Control and prevention of corrugated board quality problems

The single-sided machine is the main equipment for the production of corrugated boxes. The quality of the semi-finished corrugated board produced by the single-sided machine directly affects the production cost of the carton. The base paper is also the main material of the carton production. About 75% of the production cost of the carton comes from For raw materials, if the number of unqualified or defective products of corrugated board produced by a single-sided machine increases, it means waste of base paper and other materials, an increase in production costs, and a decrease in production profits. In the current carton industry is generally in a low-profit market environment, the production technology of single-sided machines is well controlled, the performance and operation technology of equipment are controlled, the quality of raw materials is controlled, the quality problems are prevented, and the semi-finished products of single-sided machines are improved. Rate, the meaning is self-evident.

1. Understanding the definition of quality standards for semi-finished corrugated board

Single-sided machine, as the equipment for corrugated board forming and processing, is the basis of the quality of carton products. The quality status of semi-finished corrugated board produced by single-sided machine has three basic characteristics, qualified products, unqualified products and defective products. Qualified products refer to the quality requirements of corrugated cardboard that fully meet the quality requirements of the relevant standards; unqualified products refer to the quality requirements of corrugated cardboard that have one or more indicators that do not meet the relevant standards; defective products refer to those between qualified and unqualified Among the products, the defective products with slight defects such as rough edges, difference in specifications, local degumming, blistering, collapse, slanting, cracking, etc. The above three standards are generally just definitions of internal standards of the factory.

The original definition of corrugated paperboard in the national standards of the light industry was to divide each corrugated paperboard (three-layer structure) into superior products, first-class products, qualified products and unqualified products according to the product use and the quality grade of raw materials. Among them, the first-class products are corrugated cardboard for the packaging of export commodities and valuables; the first-class products are corrugated cardboard for the packaging of domestic products; and the qualified products are corrugated cardboard for the packaging of short-distance and cheap commodities. The three types of standards also divide four standard values ​​to meet the requirements of different product packaging. The original national standard also stipulated that the bonding strength of corrugated cardboard should not be less than 588N / m; the delivery moisture of corrugated cardboard (according to online moisture) is 14 ± 2%; the appearance quality of corrugated cardboard requires that the surface should be smooth, clean and not allowed There are missing materials and thin edges. The cut edges should be neat and firmly bonded. The sum of the degummed parts should not exceed 20cm2 per square meter. Non-conforming products refer to products that are determined to be unqualified in batch quality according to sampling rules.

Practice shows that some quality indicators of superior products may fail to become first-class products or qualified products, and some quality indicators of first-class products may fail to become qualified products. However, the single corrugated cardboard referred to in the national standard is a corrugated cardboard formed by bonding two layers of boxboard paper and a layer of corrugated corrugated base paper. The two-layer corrugated cardboard produced by a single-sided machine and a single unit is not subjected to cladding processing, and its burst resistance and edge pressure strength will be greatly reduced. Therefore, the national standard of corrugated cardboard cannot be applied. Up to now, there is no single-sided corrugated cardboard in our country. The standard of machine semi-finished corrugated board, companies with more general systems are all using their own enterprise standards to control the semi-finished corrugated board in the production process. However, the enterprise standard is not necessarily detailed, complete and accurate. In practice, Attention should be paid to continuous analysis and summary in order to make appropriate revisions and improvements so that the standard can play a better role in promoting the production process and operating technology. [next]

2. The impact of poor quality of single-sided machine semi-finished products on post-processing production

After the production of the single-corrugated semi-finished cardboard of the single-sided machine, the pre-printed carton face paper is laminated with the two-layer single-corrugated cardboard by the coating machine to form the three-layer structure of the single-corrugated cardboard, and then it can be processed by die cutting Finished carton products. It can be seen from the characteristics of the post-processing production process of the carton that maintaining the flatness of the corrugated cardboard has a crucial role in ensuring the quality of the mounting and die-cutting precision of the cardboard. If the semi-finished corrugated board produced by the single-sided machine shows obvious warpage deformation, it will affect the normal paper feeding of the automatic laminating machine and the accurate positioning of the corrugated board. Some corrugated cardboard curling deformation is more severe, and the operator of the laminating machine has to deform the warpage The corrugated cardboard is folded in the opposite direction to keep the flatness required for automatic paper feeding. However, after the corrugated cardboard is folded and damaged, the compressive strength of the carton after molding will be greatly reduced. If the corrugated cardboard of the single-sided machine is severely warped, after the laminating machine is manually mounted, the three-layer corrugated cardboard is also prone to arc-shaped warping. When the semi-finished product is die-cut on the die-cutting machine, it will also give Normal paper feeding and positioning cause certain obstacles and affect the forming quality of the carton. Therefore, in the production process of the single-sided machine, we must pay attention to controlling the moisture and flatness of the online corrugated cardboard, which is the basis for ensuring the quality of the carton.

