Corrugated box manufacturing process flow and failure analysis

First, the base paper

1. Kraft Linerboard Kraft Linerboard is generally divided into pure wood pulp kraft linerboard and kraft liner paper. Pure wood pulp kraft linerboard is made from 100% wood pulp. Kraft noodle paper is made from waste pulp, etc. as base pulp pulp noodle. All physical properties of pure wood pulp kraft linerboard exceed that of kraft linerboard, but the cost is higher.

2. Corrugated paper Corrugated paper is made from broad-leaved half-fiber wood pulp or wheat straw pulp. Its quantification is generally low, but corrugated paper forms a skeleton in corrugated paperboard after molding at a certain temperature and pressure.

Second, corrugated board structure and specifications

The high-strength paperboard made by bonding face paper on corrugating medium (corrugated like corrugated section) pressed by a corrugating machine is called a corrugated paperboard. The corrugated paperboard is basically similar to the arches in terms of its stress, it has a large rigidity and good load-bearing capacity, and it is full of elasticity and high shockproof performance.

Corrugated shapes are directly related to the compressive strength of corrugated board. According to the corrugated paper core shape, corrugated cardboard can be divided into U-shaped, V-shaped and UV-shaped.

U-shaped corrugated board has good stretching tension, elasticity, and high energy absorption. Within the elastic limit, the corrugated iron can still be restored to its original shape after pressure is removed.

V-shaped corrugated board has good compressive strength, but when the pressure exceeds the limit it can withstand, the corrugated board will be quickly destroyed.

UV corrugated paperboard has the advantages of U-shaped and V-shaped corrugated paperboard, and is widely used.

In addition to corrugated shapes, corrugated board properties are also related to corrugated specifications. Generally divided into A type, B type, C type, E type, various corrugated specifications are as follows:

Corrugated and ragged plates in different directions of compression compared to 楞-type peak height /mm number of turns /m Plane pressure plate along the lateral pressure along the longitudinal compression
A 4.5~5.0 120+-10 4 4 1
B 2.5~3.0 170+-11 2 2 3
C 3.5~4.0 140+-10 3 3 2
E 1.1~1.4 320+-13 1 1 4

A-type corrugated board has excellent shock-proof cushioning. C-type corrugated board has shock-resistance similar to Type A. Types A and C corrugated board are used for outer packaging. B-type corrugated flat has strong compressive capability, and the number of corrugations per unit length is larger, and there are more supporting points in the face paper and the liner paper, so it is not easily deformed and the surface is flat. Good for good printing results. B-type corrugated board is mostly used for packaging. E-type corrugated board is the finest type of corrugated board and can print higher-quality graphics. Its strength is similar to cardboard, but lighter and cheaper than cardboard. Used for inner packaging.

Corrugated board can be divided into single-flange corrugated board, three-layer corrugated board, five-layer corrugated board and seven-layer corrugated board according to the composition type.
The single-flange corrugated cardboard is formed by bonding a single sheet of paper and a corrugating medium, and is rarely used alone as an outer package, and is mostly used as an inner package and a packing liner.

Three-layer corrugated paperboard is made by sticking a single piece of paper on both sides of a corrugating medium. It is mostly used for medium or small outer packaging carton.

The five-layer corrugated cardboard is formed by bonding the surface, the inside and the back of the three sheets of paper and two corrugated core papers, and the order is the noodles, the corrugated core paper, the core paper corrugated paper, and the paper. Five-layer corrugated cardboard has greater strength than three-layer corrugated cardboard and is stable to load, allowing large-sized, heavy-loaded cartons to be made.

Second, the printing of cardboard

1. The leading edge feed section includes side guide positioning, feed door, rear stop, and feed roller pressure point.
A hopper is formed by the side guide, feed door, rear stop and feed table. The rolled corrugated board is stacked in this hopper. The paperboard is fed from the bottom of the pile through the feeding conveyor, the vacuum device is opened, the feeding conveyor is lifted up, and the bottom sheet is touched and sucked. When the paperboard passes through the feeding roller, the feeding conveyor belt descends and is pulled by the feeding roller. Cardboard advances to the next stage.

2. The printing part includes ink roller, plate cylinder, impression cylinder and traction roller.

WORD series corrugated board printing press adopts scraper closed circulation system. Its characteristics are: ink through the ink hose to the scraper slot, the upper and lower scraper respectively and the anilox roller is inward 30-35 degree angle, the scraper gently scratches the ink on the anilox roller, so that it becomes a uniform thickness Ink film. The anilox roller then transfers the ink to the printing plate, the corrugated cardboard facing down, passing between the plate cylinder and the impression cylinder, adjusting the gap between the plate cylinder and the impression cylinder, so that the graphic information on the printing plate is Transfer to corrugated board to complete the printing process. In the adjustment process, the gap between the impression cylinder and the plate cylinder, the gap between the plate cylinder and the anilox roller, and the gap between the up and down rollers should be controlled.

(1) Anilox Roller The roll machine of the company's WARD machine is 250LPI (200LPI for EMBA machines). The honeycomb (hexagonal) mesh has an engraving angle of 60 degrees. With the same number of screen lines anilox rollers, the number of honeycomb-shaped screens is 15% more than that of quadrilateral screens. The use of the anilox roller greatly improves the resolution and ink content of the image, making the image thicker and clearer, and is an ideal anilox roller.

Print failures that occur during the printing process are attached

(2) Full-page printing Full-page printing is required during the printing process and is prone to print failures. Because full-frame printing, the printing of large format, the ink layer to maintain uniformity, not only the high degree of smoothness of the corrugated board, and the pressure between the rollers should be appropriate, the pressure is too large, the corrugated cardboard corrugated shape is damaged, The compressive strength of the board is affected; the pressure is too low, and the ink layer on the printing plate cannot be evenly transferred to the board, resulting in a printing failure such as whitening.

3. Die-cutting and slotting section The cardboard is fed into the pressure line device through the pulling roller to perform the longitudinal (in the same direction as the ridge) lines. The longitudinal indentation limits the width and length of the carton. The creasing device consists of a pair of rotating shafts and four pairs of indentation rollers. The number of indentation rollers is determined according to the requirements of one cardboard box or two cardboard boxes. The former uses four pairs of rollers and the latter only uses two pairs of indentation rollers. Before operation, the upper and lower rollers must be aligned and adjusted. Breaking, crimping operations, the most notable is the trimming quality and indentation moderate. Both are related to the water content of the cardboard itself. When the water content is between 10% and 13%, the cardboard has good stiffness, and the sharp knife can be cut into straight and straight incisions. If the water content exceeds 13%, the paperboard compressive strength is reduced by 9% for every 1% increase in water content. The stiffness of the corrugated board will also decrease, and the edges of the corrugated paperboard will have burrs, and even a "closed" phenomenon will occur. Squashed. Corrugated board moisture content is too small, less than 7% will lead to paper fiber embrittlement, resulting in indentation is not obvious or the pressure line rupture. The slotting device is mounted on the circular blade base by two upper and lower arc blades. Adjust according to carton requirements.

4, after the processing using the SIMCA automatic baler. The corrugated paperboard with the printed die-cut slotted material is spliced ​​and folded at the tongue joint by a SIMCA automatic laminating machine to produce a finished product. Then stacked by hand to complete the entire process.