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Problem Solutions and Trouble Shooting: negative Toray Plates

Problem Description or Explanation	Possible Cause / Solution
Scratches on the plate (horizontal direction)	Incorrect cleaning of the plate in the press Solution Wash-up the plate by using a clean soft wipe containing sufficient plate cleaner PC-1. Apply stop-out solution ST-1 when necessary.

Problem Description or Explanation

Possible Cause / Solution

Scumming at the edges of deleted areas

Rough surface of the ST-1 coating

Solution

Rub off the coating gently with a soft, wet wipe with PC-1 and apply fresh ST-1.

Too thick ST-1 coating

Solution

Use a fresh ST-1 with a new applicator tip. Dilute ST-1 with PC-1 and spread it by using a small piece of wipe.

Drying time of deletion fluid ST-1 is too short

Solution

Correct drying time of ST-1 is 3 min. Use hot air if necessary.

Problem Description or Explanation

Possible Cause / Solution

Scratches on the printing plate (in vertical direction)

Incorrect plate making

Solution

Refer to our attached user´s manual.

Incorrect mounting of plate into the printing press

Solution

Take care not to touch the plate at the saftey bar of the printing machine.

Hard particles on the rollers

Solution

Check the ink form rollers and remove hard particles or wash-up the rollers.

Incorrect materials used for the hickey picker

Solution

Use soft rubber (silicone) roller as a hickey picker. Hard rubber may scratch the silicone surface of the plate.

Dirt on the hickey picker roller

Solution

Clean the hickey picker roller.

Problem Description or Explanation

Possible Cause / Solution

Background scumming (toning)

High printing press temperature

Solution

Adjust the air condition in the printing room and cool the press by chilled air. Modern waterless offset presses have the option to cool the plate cylinder and/or the vibration rollers by independent water circuits.

Unsuitable ink for the press temperature condition (viscosity is too low)

Solution

Check the press temperature and use an ink of higher viscosity. Add 0.5 - 1% of anti-toning additive if necessary.

Too much ink on the rollers

Solution

Reduce the amount of ink by sheeting off.

Oily residue on the rollers / wrong roller washing solvent

Solution

Wash rollers with PC-1. Check whether machine oil drops into the rollers during press operation.

Incorrect roller adjustment

Solution

Minimize the form-roller / vibration roller pressure (of the last form roller).
Reduce the pressure of the last form roller onto the plate.
Check for unevenness of the roller pressure over the total roller length.

Plate flapping at the gripping edge

Solution

Check if the plate grip is tight.

Large image coverage

Solution

Use ink of higher viscosity

Problem Description or Explanation

Possible Cause / Solution

Poor ink laydown / Hollow dots / Poor gloss

Low press temperature

Solution

Warm-up the press by running the machine without feeding of sheets/cards.

Usage of unsuitable ink for the press temperature (ink viscosity and tack is too high)

Solution

Check the press temperature and use an ink type which suits accordingly. Viscosity can be adjusted by adding reducer to the ink (max. 5%).

Cold ink can

Solution

Warm up the ink cans up to 20°C (70°F) before taking the ink out.

Insufficient agitation of ink

Solution

Agitate the ink well in the ink duct of the press. Close the ink duct keys a little and increase the rotation angle of the ink duct roller accordingly.
Use a harder type of ink rollers ( 40-45° shore A).

Insufficient quantity of ink on the rollers

Solution

Increase the volume of ink on the rollers.

Unsuitable blanket or its underpacking

Solution

Use a quick release, semi-compressible blanket type. Check for the thickness of blanket underpacking and use paper sheets of calibrated thickness.

Low impression pressure

Solution

Increase the impression pressure.

Bad form roller condition

Solution

Check the quality of the form roller surface and make sure that it is smooth.

Problem Description or Explanation

Possible Cause / Solution

Ghosting effect (happens mostly in solid image areas containing white patterns)

Pressure of vibration rollers to form roller is too low

Solution

Check the contact pressure nip and increase the pressure if necessary.

Linear movement of vibration roller is not suitable

Solution

Reduce or increase the length of the linear vibration roller movement. It might be necessary to leave the standard settings of the press in some cases, depending on the characteristic/design of the image.

Starting point of linear vibration roller movement is not suitable

Solution

Change the beginning of linear vibration roller movement, relative to the plate cylinder position.