3. Analysis and control requirements of quality problems in semi-finished single-sided machine

The production process shows that the quality of the corrugated cardboard produced by the single-sided machine is good, and the pass rate of the carton quality is reliably guaranteed. The author found in quality tracking management that sometimes although the raw materials are qualified, due to the improper control of the production technology and operation technology of the single-sided machine, such as speeding up to speed up production, it is easy to be caused by the short heating time of the cardboard and the corrugated peak Insufficient glue coating reduces the forming hardness of the paperboard and is prone to the problem of reduced adhesive strength. It is worth mentioning that if the single-sided machine with inadequate facilities is equipped and the speed is too fast, because the machine is difficult to quickly and evenly adjust the moisture of the base paper, when the moisture content of the tile paper and the inner paper is very different, The difference in the deformation coefficient of the base paper makes it very easy for the corrugated board to warp and deform significantly. Therefore, the production speed of the machine should be based on the moisture content of the base paper, the quality of the base paper, the preheating area and the temperature, etc., and comprehensively consider a reasonable degree. The author believes that the production running speed of the single-sided machine is slightly higher than the medium speed, which effectively maintains the accuracy of the equipment, improves the forming hardness of the corrugated cardboard, maintains the balanced moisture of the corrugated cardboard, and reduces the occurrence of warpage, reverse corrugation, and slant Fluffing, foaming, degumming and other quality problems are practical control measures. [next]

4. Pay attention to the detection and control of the single-sided machine semi-finished corrugated cardboard

Because the two-layer corrugated cardboard produced by the single-sided machine is difficult to accurately detect the edge pressure strength value, it is often only by the touch of the hand to determine the hardness and quality of the corrugated cardboard molding. However, such detection is only a rough and rough quality judgment after all, lacking scientific, Accurate data brings certain difficulties to the process control of the production process.

For this reason, in the inspection practice, the author invented a method for detecting the plane strength of the two-layer corrugated board, and obtained scientific detection data, which is beneficial to accurately analyze the control of the production process of the single-sided machine. The practice is:

First make a cylindrical cast iron base with a diameter of 11.7cm, and the thickness specification is 2cm. In this way, the plane compressive strength of corrugated cardboard can be detected using an electronic compressive strength tester. Before testing, first take a single tile (two-layer) corrugated cardboard, and use YQ-Z-7 type quantitative sampling knife to punch out several standard samples (area of ​​100cm2). When testing, first place the cylindrical bottom bracket on the lower pressure plate of the tester. After zero-adjusting the instrument, you can place the circular sample on the cylindrical bottom bracket for testing. When the sample is crushed, the screen The data shown is the plane compressive strength of the sample. The test practice shows that when the temperature, speed or adhesive of the single-sided machine is well controlled, the plane compressive strength of the corrugated cardboard is high. This method is used to test the forming hardness of corrugated cardboard. For those cartons specified in the contract to use a certain quality grade of base paper for production, the plane compressive strength technology of the two-layer semi-finished corrugated cardboard can be developed through the inspection and comparative analysis of corrugated cardboard. Indicators, with the company's internal control quality standards, can play a better role in controlling online semi-finished products.

The semi-finished corrugated cardboard of the single-sided machine, in addition to its flat compressive strength, should also be tested for its bonding strength. The corrugated layer is well bonded to the inner paper, and its overall strength is high. Usually the production site is generally used "Tear-off method" tears apart the tile paper and the backing paper to see the degree of fluffing of the paper surface to determine the bonding quality. The laboratory can use the electronic compressive strength tester to test the bonding strength of the corrugated cardboard and obtain the test data as Basis for quality judgment. In addition, the thickness inspection of corrugated cardboard can not be ignored. If the corrugated roller is worn or the gap between the rollers is not adjusted properly, it will affect the thickness of corrugated cardboard. The thickness of corrugated cardboard is an important indicator of customer quality requirements. Failure to meet the standard requirements will result in batches of unqualified products. Therefore, the production process must pay attention to the detection of the thickness of corrugated cardboard. A standard thickness gauge can be used to detect the unqualified products. [next]

5. Pay attention to the correct use and maintenance of the single-sided machine

Corrugated rollers are the core components of single-sided machines and molds for forming corrugated cardboard. They play an extremely important role in the processing quality of corrugated cardboard. Therefore, we must pay attention to the correct use and maintenance of corrugated rollers. Generally, the position of the lower corrugated roller of a single-sided machine is fixed, and the upper corrugated roller exerts a certain pressure on the lower corrugated roller by means of spring, air pressure or oil pressure.

