Basic Ink Jet

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INK JET

BASIC INK JET KNOWLEDGE

Edition anglaiseIMAJE SA reserves the right to alter the specifications and the design of these products at any time without giving prior notice.

Reproduction, in whole or in part, is not allowed.

A18034 B 1

Imaje S.A.Head Office

9, rue Gaspard Monge

BP 110

26501 Bourg-lès-Valence Cedex

France

Tel.: (33) 4 75 75 55 00

Fax: (33) 4 75 82 98 10

http:// www.imaje.com



Date of Document version Modified pagesedition

REVISION

Updating the « Basic ink jet knowledge »

•The revision index A corresponds to the first edition of this manual.

• The revision index changes with every modification.

The modified pages are mentioned in the following table. This one indicates all updating since the firstedition.

This document was written by Alain GIRANTHON under the supervision of Gerard TERDJMAN

and corrected by Steve MARTIN.

A18034 B 2

June 1997 A First editionApril 2003 B All



IMAJE INK JET

BASIC INK JET KNOWLEDGE

S

o m m

a i r e

A18034 B 3

1-Matrix printing1-1- Matrix principles1-2- Raster principles1-3- Raster structure

2- Consumable products2-1- Definition2-2- Composition2-3- Comparison of ink bases2-4- Physical characteristics of an ink

2-4-1- Conductivity2-4-2- Ink life2-4-3- Viscosity2-4-4- Operational pressure2-4-5- Pigmented inks

3- Controlled VS uncontrolled ink jets3-1- Uncontrolled jet3-2- Controlled jet

4- IMAJE deviated continuous ink jet4-1- Pressure modulation4-2- Break point4-3- Factors effecting jet speed and break point

Mode 1: Constant viscosity and constant constant pressureMode 2: Free viscosity; controlled pressureMode 3: Constant concentration

4-4- Recuperation of non-deflected drops4-5- Drop charge4-6- Charge and phase detection4-7- Drop management4-8- IMAJE printhead4-9- Drop trajectory control (management )

4-9-1- External forces4-9-2- Aerodynamic forces4-9-3- Electrostatic forces4-9-4- Solutions

4-10- Print quality VS print speed in IMAJE ink jet printer 4-11- Printing mode control

4-11-1- Drop charge control process4-11-2- Data management



1 MATRIX PRINTING

1-1 Matrix principles

Definition:

A set of lines and columns. Each square within the matrix can either contain or not containa dot. A set of dots is called a character or symbol.

Example:

7X6 matrix:

1-2 Raster principles

Definition:

A raster is simply one vertical column of dots.In our example (a 7x6 matrix = 6 rasters of 7 dots ea.), there is a maximum of 27 combinations(= 128). We can produce 128 different rasters. An empty raster is used to separate twocharacters.

So, a symbol defined on an x-y grid will be formed by a series of rasters.Ink jet technology can print only one raster at the same time, for printing afull symbol it is necessary to have one of the following motions:

- Print head movement (10%)- Product movement (90%)

A18034 B 4

o o o o

o o o o

o o o o

ooooooo

Full raster Empty raster



1-3 Raster structure

Two different technologies are used:

A) Deviated continuous ink jet

A series of drops coming from one jetare proportionally deflected to createrasters.

This technology is called “Continuousink jet” (drops printed in series).

All rasters have the same number of drops.The figure shows 7 drops.One or several drops are charged

and then deflected onto the product.The others are recuperated by a gutter

(Recovered with vacuum).

B) Drop on demand1. Low-resolution type

A set of nozzles generates drops. Eachnozzle is dedicated to mark one specific dropwithin the raster.

Each nozzle is managed by an electro-valve.

This technology is called “Drop on demand”(drops printed in parallel) and it is usuallyused to print large characters on porous

products (cardboard for example.)

2. Hi-resolution typeUtilizes a piezo-electric resonator tocreate drops.

= Valve with coil or piezo-electricalcontrol.

