Comprehensive control on the sealing process of tinplate cans

Tinplate tin cans are currently worse than the previous year from the overall market situation. There are various problems in the overall quality, mainly in the aspects of film properties, weld seams, sealing, sterilization, and sealing. This article only talks about the comprehensive control of the sealing process in the production process of empty cans, for reference only.

I. Analysis of the influencing factors of double crimping from the principle of sealing

The sealing process of the tin barrel can is completed by the double crimping method. The double hemming method refers to two winding rollers with different groove shapes. By the two feeding movements in the order, the hook edge of the can lid is hooked with the can body flange at the joint of the can body and the can lid. , pressing, to achieve the purpose of sealing purposes. Simply put, the first side is rolled and the two sides are pressed tightly.

In the sealing device, the wrapping roller and the upper tray of the upper pressing head are generally referred to as three sealing elements. The correct groove shape of the roller, the proper position of the indenter and the appropriate driving force of the tray are necessary to ensure proper sealing. (See Figure 1) It is not difficult to see that the three elements of sealing are the basic components of the sealing equipment, and they are also the basic factors affecting the double crimping.

There are several factors that affect the double crimping:

1. Physical properties of tinplate materials

Such as material, hardness, etc., especially relatively small tank diameter (such as 202 diameter tank). If the tinplate material is thin and hard, the difficulty of the denseness will be greater, because in this case, the material deformation of the material during the double crimping process is less, and the wrinkles are larger.

2, the appropriate sealing pressure

As shown in Figure A1, during the rotary motion of the phase can body, the winding force P of the roller groove is combined with the can lid by three different directions: radial force Pr, axial force Pa and tangential force Pt. The synthesis of force. Among them, the function of the first winding force P1 is mainly the bending deformation of the material around the can body and the cover, and the two-time sealing force P2 is mainly represented by plastic deformation. The calculation of the two rolling forces is carried out by energy balance and plastic deformation. Generally, the two winding force is 2 to 3 times the head winding force.

In the actual operation process, the proper sealing force is achieved by the proper matching position relationship between the winding roller, the pressing head and the tray tray (such as the adjustment of the inner and outer gaps of the roller and the pressure head).

3, the process size of empty cans

Different tank-shaped can lids and cans should meet the corresponding technical requirements, such as poor welding before sealing (>0.5mm tailing, welding crack), too large and too small edge will affect the empty can Coiling performance.

4. Groove shape and material requirements of the coiled roller

In general, different cans of sealing rollers have different groove shapes. Generally, the grooves of the head roller are deep and narrow, and the grooves of the two rollers are wide and shallow. At present, the reel used in domestic sealing equipment is mostly medium carbon steel, such as 45#, 40Cr, the service life is short, the output is limited to 20,000 to 300,000 cans; the reel used in advanced sealing equipment is generally 4Cr13, 9Cr18 and other stainless steel. It is made by vacuum heat treatment, which has high hardness, good wear resistance and long service life, and can be manufactured in a million tanks.

Among the three elements of sealing, the coiled roller is a wearing part, which should be polished or replaced with 1 000# or 1 200# water-based sandpaper according to the production conditions, so as not to affect the process performance of the crimp sealing.

5, the coating state of the seal coating

The correct coating distribution of the inner film of the can lid is about 70% in the hook edge and about 30% in the plane. In addition, the amount of the modulus must meet its own process requirements. If the amount of glue is too large, the glue is formed, and the amount of glue is too small to function as a sealing filler.

6, the operator's correct operation and adjustment

The skilled technical skills and level of operation of the operator, as well as the necessary routine maintenance and care, are also a factor influencing the double crimping. For example, when the tank type is changed or the coil sealing abnormality needs to be adjusted as necessary, it is also crucial to adjust the correct and reasonable adjustments in addition to the necessary parts. Generally, under the appropriate driving force of the tray, first check the Tc value (2.20Â±0.10mm) of the width of the head side, and then visually measure the tightness of the curl around the lid. When the two sides are finished, the seal is tested. Check for appearance defects and various dimensional process requirements. Make correct adjustments and judgments for the formation of different defects before making adjustments.

Note: (1) The size specification is measured by anatomical experiment; (2) The head side curling is the basis and premise of the two-side crimping, and it is generally checked at least once a week during normal production.