The lower corrugating roller acts as the active roller, and its corrugated teeth mesh with the upper corrugating roller, and at the same time, the upper corrugating roller is driven to rotate synchronously by the roller surface to achieve corrugated forming. In order to ensure the even and smooth operation of the corrugated roller, the chain must not be too loose or too tight, otherwise the position of the roller should be adjusted appropriately. Corrugated shaping is achieved by a certain clamping force between the upper and lower corrugated rollers. This clamping force comes from the left and right sides of the upper corrugated roller, which is also the reason why the roller is easily distorted and deformed. In order to obtain a uniform distribution of pressure along the width, the roller needs to have a middle crown to compensate for the pressure. Deformed.

In the production process, we must pay attention to prevent the abnormal pressure load of the corrugated roller to reduce abnormal wear, which requires that the matching pressure of the corrugated roller must be mastered, that is, the upper and lower rollers must be controlled The gap and parallelism are very important in production. In addition to the correct use and adjustment of corrugated rollers, attention should also be paid to the maintenance of corrugated rollers. The bearings of the corrugated roller shaft head are prone to damage after a period of use, which will affect the normal engagement between the corrugated rollers and make the corrugating rollers resistant The increase will aggravate the wear of mechanical parts, and the quality of the corrugated cardboard produced will also be affected. Therefore, it should be inspected in time and the problems found should be dealt with in time. The "tooth surface" of the corrugated roller is easy to wear during the corrugating process, which makes the cardboard corrugation lower and affects the strength of the carton. Therefore, it should be tested frequently. If there is obvious wear, the re-plating layer should be removed to ensure that The quality of corrugated cardboard. Usually pay attention to the cleaning and cleaning of paper dust and impurities on each roller surface to prevent the abrasion of roller tooth grooves by foreign objects; the lubrication parts should be lubricated in strict accordance with the regulations to ensure the normal lubrication of the machine parts; during the mechanical operation If there is abnormal noise, it should be stopped in time to check and eliminate the fault, to avoid abnormal damage caused by the machine running with disease. [next]

6. Pay attention to the quality control of the paper distribution of the single-sided machine

The semi-finished paperboard produced by the single-sided machine is composed of box board paper and corrugated paper. If the moisture content between them is too large, then the base paper will absorb the binder and heat, and the expansion and contraction of the base paper will also change. Obviously increased, it is easy to cause the warpage of the cardboard, on the one hand affect the quality of the post-process mounting, increase the probability of non-conforming products, on the other hand, the overall strength of the carton will be significantly reduced. Therefore, before the paper roll is put into the machine, the moisture content of the base paper should be tested first, and the cardboard and corrugated paper with the similar moisture content should be selected for matching forming processing to prevent the corrugated cardboard from warping due to the excessive difference in the expansion and contraction rate of the base paper Deformation phenomenon, reduce defective products.

7. Pay attention to the control of the glue application mechanism of the single-sided machine

The role of the single-side machine glue application device is to apply adhesive to the corrugated peak of corrugated paper, so that it is bonded to the cardboard paper to form a single-sided corrugated board. It is mainly composed of glue roller, glue roller, scraper, glue groove and so on. When the single-sided machine is operating normally, the bottom of the glue roller is in contact with the adhesive in the glue tank and rotates at a uniform speed. The adhesive is brought up, the amount of glue is appropriately limited by the uniform roller, and the fixed amount of adhesive is applied to the corrugated peak. on. The surface of the sizing roller has the structure of fine grinding and polishing, and the surface of the roller is processed into a net shape, so that the glue is evenly applied to the corrugated peaks formed. The amount of glue is generally required to be about 1.5mm wide. The gap between the sizing roller and the lower corrugated roller should also be adjusted. In general, when the glue is satisfied, the gap should be as small as possible. The sizing roller is used to control and adjust the amount of glue on the surface of the sizing roller. Therefore, it is important to adjust the gap between the sizing roller and the sizing roller. The gap is generally between 0.2mm and 0.3mm. The squeegee roller is also equipped with a scraper blade, whose function is to scrape off the adhesive on the surface of the squeegee roller, so that the roller surface can perform the next cycle of work in the state of no adhesive. The role of the glue tank is to hold the adhesive and circulate the supplied adhesive, so that the adhesive will not condense by heat to reduce the viscosity and maintain a certain height. Normally, according to the usage of the glue application device, it should be cleaned in time to clean the paper dust and impurities that affect the viscosity of the adhesive, to ensure normal glue application and improve the adhesion quality of corrugated cardboard.

The quality control of the single-sided machine's semi-finished corrugated cardboard involves all aspects of the production process, and the correct control of the operating process technology, the correct use and maintenance of the machine are the crucial control links, which requires us to pay attention to the production process technology. At the same time, careful inspection and control of the quality of semi-finished corrugated cardboard through the production process, not only can effectively prevent the occurrence of semi-finished cardboard processing quality problems, but also can better improve the processing quality of corrugated cardboard to meet the processing quality of the subsequent process The requirements laid a solid foundation for improving the quality of carton products.

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