A18034 B 5

P

A

A



Piezo-electric resonator principle:

A voltage is applied to a synthetic quartz crystal. The quartz length changes with the voltageapplied, the higher the voltage, the shorter the crystal and vice versa. When the quartz lengthdecreases, ink is pulled in. When the quartz length increases, the ink that was pulled in is now

pushed out. Thus the resonator acts like a valve. The ink that is pulled in is at a lower

temperature and thus a higher viscosity than the ink that is pushed out.

IMAJE makes and distributes this type of machine.

C) binary jet

It is an expensive technology. Fifty to one hundred nozzles are used (deviated continuous ink jet). Very precise printing is possible.

A18034 B 6



2 CONSUMABLE PRODUCTS

2-1 Definition

Consumable products are primarily bases (inks) and additives (solvents).

Ink is a liquid composed of specific proportions of different components.Additive provides the ability to manage ink viscosity (thickness).

2-2 Composition

Base:- Binder: Mostly natural or synthetic resins. The binder provides adhesion and cohesion. The resin(s) bind to the substrate. The binder resists abrasion, solvents, heat, etc.

- Modifier: The modifier is used to increase stability, prevent oxidation, provide conductivity, reduce foaming and it is also an anti-fungicide.

- Solvent: Dissolves the ink components, dilutes and stabilizes the ink and promotes adhesion by means of superficial attack. Additionally, additive (solvent) provides viscosity managementcapability.

- Colorant: Soluble dye, solid pigment or mineral compound.

-Soluble dye is easy to use and to run through the printer but it could migrate into the

product.

-Solid pigment stays in suspension in the liquid. It provides a solid mark that isresistantto daylight, weak acids or bases and does not migrate.

-Mineral compound (pigments such as; talc, kaolin, etc.) are heavier and moreirregularly shaped than solid organic pigments.

They require a special printer (SI printer) to prevent erosion and sedimentation.

A18034 B 7



Additives:

Each additive is a special liquid used to dilute one specific ink. This dilution provides:

- Ideal conditions for optimum machine (printer) performance ⇒ Machine-ability

- Ideal conditions for optimum printing

⊗ print quality ⇒ Print-ability

⊗ versatility

Additive types:

- Base 1 additives (methyl-ethyl-ketone [MEK]): Quick evaporation (drying), manyapplications, irritant.- Base 2 additives (alcohol): Medium evaporation (drying), used when base 1 is

prohibited.- Base 3 additives (water): Minimal to no evaporation, used on porous products.- Base 5 additives (mixed): Specific applications.

Some applications may also require:- Special cleaning products- Special rinsing (flushing) products- Anti-clogging products- etc.

2-3 Comparison of ink bases

Key : 1= very low...3= correct....5= excellent

A18034 B 8

Base 1 Base 2 Base 7

Machine-ability

Print-ability

Toxicology

Ecology

4

4Any product

3Non toxic

Irritant

3

3

3Porous

4

3

4

3Porous

5

3



2-4 Substrate types: Five main families

1. Pastes and Papers Porous supports : Wood, pastes and unbleached

cardboardsTitan-coated papersCellulose nitrate

Non poroussupports : Calendered papers

Greaseproof treated papersCellulose acetateEthylcellulose

2. Plastic foils

Rigid supports : rigid PVCPA polyamid* ** ***PE polyethylen* ** ***PP polypropylen* ** ***PVAC polyvinyl chloracetate, PVOH polyvinyl alcoholPUR polyurethan

PC polycarbonat, CAB cellulose acetobutyratePET, PETP polyethylen terephtalate, PBT polybutylen terephtalatePS polystyren, ABS, SAN... styrenated copolymersTyvek... non-wovens

Flexible supports : plasticized PVCPA polyamid* ** ***PE polyethylen* ** ***PP polypropylen* ** ***PVDC polyvinyliden-chlorid

