lecture 8 - Material Jetting Flashcards
Learning objectives • Know the 5 stages of the material jetting process • Understand continuous and drop-on-demand printing methods • Understand the two main actuation methods for DoD printing • What are the different jetting materials and curing methods • Why material fluid properties are key for “jetability” • Know the different potential material jetting issues • Explain the advantages / disadvantages of material jetting
Define Material jetting
Droplets of build material are selectively deposited
What 5 principles in order formulate material jetting
- droplet ejection
- droplet flight
- droplet impact
- droplet spreading
- droplet solidification
Name the two 2 General jetting techniques
Continuous
Drop on demand
Describe the continuous flow system
1. Electromechanical device causes pressure oscillations to propagate through the fluid which eject through a nozzle. The jet breaks into droplets. 2. An electrostatic field charges the droplets. 3. The charged drops are directed to their desired location. If nothing is being printed the ink is directed to the catcher for recycling bank into the material reservoir
Why do droplets form
Rayleigh Instability-Fluid tend to minimize their
surface area.
Drop on demand
individual droplets are produced directly from the nozzle.
Pressure pulses in the nozzle cause the fluid to be expelled.
An actuator produces the pressure pulses
The most common actuators are thermal and piezoelectric however
electrostatic, acoustic and others types have been investigated.
Continuous VS DOD
Continious(its shit with current tech)
-Issues with environmental exposure with material
recycling through the gutter
DOD High placement accuracy Smaller droplet size Low waste Wider range of materials
what are the 2 methods of drop actuation
Thermal jetting
Piezoelectric
Pros and cons of both actuation methods
• Thermal jetting
Pros
Print heads are cheaper
Cons
Χ Burnt material on the heating element reducing
lifetime and performance of print head
Χ Thermal cycling may lead to degradation of the
material and loss of the desired functional properties.
Piezoelectric
Allows a wider variety of materials as there is no
requirement for a volatile component
Allow more viscous materials
can metals and ceramics be jetted?
NOPE
Jetting materials
Ink
Waxes
What affects jettibility?
Viscosity- Major factor as the fluid must refill reservoir
Surface tension - high enough to prevent dripping
pros cons of material jetting
Pros
Good edge quality
High resolution
Multi materials possible for different mechanical properties
Cons
Limited material choice - no metals /ceramics
polyjet Pros/cons
uses jetting to dispense UV material
Pros
Dissolvable supports
Multi materials
Smooth surfaces
Cons
High material cost
Waste of material through roller
Draw polyjet
see notes
