Production method of color-printed tinplate special-shaped can

Abstract

The invention relates to the field of manufacturing of metal containers, in particular to a production method of a color printing tinplate special-shaped can, which comprises the following steps: before expansion treatment of radial expansion is carried out on a cylindrical can body, first flanging treatment is carried out on an opening of at least one end of the can body to form an annular reinforcing structure with a specific geometric configuration; and after expansion treatment is completed, second flanging treatment is conducted on the annular reinforcing structure, so that the annular reinforcing structure is formed into a final flanging meeting the seaming requirement. According to the embodiment of the invention, before the tank body is subjected to the bulging process, the metal material of the tank opening is folded outwards to form the annular reinforcing structure with the specific size and angle, so that the moment of inertia of the cross section of the tank opening is increased, and the stress concentrated on the edge of the tank opening is dispersed to the whole annular reinforcing structure in the subsequent bulging process; therefore, the bending and deformation resistance of the tank opening is improved.

Description

Technical Field

[0001] This invention relates to the field of metal container manufacturing, specifically to a method for producing a color-printed tinplate irregular-shaped can. Background Technology

[0002] Three-piece metal cans, especially irregularly shaped cans with special contours such as drum shape and bottle shape, occupy an important position in the food and beverage packaging market due to their unique aesthetic design and excellent grip. Their traditional production process usually includes: cutting, rolling and welding pre-printed tinplate sheets to form a standard cylindrical can body, and then plastically deforming the can body through a key bulging process to obtain the designed irregular contour.

[0003] The expansion process is the core step that determines the final quality and production cost of irregularly shaped cans. In this process, the cylindrical can body is placed in a mold and expanded by radial pressure applied from inside. This process causes the can wall material, especially the opening edges at both ends of the can body (i.e., the can mouth), to bear huge tensile stress. Since the can mouth is a free end and lacks structural constraints, stress is easily concentrated here, which can lead to serious defects such as material tearing, wrinkling, or uneven deformation. These defects not only directly lead to the scrapping of the can body, but also make it impossible for the subsequent sealing with the can lid to meet the strict airtightness standards, which seriously affects the yield and reliability of the product.

[0004] To alleviate this problem, a common practice in the industry is to add a "flaring" process before expansion, which involves slightly enlarging the diameter of the can opening. For example, a method disclosed in Chinese utility model patent CN208531030U involves flaring the can opening before expansion.

[0005] However, this method is essentially a pre-stretching of the material, which has limited effect on improving stress concentration. Therefore, it can only support a small bulging range (for example, the diameter increase of the bulging process disclosed in this patent is only 4.7%). When the market needs more exaggerated and visually impactful can designs, that is, a larger bulging range, the existing process is difficult to solve the problem of can mouth tearing.

[0006] Therefore, how to fundamentally solve the problem of stress concentration at the can opening during the expansion process and achieve the production of irregularly shaped cans with large deformation and high quality is a technical bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a production method for color-printed tinplate irregular-shaped cans, which aims to significantly enhance the structural stability of the can opening during the expansion process, effectively prevent tearing and deformation, thereby improving the quality and yield of the final flanging.

[0008] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0009] A method for producing color-printed tinplate irregular-shaped cans includes the following steps:

[0010] Before the radial expansion of the cylindrical tank body, the opening at at least one end of the tank body is first flanged to form a ring-shaped reinforcing structure.

[0011] After the expansion process is completed, the annular reinforcing structure is subjected to a second flanging process to form the final flanging that meets the roll sealing requirements.

[0012] Furthermore, the first flanging process includes applying a first axial pressure to the opening of the can body to form the annular reinforcing structure with a flanging angle of 10° to 16° and a flanging width of 1.2 mm to 1.5 mm.

[0013] Furthermore, the first axial pressure is 4000N to 5000N.

[0014] Furthermore, the second flanging process includes applying a second axial pressure to the annular reinforcing structure to form the final flanging with a flanging angle of 5° to 10° and a flanging width of 2.8 mm to 3.2 mm.

[0015] Furthermore, the second axial pressure is 5000N to 6000N.

[0016] Furthermore, the tank body is formed by rolling iron plates into a circle and joining them together, and then welding the joining edges together using a resistance welding process.

[0017] Furthermore, the iron plate is tinplate, and the thickness of the iron plate is 0.2mm-0.3mm.