Problem Description or Explanation

Possible Cause / Solution

Hickeys

Paper dust accumulates on blanket and plate

Solution

Use proper sheet/card material which is not dusty.
Do not use waste sheets to start and to adjust the press.
Use a soft hickey picker rubber roller.

Hard particles coming off both ends of rollers

Solution

Wash up the ink rollers.

Problem Description or Explanation	Possible Cause / Solution
Poor wet-on-wet trapping	Poor laydown of ink Solution See our explanation at ´Poor laydown of ink´. Adjust tack between the inividual colours. Check printing density of the previous colour and reduce the ink level.

Problem Description or Explanation

Possible Cause / Solution

Back trapping

Too much ink printed on the sheet

Solution

Keep the normal ink density during printing process and do not try to match the proof by using too much ink.
Check the ink lay-down quality first and consider our mentioned recommendations before increasing the ink level too much.
Check your films and plates and study our explanation about ´Poor reproduction of high-light dots´.

Incorrect tacks between the individual colours

Solution

Adjust tack between the inividual colours.

Problem Description or Explanation

Possible Cause / Solution

Plate wear is too fast

Pressure is too high

Solution

Check the plate packing (pressure) and blanket packing (pressure) and re-adjust it according to press specification.

Abrasive spray powder

Solution

Avoid to use too much spray powder.

Problem Description or Explanation

Possible Cause / Solution

Poor reproduction of high-light dots

Poor vacuum contact

Solution

Check the vacuum frame and the condition of the rubber sealing.
Extend the time of vacuum contact.
Insert clear film strips between the film and the plate in order to obtain an air channel.

Exposure time is too short

Solution

Check whether the UGRA grey scale (2-4 microns) is correctly visible on the plate.

Insufficient transparency of the film negative

Solution

Extend the exposure time.

Insufficient development of the plate

Solution

Develop the plate again by hand.

When you use an automatic processor check following items:

The brush pressure is even and not too weak
The pre-treatment shower works correctly
NP-1 fluid is full and fresh
The used brushes are not old (limit. 20.000 passes)
Temperature of NP-1 (approx. 40°C)

Plate is too old

Solution

Use a new plate. Usually, plates which are older than 12 months become difficult to be developed. Toray guarantees a proper function of the plate up to 6 months after delivery.

Too low room temperature / humidity (relevant for manual development of positive/negative plate type)

Solution

Develop the plate under normal room conditions. When the room temperature or humidity is too low, it is difficult to develop the plate correctly.

Problem Description or Explanation

Possible Cause / Solution

Poor reproduction of shadow dots and silicone pealing

Poor vacuum contact

Solution

Check the vacuum frame and the condition of the rubber sealing.
Extend the time of vacuum contact.
Insert clear film strips between the film and the plate in order to obtain an air channel.

Exposure time is too short

Solution

Check whether the UGRA grey scale (2-4 microns) is correctly visible on the plate.

Insufficient transparency of the film negative

Solution

Extend the exposure time.

Too aggressive development

Solution

During hand-development, don´t rub the plate too aggressively. For machine development, check whether the brush pressure is even and not too strong.

Problem Description or Explanation

Possible Cause / Solution

Dirt and film edge reproduction on the plate

Insufficient cleaning of frame glass and/or the negative film

Solution

Remove dirt by wiping the glass by a damp sponge and a little soap to eliminate the static build-up.

Exposure time is too short

Solution

Check whether the UGRA grey scale (2-4 microns) is correctly visible on the plate.

Others

Solution

Expose the background areas by using proper masks.

Problem Description or Explanation	Possible Cause / Solution
Scratches on the plate (horizontal direction)	Incorrect cleaning of the plate in the press Solution Wash-up the plate by using a clean soft wipe containing sufficient plate cleaner PC-1. Apply stop-out solution ST-1 when necessary.

Problem Description or Explanation

Possible Cause / Solution

Image reappears after deletion

Deletion fluid was put on oily surface

Solution

Clean the the image areas with PC-1 and dry the area before using the deletion fluid.

Old deletion fluid ST-1

Solution

Use new ST-1 and renew the applicator tip frequently.

Inefficient ST-1 coating

Solution

Apply a coating of moderate thickness.

Drying time of deletion fluid ST-1 is too short

Solution

Correct drying time of ST-1 is 3 min. Use hot air if necessary.

Frequent plate cleaning of deleted areas

Solution

Avoid to clean deleted areas excessively.

Usage of wrong plate cleaning solvents

Solution

Use the correct plate cleaner PC-1.

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