Technical design and pattern making issues of garment bags, 99% of the content is mentioned

The manuscript design of garment bags is the first step in the design and manufacturing of garment packaging. Unreasonable manuscript design will increase the difficulty of printing, reduce the printing yield, may also cause difficulties in slitting and bag making processes, or even cause the entire batch of products to be scrapped, thus affecting the delivery time.

Garment bag manuscript design generally has two categories: one is artistic design, the other is technical design. Artistic design belongs to art issues. Shunxingyuan Packaging, a professional flexible packaging manufacturer, mainly discusses technical design and plate making today, hoping to help enterprises that use packaging bags for packaging products.

I. Design of photoelectric mark

In the automatic packaging process of bag making or composite materials, positioning heat sealing and positioning cutting are often required, so it is necessary to set photoelectric marks in the manuscript for positioning.

During design, the photoelectric mark can generally be placed at the bottom of the bag, which is more aesthetically pleasing.

The photoelectric mark can be on one side or both sides of the roll material. However, it is recommended to have both sides, so as to avoid the situation where the photoelectric mark is on the left side of some roll materials and on the right side of others during use, requiring constant adjustment of the photoelectric eye position.

The size of the mark also has certain requirements, and different packaging machines have certain differences. Generally, the width of the mark is required to be greater than 2mm and less than 10mm, and the length is greater than 5mm.

The width of the mark (less than 2mm) may affect the normal tracking of the equipment due to weak signal, while a mark that is too wide (greater than 10mm) is not only unaesthetic but also reduces the tracking and positioning accuracy.

The length of the mark should generally be greater than 5mm. In the packaging process, due to the shaking and deviation of the film, a mark that is too short may cause the mark to deviate from the position of the photoelectric eye, resulting in inability to track.

The mark generally uses a dark color with a large contrast to the background color, preferably black. Red and yellow should not be used as marks, nor should the same color as the photoelectric eye be used as the mark color. For example, if the photoelectric eye emits green light, light green should not be used as the photoelectric mark color, because the green photoelectric eye cannot identify green.

If the background color is dark (such as black, dark blue, dark purple, etc.), the mark should be designed as a light-colored hollow white mark.

For bag making machines, there is generally a microcomputer-controlled electric eye tracking system with fixed length. It can select the effective photoelectric eye signal within a certain range (generally the signal is effective within ±3mm of the fixed length), and the text and patterns in this range can be "ignored", so the mark can be omitted.

However, it should be noted that too small or short text patterns cannot be used as tracking points, nor can arc-shaped or oblique patterns be used as tracking points. If there are no suitable tracking points, a mark must be designed.

The electric eye system of general automatic packaging machines is a simple recognition system.

It does not have the intelligent fixed-length function like a bag making machine, so no interfering text and patterns are allowed in the longitudinal photoelectric mark range of the film, otherwise, the equipment will mistake the interfering text and patterns for photoelectric marks during the packaging process, causing recognition errors.

Of course, some more sensitive electric eyes can precisely adjust their black and white balance. For some light-colored interference signals, they can be removed by adjustment, but interference signals of colors similar to or darker than the mark cannot be removed.

The spacing between marks is used for length setting, so the error between the actual spacing and the design value cannot be too large, generally only ±0.5mm error is allowed.

For many automatic packaging equipment, the negative deviation has better tracking effect than the positive deviation, so it is recommended to design it as a negative deviation.

For some automatic packaging machines, only when the spacing between marks is negative deviation can they work normally. Some automatic packaging machines not only require negative deviation for the spacing between marks, but also have very high precision requirements, such as the vacuum adsorption tracking and falling automatic packaging machine of German Siebler company, which requires the error between each mark not to exceed: －0.02、－0.08.

Aluminum plating or pure aluminum has strong mirror reflection, which will affect the recognition of the electric eye. It is recommended to print a white background on the composite film mark. For transparent composite films, because they will be affected by the color of the items in contact with them, it is also recommended to print a white background on the mark to reduce interference from other background colors.

For some multi-row packaging machines, only one set of electric eyes is needed in principle, and this set of electric eyes is generally placed in the middle of the composite film roll. After packaging, it can be retained in the finished product or removed as an edge.

If it is retained in the finished product, there will be a problem: some products in the same batch have marks and some do not. In order to avoid this difference, marks can be printed on each row of packaging materials in multi-row packaging machines (although only one row of marks is needed for the packaging machine).

II. Design of printing technology

Many art experts, when designing manuscripts, only consider the art aspect or the flat printing process, without fully considering the particularity of gravure printing technology.

From the perspective of gravure printing technology, the manuscript design of garment bags should pay attention to the following points:

1. The register accuracy of gravure printing can only reach 0.2mm, so text and graphics (especially text) with strokes less than 0.4mm cannot be printed using multi-color superposition, but only with a single ink, otherwise it is easy to cause ghosting.

