Functions of the Inking System:

• Transform the ink from a thick paste into a fluid, printing condition.
• Deposit a think, uniform film of ink on the image.
• Evaporate some of the water picked up from the plate.
• Pick up particles of foreign matter from the plate and hold them until the system is cleaned.

Parts of the Inking System

• Fountain section
• Distribution section
• Form roller section

The fountain section

• includes ink fountain, fountain roller, and ductor.
• meters a supply of ink to the roller train.

The distribution section

• is a series of alternating steel (or copper-clad) and resilient rollers which condition and distribute the ink while carrying it through the system.

• The steel rollers are called drums, vibrators, or oscillators.
• Smaller steel rollers are called riders or intermediate rollers.
• Soft distributor rollers transfer the ink between drums and can also be used as riders.

The form roller section

System #1

• A large central drum (1) carries the entire flow of ink.
• The drum rotates the same direction as the plate cylinder, so the last-over forms (#2) receive more ink than the first-over forms (#2a). Better systems give more ink to the first-over forms. Therefore, this is NOT good.
• The system has hard and soft-covered rider rollers (4).
• It has forms of three different diameters­only two inside rollers are the same diameter. This is good because better systems have forms of varying diameters.
• Lots of air-space around the rollers allows water to evaporate (good).

System #2

• The large drum of System #1 is replaced by a small roller (1).
• In comparison to System #1, this system has three additional vibrators (5). Better systems have multiple vibrators, so this is good.
• The system provides more ink to the first-over forms than to the second-over forms. This is good.
• A rider roller contacts two inside forms (4a) that helps transfer ink from the first-over forms to the second-over forms.
• The system has forms of two different diameters: the inside two are the same diameter and the outside two are the same diameter. This is NOT good.

System #3

• This is a system that might be found used on the underneath side of a perfecting press.
• Gravity does not affect ink flow because of high speeds.
• Lack of space necessitates the complex pattern.
• Ink flow is heaviest to the last-over forms (not good).
• Lack of sufficient air space around rollers decreases the evaporation of water from the system.

System #4

• Has only three ink-form rollers. Better systems have more ink-form rollers, so this is NOT good.
• A large central drum is used, but it does not carry all the ink (the orange roller numbered 4 at the right of the diagram carries some ink directly to the right side of the system without it passing through the central drum).
• Form rollers #1 and 2 receive the most ink (this is good).
• The system has many riders. This is good because riders help condition the ink, evaporate water, and collect foreign matter.

System #5

• All forms have different diameters (this is good because different-diameter forms help remove image repeats and ghosts).
• Each form roller is inked by a separate vibrator (this is good to help eliminate image repeats and ghosts).
• Each form receives less ink than the one preceding it (this is the best possible ink lay-down scenario--most applied by #1, least by last-over form).

The ink fountain

• Is a reservoir of ink.
• V-shaped trough is formed by the fountain blade or wedges and the ink fountain roller.

The ink fountain blade

• May be a single metal spring-steel blade or a series of independent wedges.
• The gap between the ink fountain roller and the single metal spring-steel blade is controlled by fountain keys (screws): the smaller the gap, the less ink flows; the larger the gap, the more ink flows.
• The gap between each independent wedge is controlled by a stepping motor connected to a control on the press operator's console.
• Open the gap where more ink is needed; close the gap where less ink is needed.

Many newer presses have automatic ink-replenishment systems that fill the fountain with ink whenever the supply decreases to a pre-set level.

• To see photographs of one brand of ink replenishment system, click here.

Setting fountain keys

• When CLOSING fountain keys, start at the center and work toward the outside.

Setting fountain keys

• When OPENING fountain keys, start at the outside and work toward the center.
• Adjustments should be made gradually--never advancing a key too far ahead of the adjoining one.
• Irregular adjustments will bend or flex the blade causing it to buckle. A buckled blade cannot be set correctly and cannot be repaired.
• The ink fountain blade should never scrape the ink fountain roller completely clean. Some ink must always pass out of the fountain to lubricate the nip.