7, the integrity of the equipment

The integrity of the sealing equipment directly affects the sealing performance of the sealing process, which is related to the operator's correct operation and maintenance.

8, the use of can lid (easy open cover or bottom cover)

In theory, the easy bottom cover produced by different manufacturers should have interchangeability with the indenter. However, in fact, there are many domestic production lines for can ends. The size specifications of the canned products produced are still different from the international regulations. The main performance is in the height of the cans and the height of the hooks. The other dimensions are not much different, as shown in Figure 2.

Therefore, in the actual use process, we should pay attention to the following aspects: (1) The material of the bottom cover should be good, not only must have certain tensile strength, but also have certain flexibility; (2) structural size; (3) dry sealant (4) Breaking force; (5) The tightness of the easy opening cover, the bottom cover and the pressing head should be appropriate (the former can be slightly rotated with each other, the latter is relatively tight); (6) The empty can production cover After sterilizing the front or the real tank, apply appropriate amount of liquid paraffin or vegetable oil to the curling part to prevent mechanical abrasion and rust.

Second, the process requirements of the double crimping from the sealing structure

The appearance requirements of the tin barrel can sealing process are mainly as follows: (1) The double crimping edge should be even and smooth, and the surface has no obvious oil stain and damage; (2) The curling part must not have sliding seal, false roll, curling and splitting, double Defects such as wire and extrusion; specifications and size requirements are mainly as follows: (1) the crimp size of different cans should meet the corresponding process size requirements; (2) the overlap length and the overlap ratio, the tightness, and the seam cover hook Complete rate.

The sealing structure of the double crimping edge can be sampled by the can edge cutter, and the hooking state of the body hook BH of the can body and the can lid CH can be clearly seen on the projector. Its five-layer structure is shown in Figure 3.

So, how do you get a good sealing structure and normal curling during empty can production or solid can filling? From the quality control requirements, we must pay attention to and meet the following points:

1, W, T, H

The three-point size (W, T, H) of the crimping sealing anatomy should be uniform and the internal dimensions (BH, CH) should not exceed the given value.

2. The overlap length OL and the splicing rate OL%.

When the aluminum alloy is easy to open, the OL â‰¥ 0.95mmm ~ 1.2mm, OL% â‰¥ 60% ~ 75%; OL â‰¥ 1.00mm when the bottom of the horse can be opened or easy to open, OL% â‰¥ 50%. OL and OL% can be used in three methods: calculation method, projector vertical method, and table look-up method.

3. Wrinkle degree WR% and tightness TR%.

The tightness of the sealing structure is an important indicator of the sealing requirements of the can. It is usually evaluated by the degree of wrinkles measured in the hook when visually anatomically experimenting, as shown in Figure 4, WR% is 0% to 20% I, 25 ~ 50% II degree, 60% ~ 100% III grade three, that is, the corresponding TR% â‰¥ 75%.

4. The completeness of the seam cover hook is JR%.

Refers to the fact that the outer crimping cover hook of the weld is not formed due to insufficient effective hooks due to the inner drooping lip. Generally, JR% is not required under the conditions of OL, OL% and TR%.

Third, the necessity and importance of establishing a three-level inspection network

The production of empty cans in tinplate cans is an assembly line operation, and problems in each production process will directly affect the normal operation of the next process. Therefore, in order to obtain a good quality of the seal, it is necessary to carry out quality inspections between the various processes, and eliminate the problems in the production process so as not to flow into the finished product.

The three-level inspection network is the production self-inspection of the process, the quality mutual inspection of the pre- and post-processes, and the quality sampling in the production process. A three-level inspection network has been established to ensure product quality. Sealing quality is inseparable from the three-level inspection network.

In the quality inspection process of the finished product, the sealing quality is an important indicator of the overall quality inspection. Under the condition of meeting the external process dimensions, the main attentions are as follows: 1. Curling, cracking, squeezing, squeezing, burring, Card cans, etc.; 2, sealing structure and size requirements; 3, sealing requirements. The empty pressure inside the empty tank is 0.15Mpa and the pressure is kept for 1min without leakage, rising tank and deformation. If the tank is under high temperature sterilization, the tank will not rise and leak.

In short, we can have a preliminary understanding of the quality and comprehensive control of the sealing process in the above aspects. We can make timely and accurate analysis and judgment when there are different defects in the quality of the edge.

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