White trap processing
In plastic packaging printing, white ink is widely used. Generally, in the printing of transparent or translucent plastics, it is necessary to use white as the base, and sometimes two layers of white are also supported. To prevent the white under the color block from being exposed due to inaccurate overprinting, white retraction should be considered before printing.
1. The white retraction can be done according to the shade of the color or the customer's requirements. The amount of retraction is generally 0.2-0.3mm.
2. If the color block is white and the side is transparent, the white can retract 0.3mm into the color block.
3. When the black and gold are entrusted to white, the white can retract 0.5-1mm into the black and gold.
4. If the color block is lighter or flat, the amount of white retraction should be small or not. For example, when the dot percentage of the color block is between 30% and 50%, the amount of white retraction can be 0.15mm; and when the dot percentage of the color block is less than 30%, white can not be retracted.
5. When placing white under a gradient pattern, white should be considered for diagonal retraction. The cyan gradient supports white, the white in the dark blue is retracted by 0.2mm, and the white in the light blue is retracted by 0.1mm, which can be shifted by the inflection point.
6. If the transparent color (not white under the ink) is adjacent to other colors, the white under other colors should be retracted by 0.2mm; if the transparent color is directly adjacent to white, the white should be expanded by 0.2mm into the transparent color to avoid leaks .
Trap processing of common software
In commonly used packaging design software, trapping can be performed manually or automatically.
1. Trap processing of backbone vector
lllustrator and FreeHand are vector-based graphics processing software, both of which can generate simple automatic trapping objects, and the function of automatic trapping is basically the same. Both create a single light-colored overprint filling area to cover adjacent color blocks; They can determine when trapping is needed between two adjacent color blocks and when trapping is not necessary, and can only trap the selected objects. Open the "trap" tool panel in the "path finder" command under the "window" menu of the lllustrator software; call up the trap function panel in the "plug-in function \ create \ trap" of the FreeHand software. The options are described below. Width (lllustrator / FreeHand): refers to the width of the trapping area. The default value in lllustrator is 0.25points, the range is 0.01-5000points; in FreeHand, you can enter the unit, such as 0.2mm.
Subtractive color (lllustrator / FreeHand): Refers to reducing the proportion of bright colors in the trapped area and reducing the degree of discoloration in the trapped area. The default value is 40%.
Reverse trapping (lllustrator / FreeHand): refers to changing the trapping direction, so that the dark color expands into the bright color area. In lllustrator and FreeHand software, automatic trapping can only handle trapping between adjacent fill patches, while trapping between fill patches and strokes, gradients, continuous tone images, and other characteristics of patterns cannot be performed.
lllustrator and FreeHand software are automatically trapped according to the brightness of the color. The trapping rules are as follows.
(1) All colors expand to black.
(2) Bright colors expand into dark colors (including spot colors and other colors).
(3) The arrangement of the brightness of the primary colors is M, C, and Y from dark to light, that is, when the magenta fill and the cyan fill are adjacent, the cyan expands to the magenta, and this is arranged in the order of K, C, M, and Y The trapping method at the time is just the opposite, this is the point to pay attention to.
2. Trap processing of base bitmap
Trap processing in Photoshop is performed under the trap command in the software's "Image" menu, it only has an option for trap width.
Photoshop software can only perform trapping by enlarging colors, and the trapping rules are as follows.
(1) All colors expand to black.
(2) Bright colors expand to dark colors.
(3) Yellow expands to magenta and cyan.
(4) The expansion of cyan and magenta is equivalent, that is, mutual expansion.
Also note the following.
(1) Continuous adjustment of the image itself does not require trapping.
(2) The pattern can only use the trapping tool when the platen is pressed.
(3) When trapping the color block and color block, there will be a break in the corner.
Professional trapping software
Professional trapping software is a powerful tool for solving trapping problems. At present, many RIPs provide inrip trapping function, which is a trapping function opened in RIP. However, this trapping method sometimes does not achieve a satisfactory trapping effect, nor can it be manually interactively corrected; if the design draft requires more trapping places or is more complicated, using RIP trapping is often an unpleasant Waiting process.
There are also some professional packaging design software such as PACKEDGE, ARTPRO, etc. There are also powerful trapping modules, but these trapping functions can only be used in their own software systems. Users must purchase both software and trapping modules. In order to use the trap function. At present, these softwares have not yet reached the level of popularity for a large number of design and prepress publishers.
Now, Esko-Graphics has launched a new DeskPack software, which mainly solves the current problems in trapping.
First of all, DeskPack provides a plug-in embedded in tlllustrator, which can directly perform various operations and controls of trapping in lllustrator software, and its trap function module (TrapX) is very powerful.
1. It utilizes the latest brightness-based trap engine ColorStitch, which can quickly and accurately handle all trapping work in packaging design. All the places that need trapping can be completed quickly with a single command.
2. It can deal well with the trapping problems between graphics, text, special fills, gradients and images, especially when dealing with trapping between gradients and adjacent color patches. You can easily trap in the form of a gradual change to avoid the trapping place being too stiff.
3. The trap layer is generated separately, and the user can be flexible. Easily edit and modify the trapping content while keeping the original file unchanged, it is a highly interactive. User-friendly trap tool.
4. The trapping parameters can be set and controlled according to the printing process.
5. The trapping of a manuscript can usually be completed within a few minutes by the Trap command. If a partial correction is made, the update can usually be completed within a few seconds.
Secondly, the DeskPack software is for the majority of lllustrator users. Ordinary pre-press personnel only need one day to master all the functions of the software. Easy to learn and use is another feature of it.
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