Offset printing this printing method is through the drum impression of glue it in with glue on the surface of the ink transfer to the paper. Due to the plastic surface is flat, without concave, so the design of printed on paper and decorative pattern is flat, no stereo feeling, poor rubber seals. Required for offset printing ink is less, the mould manufacturing cost is lower than gravure.
Fundamental Principles:Oil and water don't mix principle;
The choice of plate adsorption principle;
Branches in assaying principle;
Indirect printing principle.
Overprint or Trapping Trap if misregister, thief easily affect beauty, while overprint easily caused by the ink layer too thick back and smearing, so wet pressure dry printing monochrome machine tend to have overprint, multi-color machine wet wet pressure tend to use trap;
Wet pressing overprint must consider the nature of the ink, first printing ink of the viscosity, adhesion must be greater than after printing ink, otherwise the printing ink will appear after inverse overprint phenomenon. After printing ink must also have high transparency;
On coating of paper printing gold ink, silver ink, the trap of gold ink, silver ink printed on white paper than on other color for color appears more thick, pure;
To print the black, if the black edition only larger area of the field image, adopt the way of trap increase the black version of the ink is printed on white paper than on other field background more thick ink overprint. But small line generally uses overprint way online printing services.
At the top do trap version is at the back of the ink layer covered for guarantee, the stuck print runs are usually based on the alignment precision of the equipment to add 0.03 ~ 0.05 mm. Such as alignment precision is 0.15 mm, then trap part generally larger 0.18 ~ 0.20 mm.
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