2. Small text and patterns should use single-color hollowing when hollowing printing, not multi-color superposition hollowing printing, and should not use the background color of the photo directly for hollowing printing. Small text and patterns are not suitable for hollowing printing text patterns and superimposing text patterns.

3. Pay attention to the size of the text and the thickness of the strokes. Too small text and too thin strokes may not be printed, often resulting in printing faults such as broken strokes or missing strokes. If the text is too small, too many and too dense strokes and thicker lines or too deep printing plate, it is easy to cause the phenomenon of "blurred characters".

4. The transfer performance of gravure printing is not as good as that of flat printing, and there is a problem of plate blocking. Generally, it should be avoided to use dots less than 10%.

Large areas of base color should avoid using screens that are too light; otherwise, the screen reproduction will be poor, resulting in uneven color and easy discoloration.

Even if it can be printed initially, the light color is susceptible to changes in hue and reduced print durability due to roller wear during the printing process.

It is recommended to use spot color printing for large areas of light color.

5. Although in principle, all colors can be produced by the superposition of three primary colors, in fact, many colors with high purity and brightness, as well as some fluorescent colors, transparent colors, gold, silver and other special colors, must be printed using spot colors, and spot color rollers must be made for printing.

6. For special inks such as pearlescent inks, due to the coarser ink particles, the rollers should be deeper.

Some inks, such as fluorescent colors and some darker transparent colors, have poor color development. To achieve darker colors, the rollers must be made very deep.

Due to coarser particles and other reasons, pearlescent inks, gold inks, and silver inks are generally not suitable for light screen printing.

7. Pay special attention to avoid excessively dense patterns and lines in a vertical position, otherwise, the printing will cause wrinkles during winding, resulting in greater pressure and ink sticking.

In this case, a moderate screen method can be used to reduce the thickness of the ink layer.

8. Expansion issues.

When a text pattern and another text pattern are completely nested and printed, the light-colored text pattern should be expanded to an appropriate size (generally 0.2-0.4mm) to overlap with the darker text pattern; otherwise, the base color is easily exposed at the junction during printing.

The amount of expansion depends on the color. If the two colors are complementary, the overlapping part will produce black lines, affecting the aesthetics, so the expansion should be minimized.

9. Color sequence issues. Generally, the inner printing goes from dark to light, while the outer printing generally uses light colors first and then dark colors. Although they look different, the order seen by the human eye is exactly the same, that is, dark colors are seen first.

In color printing with photos, the three primary colors should be printed continuously, without inserting other spot colors in between, otherwise it will be detrimental to the overprinting of the three primary colors and the blending of the ink layers, resulting in poor photo effects.

10. Screens have different thicknesses. With the same percentage, coarse screens are generally easier to reproduce. However, if the screen of the text pattern is too coarse, the lines of the strokes will not be smooth, affecting the aesthetics.

When designing the screen, it should be noted that some colors (such as dark green) are difficult to obtain smooth and bright printing effects within a certain screen percentage range, and tear-like or wavy patterns may appear.

III. Design of Printing Colors

Art designers are often familiar with paper printing and often use the colors on the paper to require plastic rotogravure printing.

The colors provided by designers are often PANTONE color standards on paper, or MCYK color values on paper. In fact, plastic printing is usually inner printing, while paper is outer printing. At the same time, the base color of the plastic film is different from that of the paper, so rotogravure printing sometimes cannot print the colors designed by the designers.

In the printing of clothing bags, special attention should be paid to the base color of the printed matter.

1、 Aluminum foil composite film

Aluminum foil, as a special material with metallic luster, is not well understood by many people in terms of its color characteristics. What color is aluminum foil? White or colorless? If you put shiny aluminum foil into a copier and copy it, the result will surprise you...Black!

Aluminum foil composite is actually a "gray" color!

When a printing film with a white background is laminated with aluminum foil, it is obvious that the resulting color is "gray-white"! Because the base color of the aluminum foil composite film is "gray", it is impossible to produce bright and high-purity colors like paper flat printing.

Although aluminum foil has the disadvantage of "gray", it has the advantage of metallic luster. Without a white background, printing ink directly on aluminum foil can produce a luster effect that paper printing does not have.

If transparent inks made of dyes are used, the luster effect is even better. Using transparent yellow can produce a shiny gold effect.

Special attention should be paid when printing on aluminum foil without a white background (especially when printing transparent inks).

Aluminum foil, as a metal rolling product, is generally divided into glossy and matte surfaces. The same ink printed on different surfaces of aluminum foil (glossy and matte) will have completely different colors and hues.

For gold-plated products with transparent inks, the brightness of the aluminum foil is reduced, the color will become darker, and the hue will be more red. In actual production, it should also be noted that the aluminum foil from different manufacturers and the rolling stripes may have large differences, resulting in inconsistent product colors.