* hot out of extruder, ** cold after pre-flaming, ***cold after Corona treatment

3. Plastic coatings

Paints and varnishes(on metal, on plastics, on wood) :

phenolicsaminoplastesepoxidsunsatured polyesters and polyurethansPVB polyvinylic butyralPTFE, Teflon, Tefzel.... fluorethens

4. Metal bare Aluminium, either fired or not precoated AluminiumTin plate

AlloysStainless steels

5. Special supportsGlass molded or pressed-blowed

Rubber before or after vulcanizationCeramic unbaked or fired

Leather Woven material coton or polyester Food and medicines

A18034 B 9



2-5 Physical characteristics of Imaje inks

2-5-1 Conductivity

The ink is electrically conductive due to it’s ingredients.To measure conductivity, we use micro siemens (µS).

Conductivity is the opposite of resistivity. Conductivity changes in relation to temperature andviscosity.

µ = 1/ρ with: ρ = resistivity

1µS = s3 x A2/ m3 x kg x 1O-6

S in Siemens; s in secondsA in amperes; m in meters

kg in kilogram

Ink QA (qualification dept.) verifies thatthe liquid’s conductivity is sufficient

between -10°C and +40°C.

2-5-2 Ink life

Ink life is limited, shelf life in the original package ranges from 9 to 12 months depending onthe ink type. In the machine, the ink is exposed to: Pollution, pressure, filtration, air contact,etc. The physical properties, predominantly electrical ones are altered. It is therefore necessaryto drain the ink circuit in accordance with the guidelines and procedures indicated on the ink technical sheets and printer documentation.

2-5-3 Viscosity

It is the resistance of a liquid to flow at a given temperature (thickness of the liquid).IMAJE verifies this characteristic in all of our inks. Viscosity is referenced by the fill time for a

defined volume through a flow governor at a constant pressure.The unit of measure is “centipoise” (cPo). Ink viscosity changes with temperature andfiltration. It’s molecular organization is then modified. As the ink is cycled more and more, thegreater the molecular modifications (viscosity changes).

Therefore, ink has a limited life. After a specific time of use and depending on the environment,it may necessary to change the ink. Since viscosity and temperature are closely related, atemperature range is associated to each ink. In other words, each ink performs best within acertain temperature range.

A18034 B 10

T°50

40

30

20

1000 1500 2000 µS

Conductivity VS temperature curve



2-5-4 Operational pressure

For the best results, adjust the printer pressure in accordance with the ink technical sheet and printer documentation.

2-5-5 Inks containing special coloring agents

To obtain some opaque colors (white, yellow, etc.) heavy, solid pigments are used.

These types of ink are unstable and their components can separate. The heavy solid pigments

are mostly of mineral origins:

- Talc- Kaolin- Zinc sulfide- Limestone.

Their density is very high (~ 4) and the particle diameter is around 4 to 10 microns.

Therefore:

- This type of ink must be continuously stirred in order to prevent sedimentation and toinsure suspension of the solid particles in the liquid.

- Pigments are abrasive and require a special (SI) ink circuit.

A18034 B 11

T°50

40

30

20

2 3 4 5 6 7 8 viscosity incPo

Viscosity VS temperature curve



Safety:

- Inks and solvents involve four main concerns: Flammability Disposal

Cleanliness (housekeeping)

Correct handling precautions (Personnel and material)

But:

IMAJE inks are not toxic

The safety instructions provided in the Ink Material Safety Data Sheets “MSDS” (see examplegiven in appendix) must be observed along with any specific national or local regulations.Applicable shipping and storage regulations must also be complied with. Additional safetyinformation may also be found in the printer documentation.

A18034 B 12



3 INK JET TYPES

3-1 The uncontrolled jet

Uncontrolled, the jet breaks in the air at an intermittent distance “d” from the ejection nozzle.

This distance depends on:

- The ink ejection speed * Property of the liquid surface in relation- The jet diameter with the molecular bonding.-The liquid viscosity-The superficial tension *.

We can see that with this type of jet:

- The drop volume is not consistent- The interval(s) between drops aren’t consistent- The distance “d” is not consistent- The shape of the drop varies

An uncontrolled jet does not work well for ink jet printing.

