FLEXOGRAPHIC PRINTING

PROBLEMS AND SOLUTIONS

​ABOUT FLEXO PRESS AND MACHINERY

Printing: A process can be desiribed as reproduction of the shapes, texts, graphics, patterns and pictures to the surface of a film material.
 
The basic printing presses (Machines) consist of four basic units.
  • Printing unit
  • Rewinder unit
  • Unminder unit
  • Drying unit

Inline Machines
The printing machines without Rewinder and Unwinder unit are inline printing machines. These machines transfer films from one machine to another machine and work as a complement to the production line.

Flexographic Printing Machines
​
   Flexo printing,  a type of direct high printing system, is a relief printing method. In the flexo printing method, the printing is carried out on a protruding rubber or photopolymer plate and the ink transfer is carried out with these protrusions on the printing cylinder. It is based on the principle that the ink on the surface of the printing plate is placed on the printing material with the pressure of the ink on the high areas. The most important advantages of this method are the low amount of ink used and quick drying of the ink.
  In the flexo printing machine, the ink is transferred from the reservoir to the film via cylinders and plate. Four of the cylinders rotate by means of gears or servo motors.


Machine Operation Steps
  • Prepare your working environment.
  • Take safety precautions.
  •  Set the print size for printing
  •  Place the printing plate properly on the machine.
  •  Be careful because the surface of the printing plate is very sensitive.
  • Connect the film reel to the unwinder Unit appropriately.
  • Attach the film coil/reel/bobin  to the center of the hub shaft.
  • Secure the hub shaft and film reel to the unwinder unit securely.
  •  Attach tip of new film reel to ongoing film using tape.
  • Connect the hub shaft to the rewinder unit.
  •  Select the the hub shaft  suitable for the width of the film to be printed.
  • If the hub shaft bobbin is air-tight, secure the bobbin with compressed air. If it is wedged, tighten  the hub shaft  bobbin so that it will not loosen.
  • Prepare the film by passing the film through the appropriate rollers.
  • If the film has passed between rollers  due to previous printing, glue /connect the new film  tip to it, otherwise re-fit it.
  • wrap around the hub shaft  of the film winding unit several times.
  • Clean the rollers.
  • Prepare the appropriate ink for printing.
  • Select the appropriate ink and mix thoroughly before pouring into the chamber.
  • Add other additives (retarder, thinner, etc.) to the ink chamber.
  • If there are dust and paint residues on the cylinder roller and plate, wipe them off with a little solvent soaked cloth.
  • After the preparations are completed, run the machine for a while on "start the cliche mod" so that the ink mixes well.
  • To ensure good mixing of the paint, ensure that the reservoir cylinder is properly pressurized over the anilox.
  • Reset the edge control unit if there is.
  • Set the brake and tension system.
  • Set the dryer temperature.
  •  Adjust the viscosity of ink by adding the ink thinner or pouring more ink.
  • Start machine at low speed by pressing Start button
  • Starting with the first printing unit, make the settings in sequence. activate the edge control unit  when the print film is centered.
  • Film tightness must be controlled and necessary tension adjustment must be made.
  • The print is continuously checked. If a printout shows any quality deviations (burrs, shadows, no prints, etc.), the necessary adjustments must be made.
  • The temperature of the drying unit must be checked. If adequate drying is not achieved, the temperature is to be increased.
  • The ink and viscosity must be continuously controlled. If ny problem occurs their deficiencies are to be resolved.

Printing Machines Production ;Errors and Possible Solution Suggestions 

During working printin results can be defective due to various reasons and factors, in order to be productive, these errors must be minimized.

Fill-in of Reverses

Resim


​During winding, the ink on the printed surface contaminates or passes the back surface of the printed material


Probable Cause
Possible Solution
​The ink film is being sent rewinder before full drying.
​
Use accelerator solvent.
Check the drying system.
Lower the viscosity.
Lower the pressure of the stripping blades 
There is solvent residue on the print surface
​Lower the ink film thickness to the minimum acceptable. Do not use excessive retarding solvent.
Excessive winding pressure .
​Reduce the coil winding pressure.
Corona treated films on both surfaces;  the printed surface is in contact with the other surface.
Reduce the coil winding pressure.
Sarım basıncını azaltınız. ​Provide more efficient drying. If necessary, use anti-blocking varnish.
​In some films plasticizers may migrate to the surface.
Sarım basıncını azaltınız. ​Provide more efficient drying. If necessary, use anti-blocking varnish.

Print Leap

Resim
​

​Some parts of the cliche do not print, ie the part of the font figure does not come out as crafted.

