Faq - Comec Italia

Q?

Smudged image

A.

Probable Cause	Possible Solution
Pad
Too hard	Use a softer pad
Too small in relation to the image	Use a larger pad
Prints over edges	Adjust the pad stroke and/or secure the fixtures
Cliché
Depth too deep	Make a new cliché
Wrong type of cliché, may need screen	Test a new cliché with a screen or use a different type of screen
Ink
Too thin	Add pure ink to thicken
Slow drying	Use a fast dying thinner
Material
Very uneven surface	Use special shaped pads or adjust pad position
Other
Fixtures are unstable	Redo them

Q?

Image appears blotchy

A.

Probable Cause	Possible Solution
Pad
Too flat	Use a more pointed shape pad
Porous, worn pad	Replace pad
Cliché
Etching depth is too shallow	Make a new cliché with deeper etch
Wrong type of etch	Make new cliché with screened areas
Ink
Too thick	Add thinner
Ink dried in etching	Clean the cliché with thinner
Material
Contaminated with oils	Clean with alcohol
Other
Machine speed too low	Increase the machine’s speed

Q?

Fine lines begin to close up

A.

Probable Cause	Possible Solution
Pad
Too hard	Use a softer pad
Roughened porous surface	Use a new pad
Cliché
Etch depth is too deep	Make a new cliché with lower etching depth or use pause to allow ink drying in the cliché
First exposure of plate-making process too long-lasting	Make new cliché with lower exposure time
Wrong type of etch	Use a different type of cliché with screened image area
Ink
Ink too thin	Reduce the amount of thinner
Too fluid; ink smears out	Use a fast dying thinner, or pause above cliché
Material
Too smooth (e.g. glass)	Clean thoroughly, to aid the ink cohesion
Other
Pad stroke is too fast. Causes ink to be forced out of etched areas	Reduce the speed of the pad stroke

Q?

Smears on edges of image

A.

Probable Cause	Possible Solution
Pad
Too flat	Use a more pointed shape
Cliché
Etch is too deep	Redo a cliché with less depth
Wrong type of screening or no screen	Use a different screen
Ink
Too thick	Add more thinner
Ink is drying too slow	Use a fast dying thinner
Material
Static charge	Use a ionizer or increase humidity
Other
Air moisture is too low	Increase air moisture up to 60-80%
Cycle time is too fast	Reduce printing speed
Pad pressure too high forcing ink outward	Decrease pressure

Q?

Ink sticks to pad surface

A.

Probable Cause	Possible Solution
Pad
Too soft	Use a harder pad
Wrong shape	Use a more pointed shape
Roughened porous surface	Replace with a new pad
Cliché
Etch is too shallow	Etch a deeper cliché if ink is drying on pad
Etch is too deep	Etch a new cliché with less depth, or use cliché pause to allow ink to partially dry on cliché
Ink
Dried on the pad	Use retarder or more thinner
Too wet on the pad, does not film well	Use a fast dying thinner or pause on the print stroke
Material
Dirty surface (grease, oil, release agents, hand sweat)	Preclean. Depending on the grade of dirtiness, with alcohol, if necessary. Wear gloves during printing
Other
Room temperature is too high	The room temperature is best at 18 – 20 °C
Pad speed too low	Increase speed in the case of ink drying on the pad
Pad speed too high	Use pause on print stroke in case of ink too wet to allow more drying time, or use cool/hot air

Q?

Mis-registration of colors in multi-color print

A.

Probable Cause	Possible Solution
Pad
Pads are not correctly assembled	Adjust pads so as they pick up images in the exact same place
Different shapes	Use equally shaped pads
Different hardnesses	Use pads of the same hardness
Cliché
Images are not in registration	Re-register artwork and etch new cliché
Ink
Image spreads more in one color than in others	Correct ink viscosity to prevent incorrect dot gain
Material
Parts collapse (e.g. plastic bottles)	Use a more supportive fixture
Other
Work piece fixtures are not stable enough	Control. Make new fixtures if necessary
Conveyor, feeder or turntable move inaccurately	Set carefully the devices movement
Fixtures are insufficiently attached	Fasten fixture screws

Q?

Opacity of ink is inadequate

A.

Pad
Porous and rough	Replace pad
Too flat and soft causing insufficient ink release	Use a firmer and more pointed pad
Cliché
Etching depth is too shallow	Etch a deeper cliché
Wrong type of screen	Test a new cliché with a different screen
Wrong type of cliché	Use a different type of cliché
Ink
Ink too thin	Thicken ink
Ink not completely transferred	Use print pause or air blower to partially dry ink for proper release
Material
Image not brilliant enough due to darkness of parts	Use double hit to lay down an additional ink layer

Q?

