Please enable JavaScript.

Coggle requires JavaScript to display documents.

A396 Lesson 12 Mindmap - Coggle Diagram

- - - - Material must flow
      - Strategies:
        
        Suspend particles in carrier liquid
        
        Dissolve materials in solvent
        
        Melt solid polymer
        
        Mix monomer/prepolymer with polymerization initiator
    - - Changes in material can change its droplet formation behaviour
    - - Depends on flight height, impact, substrate wetting, interaction
      - Factors causing negative effects:
        
        Smaller droplets break --> deposited material spread over large area --> intended --> deposition does not have well defined boundaries
    - - Eg:
        
        Solidification of melted material
        
        Evaporation of liquid portion of solution
        
        Curing of photopolymer
    - - Each layer must be fully bound to previous layer --> prevent delamination
        
        Must not damage underlying layer
      - Can be improved by using devices that smooth the surface
    - - Nozzles
        
        Clogged due to small size
        
        Hence, -need to do purge and cleaning cycles, -replaceable nozzles, -needed complex sensing system to identify and compensate for malfunctioning or inconsistent nozzles
    - - can be improve by producing many small droplets very closely
      - Cannot be achieve by increasing nozzle density due to limitations & overlapping of thermal / pressure differential used in adjacent nozzles
        
        However, can make multiple passes over the same area
  - - - Droplets are formed only when individual pressure pulses in nozzle cause the fluid to be expelled that is created at specific time by thermal, electrostatic, piezoelectric, acoustic or other actuators.
    - - characterized by manipulation of a continuous fluid stream inside usually-confined microchannels.
  - - - Drops deposited rapidly, substrate is at elevated temperature --> reduce solidification angle --> results in ball-like depositions
      - Smooth lines formed in small range of droplet frequency
        
        Dependent on sweep speed, droplet size and solidification angle
      - Low droplet speed
        
        Low sweep speed: Discontinuous deposition High sweep speed: Continuous deposition
      - High droplet speed
        
        Low sweep speed: Bulging occurs
        High sweep speed: Splashing occurs
    - - Work is required to improve the rheology
      - Suspension of up to 40% solids loading
        
        Higher concentrations of suspended powder --> prohibitively high viscosities
        
        Green part must be burnt out and sintered
        
        Final product is about 80% dense but dimensions are subjected to dramatic shrinkage
    - - Electronic applications
        
        Formation of traces
        
        Connections
        
        Soldering
      - Challenge:
        
        High melting point --> damage components of printing system
- - - - Infiltrant used to form ceramic binder
      - Metal Binder Jetting: Parts produced in their green state. High porosity of these green parts makes them fragile and limits their mechanical properties.
        Solution: Post-processing such as curing, sintering or bronze infiltration help reduce internal porosity and enhance the strength and resistance of the part.
        Time consuming to the overall process.
  - - - 1) Poor accuracies
        2) not suitable for structural parts
  - - - Stainless steel, Aluminum, Silver
    - - ABS, PA, PC, PMMA
    - - Glass, Sand
      - Green part is subjected to thermal decomposition -> remove polymer binder
      - Furnace temperature increased until the ceramic's sintering temperature
      - Infiltrant can be used to form a ceramic binder
      - Or to infiltrate a metal to form a ceramic-metal composite
    - - Fine powders needed -> does not flow well and spread into the defect-free layers
    - - Hydrogen atmosphere is introduced
        
        Reaction occurring between hydrogen and oxygen atoms --> converts into metal
        
        After reduction, metal particles are sintered to form metal part