Possible Cause

​Possible Solution
​The cliché platen is poorly prepared.
 A new cliche.is needed.
The printing cylinder is not working properly.
​Check the force settings of printing Cylinders again.
The cliche roller is making  jog
Check the centering of the cliche plate cylinder and the gears and the wear of the bearings and also check the smoothness of the plate cylinder shaft. Check that if the gear system is clean and has no obstacle.

​Stretching Lines

​Stretching lines is undesirable lines along the print, except the figure or the picture.

Possible Reason

​Possible Solution
​The anilox or "rubber of the ink transfer cylinder" is damaged.
The hard spots on the anilox destroy the transfer roller. Fix the anilox and transfer cylinder rubber.
​The scraper blade may be damaged.
Sandpaper the blade or replace it with the new one.

Blocking

During the unwinding of the material.It is difficult  when layers stick together.

​Possible Cause

Possible Solution
​The ink dries slowly.
​Check the drying systems.
Do not use slowing solvents in excessive amounts.
​Solvent residue mixed to in the ink film.
​Check the solvent mixture.
The material is wrapped in hot temprature.
​Use a cooling cylinder.
​The winding pressure is too high.
​Reduce the winding pressure.

Coil Ripple

​​The film is not correctly wrapped due to the incorrect orientation and fluctuation during printing.

​Possible Cause

​Possible Solution
​The printer is out of sync.
​Take a look at the machine settings.
Unknown materials are present on the printing cylinder.
Clean the cylinder surfaces.
Excessive temperature is applied for  printing material type. (ie;polyethylene)
​​Reduce the drying temperature.
​Bobbin guides are not working or are out of adjustment.
​Clean and check the coil guides.

Mottle/Speckle

Resim
​



​​There is a spotted appearance on the printed surface and the clearness is lost.

​Possible Cause

Possible Solution​
​Weak ink is used (less stickiness).
Increase the viscosity by adding more ink. Add varnish to increase adhesion.
​​The cliché platen surfaces are bad.
Use a  new cliche platen.
​The width of the anilox cell wall is too large.
​Check for anilox wear. Use new anilox
There are unkown materials such as dust, burrs on the surface of the plate.
​Clean the cliché platen thoroughly.
​The surface of the printing cylinder is dirty or hollow.
Clean the grease, ink, wax and the unknown materials like them on the surface of the print cylinder.
​Material surface is not uniform
​​Change the printing material or use a softer plate.
​Non-uniform absorbent surfaces.
Smoother cliche or more opaque ink might solve the problem.
​The ink spreading ability is bad.
​Consult your ink supplier or technical staff.
​​The ink may be dirty.
​​Change the ink or add new ink.

​​Filling.

​​Ink accumulation on the surface of the plate.
This is the case of  the filling of trams and lines in fine prints and patterns.

​Possible Cause

​Possible Solution
​There are pigment residues in the ink.
​Use good crushed ink.
​Unwanted unknown dust, fibers, dirt or metal particles are present in the ink.
​Use the ink after filtering 
Extremely thin text and tram design.
Tasarımı tekrar gözden geçiriniz.
​The printing roller rubber is very soft
​Use harder rubber than existing hardness
​The pressures are too high
Set the pressures.
​The cliché layer is getting too much ink.
Use anilox with less ​transfer volume or adjust stripping blades.
The Ink drying very quick.
​Use "redardant" solvent or increase printing speed.

​Pale print

Resim


​Unclear printing, lack of contrast or misty printing.

​Possible Cause

​Possible Solution
​The cliché platen layer is weak or worn.
​Use  New The cliché layer which is not weak or worn..
​The plate pressure is too high.
​Reduce the pressure. Use padded cliche adhesive tape.
​Viscosity is very low.
​Increase the viscosity by adding new ink.
​​The inks may be dirty.
​​Use new, more transparent process colors.

​Excess of Ink on Cliche Platen

This case happens When the cliche takes too much ink.

​Possible Cause

​Possible Solution
​Insufficient solvent thinning.
​​Thin the ink by lowering the viscosity.
​The ink transfer cylinder clearance is too high.
​Check for the cylinder clearance setting, reduce the clearance.
​The anilox parameters are wrong.
Contact the manufacturer of anilox which is be suitable for printing material and design.
​The scraper blades are in correst position or old.
​Make a blade adjustment. If the blade is worn, replace it with the new one.
​Solvent imbalance can increase the viscosity.
​Consult your ink supplier and technical staff.