3-2 The controlled jet

The objective is to obtain drops with:

1 consistent diameter

2 consistent interval(s)3 consistent break point occurrence4 consistent distance “d”

IMAJE has developed a technology that provides controlled drop diameter, regular interval(s) betweendrops and consistent break-off point position. It is the “Deviated continuous ink jet”

A18034 B 13

d

P



4 CONTINUOUS DEVIATED INK JET

4-1 Pressure modulation

In order to correctly control the jet and the drops, a pressure variation is added to the fixed pressure, this cyclic jet pressure modulation enables the creation of perfectly calibrated drops.

Principle:

A piezo-electric resonator “R”drive (vibrates) a stainless steel bar “B”which is immersed in the ink.

Reminder:

The piezo-electric crystal (resonator) is atransducer that changes electrical power into mechanical power.

The resonator is supplied with anAC voltage at a fixed frequency(approx. 100 Khz) and an adjustable

amplitude.

A consistent break-off point is thusobtained with a perfectly controlled

distance “d”.This “d” is less than that of anuncontrolled jet.

Drop formation is stable in time and space:- all the drops have the same

diameter - all the drops are separated by the

same time (distance)

The superficial tension (see page 10)

contributes to this stability.

THE TWO MOST IMPORTANT FACTORS FORGOOD PRINT QUALITY ARE

INK & JET SPEED (a function of pressure and viscosity)

A18034 B 14

P

P = C

Modulation Freq.

R

B

Fo

P

d

t



4-2 Break-off point

The break-off point must occur exactly in themiddle (top to bottom) of the charge electrodes(electrostatic charge).

The charged drops will then be deflected by thedeflection (EHT) electrodes to obtain a raster.

4-3 Factors that effect the break point and jet speed

The break-off point stability in space depends on jet speed stability.

- Ink temperature- Ink viscosity

- Ink pressure- Nozzle diameter

all have an influence on the jet speed.

It is difficult to control the temperature (response time is too long). With a fixed nozzlediameter, three working modes are possible:

A18034 B 15

MODE 1 (Series 2 & 3)Viscosity and pressure ranges are regulated, but are independent of each other.

MODE 2 (Series 4)

Viscosity and pressure ranges are regulated, but are independent of each other.Pressure is controlled by jet speed in a closed loop format.

MODE 3 (Series 7)Concentration (ratio of ink to additive) is managed in conjunction with

pressure being controlled by jet speed in a closed loop format.

Break-off point

In center of charge electrodecenter



MODE 1: Viscosity and pressure ranges are regulated, but are independent of each other.

Viscosity must be regulated. This regulation can be achieved by addition of base or additive.

In mode 1, viscosity is regulated within a certain tolerance and is considered to be constant, inreality it is variable. Pressure is regulated within a tight tolerance and is considered to be a

constant, in reality there are small fluctuations.

With a constant viscosity and a constant pressure the jet speed would also be constant eventhough it is not specifically regulated. In reality (Series 3 printer) the jet speed was consistentlywithin a range but not constant.

* = notregulated

Note:

If temperature changes, resulting in a viscosity change, a correction occurs by addition of additive.

Therefore:

- Viscosity must be continually measured- Constant pressure must be maintained.

This option has some drawbacks:

- When viscosity changes, the response time for the correction is relatively slow. Thisresults in an out of tolerance jet speed for the length of the correction time.

- Each solvent addition solves the problem but also alters the ink base.

A18034 B 16

nominal speed

nominal pressure

speed

viscositytolerance

speed

tolerance*

viscosity



Block diagram:

This principle was used in the SERIES 1, 2 and 3.

A18034 B 17

Long cycle time

THEORETICALLYCONSTANTVISCOSITY

VISCOSITYMEASURE-MENT

CONSTANTPRESSURE

(+ / -)

ASSUMEDCONSTANT

JET SPEED(not measured)

ADDITIVEADDITION



MODE 2: Viscosity and pressure ranges are regulated, but are independent of each other. Pressure is controlled by jet speed in a closed loop format.

