FAQ of Printing Plates

Questions

Check Programme

Causes

Answers

Exposure Virtuality (halation)

Exposure operation

Plate rumple

Be careful to improve ways of holding plates. Enforcement should meet natural strain and straight

Exposure

Light source is too near to the plate  

adjust the distance between light source and plates higher than the plate diagonal

Exposure

dirt on the film and the exposure glass

Clean film and glass with clean soft cloth and glass cleaner. reduce the stains and spots on the exposure glass as much as possible

Exposure Imbalance

Exposure

Light source is too near to the plate

Adjust the distance between light source and plate higher than the plate diagonal

Exposure

Light source is not placed correctly

Place the light source correctly. Put the plate right under the light source

Image defects

Exposure

Spots on the exposure glass in the exposure frame

Clean film and exposure glass with clean cloth and glass cleaner. Reduce spots on the glass as much as possible.

Low run length

Exposure

Underexpose negative plate

Check the solid steps after the plate is exposed through gray scale. Increase exposure.

Development

Overdevelop

Check the dilution of the developer, developing temperature and developing time.

Adjust printing pressure, Roller pressure

Pressure between plate cylinder and blanket cylinder is too high

Decrease plate cylinder-blanket cylinder pressure and check regularly.

Blanket

Elasticity of the blanket becomes worse

Replace blanket

Operation

Overexpose the positive plate

Check the clear steps after the plate is exposed, Reduce exposure

Fountain solution

Concentration change of fountain solution

Use fountain solution replenishment equipment

Ink shortage

Gumming

Gum solution is too thick or coating is not uniform

Dilute the gum solution or adjust coating method of gum solution to make gum coating uniform

Baking

Baking solution is too thick

Coat the baking solution uniformly on the plate surface with sponge

Adjust printing pressure

The pressure between the plate cylinder and blanket cylinder or the pressure between the printing cylinder and blanket cylinder is too low

Increase the pressure between the plate cylinder and blanket cylinder and the pressure between the printing cylinder and blanket cylinder and check regularly

The contact pressure between plate cylinder and ink roller is too low

Increase the contact pressure between plate cylinder and ink roller. Check regularly

The contact pressure between fountain roller is not right

Adjust the contact pressure between fountain rollers.

Blanket

Rough deformed

Check regularly and recover well.

Fountain solution

Fountain solution is too much

Adjust the contact pressure between fountain rollers.

Dot gain

Exposure

Overexpose (negative);                     Underexpose (positive)

Check exposure

Development

Underexpose (positive)

Check the concentration, temperature of developer and developing time.

Adjustment of printing pressure

The pressure between plate cylinder and blanket cylinder or between printing cylinder and blanket cylinder is too high

Check the printing pressure regularly.

Adjust the ink in the in filler

Accepting ink is too much

Reduce the ink on the roller

Fountain solution

Ink is over-emulsified

Check fountain solution

Dot Loss

Exposure

Overexpose (positive)

Check the clear steps of gray scale

Development

Overexpose (positive)

Develop under the control of gray scale. Check the develop activity.

Adjust printing pressure

The pressure between plate cylinder and blanket cylinder or between printing cylinder and blanket cylinder is too low

Check the pressure between plate cylinder and blanket cylinder or printing cylinder and between printing cylinder and blanket cylinder.

Plate contamination

Fountain solution

Fountain solution is not enough

Increase the amounts of fountain solution.

Scum

Exposure

Exposure time is too long (negative)

Check the solid steps.

Under-exposure (positive)

Check the clear steps.

Development

Under-exposure (positive)

Develop under the control of gray scale and check developer activity.

Retouchment

Image remover is not removed completely

Rinse and remove the image remover after retouchment.

No gumming

Gumming gum solution.

Gumming

Gum solution is diluted too much

Concentrate gum solution.

Baking

Baking solution is too think

Adjust the coating weight of baking solution.

Adjustment of printing pressure

The contact pressure between ink roller is too high

Decrease the contact pressure between ink roller and check regularly.

Fountain solution

Fountain solution is deficient

Increase the amounts of fountain solution.

The concentration of fountain solution is too low

Increase the concentration of fountain solution.

Rubber cover is aging

Replace the rubber cover.

Ink in the filler

Accepting ink is too much

Reduce ink on the ink roller.

Printing plate is starting

Plate scratch, fingerprint, spots

After cleaning the plates with cleaner for plates, wipe plate surface well immediately.

Blanket in the transfer

Blanket is aging

Replace blanket.

Ink color

Adjust roller pressure

The roller is aging

Check the roller pressure regularly

The amounts of fountain solution

Over-emulsified ink

Check fountain solution

Double Imager

Adjust roller pressure

The pressure of fountain water roller is not right

Check the roller pressure regularly

Fountain solution

Fountain solution is too much

Reduce fountain solution

Ink color is too light

Fountain solution

Ink is over-emulsified. Fountain solution is too much

Reduce fountain solution and check fountain solution