​Weak Ink

Resim
​

​The color intensity of the ink on material is weak

​Possible Cause

​Possible Solution
​The ink is excessively thinned (viscosity is low).
Increase viscosity with new ink addition.
​The ink transfer cylinder clearance is very low.
​Check the cylinder clearance setting and increase the clearance if necessary
​The anilox parameters are wrong.
Contact the manufacturer of anilox which is be suitable for printing material and design.
​The anilox is extremely worn.
​Use new anilox.
​Anilox is dirty or cells are blocked.
​Clean the anilox with appropriate cleaning liquids and brush. Clean the anilox periodically.
​Heavy pigmented inks may have soft sagging.
Mix thoroughly before discharging the ink into the reservoir.

​Shadows

​It is a case of unwanted lines around the print.

​Possible Cause

​Possible Solution
​The pressure between the material and the plate is too high.
​Restore the force settings. Reduce the pressure.
​​Platen which is  used are bad conditions
​Clean the plates with solvent.
​​The edges of the cliché platen are distorted.
​Use new cliché platen.
​The cliche cylinder does not revolve around its axis.
​Check the axis settings.
The platen is too hard.​
Use smoother platen.
​The cliché adhesive tape is thin or very hard.
Use a more elastic or padded type cliche band.

Weakness of Ink Transfer

​The cliche does not transfer enough ink in full or partial.

​Possible Cause

​Possible Solution
Anilox can not give ink to second of the two cliches that receiving the ink from the same region  but while the first ​of the two cliches is able to recieve the ink.
Change the platen cylinder diameter or set the inking cylinder and the anilox cylinder speed ratio.
​The anilox surface is dirty or clogged.
​​Clean the anilox with appropriate cleaning methods. Use a brush. Periodically clean up.

​​Fast drying of ink.

​The ink is dried on the anilox and plate, and there is insufficient transfer to the material.

​Possible Cause

​Possible Solution
​​Solvent selection is wrong.
​Make solvent selection correctly.
​Airflow are present near the cliché anilox contact zone.
​Reduce airflow.
Hopper caps are not used.
​Hopper caps must be used.
​Working with incompatible ink.
​Use appropriate ink for the material to be printed. If necessary, consult your ink supplier and technical staff.

​​Slow Drying Ink

​The ink is on the material to be dried, smudged, backed or blocked.
​

​Possible Cause

​Possible Solution
​Solvent seçimi yanlıştır.
​Solvent seçimini doğru yapınız.
​Kurutma sistemi yetersizdir.
​Kurutma sistemini baskı hızını karşılayabilecek şekilde yeniden ayarlayınız.
​Mürekkep seçimi yanlıştır.
​Mürekkep seçimini doğru yapınız.
​Mürekkep baskı viskozitesi çok yüksektir.
​Viskoziteyi azaltınız. Viskozite ölçümleri her 20–30 dakikada bir yapılmalıdır.

​Bleeding

The bottom color spreads into the upper color.

​Possible Cause

​Possible Solution
​​The bottom color is very slow drying or the top color is drying too fast.
Adjust the drying speed. The previous color must be dried up to prevent spreading into.
​It is the plasticizers in the material that affect the ink lacquer.
​Use materials containing unknown plasticizers with caution and preferably do not use lacquered ink.

Print Shift/Slide


One part of the design does not overlap with the other as it should make perfect borderlines.

​Possible Cause

​Possible Solution
​The cliché is poorly placed.
​Replace Cliche platen, readjust it.
​​Coil winding pressure is wrong.
Adjust rewinder winding pressure
​The rewinder temperature is too high.
Adjust rewinder temperature.
​​Carrier rollers are braking.
Ensure that the carrier rolls rotate freely or at the pressure speed.
​Thickness deviations available in printing material
Contact the manufacturer of the printing material. Use more qualified material..
The reel rolling tension is wrong.
Adjust the reel rolling tension.

​Fragile Structure in Film

​​The printing material loses its elasticity and has a fragile, hard structure.

​Possible Cause

​Possible Solution
​Reduction of plasticizer in film material due to excessive temperature in drying system.
​Check the coil temperature.

​Swelling of Cliche Platen

The size of the cliche platen grows over time and its softness increases.

​Possible Cause

​Possible Solution
​The ink or solvents which are used are not suitable for cliche platen
Do not use solvents that are not recommended for the cliche platen being used. Consult ink and cliche platen manufacturers.
​The use of excessive foam breaker /Antifoam can create a clogging swelling.
Reduce the use of foam breaker/Antifoam.

​​Unwanted Odor

​​The printed surface has an unwanted odor.