Ink agitators

• An ink agitator is a motorized cone that moves back-and-forth in the fountain to work the ink--keeping it fluid--and force it into the nip.
• Fluid ink flows easier down in the fountain and the ink will not "ball-up" or back away from the nip.
• Ink agitators prevent the formation of dried-ink-skin on the surface of the ink in the fountain.

Ink fountain divider

• An ink fountain divider allows the feeding of multiple colors if ink onto the rollers at the same time
• Oscillation (vibration) of ink drums must be reduced (most presses allow the amount of oscillation to be adjusted).
• Two dividers should be used with water-wet rags between them to completely break the two colors.

Two-color splits on one-color press

• A simple example of a two-color split on a single- color press is shown at right. Instead of two press runs, both colors are printed at the same time. Half the fountain is used for one color and half for the other. The inks are kept separate by dividers in the fountain. This process eliminates additional plate cost and press time. The sheet can be backed-up if desired.

Multiple splits on one-color press

• The possibilities of color combinations are virtually unlimited. In the example at right, four colors are used requiring three dividers.

Multiple splits on two-color press

• One of the most popular uses of ink fountain dividers is achieved with a two-color press. In the example at right, the first fountain, divided twice, would supply three colors. The second printing unit prints the key color only and is undivided. This system allows a wide range of colors at two-color cost with a minimum of additional makeready time.

The fountain roller (orange roller at right)

• The fountain roller rotates periodically against the fountain blade.
• The amount of rotation is adjustable by a ratchet device or with a variable device such as a motor.
• Rotation, combined with key settings, meters the ink to the rollers.

Interaction between fountain roller swing and ink transfer

• The fountain blade setting determines the thickness of the ink flow.
• The rotation determines the area of the ductor roller covered by ink.
• The rotation, or "swing," should be set as great as possible to deliver a large area of ink to the ductor. This affects an even flow of ink to the distribution section of the rollers.

The ductor roller (green roller at right)

• The ductor roller is a resilient roller alternately held in contact with the fountain roller to pick up ink, then in contact with a vibrator (or other distribution) roller to distribute the ink.
• The amount of ink applied to the ductor depends on the fountain-roller rotation and ductor dwell (how long the ductor remains parked at the fountain roller).
• The ductor shuts off when the press is not printing.
• Because all ink flows through the ductor, it must have a uniform surface and be parallel to the distributor rollers.

Ductor timing

• When the ductor contacts the distributor roller, it may jar the rollers causing "gear" streaks. To prevent this, the ductor should be set to contact the vibrator when the forms are above the plate cylinder gap.

Spiral-cut ductor

• If a very small amount of ink is required, a spiral-cut ductor may be used.

The distribution section

• The distribution section consists of alternating hard (orange in the illustration at right) and soft (green at right).
• Hard rollers are usually steel, but can be hard rubber, bakelite.
• The very best material for hard rollers is copper because it is naturally hydrophobic.
• Soft rollers consist of steel shafts with rubber or synthetic rubber covering.

Replenishing ink

• The inking system must be set to replenish ink on the plate according to the plate's demand.
• The ink-film on the form rollers should be uniform even though the fountain is set (in the illustration at right) to deliver more ink to one side of the plate than to the other side. When more ink is used on one side, the distribution section must replenish more to that side.

Setting amount of oscillation according to plate demands.

• Set much oscillation for even plate coverage.
• Set little oscillation when keys are adjusted to allow more replenishment on one side than the other or when using split fountains.

Ghosting

• Set maximum oscillation to prevent ghosting as shown at right.

Types of rollers in the distribution section:

Vibrators

• Vibrators (oscillators or drums), shown as large orange rollers in the diagram at right, are fixed in the frame of the press (non-adjustable) and are driven by gears.

Distributors

• Composition-covered (rubber) rollers, shown in green in the diagram at right, are driven by friction from the vibrators.
• Carry the ink from vibrator to vibrator.
• Should be of different circumferences to even out the ink.
• When ink is transferred from roller to roller it becomes conditioned. It is better to have many distributors for this reason.

Riders

• May be rubber or steel (the small orange hard roller in the diagram at right is a rider roller).
• Help condition the ink.
• Do not transfer ink from roller to roller.
• Help evaporate water by exposing more surface area to the air.
• Good systems have lots of riders.

