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Tech TalkWaveform and Drop OptimizationSeptember 7-8, 2016Renaissance Schaumburg Convention Center Hotel, Schaumburg (Chicago), Illinois USA
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Ink and characteristicsPrinthead architectures and commonalitySingle drop optimizationMeasurement Equipment and Drop VisualizationMulti Drop and Gray ScaleVelocity OptimizationFrequency Response
What are we talking about?
An ink needs to be tuned for the target printheadThe best operating points need to be chosen, not the fastestYou may have a really good ink but you need to thoroughly characterize the ink using a drop watcher2
Harmony
Ink is centralInk must perform both on the media and in the printheadThe characteristics required for media conflict with the characteristics required for jetting quality and reliabilityDry quickly on media but not dry in headFlow in printhead but not penetrate mediaAdhere to media ewith good fastenss but do not harden on printhead
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Ink and Fluid Carriers
SolventUV CureH2O
Melt
Dyes and Pigments Create Colors
Many differing types of inksAll are either dye based or pigment basedAll act different in the printhead4
Ink Physical PropertiesStatic easier to measureViscositySurface TensionContact angleTemperatureDensity specific gravityFiltration TimeConductivityParticle Size
Dynamic difficult to measureViscosity vs. shear rateDynamic Surface TensionElasticityThermal hysteresis (viscosity)
Dynamic Characteristics are unique to 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 employed5
Printhead Architectures
Shared Wall Shear Mode
D15
Ink Chamber is is made form the piezo7
Push Mode
d33
Bend Mode
d31
Nozzle, Chamber, ActuatorBasic geometries are alike:Ink manifold to deliver inkChamberActuator changes volume of chamberNozzle - outputs drop and refills meniscus from chamberFollow acoustic mode theory and modellingPressure waves travel at speed-of-soundCapillary pumping action
All inkjet architecture are common, each hasNozzlwInk chamberActurator change volume of chamberRestriictor so ink doesn't flow back to manifoldDneser ink has faster speed of sound
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Chamber Pressure and SettlingElectric field causes piezo to change shapePiezo quickly changes chamber volumeCreates a pressure wave in the chamberUsually settles within 100 microseconds
Note: Plot is from a computer model
HelmholtzResonance
The piezo changes shape when a voltage is appliedThis changes the volume of the chamber and creates a pressure wave in the fluidFollows a natural settling before returning to restCurves are generated by modeling. Actual measurements in the chanber are not practical. 11
Optimize waveform
Single Drop Pulse Width OptimizeVelocity Adjustment adjust voltage for 5-9 meters per secondPlot single drop frequency response velocity and sizeOptimize double pulse for two dropPlot 2-drop frequency responseRepeat for 3-drop, 4-drop, etc.
Waveform Optimization Steps
Adjust for optimum single pulse waveformAdjust velocity below 5 is too slow for good control above 9 usually create drop breakupPlot frequency response for drop velocity and drop size13
Action!
Piezo increases the volume in chamberThe meniscus pulls back from the nozzle & ink flows in from manifoldPressure wave moves through chamber at the speed-of-soundWave crashes into wall of chamber and reverses directionAt the precise time, the piezo collapses creating a second wave, adding to the firstA drop is ejected
You have to feel the energy and emotionPretend Im the set director and youre the actor14
Optimum Pulse Width
Change the pulse width and measure drop velocityPerform at a low frequency to avoid settling effectsYou should see a nice drio formation15
Adjust for Drop Velocity
Higher Voltage increases Drop Velocity and SizeOptimize velocity between 5-9 meters per secondGood drop formation and no satellites
Adjust voltage for DV between 5-9 m/s16
Optimization and Print Gap
Printhead1 -5mm Motion
Air currentsLarger GapHigher VelocityLarger Dropse = mv2Smaller GapsLower VelocitySmaller Drops
5 9 meters per second
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Uniform Drop
Drop Visualization Equipment
Drop Visualization SystemMeteor Drop Optimization Software
Meteor Waveform Editor
Hardware and softwareDrive electronics, camera , strobeDrop Optimization software to adust drop rates and patternsWaveform editorImage anaysis20
Drop Tuner Waveform EditorPrint Head Configuration and Driver Tools
And now a word form our sponsorSeriouslt, Meteor has htes units in oeration globallyUses the same drive electronics and software as in the printer21
Drop Visualization
Drop Measurements
Satellites are not good
drop size(s)
Drop Size Multi-Drop Grayscale27
Multi-Drop Technology Gray Scale
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 dropsComplete drop forms before hitting substrate
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Chamber Pressure, Settling & multi-DropElectric field causes piezo to change shapePiezo quickly changes chamber volumeCreates a pressure wave in the chamberUsually settles within 100 microseconds
Subsequent drops are ejected when chamber is very active
The piezo changes shape when a voltage is appliedThis changes the volume of the chamber and creates a pressure wave in the fluidFollows a natural settling before returning to restCurves are generated by modeling. Actual measurements in the chanber are not practical. 28
Multi Drop Waveform
The settling waveform affects the subsequest drops29
Plotting drop Characteristics
Velocity vs Voltage
Drop Size vs Voltage
Frequency versus Velocity
Frequency versus Drop Size
Now do it all for each color in your system
Drive Voltage vs. Velocity
Drop Volume vs. Drive Voltage
Drop Velocity vs. Frequency
Drop Volume vs. Frequency
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Consistent Drop PlacementConsistent Drop VolumeImproved Color ManagementRobust jetting with high operating marginsLonger time between maintenance cyclesMakes the formulator look goodOptimizing Jetting & Waveform Achieves
Thats what Im talking about!
Now the ink is characteriszedSystem operating parameters are set for best quality and performanceAnd the output is perfected Yah, thats what I39
Guttenberg Press ~1439Hey, Johannes, You knowthis is all going to be digital some day - Guttenberg Assistant
ALMOST 500 YEARS FOR THE DIGITAL TRANSFORMATIONJust getting started40
Thank YouTTP Meteor Ltd.Melbourn, Herts. SG8 6EE. UKMike RaymondTechnical Sales Business Developmentttpmeteor, Philadelphia Office, USA+1 302 514 [email protected]
Sourceshttp://www.nt.ntnu.no/users/skoge/prost/proceedings/ifac11-proceedings/data/html/papers/1129.pdfhttp://seeen.spidergraphics.com/cnf5/doc/Ink%20formulation%20tutorial.pdfManipulating drop performance in piezo electric inkjetHerman Wijshoff, Oc-Technologies B.V., Venlo, the Netherlandshttp://www.slideshare.net/MikeRaymond/edit_my_uploads
Manipulating drop performance in piezo electric inkjetHerman Wijshoff, Oc-Technologies B.V., Venlo, the Netherlands