Most Xeikon based printing units are reel fed and use corona discharge to attract the toner to the paper. The printing process can be divided into 4 major steps for the reel fed machines:
1. Paper Conditioning
The paper web is fed through the machine; constant web tension is a key issue
The heated roller attains required polarity and moisture content
The cooling unit adjusts paper temperature
2. Toner Transfer
The toner is attracted from a charged drum to the paper via an electric charge applied to the back of the paper
Colours printed in duplex are applied simultaneously in the order Y-C-M-K
3. Fusing
The printed image consists of loose toner particles before passing through the fuser
Non-contact fusing: toner particles are softened and fused onto the paper and each other by heat
4. Glossing Unit
This unit is used similarly to a soft calender to enhance the print gloss of digitally printed images
Digital paper used in the Xeikon based printing technologies has a reduced moisture content and should always be stored in its moisture resistant wrapping. The reels have to be splice free to avoid problems in the machine. For optimum toner transfer and fusing, the paper must have a correct electric charge acceptance and decay behaviour, which is partially controlled via the relative humidity in the paper, but also throught additives in the paper and/or coating formulations. For good finishing and converting results, the paper has to be flat after printing. Good folding properties are critical especially due to the hot temperatures in the fusing step.
Handling and mounting of silver digital reels Inspect the reel for any edge damage before mounting on the press. The reel must have an even web tension over its entire width. Correct mounting of the roller on the input paper shaft must be ensured, and the paper must be properly fed into the press. Finally, select the correct file or runnability parameters before starting the print run.
Duplex printing Most silver digital papers are suitable for one-pass duplex printing. silver digital supergloss is cast-coated on one side of the paper only.
Storage of silver digital reels silver digital reels should be allowed to condition in their wrappers for at least 24 hours in the print room before use. M-real has provided boxes with handles for its 32cm reels, to ease handling and to protect the paper. Reels should be kept in their moisture-proof box or plastic bag between print runs. The relative humidity level in the storage area or print room is very important. The recommended level is 35% with a normal room temperature of 19ºC to 23ºC in both paper storage and print room facilities. Many paper defects in the print room are caused by static electricity, shrinkage, curl, and wavy and tight paper edges, which can be related to moisture and temperature control problems.