In this application, jet speed measurement is required.

Operating mode:

- If temperature changes the viscosity changes, creating a jet speed variation.

- The viscosity regulation process is a very slow process, so we have to maintain viscosity between acceptable limits to avoid too much pressure variation.

Note:

1) Although jet speed can be precisely controlled, viscosity regulation can alter the base (highdilution) if the temperature change is rapid. Evaporation is also a factor.

2) In the case of a rapid change from low to high temperature we may have to change the ink.

(time)

A18034 B 18

long cycle

BASEADDITION

BASEADDITION

ADDITIVEADDITION

SERVO-CONTROLLEDPRESSURE

(within limits)

VISCOSITYMeasurement

CONSTANTSPEED JET

JET SPEEDMEASUREMENT

JET SPEEDMEASUREMENT

PRESSUREGENERATION

PRESSURE SERVOCONTROL

PRESSURE SERVOCONTROL

REFERENCE

This technology is utilized on the SERIES 4.



MODE 3: Concentration (ratio of ink to additive) is managed in conjunction with pressure

being controlled by jet speed in a closed loop format.

Concentration is simply the ratio between elements in a mixture. Here it is the ratio of baseto additive.

Principal:

Temperature measurement is added to the previous parameters in mode 2.

A curve; P = f (t°) is stored in the printer’s memory for each type of ink. This curve iscalculated by the formula: V = f (t°) and provides the right pressure needed for aconstant jet speed (~ 20 m/s) regardless of the temperature (within the ink’s limits).A large pressure range may be obtained.

Constant viscosity must be maintained.

During operation two cases are possible:

The reference pressure for a given The reference pressure for a giventemperature results in temperature DOES NOT result inthe correct jet speed. the correct jet speed.

Then concentration is optimum. Then the concentration is not optimum.

- In this case the machine modifies the pressure to obtain the correct jet speed

in order to obtain good print quality.

- Concentration will then be corrected inorder to maintain jet speed at the correctreference pressure value within the curve(P = f (t°).

A18034 B 19

P

T°

CONSTANTCONCENTRATION

CURVE



ACTUALPRESSURE

JET SPEEDREFERENCE

JET SPEEDREFERENCE

CONCENTRATION

ADJUSTMENT

CONCENTRATION

ADJUSTMENT

ADDITIVEADDITION

BASEADDITION

CONSTANTINK

CONCENTRATION

CONSTANTINK

CONCENTRATION

CONSTANTSPEED

JET

JET SPEEDMEASURMENT

PRESSUREREGULATION

P=f(t°)

P=f(t) Act. P

when dif.

T°

Block diagram (S7 printer):

A18034 B 20



4-4 Recuperation

While the jet is running, the machine is not always printing, therefore not all the drops are deflected.The unused drops are recuperated.

For this purpose, a recuperation gutter is located at the bottom of the print head.

To prevent gutter overflow, the drops are recuperated (recovered) with vacuum.

A18034 B 21

Charge

Detect

Deflect

Vacuum

Recuperation Gutter



4-5 Drop charge

A specific charge value is applied to each drop within the raster. This is accomplished at the chargeelectrodes.

The drops not used for printing are not charged (a test signal is applied).

For each position within the raster, there is a corresponding drop charge. A drop can receive from 25to 270 Volts of charge. There are 24 possible positions (27 for some barcodes).

The resistor “R” is the resistance representing the jet of ink from the nozzle to the break-off point.

The capacitor “C” is created by the surface of the charge plate and the surface of drops still in contactwith the jet.

The of time delay of the R C circuit must be as short as possible due to the rapid drop formation time.

Calculation elements:

- Ink conductivity (variable parameter not controlled by the machine).

- Drop surface (fixed parameter for each type of ink).

- Thickness and nature of the dielectric (fixed by construction).