​Possible Cause

​Possible Solution
The reaoson is remaining trace amounts solvent in the dry film.
Adjust the solvent balance and avoid solvents that evaporate too slowly.
Check the efficiency of the drying system. If necessary, increase the temperature.
slow down the print speed.
​To reduce the cost, do not use solvents that are not recommended for ink.

​Foaming in ink

​The ink is foamed during circulation in the chamber.

​Possible Cause

​Possible Solution
Ink foam breaker / anti foam balance is wrong
​Consult your ink supplier and technical staff. If necessary, add foam breaker/ anti foam
​Ink is pouring down from too high during return.
​Check for return position. If possible use a horizontal sloping surface.
​The hopper and transfer rollers are spinning fast.
Check for the speed of The hopper and transfer rollers if spinning fast.
​The pump system is running very fast.
​​Check the circulation pump.

Jelly/ Mush/ Slush

​​Disruption of ink flow /fluidity/ liquidty , ink easily sticks to the surfaces it touches.

​Possible Cause

​Possible Solution
​Incorrect solvent is used in the ink system or solvent mixture ratios are improper
​Do the correct solvent addition.
Consult your ink supplier and technical staff.

Fringed

improper printing of edges and border lines in print.

​Possible Cause

​Possible Solution
The pressure between the anilox cylinder and the plate cylinder is unstable.
Set pressure between the anilox cylinder and the plate cylinder 
The ink is drying on a plate or anilox.
Make solvent selection correctly. Keep the hopper covers closed.
​The ink transfer cylinder clearance is unstable.
Correct the ink transfer cylinder clearance.
​The ink transfer cylinder is bad or worn.
​Correct the surface of the transfer roller or replace it with the appropriate one.
​No viscosity control yet.
​​Adjust the ink viscosity.
​The fibers and dust on the surface contaminate the cliché.
Select clean material on the surface and avoid using too much sticky ink..
Static electricity charged.
​​Use a static-dissipating wire rod

​Repeating Holes

​It is the case that small holes with the same shape are reprinted

​Possible Cause

​Possible Solution
​The ink builds up very quickly on the anilox. And the cliché is not making the necessary transfer.
​Use deaerating solvent. Keep the hopper covers closed. Check the interval drying system.
​The anilox is worn out.
​Check the anilox. Replace with new if necessary.

Ink not  sticking enough.

The ink does not give adhesion to the printing surface. When rubbed ink comes out.

​Possible Cause

​Possible Solution
​Wrong choice of ink.
​Consult your ink supplier and technical staff.
​The ink is too thin.
​Increase the viscosity by adding new ink.
Treatment was not enough

​Check for surface of film for adequate treatmentment, Check the treatment with  pen. For good adhesion (adherence) the material surface tension should be equal to the ink surface tension.
​The material surface may be dirty or greasy.
​Contact the manufacturer of the printing material.

​Pinhole Image

In the case of Pinhole image  there is a perforated image with the pin-tip size stains.

​Possible Cause

​Possible Solution
​The surface of the printing materials is defective.
​Contact the manufacturer of the printing material.
The ink can not form a continuous shape on the material.
​​Increase the applied film thickness. Check the pressure setting of the anilox platen cylinder and the platen roller to the material. Raise if the force settings are low. Consult your ink supplier and technical staff.
Too much foam breaker / anti foam is  used.
Add new ink. Do not use excess amount of foam breaker./anti foam.
​The printing cylinder is dirty.
​Clean the printing cylinder when it is dirty.
The ink builds/ dries up too fast, the spread is not complete.
​Add slowing solvent, increase printing speed.
​​The anilox is very worn.
​Check the anilox. Replace with new.

Plucking

The first color that is printed is transferred from the material surface to other  cliche surfaces

​Possible Cause

​Possible Solution
​The first color dries slowly.
Add "accelerator" solvent to  the first color ink. Increase the drying temperature in between color groups.
​The second color is drying very fast
​Add "slowing" solvent into the second color. Check the drying system.
​The viscosity of the second color is very high.
Reduce the viscosity of the second color 

​Weak Ink Transfer

​The ink can not be sufficiently transferred to the surface of the material.

​Possible Cause

​Possible Solution
​The ink is too thin.
​Add new ink
​The ink is drying in the cliche platen
​​​Add "slowing" solvent into the second color. Check the drying system
​The material does not accept ink.
​Consult your ink supplier and technical staff. Make the appropriate ink selection.
​Pressure settings are  not correct.
Check pressure settings.
Flexography Troubleshooting