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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 7775Mike.Raymond@ttpmeteor.com

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