Distortion in printed image

A.

Probable Cause	Possible Solution
Pad
Wrong shape	Use a different shape pad
Too soft or too hard	Use different hardness
Image too close to pad edge	Move or replace pad
Cliché
Etched too deep	Coupled with thin ink, the smudge caused is often mistaken for distortion
Ink
Too thin + etched too deep	Causes smudging (see above)
Material
Moves or collapses	Use special fixtures or appropriate pads
Other
Unsuitable work piece fixtures	Modify the fixtures to achieve support on all positions of the product
Fixtures movement	Check fixtures
Printing on angles	Change fixture grade

Q?

Uneven ink thickness

A.

Probable Cause	Possible Solution
Pad
Wrong shape	Use a different shape
Cliché
Wrong cliché type	Use steel cliché to prevent ink “scooping”
Wrong etching depth	Make a new cliché controlling depth
Wrong type of screen	Test a new cliché with a different screen
Wrong orientation	Change cliché orientation
Ink
Too thin	Reduce the amount of thinner
Too thick	Add more thinner
Insufficient mixing of ink and additives	Mix the ink thoroughly before putting it into the inkcup.
Material
Odd shaped surface	Use suitable pad
Other
Doctor blade too soft	Use firmer doctor blade or convert to hermetic inkcup system

Q?

Color transfer between pads on multi-color jobs

A.

Probable Cause	Possible Solution
Pad
Porous, worn surface	Replace pad
Cliché
Etching is too deep	Etch a new cliché with less depth
Wrong percentage and DPI of screen	Test a new cliché with a different screen (higher DPI screen for smaller areas & details)
Ink
Ink contains too much thinner	Add more pure ink
Ink is drying too slow	Use a fast drying thinner, blow air, or use pad delays/pauses to give inks time to dry
Material
Very smooth surface. Substrates which cannot be notched by the thinner (e.g. glass) are especially problematic	Use hot/cool air on part during the print, or use pauses before printing
Substrates contaminated with oils	Clean parts before printing.

Q?

Small pinholes are apparent

A.

Probable Cause	Possible Solution
Pad
Surface is damaged	Replace pad or place it so that damaged area won’t interfere with image
Pad is too flat	Use pointed shape pad
Too soft	Use a harder pad
Cliché
Bad etching due to error or dust during exposure stage	Redo the etching
Ink
Ink is too thick	Add more thinner
Material
Rough surface	Use a firmer pad
Dirty parts	Clean them before printing
Other
Ink contaminated with silicone or oils	Replace with new ink

Q?

Ink does not meet adhesion requirements

A.

Probable Cause	Possible Solution
Pad
Too much silicone on surface	Clean new pads with alcohol before use
Cliché
Etched too deep	Redo a deeper cliché
Ink
Wrong type of ink	Use the suitable ink according to the technical data sheet
Probable need for two-component ink	Use two-component ink with hardener
Incorrect ratio of ink to hardener	Remix ink with correct ratio by weighing ink and hardener
Material
Dirty surface	Pre-clean with alcohol
Other
No/insufficient pretreatment	Check pretreatment procedure. If necessary, repeat it
Polymerization time not respected	Let the pieces stand for longer time before testing
No/insufficient after-treatment	Use heat tunnel and in some situations do the flame treatment

Q?

Blurred print or sharpness problem

A.

Probable Cause	Possible Solution
Pad
Too soft	Use a harder pad
Wrong shape	Use a different shape
Cliché
Inaccurate etch	Make a new cliché
Etching is too deep	Etch a new cliché with less depth
Wrong type of cliché	Use the suitable cliché type (e.g. steel in place of polymer).
Wrong type of screen	Test a new cliché with a different screen
Ink
Ink is too thick	Add more thinner
Ink is too thin	Reduce the amount of thinner.
Slow drying	Use a fast drying thinner or cliché pause
Material
Dirty surface	Pre-clean
Rough, grainy surface	Switch over to other material, if possible, or try a harder pad
Printing near edges	Fixtures must support the pad to prevent slippage
Other
Work piece fixtures are not stable enough High speed causes pad vibration	Make new fixtures Decrease speed. If necessary, pause the pad at front position before releasing the ink to avoid vibrations of the pad during printing