There are many key elements that determine high, defect-free and reproducible print quality. These include; optimal Printing inks application and color saturation, color stability throughout the print run, good sharpness and contrast, reproduction of image tonal transitions and good fit in the printing process.
Print matching is the precise alignment of ink combinations on a substrate. Improper matching even in the smallest degree can completely distort the print. Incorrect matching directly affects the accuracy of the design/image reproduction and its repeatability. It also causes production downtime necessary to resolve problems created in the print.
Incorrect print fit means for the printer:
- Wasted time
- Wasted materials - substrate plus printing inkss
- Additional machine and human labor costs
- Delays in delivering finished prints to the customer
In a nutshell high costs!!! How to avoid them? Learn about the most common causes of misfit printing.
-
Inaccurate fixing / centering of the plate
Whether you use cameras, mirrors, or the naked eye, you must accurately determine the centerline of the printing cylinder, Printing plate , or printing sleeve. The cylinder or sleeve must be mounted in the same location and orientation.
-
Concentricity of the pressure cylinder
The concentricity of the cylinder (the tolerance zone for the center points of the cylindrical or spherical part) must be as close to perfect as possible. A dial indicator capable of showing errors of up to 0.0001 inch should be mounted on a magnetic base and used to take measurements from the center and near each end of the cylinder. Flexographic printing guidelines state that total runout concentricity should be no greater than about 0.0005 inch.
-
Condition of the cylinder / photopolymer plate / bushing
Physical defects, accumulation of printing inks and grease can easily distort the reproduced images. Therefore, thoroughly clean the plate, cylinder and sleeves of dirt. Check the printing surface for damage such as nicks and dents.
-
Condition of the printing cylinder gears
Missing cylinder teeth and lack of concentricity can cause problems with print misfit. Make sure all gears are intact and properly aligned. The print cylinder pinion must fit the cylinder journal with a tolerance of no more than 0.002 inches. Also make sure that the gears are free of excess grease and foreign materials.
-
Irregular rotation of the cylinder
Dragging or unstable rotation of the cylinder prevents accurate transfer of Printing inks. The photopolymer will not contact the substrate at the right place and time.
-
Incorrect control of web tension
Web tension is a system that includes:
- Sensor
- Controls
- Winder and unwinder
- Web
The sensor transmits error signals to the controller to adjust the web speed difference. Correct positioning of the sensor is crucial in this case. The web must be fed with an equal level of tension while the roll diameter changes at the same time.
-
"Wandering" Web
Any lateral movement of the web will cause misregistration of the print. Control the tension and guidance of the web to maintain a stable base.
-
Abnormal tolerance
Variations in the print fit can cause two letters, words or printed images to overlap. The overlaps in the design should be prepared taking into account the technological capabilities of the printer, the specifics of the project or the skills of the printer.
Many things can go wrong on a printing press, but always make sure mechanical Components and calibrations are correct before printing. This will help you avoid the costly consequences and stress of misfitting flexo printing. Good luck!
