The document discusses optimizing inkjet printhead performance through waveform design and drop visualization. It describes how printhead architecture works to eject ink drops via piezoelectric actuation. Key aspects of optimization include adjusting pulse width to control single drop velocity and size, multi-drop waveform design for grayscale printing, and using measurement equipment to visualize drops and optimize characteristics like velocity and volume. The goal is to achieve consistent, uniform drops for improved color management and print quality.
IMI Waveform and Drop Optimization - Raymond 20160908 v1.0
1. Tech Talk
Waveform and Drop Optimization
September 7-8, 2016
Renaissance Schaumburg Convention Center Hotel,
Schaumburg (Chicago), Illinois USA
2. • Ink and characteristics
• Printhead architectures and commonality
• Single drop optimization
• Measurement Equipment and Drop Visualization
• Multi Drop and Gray Scale
• Velocity Optimization
• Frequency Response
What are we talking about?
10. Nozzle, Chamber, Actuator
• Basic geometries are alike:
• Ink manifold to deliver ink
• Chamber
• Actuator – changes volume of
chamber
• Nozzle - outputs drop and refills
meniscus from chamber
• Follow acoustic mode theory and
modelling
• Pressure waves travel at
speed-of-sound
• Capillary pumping action
11. Chamber Pressure and Settling
• Electric field causes piezo to change shape
• Piezo quickly changes chamber volume
• Creates a pressure wave in the chamber
• Usually settles within 100 microseconds
Note: Plot is from a
computer model
Helmholtz
Resonance
13. 1. Single Drop Pulse Width Optimize
2. Velocity Adjustment – adjust voltage for 5-9 meters per second
3. Plot single drop frequency response – velocity and size
4. Optimize double pulse for two drop
5. Plot 2-drop frequency response
6. Repeat for 3-drop, 4-drop, etc.
Waveform Optimization Steps
14. Action!
• Piezo increases the volume in
chamber
• The meniscus pulls back from
the nozzle & ink flows in from
manifold
• Pressure wave moves
through chamber at the
speed-of-sound
• Wave crashes into wall of
chamber and reverses
direction
• At the precise time, the
piezo collapses creating a
second wave, adding to
the first
• A drop is ejected
16. Adjust for Drop Velocity
• Higher Voltage increases
Drop Velocity and Size
• Optimize velocity between
5-9 meters per second
• Good drop formation and
no satellites
17. Optimization and Print Gap
-Printhead
1 -5mm
Motion
Air
currents
Larger Gap
• Higher Velocity
• Larger Drops
e = ½ mv2
Smaller Gaps
• Lower Velocity
• Smaller Drops
5 – 9 meters
per second
28. Chamber Pressure, Settling & multi-Drop
• Electric field causes piezo to change shape
• Piezo quickly changes chamber volume
• Creates a pressure wave in the chamber
• Usually settles within 100 microseconds
Subsequent
drops are
ejected
when
chamber is
very active
39. • Consistent Drop Placement
• Consistent Drop Volume
• Improved Color Management
• Robust jetting with high operating
margins
• Longer time between
maintenance cycles
• Makes the formulator look good
Optimizing Jetting &
Waveform Achieves
That’s
what I’m
talking
about!
41. Thank You
TTP Meteor Ltd.
Melbourn, Herts. SG8 6EE. UK
Mike Raymond
Technical Sales – Business Development
ttpmeteor, Philadelphia Office, USA
+1 302 514 7775
Mike.Raymond@ttpmeteor.com
-
An ink needs to be tuned for the target printhead
The best operating points need to be chosen, not the fastest
You may have a really good ink but you need to thoroughly characterize the ink using a drop watcher
Ink is central
Ink must perform both on the media and in the printhead
The characteristics required for media conflict with the characteristics required for jetting quality and reliability
Dry quickly on media but not dry in head
Flow in printhead but not penetrate media
Adhere to media ewith good fastenss but do not harden on printhead
Many differing types of inks
All are either dye based or pigment based
All act different in the printhead
Printhead specificiaons are based on a specific fluid used for manufacturing test. It is just a target.
The characteristics of your ink can be quite different.
Tuning is required for optimum jetting; empirical methods are employed
Ink Chamber is is made form the piezo
All inkjet architecture are common, each has
Nozzlw
Ink chamber
Acturator – change volume of chamber
Restriictor – so ink doesn't flow back to manifold
Dneser ink has faster speed of sound
The piezo changes shape when a voltage is applied
This changes the volume of the chamber and creates a pressure wave in the fluid
Follows a natural settling before returning to rest
Curves are generated by modeling. Actual measurements in the chanber are not practical.
Adjust for optimum single pulse waveform
Adjust velocity – below 5 is too slow for good control – above 9 usually create drop breakup
Plot frequency response for drop velocity and drop size
You have to feel the energy and emotion
Pretend I’m the set director and you’re the actor
Change the pulse width and measure drop velocity
Perform at a low frequency to avoid settling effects
You should see a nice drio formation
Adjust voltage for DV between 5-9 m/s
Hardware and software
Drive electronics, camera , strobe
Drop Optimization software to adust drop rates and patterns
Waveform editor
Image anaysis
And now a word form our sponsor
Seriouslt, Meteor has htes units in oeration globally
Uses the same drive electronics and software as in the printer
Contrary to popular belief printheads really only have a single drop size. This is called the native drop.
Larger drop sizes are created by quickly jetting more drops
Complete drop forms before hitting substrate
The piezo changes shape when a voltage is applied
This changes the volume of the chamber and creates a pressure wave in the fluid
Follows a natural settling before returning to rest
Curves are generated by modeling. Actual measurements in the chanber are not practical.
The settling waveform affects the subsequest drops
Now the ink is characteriszed
System operating parameters are set for best quality and performance
And the output is perfected – Yah, that’s what I’
ALMOST 500 YEARS FOR THE DIGITAL TRANSFORMATION
Just getting started