Metal Packaging Container Micro-Wrinkle Structure Technology Application

First, the introduction of micro-crimping Since the 1960s, the market for metal packaging containers has been dominated by other non-metallic packaging containers. However, because metal materials have certain mechanical properties that cannot be possessed by other packaging materials, such as high strength, high hardness, high barrier property, and high heat resistance, metal containers have always been active on the stage of packaging products. The production volume is second only to paper containers and plastic containers. However, in order to maintain a competitive situation for non-metallic packaging containers, the metal can making industry has always been reluctant to spare, always thinking about how to be invincible in this competitive situation. Among them, reducing the production costs of metal containers is the only way. With the constant emergence of new technologies and the reduction in the use of metal materials, this goal is gradually being realized. One of the new technologies to achieve this goal is the micro-crimping technology for the metal container molding process. Mini-crimping technology has achieved satisfactory results in reducing the thickness of sheet metal and reducing the area of ​​materials and reducing the consumption of other materials.
The micro-heming structure is a brand-new molding process technology that aims to optimize the processing costs of metal cans. According to this technology, the double crimping of the higher strength of the can body and the smaller size of the can end result in a significant reduction in the structural size of the conventional metal container. Due to the reduction of the countersunk head and the modification of the curled structure, the size of the trimming of the can lid is significantly reduced. Due to the improved can lid and shortened flange size, the can height of the three-piece can can be reduced by more than 5mm. At this point, the can only need one-third of the paint. Therefore, the spray amount on the outer and inner wall surfaces and the end surfaces of the metal cans is significantly reduced, the inner and outer color strips are also reduced, and the weld seams are also reduced. In addition, the shortening of the three-piece can body can also increase the output of the production line.
In terms of structure, although the micro-crimping is similar to the traditional crimping, the structural dimensions of the former are only about half that of the traditional standard crimping.

Table 1 Comparison of Standard Crimping and Miniature Crimping

Name Traditional Crimping (mm) Miniature Crimping (mm) Can lid cutting edge 88.50 81.50 Countersunk lid 3.20 1.60 Sheet thickness 0.22 0.16 Cover hook width 2.00 1.00 Body hook width 2.00 1.00 Can body punching height 98.70 93.50

In the cold stamping process, although different die or other tools are used for punching and flanging of the can ends, the same production equipment and machines can be used, and micro-crimping is also applicable to steel and aluminum. The two-piece can forming process. No matter what type and size of metal packaging containers, micro-crimping technology can bring cost-saving benefits. If the container is reduced by a number of dimensions, it can save an average of 10~20% of the material and processing costs.
The new technology for micro-crimping was first proposed at the 5th International Tin-Tron Academic Conference in 1995. The meeting also introduced pilot projects for evaluating micro-crimp technology. The results of several tests have shown that this technology is fully applicable to metal packaging containers for various foods, including food packaging that requires heat treatment. The preliminary practical situation in the past ten years shows that the micro-crimping technology shows outstanding advantages in various types of products in metal containers. For the can manufacturer, the size of the can body punching height and the length of the end trimming are significantly reduced, and the amount of sealant at the can end is reduced. In the canning production line, productivity has increased significantly. At the same time, electrode consumption, interior and exterior coatings and color bars have all been reduced, and packaging and transportation costs have also been reduced. As a packaging company for metal container users, it will also benefit from a number of features that reduce pollution, reduce inventory space, reduce transport volume, reduce canning costs, and produce high-quality double hemming structures. In addition, the streamlined structure of the micro-crimping is more aesthetically pleasing, and it makes it easier to crush than a conventional metal can and easy to use after-treatment. From the perspective of economic prospects, the cost savings can be estimated by analyzing and comparing the sizes and types of several two-piece cans and three-piece cans. Of course, the more purchases, the more the final cost reduction will be.

Second, the commercialization of new technologies The Packaging Technology Research Center belonging to a Brazilian technological institute is very interested in this miniature crimping structure. After conducting a series of vibration, impact and vertical loading tests on this miniature crimp, it was found that The structure has very good dynamic mechanical properties. As a result, they believe that the metal cans micro-crimping technology can replace the conventional hemming process method, and these excellent properties can be obtained even with ultra-light metal sheets. The first user of this miniature crimped metal can is CICA, a Brazilian food company owned by a group company in the United States. The food company has transformed two tomato food processing lines to use this new miniature crimping technology. From 1993 to 1996, the company shared more than 100 million new crimped metal cans.
Through several years of use by CICA Foods, it has been shown that various metal cans of the micro-crimping structure have almost the same defect rates as those of the standard conventional double-crimp metal containers. At the same time, the company's quality record for a miniature crimped metal can shows that its quality is more consistent than that of a standard double crimp. Therefore, this company is currently more inclined to adopt micro-crimping technology. In addition to South America, this new technology has also been used for many years in North America and Central America. For example, many practical tests have been conducted on food, vegetables, and certain metal cans. Due to the good trial results in beans and cereals, CICA Foods decided to shift its production line to this new hemming process technology.
The U.S. Department of Agriculture has stated that since this micro-crimping technology can provide similar performance to the conventional double-crimping process structure, it is permitted for food packaging such as canned meat and poultry. According to the test results and the provision of samples, the US FDA (Food and Drug Administration) also issued the same opinion. The United States CMI (Metal Can Manufacturers Association) issued a technical manual on micro-crimping manufacturing processes and its operating instructions and other documents.