A18034 B 22

R

C

VOLTAGEGENERATOR Vcc = 25 to 270v

Charge plate

Break-off point

INK



QUESTION(s):

- How to perfectly charge the drops?

- How to be certain that the drop charge is constantly correct?

To correctly charge a drop, the voltage must be present during the entire time required for dropformation. Full drop formation is the time from a solid stream, until the drop is separated.

The possible charge conditions are as follows:

- Only the drop in contact with the jet can be charged.

- If charging stops while the drop is still in contact with the jet, the drop is discharged throughthe jet.

- If the drop separates too early (before receiving a complete charge) the charge value will be

incorrect.

- Only the drops charged when the drop is still in contact with the jet stream and separate just before the voltage switches off, are correctly charged.

Drop-charge testing is performed whether the machine is printing or not.

Note: The drop charge voltage can be positive or negative. With a one jet printer,charges are positive (drops are negative).With a two jet printer, one jet has positive charges and the other has negative charges(see diagram below). Two identical charges (positive for example) would require larger

printhead dimensions.

A18034 B 23

V = 0 volt

+v 0v -v

V = +v

+v 0v +v 0v

-

+ ++ +

- -- - - - - -

0v

B

- -- -

+ ++ + + + + +

0v

+

A

V = HV(very high voltage)



4-6 Charge and phase detection

In order to find the best “Phase” to charge drops, the internal computer does a sequential search.Eight different positions of break-off point are tested and the computer selects, from these eight, the

best “Phase” for the greatest charge accuracy.

In order to clarify this principle, refer to the diagram(s) below. The numbers are only for example andclarity of understanding.

A18034 B 24

Charge plate

Detectionelectrode

To or To+16 To + 2µs To + 4µs To + 6µs To + 8µs To + 10µs To + 12µs To + 14µs

1

2

3

4

5

6

7

8

0

0

~1

11

1

0

0

Computer interpretation

Charge plate



The drop ejection frequency is 62,500 Hz or in other words a period time of 16µs.

The “Phase” is the drop position within the charge plate when the charge voltage is switched on.

On the diagram above, the charge periods are in gray and numbered 1 to 8. Each period is 8µs long.The machine starts it’s test:

- The first charge (8µs duration) starts at To. On the diagram the drop is already separated.- the 2nd at To + 2µs- the 3rd at To + 4µs- ................- the 8th at To + 14µs

The drop is monitored by the detection electrodes, which measure the drop charge.Each drop is classified:

- Good = 1- Bad = 0

The computer selects the 2nd good drop to determine the right adjustment (“Phase”) only when thereare 3 good drops in succession.

When the machine is not printing it constantly tests the charge and phase for each drop.

It is not practically possible to check only one drop, one drop generates too low of a voltage in thedetection electrodes.

4-7 Drop management

When the machine is not printing, it tests drop charge and fine tunes the charge parameters to preventany parameter drift.

The test starts at the end of each printing period and stops at the beginning of the next printing period.

It is very difficult to precisely measure a charged drop. The energy is too low (charge of 10 V for thedrops not deflected and recuperated by the gutter).Therefore, groups of 7 drops are measured. The 7 drops all have the same charge.

We do not increase the phase between each drop, but between each group of drops (+ 2µs every time).

A18034 B 25



We obtain the signal shown below at the detection electrodes (after amplification):

A group of 7 charged drops is measured and will generate a signal proportional to it’s charge.

A18034 B 26

7 x 16µs

7 drops with the same phase

7 x 16µs

7 times the same 7 times the same

( 7 x 16µs ) + 2µ

( 7 x 16µs) + ( 7 x 16µs ) + 4µs

detection threshold

Aplified signal

low signals

8 time (drops) separated by 2µs



4-8 Printhead functions

A18034 B 27

Pressure P = Constant

piezo-electric resonator for

pressure modulation

Drop charge

Drop detection

Deflection plates

Vacuum

Recuperation gutter



4-9- Drop(s) trajectory control

4-9-1 External forces on the drops

In reference to the description above we have two internal forces:

External forces:

- Aerodynamic drag effect (movement in air).- Electrostatic interaction between charged drops.