[0018] Furthermore, after the welding step, the process also includes a step of applying a coating to the weld area and drying it.

[0019] Furthermore, prior to the step of rolling and joining the iron plates, a step of color printing on the iron plates is also included.

[0020] Furthermore, the color printing includes the following steps: applying white porcelain oil or base oil to the iron plate, and forming a protective varnish coating with a thickness of 5μm to 6μm on the white porcelain oil or base oil.

[0021] The advantages of this invention compared to the prior art are as follows:

[0022] In embodiments of the present invention, before the can body is bulged, the metal material of the can opening is folded outward through a first flanging process, transforming the fragile, thin-walled free end of the can opening into a ring-shaped reinforcing structure. This effectively disperses and bears the tensile stress concentrated at the can opening during the subsequent intense bulging process, suppressing local instability. Furthermore, the ring-shaped reinforcing structure can be further processed through a second flanging process into a final, dimensionally accurate flanging for sealing. Attached Figure Description

[0023] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0024] Figure 1 This is a process diagram of the irregular-shaped can according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram showing the dimensions of the annular reinforcing structure according to an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram showing the final flange dimensions according to an embodiment of the present invention;

[0027] Figure 4 This is a final dimension drawing of an embodiment of the present invention. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0029] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In the production of irregularly shaped cans, bulging is one of the most critical and challenging processes. The cylindrical can body undergoes severe plastic deformation under the action of the mold, and the can wall material is subjected to enormous tensile stress. Especially at the can opening, where it is a free end, stress concentration is particularly severe, making it prone to defects such as material tearing, wrinkling, or uneven deformation. This not only damages the integrity of the can body but also makes it impossible for the subsequent sealing with the can lid to meet the precise airtightness requirements, resulting in product scrap and reduced yield.

[0031] For example, Chinese utility model patent CN208531030U discloses a method for manufacturing a beverage can. The method involves first expanding the opening of a can with an initial diameter of 57mm to 63mm, and then bulging it to 66mm. The diameter increase from the bulging process is only 4.7%, which is a limited increase. If the bulging process is not carried out first, the risk of tearing and irregular deformation of the can opening is high, and the quality consistency of the final flared edge is difficult to guarantee.

[0032] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0033] This embodiment aims to describe a method for producing a color-printed tinplate drum-shaped can, the process flow of which is as follows: Figure 1 As shown, the specific steps include:

[0034] Step S1: Substrate processing and can body preparation.

[0035] Tinplate (tin-plated thin steel sheet) with a thickness of 0.25mm is selected as the substrate. First, a layer of white enamel is applied to the substrate surface as a primer to improve the adhesion of subsequent inks. Then, the customer-customized color pattern is printed onto the substrate using a high-precision printer. After printing, the substrate undergoes a varnishing treatment, which involves applying a protective varnish layer with a thickness of 5μm to 6μm to its surface and curing it in an oven. This varnish layer not only enhances the product's gloss and abrasion resistance, but more importantly, it protects the printed graphics from scratches or damage during subsequent machining processes such as stamping, flanging, and bulging.

[0036] The processed color-printed tinplate sheets are precisely cut into pre-set sizes using a high-precision shearing machine. The sheets are then rolled into cylindrical shapes, and their butt joints are firmly welded using resistance welding to form a cylindrical can body with an initial diameter of 114mm.

[0037] Step S2: Weld repair coating and drying.

[0038] The high temperatures during welding can damage the protective coating on both sides of the weld area. To ensure the product's corrosion resistance and food safety, the weld must be repaired. Using automated equipment, food-grade powder coating is sprayed onto the inner weld of the can, while anti-rust coating is sprayed onto the outer weld. The can is then placed in a hot air circulating drying oven, where it is dried under precisely controlled temperature and time to allow the repair coating to fully cure and form a seamless bond with the original coating.

[0039] Step S3: First flanging process.

[0040] The cylindrical can body (initial diameter 114mm) that has been recoated and dried is sent to the flanging station. The flanging equipment applies a first axial pressure of 4000N to 5000N to the open end of the can body, causing the can mouth to fold outward, forming a ring-shaped reinforcing structure with a flanging angle of 10° to 16° and a flanging width of 1.2mm to 1.5mm.