The form-roller section.

• Two to four rollers that apply ink to the dampened plate.
• Forms should have different diameters to minimize ghosting.
• The surfaces of ink forms must be in perfect condition because defects (holes and the like) will affect the inked image.
• Uneven form rollers cause improper ink transfer to the plate.
• Form rollers "drop" automatically when the press starts printing and "lift" automatically when the press stops printing. They may also be turned on or off manually.

Hickie pickers

• Special covered rollers may be placed in the #1 form roller position to pick hickies off the plate.
• The pattern caused by the hickie picker will be "polished off" by successive rollers.
• To view a photograph of a hickie picker, click here.

Setting form rollers

• Forms must be set to both plate and drums.
• Pressure should be light. Excessive pressure can damage the roller.

Checking form-to-drum pressure

• The press is not inked-up.
• A "sandwich" of two wide sheets with a narrower one in-between is rolled between the form and drum on each side of the press (see illustration at right).
• Pulling on the center--narrow--strip indicates pressure between the rollers.
• There's no precise gauge--set pressure to minimum to give good position ink transfer.

The "picture" method

• The press is inked up.
• Stop the press and let it sit for a minute.
• Jog the press sharply.
• View the line that shows a "picture of the pressure."
• The line should be about 3/16" wide.

Checking form-to-plate pressure using the "picture" method

• The press is inked-up and stopped.
• Manually drop the form rollers to the plate, then lift the forms off the plate.
• Jog the press to view the stripe(s).
• The stripes should be about 1/8" wide and even all the way across the plate.
• The last-over form should have less pressure (about 1/16" wide stripe). This form acts to polish the ink laid-down by the previous forms.
• Actual width of stripes depends on press manufacturer's specifications as well as age and condition of the press and the rollers.

Setting form-to-drum and form-to-plate pressures

• Done through the use of eccentrics.
• Care must be taken so that eccentrics are not 180 degrees out of line. In such a case, the pressure will appear equal, but the roller will not be parallel to the vibrator roller.

Importance of using correct form-to-plate pressure

• Excessive pressure may cause the forms to "bounce" at the plate cylinder gap and skip over the lead edge of the plate without inking it.
• Rollers striking the lead edge of the plate cause severe plate and roller wear.
• Heavy pressure causes blurred images.
• If the form roller-to-plate pressure is greater than the form roller-to-vibrator pressure, the form rollers will skid on the plate and will cause streaking.
• If forms are set too tightly to the plate, they will act as squeegees and prevent ink from flowing onto the image.

Adjusting form-to-plate pressure

• Must be done after form-to-vibrator pressure is set.
• Is accomplished using different methods on different presses.
• Pressure should always be less than form-to-vibrator pressure.

Teamwork

Since many adjustment and maintenance procedures involve more than one person, the entire press crew must function as a team. Responsibilities should be assigned so that each member of the crew understands exactly what his or her duties are. All crew members are responsible to be careful not to endanger others as well as to protect themselves. A clear system of signals should be developed to coordinate the press crew on operations which require that the press be periodically started, as when cleaning the rollers on the press. Each crew member must know the signals and use them. Cooperation of the press crew makes the job safer and easier for all.

A system of reporting is part of safe operating procedures. All accidents should be reported immediately, and their causes noted and eliminated. First aid should always be administered, even for minor injuries, because the chemicals and materials in the pressroom increase the danger of infection. If an alert crew member finds a more efficient way to perform a particular operation, he or she should analyze it to be sure no safety hazards are involved. Operating procedures can always be improved, but safety must not be sacrificed. Any crew member who notices that part of the press requires repair or is in dangerous condition should report it immediately. The report should be followed-up to insure prompt corrective action. Inspection then becomes part of the normal operation and cleaning procedures, and many accidents and press troubles can be prevented.

Housekeeping

• All tools and materials used in adjustment or maintenance must be returned to storage or disposed of properly.

Housekeeping

• Waste rags with solvents should be stored or discarded in self-closing, metal containers.

Housekeeping

• Walkways and floor must be kept dry and free of grease, ink, oil, paper, rags, and so on.