A18034 B 28

Charge plates

Detection plates

Product

F2 = f (M ; V) with M = drop mass and V = initial speed of drop

F1

= f (Ch) with Ch = charge



4-9-2- Aerodynamic forces

The drops have a very high speed (20ms; ~ 72 km/h {45MPH}). Their drag consumes thestored kinetic energy. The consumption of energy is maximum for the drops at the head of thegroup and minimum for the drops at the back (like a bicycle).

The theoretical drop trajectory is a parabola between the deflection plates and following astraight line (tangent to the parabola). The drops relative position(s) are defined by their chargevoltage and charge order.

If we do not correct for these forces, the raster will be deformed.

A18034 B 29

Recuperation gutter

Product

1

2

3

4

5

Drops 2 and 3 are in the wake of drop 1 and they loseless energy than drop one. Distance between dropsis not constant and decreases.

Drop 4 is less protected than drop 2 and 3 and 5 is stillless. These two drops may drift.

Theory Reality



4-9-3 Electrostatic forces

Two successive drops can have any charge value.Two drops with the same polarity push each other away. The higher the charge, the higher therepulsion (the same as two magnetic poles)Two drops with a very different charge have virtually no interaction.

Therefore, we must never have two successive drops with a high charge.

4-9-4 Solutions

- To correct trajectory defects caused by aerodynamic drag:

During the printer’s design, the difference(s) between the real and theoretical trajectorieswere precisely measured in all possible configurations. The product was at a fixeddistance from the head.

Corrected charges were calculated for each configuration and stored in the machines.

The drawing below presents the theoretical and corrected voltage values that we canobserve on an oscilloscope.

A18034 B 30

Chargevoltage

t

= theoretical charge

= corrected charge

Note:The little shifts in the time axisare only for clarity.



NOTE: J2000, J1000 S1, S2 and S3 use 8 bits encoding to calculate thecharge voltage for a drop. In this case the resolution is approximately 1 volt.

J1000 S4 and S7 use 12 bits encoding, the resolution is less than 0.1 volt.

- To correct electrostatic trajectory defects:Two consecutive highly charged drops push each other away. This problem is solved if we

separate the two drops. To accomplish this, we only have to change the charge order and their raster position.

For a 24 dot raster, following the same principle, we obtain the following:

A18034 B 31

Chargevoltage

Printingsequence

Emissionsequence

7 6 5 4 3 2 1

110

100

90

80

70

60

50

7

6

5

4

3

2

1

EXAMPLE WITH A 7 DOT RASTER

Emissionsequence

Printingsequence

Chargevoltage



WARNING: These corrections are only valid for a fixed printing distance, otherwise the drops diverge.

4-10 Speed VS Quality in an IMAJE printer

Three possibilities:

- Speed is the priority ⇒ High speed

- Quality is the priority ⇒ High quality

- Speed & Quality compromise ⇒ Quality

High speed

We are looking for the highest printing speed.

= =

With: Density = number of drops in one mm.Dots / raster = number of dots in each raster Drop time = drop creation time

To increase speed we have to act on one of these three (above) parameters.For a fixed dimension drop it is not possible to act on the drop creation time.Therefore we have to act either on the density or on the number of dots in the raster.

V increases when the number of dots in the raster decreases.

For example with a G head, we recommend that the customer uses a 5x7 raster with a2.8 dots / mm density (resolution). Printing distance is fixed at 10mm (head to product.)

We apply charge correction and emission sequence principles.

When all the drops created are printed, the term “high speed” is used .

In these conditions, the maximum product movement speed is near 3 M/s with 7dots / raster,G head.

A18034 B 32

VDistance

Time

1

density x dots / raster x drop time



Options:

A - To increase speed, we modify the number of drops per raster:

= =

We omit one drop in a full raster with a 7x5 matrix. Drop position is slightly modified.

