Analysis of common typical problems in the production of aluminum cans and easy-open lids and their solutions

Analysis of common typical problems in the production of aluminum cans and easy-open lids and their solutions

As we all know, two-piece aluminum cans have many advantages, such as: light weight, easy to carry; not easy to break, good safety; excellent sealing, long shelf life of the contents; beautiful printing on the can body, eye-catching; good thermal conductivity, canned drinks Fast cooling; filling is faster and more efficient than other packaging materials; easy to stack and transport; cost-effective; 100% infinitely recyclable, the highest recovery rate of any packaging container, conserves resources and minimizes waste The emergence of is conducive to sustainable development. . . .

These advantages have earned the two-piece aluminum can the position of the best beverage packaging container in the minds of consumers in the United States and Europe, and the demand has remained high for a long time. According to incomplete statistics, in 2016, the market demand for aluminum cans (lid) in the United States alone was about 100 billion sets. In contrast, the market demand for aluminum cans (covers) in China is about 38 billion to 40 billion sets, and the market growth space is very large.

Common problems in the production of aluminum cans and lids

However, whether from the product itself or the production process, the production difficulty factor of aluminum cans (lid) is relatively high. On the one hand, from the point of view of the product itself, the aluminum cans (lid) are thin and "delicate" due to the aluminum material, and the deformation during the manufacturing process is relatively large, making the "growing" process difficult. On the other hand, from the perspective of production technology, the production of domestic aluminum cans (lid) is high-speed automated mass production, and the can (lid) technology is purely imported, which is still in the process of reference and application, and it is necessary to continuously accumulate experience to seek progress.

Due to the above two reasons, many problems are prone to occur in the production process of aluminum cans (covers). Among the common problems in can body production, the four most typical problems are necking wrinkle, can bottom blackening, can inner wall stripes and can body printing. In the production of can lids, the five common typical problems include failure to open the lid, slag on the lid surface of the lid, feathers on the pull ring lid, air bubbles and partial glue breakage in the lid sealant, and pressure on the aluminum chips of the sheet lid. Injury (crack) cover.

Failure to open the easy-to-open cover and its handling measures

The failure to open the easy-open lid means that the pull-tab of the easy-open lid is pulled off when the lid is opened, and the tongue piece cannot be opened normally or completely, which makes it difficult for consumers to drink the beverages packaged in the can.

Analysis of Causes There are internal and external causes for the failure of easy-open lids to open. As far as the internal factors are concerned, the notch allowance is too thick, the rivet diameter is too small, the riveting of the pull ring is not good (that is, the riveting pattern is not standardized), as long as there is any one of the above conditions, or a combination of factors will lead to this. class problem occurs.

From the perspective of external factors, if the pull ring has been deflected by a large angle when the consumer opens the pull ring, the opening failure caused by the improper opening method is more common in life.

Treatment recommendations should be dealt with for reasons of different nature. If it is an easy-opening quality problem, that is, the opening fails due to internal reasons, the related products need to be scrapped. If the opening fails due to improper opening methods, it is necessary to try to remind consumers to adopt correct opening methods to avoid the occurrence of the above problems.

 Easy-open cover slag and treatment measures

Easy-open cover slag refers to the presence of brown or brown tiny particles on the surface of the easy-open cover and the empty cover, generally the sheet cover is more prominent.

Cause Analysis These tiny particles actually come from the aluminum material, that is, the slag in the manufacturing process of the aluminum material. When the aluminum material is dried in the oven after the surface is coated with glue, the slag that may exist in the oven falls on the surface of the aluminum material and adheres to it. Dark microscopic particles are formed on the paint. Because the color of the particles is often close to the color of the coating, video inspection may not be able to identify them effectively.

Treatment suggestion Because the slag factor is difficult to overcome, this phenomenon is a problem that is difficult to completely avoid in the manufacturing process of aluminum material, especially sheet aluminum material. At the same time, because the slag will be firmly fixed on the surface of the aluminum material together with the solids in the coating after the coating is dried, and the surface of the aluminum material will be coated with a layer of varnish and dried after the coating layer is dried. Such a production process is enough to ensure that the slag will not fall off, so such tiny particles will not have a negative impact on the food safety of the contents, and brand customers can use it with confidence. As for the empty can factory, the problem can be fed back to the aluminum supplier to try to improve it.

Pull ring cover feathers and treatment measures

Pull-tab feathers refer to the coating residues of different degrees of "feather" at the opening after the pull-tab-type (RPT) easy-open lid is normally opened, which only affects the appearance and basically nothing else.

Cause analysis The root cause is the poor adhesion of the local coating on the easy-to-open aluminum cover.

Handling Suggestions The feather membrane must not fall off and must remain on the cover or on the pull ring, which is the most basic requirement.

On this premise, we classify the feathers according to the remaining amount of feathers (Fig. 4). The grade 1 can be used directly, and the grade 1.5 within one-tenth of the perimeter of the notch can also be used, otherwise it will be scrapped. 

Easy-open lid sealing glue bubbles, local glue breakage problems and treatment measures

Easy-open lid sealing glue bubbles and partial glue breakage refer to the phenomenon of different degrees of air bubbles or local glue leakage (lack of glue) after the easy-opening lid sealing glue is applied.

Cause Analysis When the water-based sealing glue is dried, the air in the glue cannot be effectively volatilized in time and remains in the glue to form bubbles. In addition, the blockage of the gluing nozzle will lead to incomplete gluing of some covers (usually occurs after the shutdown and the initial startup).

Handling suggestion Since it only affects the appearance of the glue, when the double roll seal adjustment is qualified, this problem will not affect the sealing effect and sealing safety of the roll seal position. The easy-open lid can be used directly.

Sheet cover aluminum chip crush (crack) cover surface and treatment measures

Sheet cover aluminum chips crushed (cracked) cover surface means that after the basic cover punch, a small amount of sheet material has short linear indentations with a length of less than 10mm on the cover surface, chuck wall or insert ring, etc., resulting in filling The drink then created a leak problem at the crush. 

Analysis of Causes Due to the fluctuation of the outer dimensions of the aluminum material, the aluminum sheet may occasionally have a misalignment problem with the basic cover punch die during the feeding process of the basic cover punch, and then short and fine chips are generated at the corners of the aluminum material. The chips adhere to the mold, and when the subsequent aluminum material enters the mold to punch the basic covers, the aluminum chips adhered to the mold will crush these basic covers.

It should be noted that after several strokes, the aluminum chips on the die will be taken away, and the stamping of the basic cover at the back will return to normal, and the problem of crushing will no longer occur.

Treatment suggestion Because the sheet cover aluminum chip crushes (cracks) the cover surface, which usually leads to leakage and makes the beverage can a low-level tank, this kind of problem tank is often identified and rejected on the can filling line, and flows into the cans. There are very few opportunities to make it into the finished drink. Even if it occurs, there is basically no need to worry about it. Just for the sake of safety, it is recommended to arrange for the isolation, review and confirmation of a small amount of finished drinks in the time period before and after the occurrence of the problem.