges
- Anisotropy
- Porosity
- Residual stresses
- Deposition rate
FFF parameters
- Temperature
- Extrusion force
- Viscosity
- Speed
- Toolpath
Polyjet
- Similar to SLA
- Multiple print head deposit material
- UV bulbs next to print heads cure each layer* Multiple materials
- Supports easier to remove
- Smoother
- Completely cured during process
Selective Laser Sintering (SLS)
- Polymers & Metals
- Powder can act as support
Electron Beam Melting
(EBM)
- Titanium or Cobalt Chrome
- Process in vacuum
- Limited size
- Increased energy efficiency
Three-dimensional printing
(Binder Jetting)
- Blend of polymers, sand or metals
- Multi-colour through binder heads
- Porous and low-strength
Laminated Object
Manufacturing
(LOM)
- Paper, plastic or metal * Bonded with heat and pressure
Three-dimensional printing:
- Printing head deposits binder onto layer of polymer, ceramic, or metallic powder
- Bed of build area lowered, another layer of powder deposited, and fused by binder
- Process repeats until all layers are manufactured
- 3D printing of metal powders can combine with sintering and metal infiltration for denser, stronger parts
Composites
Composite material: Combination of two or more chemically distinct and insoluble phases with a recognizable interface
Composite properties and structural performance superior to constituents acting independently
Dispersed phase and Continuous phase
Dispersed phase or fibers typically made of glass, carbon, or boron, among other materials
Continuous phase or matrix can be thermosets, thermoplastics, metals, or ceramics
Reinforced plastics (PMCs or FRPs)
Reinforced plastics (PMCs or FRPs) have high specific strength and stiffness, good fatigue resistance, and are relatively easy to design, fabricate, and repair
Metal-matrix composites (MMCs)
Metal-matrix composites (MMCs) have higher toughness, ductility, and resistance to elevated temperatures, but are more difficult to manufacture
Ceramic-matrix composites (CMCs)
Ceramic-matrix composites (CMCs) offer highest resistance to temperatures and corrosive environments
Manufacturing techniques for PMCs
Manufacturing techniques for PMCs include fiber impregnation (prepregs, sheet-molding compound, bulk-molding compound, thick-molding compound), molding of reinforced plastics, filament winding, pultrusion, and pulforming
Many composites require curing (controlled high temperatures) to achieve peak strength after forming
Spray layup and hand layup (contact moulding)
- Series of processes using a single mold, also known as open-mold processing
- Contact molding is the simplest method, with hand layup being a common technique:
- Materials placed in proper order (matrix and fibers)
- Shaped in mold by hand with roller
- Squeezing action of roller expels trapped air bubbles and compacts part
- In spray layup:
- Molding done by spraying materials into mold
- Resin and chopped fibers sprayed over mold surfaces
- Rolling of deposited materials may be necessary in the process
Filament winding
- Filament winding: Process combining resin and fibers during curing to develop composite structure
- Used for producing axisymmetric parts like pipes, storage tanks, and even non-symmetric parts
- Parts produced on rotating mandrel
- Reinforcing filament, tape, or roving wrapped continuously around form
- Reinforcements impregnated by passing through polymer bath
Filament Welding
- Filament winding process can be modified by wrapping mandrel with pre-preg material
- Products highly reinforced, resulting in very strong structures
- Parts as large as 4.5m in diameter and 20m long can be made
- Used for strengthening cylindrical or spherical pressure vessels made of materials like aluminum and titanium
- Metal inner lining makes the part impermeable
Welding
- Joining processes add mechanical components to base component to form assembly
- Some joining techniques considered as additive technologies
- Permanent joining techniques include welding, brazing, and soldering
- Welding involves melting and subsequent solidification of two parts to form strong joint
- Welding processes categorized into fusion welding (base material heated to melting) and solid state welding (parts joined under pressure or combination of pressure and heat below melting point of base metal)
Resistance welding
Resistance welding: utilises a combination of heat and pressure where the heat is generated
by electrical resistance to current flow at the interface of the two parts to be welded.
Oxyfuel gas welding
Oxyfuel gas welding: In this technique, various fuels mixed with oxygen are burned to
generate the required heat and melt the material
Arc welding
- Arc welding: Heating and melting of metal achieved through electric arc
- Electric arc: Discharge of electric current across gap in circuit
- Energy from arc produces temperatures of 5000°C and higher, sufficient to melt any metal
- In most arc welding processes, filler material added to increase volume and strength of joint