Housekeeping

• Neatness in housekeeping can prevent accidents such as slipping and tripping.
• Time spent in keeping the area clean makes it easier and safer to move around in, and makes tools and materials easier to find.

Personal cleanliness

• Press operators may become sensitive to pressroom chemicals under short- or long-term exposure.
• Prevention is the only cure, so exposure to chemicals should be avoided.
• Keeping hands clean provides the best protection against reactions. Therefore, protective clothing, such as gloves and goggles, should be worn when handling chemicals.
• Exposed skin surfaces should be washed immediately after contact.

Cleaning the ink fountain

• Must be thoroughly cleaned when changing colors to prevent color contamination.
• All parts of the fountain must be clean.
• Keys should be removed periodically and cleaned to make them easy to turn and to prevent them from being stripped due to dried-ink deposits.

Cleaning the ink fountain

• When replacing keys, tighten them gradually from the center outwards to avoid bending the blade.

Cleaning the ink fountain

• Cleaning the fountain eliminates a major cause of hickies--dried ink particles sticking to the plate.

Safe use of ink cans

• Do not pry open ink cans with a screwdriver or sharp tool; it leaves a sharp, jagged edge on the can.
• When a can lid is stuck, the corner of an ink knife should be inserted under the lid and run completely around the can.

Wash-up machine operation

• Wash-up machines provide a quick method for removing ink from the roller train.
• The plate does not need to be removed to wash up when a wash-up machine is employed. (This allows the operator to continue running the same job the next day with few adjustments to be made.)
• Wash-up machines are composed of an adjustable squeegee and a drip pan or trough.
• Solvent is applied to the rollers and the squeegee scrapes the dissolved ink off of one of the drums.
• The wash-up blade must be clean and flat without nicks or grooves.

Washing up a press

• Half of the rollers should have solvent applied at one time.
• If the entire roller is wet, the rollers will slip and stop turning.
• The forms should not touch the plate during wash-up.
• After wash-up the plate should be re-gummed.
• Rollers must be dry when wash up is finished. In not, the wet rollers may stick together and, then the press is started, peel apart (another cause of hickies).

Care of composition rollers

• The wash-up machine does not eliminate the need for periodic hand wash-up of rollers.
• Manual wash-up removes glaze (dried gum arabic) and cleans the ends of the rollers (prevents ink build-up).

Effect of ink build-up

• Ends of rollers can crack
• Particles of build-up can fall into the inking system and cause hickies.
• The built-up ink can contaminate new ink colors.

Glazed rollers

• Glaze is caused by residue from wash ups.
• If ink, gum arabic, or oil dry on the rollers, glaze is hastened.
• Glazed rollers are hard and shiny. Hardness of rollers is specified by press manufacturer and measured with a durometer.

Effects of glazed rollers

• Ink does not stick to glazed rollers, so ink distribution is ruined.
• Glazed surface lacks traction, so rollers skid.
• Water is difficult to control.
• Particles of glaze cause hickies.

Two-step wash up

• Two-step washes prevent glaze.
• Two different solvents are applied
• Step one dissolves water-based chemicals (such as gum arabic and paper dust). This chemical is applied first and allowed to mix in with the ink.
• Step two dissolves oil-based chemicals (such as ink). It is applied after step one has mixed with the ink. The wash-up machine is engaged and the step two solvent carries the ink and the step one solvent to the drip pan or trough.
• Care must be taken to remove all the step one solvent.

Care of steel rollers

• A major problem with steel rollers is "stripping," when the ink refuses to stick to the ink rollers.
• Steel is naturally hydrophilic, so gum tends to stick easily to steel rollers. This causes the rollers to reject ink.

Causes for roller stripping

• Poor wash-ups often leave gum on the rollers.
• Too much fountain solution being run causes excess gum to get into the roller train.
• Too much gum in the fountain solution.
• Excessive gum cause buy improper gumming of the plate.
• Running plates containing little image (such plates require lots of fountain solution--see cause 2 above).
• Uninked or slightly-inked ink rollers.

Preventing roller stripping

• Keep rollers clean
• Check pH and gum levels in the fountain solution.
• Use copper instead of steel rollers (copper is hydrophobic).
• Use a copperizing solution on the rollers.