Speed increase is 17%. This is the “ultra rapid” 7 dot font.

- With the same method, we can print 4 dots in a 5 dot raster.

Speed increase is 25). This is the “ultra rapid” 5 dot font.

B - Another possibility: The drop creation time is decreased. Consequently, the dropsize decreases. The dots are smaller which makes the print less visible.

A special head (M head) is used. This is the “Hyper high speed” font.

A18034 B 33

VDistance

Time

1

density x dots / raster x drop time

Standardraster

Modified

(faster) raster



High quality

Speed is sacrificed to gain quality.To control aerodynamic and electrostatic effects a different method is used.One out of 4 drops is charged (average value*) in a 16 dot raster.

Non-charged drops are recuperated by the gutter.

Therefore, there is a large distance between charged drops and there is neither electrostaticinteraction (4 times less distance, 16 time less interaction) or aerodynamic interaction (all dropssupport the same drag).

The printing speed is divided by 4.For a 7 dot raster one out of 3 drops is charged (average value).

The printing speed is divided by 3.Drop charge and emission are in the same order.

Advantages:

Printing is possible from a greater distance (as far as 30mm).

Precisely formed, very straight printing.

This is the High quality font.

A G head with a 7 dot raster has a printing speed limit of just below 1 M / s.

* : One drop out of two for low charges, one drop out of 6 for high charges.

- Quality

Every other drop is charged (average value).

Head to product distance is fixed at 10mm.

It is a compromise between high speed & high quality (described above).

From the “high speed” we use the head to product distance (10 mm).

From the “high quality” we use the linear charge mode (every other drop is charged).

A18034 B 34



4-11- Printing mode control

4-11-1 Drop charge control process

There are three principal memory areas in the printer:

Characters in 2 positions:

A and ∀ for 5, 7, 12

and 16 dots.

3 complete fonts2 incomplete fonts

Logos (up to 80 rasters)

T1 = T5T2 =T3 = T4

* : To write messages, standard message library.

** : GCG = Graphic character generator. T2 = T3 = T4

A18034 B 35

T1 T2 T3 T4 T5

T1 T2 T3 T4 T5

C1 C2 C3 C4 ... ... ... ... C 90 ...C98

0 210 210 210 0 0 210 210 210 .. .. ....

180 0 180 180 180 180 0 180180 .... ....

145 0 145 145 145 145 0 1450 .... ....

117 117 0 117 0 117 117 1170 .... ....

87 0 87 87 87 87 0 87

87 .... ....

60 0 60 60 60 0 0 0 0

0 0 25 25 0 25 25 2525 .... ....

T1 T2 T3 T4 T5

A C4 C2 C2 C2 C4

B C4 C7 C7 C7 C5

C

....

..

41 - 42 - 43 - 45 - 20 - ...........

Area 1100 Kbytes

« MASTER »

Corectedchargevoltagevalue

c

Area 220 Kbytes

File CGC**

Area 37 Kbytes

Messages *

T1 T2 T3 T4 T5

(ASCII bytes series)



Stored element access:

For S4 and S7 family Standard technology

Calculations of the table values are made either by Imaje or sometimes by the customer with specialsoftware (graphic editor).

This method is used in all the machines except the S7S.

A18034 B 36

A

Calculation rules (algorithm)for high speed, quality andhigh quality. Fonts ( or forms of the

characters) stored in area 2(machine memory).

)

Table of drop chargesstored in area 1(machine memory).



Fonts (characters)Calculation rules

A

IMAJE ink jet printer

S7S printer

It is a new, “real-time” technology.

The S7S calculates the drop chargefor each raster (5 times per

character with a 7x5 matrix).During raster printing, the microprocessor calculates the next raster.High speed, high quality andquality algorithms are included.There is no master file (area 1).

Advantages: Less memory neededgreater flexibility.Many fonts are available: RussianChinese, .........

.

A 32 bits microprocessor is included. It is a special customized component designed specifically

for Imaje.

Documents

Basic Ink Jet