[0041] The ring-shaped reinforcing structure transforms the originally simple and weak ring edge of the can opening into a reinforcing ring with an "L"-shaped cross-section, significantly enhancing the circumferential stiffness of the can opening and providing strong structural support for subsequent large-scale expansion.

[0042] Step S4: Expansion treatment.

[0043] The can body with a ring-shaped reinforcing structure is sent into the expansion station. A mechanical segmentation mold is placed inside the can body and expands radially outward. Under the strong action of the mold, the diameter of both ends of the can body increases significantly, thus forming a pre-designed waist drum-shaped irregular can body.

[0044] In this embodiment, the initial diameter of the can body is 114mm. After expansion, the maximum diameter of the can body reaches 131mm, with a diameter increase of up to 14.9%, which far exceeds the expansion range of only 4.7% in the prior art.

[0045] During the bulging process, the annular reinforcing structure formed in step S3 plays a crucial supporting and protective role, ensuring that the can opening does not tear or deform excessively during the intense material flow.

[0046] Step S5: Second flanging process.

[0047] After the expansion is completed, the can body is sent to the next flanging station. The flanging equipment applies a second axial pressure of 5000N to 6000N to the open end of the can body with the ring-shaped reinforcing structure to perform a second flanging process.

[0048] The second flanging process involves fine-tuning the ring-shaped reinforcing structure to create a final flanging with a flanging angle of 5° to 10° and a flanging width of 2.8mm to 3.2mm. This final flanging meets the requirements for subsequent double-sealing with the can lid.

[0049] Step S6: Sealing and Inspection.

[0050] The can body with the final flange and the can lid are fed into an automatic sealing machine together, and the final flanges of the can lid and the can body are rolled together to form a strong and airtight double flange.

[0051] Finally, the finished cans undergo quality inspection, including visual inspection using a machine vision system and sealing tests using a water bath leak detection method, to ensure that every product leaving the factory meets quality standards.

[0052] The core idea of ​​this invention is:

[0053] By applying axial pressure to the tank body, a ring-shaped reinforcing structure with a specific angle and width (i.e., ring-shaped reinforcing structure) is actively formed at the tank opening, which enhances the tank body's resistance to deformation during the subsequent large-scale expansion process. This achieves the elimination of the flaring step in the traditional process and allows for direct expansion.

[0054] Without tearing or wrinkling the can opening, the can body diameter can be increased by up to 14.9%, which is significantly higher than the expansion range of traditional processes, thus enabling the production of irregularly shaped cans with larger capacity and more visual appeal.

[0055] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered as falling within the scope of protection of the embodiments of the present invention.

Claims

1. A method for producing color-printed tinplate irregular-shaped cans, characterized in that, Includes the following steps: Before the radial expansion of the cylindrical tank body, the opening at at least one end of the tank body is first flanged to form a ring-shaped reinforcing structure. After the expansion process is completed, the annular reinforcing structure is subjected to a second flanging process to form the final flanging that meets the roll sealing requirements.

2. The production method according to claim 1, characterized in that, The first flanging process includes applying a first axial pressure to the opening of the can body to form the annular reinforcing structure with a flanging angle of 10° to 16° and a flanging width of 1.2 mm to 1.5 mm.

3. The production method according to claim 2, characterized in that, The first axial pressure is 4000N to 5000N.

4. The production method according to claim 2, characterized in that, The second flanging process includes applying a second axial pressure to the annular reinforcing structure to form the final flanging with a flanging angle of 5° to 10° and a flanging width of 2.8 mm to 3.2 mm.

5. The production method according to claim 4, characterized in that, The second axial pressure is 5000N to 6000N.

6. The production method according to claim 1, characterized in that, The tank body is formed by rolling iron plates into a circle and joining them together, and then welding the joint edges together using a resistance welding process.

7. The production method according to claim 6, characterized in that, The iron plate is tinplate, and the thickness of the iron plate is 0.2mm-0.3mm.

8. The production method according to claim 6, characterized in that, Following the welding step, the process also includes a step of applying a coating to the weld area and then drying it.

9. The production method according to claim 6, characterized in that, Before the step of rolling and joining the iron plates, a step of color printing on the iron plates is also included.

10. The production method according to claim 9, characterized in that, The color printing includes the following steps: applying white porcelain oil or base oil to the iron plate, and forming a protective varnish coating with a thickness of 5μm to 6μm on the white porcelain oil or base oil.

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