Quality Management of Packaging and Printing--Quality Control Experience (I)

With the continuous development of China's market economy, packaging printing, as an important branch of the printing industry, has increasingly highlighted its important position. Especially in recent years, the introduction of a large number of foreign advanced production lines and the further improvement of the performance of domestic equipment have greatly improved the quality of packaged printed matter. Packaging printing is different from other printing, it has its own characteristics, these characteristics are the main points of packaging and printing quality control. Based on the work experience, the author discusses the following points of experience.

Production process

The formulation of the production process is the main link in production and is an important part of product technical preparation. It is the key and guarantee for stabilizing, improving product quality, controlling costs, reducing consumption, and improving efficiency. This is even more true for packaging and printing companies. The development of reasonable and correct production processes is a prerequisite for quality control of packaging and printing.

Packaging printing is a special entrusted processing and manufacturing industry. Its product processing requirements come from two approaches: one is the packaging of new products designed and manufactured by the company; the other is the provision of samples by end customers, and the company reproduces the products as they are.

The production of packaging new products designed by this company is relatively easy, and the process can be formulated according to the company's process management system. It is more difficult for the product to be reproduced as it is, and the following points need to be noted when the process is formulated.

1. Determination of the printing method

Non-package printing is mainly based on a single printing method on the same product, and rarely uses two or more printing methods. In order to achieve a certain purpose or effect, all existing printing methods are often used in packaging and printing production, and often a combination of multiple printing methods is used on the same product, for example, gravure printing, four-color printing, and screen printing. Do special effects and so on.

Different printing methods will inevitably lead to different final results of printed products. The first step in the development of the process is to determine the printing method of the product, offset printing, gravure printing, or screen printing products using a single printing method or a variety of printing methods to work together. This is the general direction of process development and can not go wrong.

2. Development of plate making process

The emphasis on printing is the copying of originals. This is especially true of packaging and printing. In particular, packaging printing imposes extremely stringent requirements on the appearance of ink. Therefore, the packaging and printing plate making process pays more attention to the following points.

(1) Confirmation of the number of outlets

Mainly refers to the confirmation of the number of flat nets and gradient nets other than the four-color images. The number of original net points shall prevail, and the influence of paper whiteness and the color shift of different brand inks shall be taken into consideration.

(2) Confirmation of spot colors

Spot colors are special colors that are pre-mixed with inks to replace or supplement four-color printing inks (CMYK). Each spot color requires the use of a special printing plate at the time of printing. Therefore, when making a plate, it is necessary to specify which colors use four colors and which colors use spot colors. Please note the following points when confirming.

1 Some spot colors, such as gold, silver, etc., can't be replaced by printing four-color inks. Some are substitutable, but there are slight differences. When the packaging product quality requirements are high, press the original printing as much as possible. Do not use four-color overprinting instead of spot colors.

2 When the performance of the printing equipment is poor, if the conditions permit, replacing the multi-color superimposition with spot colors as much as possible, the printing quality will be stable, but the cost will increase.

(3) Confirmation of printing color sequence

The color of printed matter is overprinted by the ink of different color cabinets. The order of the overprinted ink is called the printing color sequence. Normal four-color printing has 24 different printing sequences. In addition to the four colors in packaging printing, spot colors are often added, so the printing sequence will be more. Only by choosing the correct printing sequence can the color of packaging and printing products be closer to the original.

3. Postpress manufacturing process

(1) Hot stamping process

Hot stamping process must first select the right type of hot stamping foil for aluminum foil according to the material of the substrate and the characteristics of the hot stamping graphic. If you still need to press the bump, and require fine, but also consider whether to use hot stamping embossing a molding process. Some hot stamping images use hot stamping hollow form. If the strokes are fine, normal hot stamping is easy to paste, and it is best to use the first hot stamping printing process. It should be noted that the use of suitable for the printing of aluminum Hot stamping foil.

(2) Convex process

If the product requires embossing and creping, then there is a distinction between embossing before embossing and embossing after embossing. These two processes have significant differences. Small text and fine lines are suitable for embossing before the crepe paper. After this type of writing, the small text and thin lines are still clear and beautiful. Large text and thick lines are suitable for embossing after crepe paper, which can make the font rounded and plump. If the embossing position and the die-cut dark line are not: during the process, die-cutting and embossing can be performed at the same time, saving man-hours and improving efficiency.

(3) Die-cutting process

The product is selected by die-cutting or pressure-bottom die-cutting, which is mainly determined by the molding effect after die-cutting the product. In general, paperboard and card card products will be pressed and die-cut, and press-bottom molding will be better. If press-bottom die cutting is selected, when the die cutter is blunt and the bottom plate is uneven, the position of the die-cutting blade is prone to burr or cut-out, requiring more attention.

4. Paper grain selection

(1) Many packaging products require whiteboard lining or corrugated cardboard. The correct approach is that the surface orientation of the facing paper and liner must be vertical, otherwise it will cause poor quality, dark lines, and corrugated quality problems.

(2) The elongation and shortening of the paper are mainly caused by the radial deformation of the paper fibers. When the relative humidity of the environment changes, the paper fiber becomes thicker or dehydrated, but the fiber length and the degree of change are small. On the paper, the paper is deformed along the length of the paper grain, and the length of the vertical paper grain is greatly deformed. Therefore, when the product has a hot stamping, embossing process, it is necessary to select the appropriate paper grain direction according to the position of the pattern, so as to avoid the paper deformation caused by hot stamping, embossing uneven position is not allowed.

(to be continued)