For aluminum foil composite films without a white background, when confirming the color, in addition to confirming that the color of the film printing is consistent with the standard sample, the luster of the aluminum foil should also be confirmed. If the aluminum foil is very bright, the brightness can be adjusted by adding matte powder or white ink to the ink.

For aluminum foil composite products, attention should also be paid to the rolling stripes of the aluminum foil. Some aluminum foil (especially the dark side of the aluminum foil) has coarser stripes, and may also have bright spots, which will affect the appearance of the product, making it look like there are scraper lines or ink dots.

2、 Aluminized composite film

Aluminized film has a brighter metallic luster than aluminum foil. Its color characteristics are similar to aluminum foil, which is "gray", and there is also a problem of the base color being "gray".

The "gray" of the aluminized composite film is also related to the thickness of the aluminized layer. If the thickness of the aluminized layer is too thin and the light transmittance is too good, there may be a big difference before lamination, but after lamination, the thinner parts of the aluminized layer will be "gray" and even black.

Aluminum-coated films generally come in two types: polyester (PET) aluminum-coated film and cast polypropylene (CPP) aluminum-coated film.

Special attention should be paid to composite products with CPP aluminum coating. During heat sealing, the PP resin will flow, causing displacement of the mirror-like aluminum coating on the CPP, thus affecting the brightness of the CPP aluminum coating.

The gloss of the aluminum-coated surface at the heat-sealing position will change from a bright metallic luster to a matte metallic color.

3、 Transparent composite film

Transparent composite films do not have the "gray" composite problem found in aluminum-coated and aluminum foil composite films, but their overall effect may be affected by the contents of the packaging (even with a white background).

It is also affected by the color of the other side of the packaging bag. Some transparent composite bags may look good before bag making, but after bag making, the hue and saturation change due to the influence of the color on the back of the bag.

4、 There are generally two types of white: yellowish white and bluish white.

For bright and high-purity orange, bluish white ink cannot be used as a base color or diluent, otherwise the color will become dull. Similarly, for bright and high-purity purple, yellowish white ink cannot be used as a base color or diluent.

Some text generally uses direct-pressure base color printing. When printing text directly on the base color, note that the base color may affect the color of the text, changing its hue and saturation.

5、 Problems in bag making and use

In the design and production process, attention should also be paid to the operability issues during bag making and slitting. Some graphic designers do not consider the errors during bag making and slitting, making bag making and slitting difficult.

The edges of the composite bag should be designed with similar colors or transparency. If the packaging bag or roll material has a large color contrast between the top, bottom, left, and right, there will be a significant contrast at the splicing points after longitudinal and transverse plate making.

Because the cutting of bag making machines, slitting machines, and automatic packaging machines cannot be absolutely accurate, there is generally a deviation of more than ±1 mm. Therefore, the bags or slit films produced will have a line with a large contrast at the cutting point, thus affecting the appearance.

For high-strength composite bags and retort pouches, to improve strength and protect the ink layer, it is recommended that the edges of the composite bag not be printed with color.

For designs with large areas of base color and no transparent edges, the plate making process must consider widening the sides by 1-2 mm after plate making. In this way, even with deviations during slitting and bag making, transparent edges or aluminum foil/aluminum-coated edges will not appear.

When designing the bag making manuscript, attention should also be paid to the size of the bag making and the longitudinal and transverse output.

The thickness of the heat-sealing knife bracket of a general three-side sealing bag making machine is about 70 mm. Therefore, when the bag is longitudinally output, the minimum width of the bag is 70 mm.

When making bags transversely, the bags can be spliced back-to-back. In this case, the minimum length of the bag is 35 mm.

If the bag making size is smaller than the above size, a special heat-sealing knife must be made.

Because the unsealed part of the composite heat edge may contain some foreign matter that cannot be cleaned, some foreign matter will deteriorate and emit an odor. If the customer requires that the heat-sealed edge must not have excess edges, the bag making must be transverse.

The human eye relies on the contrast between text, patterns, and the base color for identification. Therefore, when designing, the contrast between the color of the text and pattern and the base color should be fully considered. Avoid using similar colors, otherwise, the small contrast will easily cause blurring.

If there is no base color, and the text or pattern is small or light in color, it generally cannot be compounded with the bright surface of aluminum-coated film or pure aluminum foil. Otherwise, the "glare" of the aluminum-coated film or aluminum foil bright surface will make the text or pattern difficult to identify.

In the process of color design and ink use, attention should also be paid to the heat resistance and light resistance of the colors.

Some special colors have poor heat resistance and should consider whether they will change color during printing drying, bag making heat sealing, and high-temperature sterilization. For products used outdoors or in contact with strong light for a long time, their light resistance should be considered.