Third, the micro-hem structure characteristics

In addition to the commonly used two-piece cans and three-piece cans, metal cans with a capacity of 900 milliliters are very popular in South America and Central America. It is only necessary to use 150 million cans of vegetable oil metal cans each month in Brazil. Obviously, this outstanding consumer market will have great potential for production, whether for steel mills or metal can factories. In particular, with the introduction of new micro-crimping technology, vegetable oil companies that use metal cans can achieve a price reduction of more than 6% of the total price. At this point, people will ask how the mechanical properties of the micro-crimped metal containers, after being subjected to external loads during their transport and during processing, can ensure the structural integrity of the containers. In order to evaluate the micro-hem structure and compare it with the standard hemming structure, the Brazilian Technical Research Center of Packaging Technology conducted a series of comparative tests on these two hemming structures.
1. Normative impact test During this test, a normal impact load is optionally applied to the two types of crimping structures of the metal cans at two angles of 45° and 67°. This impact load was determined in accordance with the standard double hemming structure test, and the impact energy applied in these two angular directions was 0.95 and 2.25 Joule, respectively. As soon as the metal cans lose their seal and undergo large deformations, they are prone to contact with bacteria in the external environment and fat canisters occur. Therefore, the reduction of the internal vacuum of the container and the change of the centerline of the can will be used as the evaluation (parameter) index of the structural integrity of the container after impact.
After testing and evaluation, it has been found that the mechanical properties of the micro-bead can be comparable to the conventional hemming structure in the impact direction of 45°, and even better than the conventional hemming structure in the 67° impact direction. The good mechanical properties of the micro-heming structure are thought to be due to its better plasticity. That is, it is more resistant to deformation when subjected to a certain impact force and has a more consistent deformation pattern. In addition, it is one of the important reasons why it has a more compact structure. Therefore, from the point of view of sealability, micro-crimping will have better effect after being impacted.
2, according to the ASTM standard test to further evaluate the performance of the micro-crimping and traditional crimping two structures, according to the ASTM (American Materials and Testing Association) of the relevant standards for comparative tests. The test piece was made of 0.16mm thick tinplate, including the can body of the container and its two ends. The test includes vibration test, drop impact test and vertical load carrying capacity test of two types of crimped metal cans. Among them, the vibration test standard is ASTM-D999/75 and the drop test standard is ASTM-D775. Through the vibration test, it can be seen that the mechanical properties of the micro-crimped metal cans are basically the same as those of the conventional double-crimped metal cans. However, the performance of the micro-rolled metal cans was even better when the cans were individually dropped and dropped into cartons in two test conditions. During transportation and storage, it was also found that the ability of micro-rolled metal cans to resist vertical compressive loads was always strong.

IV. Development of micro-crimping In South America, all metal cans are processed using plates of the same specification and thickness of 0.16 mm, because steel mills in the region do not produce steel with a thickness of less than 0.16 mm. However, some steel companies in the European region can produce 0.14mm, 0.12mm?, and 0.08mm thin steel sheets, which provides a great potential for the production of micro-edged metal cans. A metal container factory in Brazil uses the above-mentioned 0.14 mm and 0.12 mm tin plates to form metal cans of different sizes in a micro-crimped structure, which are mainly used for canned tomato and meat products. In these factory production lines, after filling the tomatoes into metal cans, micro-crimping was performed at 95° and pasteurization was performed. These process programs can run on the same device. In another production plant, the meat metal cans are automatically filled and then crimped on a semi-automatic crimper and placed in a stable cooker at 121° for 60 minutes while the cooling process is negative Completed under pressure.
Production over the past few years has shown that the size verification and visual inspection results of the miniature crimping structures are satisfactory. In all metal cans processed with 0.14mm and 0.12mm steel plates, the molded can lid hooks are very slippery and there is no structural instability or upset on either the mini-crimped edges of the two products or on their materials. Wrinkle phenomenon. These metal cans all have the same good structural integrity and also have a good seal. If compared with conventional double-rolled metal cans, the overall weight of these metal cans can be reduced by approximately 35%.
From the above, it can be seen that the test results and practical responses obtained on such a metal container with a micro-heming structure are all very successful. At the same time, it also shows that this miniature crimping structure has the potential to further reduce the amount of material used. The optimization of reducing the weight of the sheet steel and reducing the size of the hemming structure will make the micro-rolled metal cans truly ultra-lightweight. Undoubtedly, the cost-effectiveness of this new micro-crimping new process and new technology will be very significant. This will make the industrial sector more competitive in the market, and it will be able to obtain a new economy in a relatively low investment environment. growth point.