On the sealing process of the hottest three piece

Three piece can sealing process (Part 1)

Abstract: This paper mainly discusses various influencing factors of three piece can sealing process from the perspective of sealing structure and principle, and expounds how to comprehensively control the sealing and quality of various food and beverage cans at present from the perspective of actual production links and quality control inspection

key words: sealing structure and principle; Influencing factors of double crimping; Three level inspection network

tinplate three piece cans at present, from the overall market situation, although compared with previous years, and the overall quality exists, mainly in the following aspects: coating performance, weld, sealing, sterilization and sealing. This paper only talks about some views on the comprehensive control of sealing process in the production of empty cans for reference only

first, analyze the influencing factors of double crimping from the sealing principle

the sealing process of tin three piece cans (or two piece cans) is completed by the double crimping operation method. The double crimping method refers to the method that two crimping rollers with different groove shapes hook and compress the hook edge of the tank cover and the flange of the tank body at the joint of the tank body and the tank cover through two feeding movements in sequence, so as to achieve the purpose of sealing. In short, it shows that the first curling is hooked, and the second curling is pressed and formed

in sealing equipment, the roll sealing roller, upper indenter and can tray are usually called the three elements of sealing. The correct groove shape of the roller, the reasonable position of the indenter and the appropriate driving force of the can tray are the necessary conditions to ensure normal sealing. (see Figure A1) it is not difficult to see that the three sealing elements, as the basic components of the sealing equipment, are also the basic factors affecting the double crimping

the main factors affecting double crimping are as follows:

1 Physical properties of the tinplate material

such as material and hardness, especially the relatively small tank diameter (such as 202d diameter tank). If the tinplate material is thin and hard, its sealing requirements will be more difficult, because in this case, the plastic deformation of the material in the process of double crimping is smaller, but the wrinkles will be larger

2. Suitable sealing pressure

as shown in Figure A1, during the rotation movement relative to the tank body, the sealing force P at the junction of the roller groove and the tank cover is the synthesis of three different directions: radial force P, the gap between the instrument industry and foreign countries, R, axial force PA and tangential force Pt. The effect of the first sealing force P (1) is mainly manifested in the bending deformation of the materials around the tank body and cover, and the second sealing force P (2) is mainly manifested in plastic deformation. The calculation of the two sealing forces is carried out through energy conservation and plastic deformation. Generally, the second sealing force is 2 ~ 3 times of the first sealing force

in the actual operation process, the appropriate sealing force is completed by the appropriate matching position relationship between the sealing roller, the indenter and the can tray (such as the matching adjustment of the inner and outer gap between the roller and the indenter)

3. The process of empty cans

the hook edge of the tank cover and the flanging of the tank body of different tank types should meet the corresponding process requirements, such as poor welding (> 05mm tailing, weld cracking) before sealing, and too large or too small flanging will affect the sealing performance of empty cans

4. The groove shape and material requirements of the sealing roller

generally speaking, the sealing roller of different tank types has different groove shapes with its upper window measurement value red. At present, many international well-known sports shoe brands have designated SEBS foaming material for the first roller, and the groove of the second roller is deep and narrow, and the groove of the second roller is wide and shallow. At present, most of the reels commonly used in domestic sealing equipment are medium carbon steel, such as 45 ＃ and 40Cr, which have a short service life and the output is limited to 200000 to 300000 cans; The winding wheels commonly used in more advanced sealing equipment are generally made of stainless steel such as 4Cr13 and 9Cr18 after vacuum heat treatment, with high hardness, good wear resistance and a service life of about ten million cans

among the three elements of sealing, the sealing roller is vulnerable, the oil delivery valve should be closed first, and should be polished or replaced with 1000 or 1200 water-based sandpaper according to the production situation, so as not to affect the process performance of crimping and sealing

5. The coating state of the sealing coating

the coating position distribution of the adhesive film in the hook edge of the tank cover is: about 70% in the hook edge and about 30% in the plane. In addition, the amount of adhesive film should meet its own process requirements. If the amount of glue is too large, it is easy to squeeze the glue, and if the amount of glue is too small, it cannot play the role of sealing packing

6. The operator's correct operation and adjustment

the operator's skilled technical skills and operation level, and the necessary daily maintenance and upkeep are also a factor affecting the double crimping. For example, when changing the tank type or making necessary adjustment in case of abnormal sealing, in addition to replacing the necessary parts, correct and reasonable adjustment is also crucial. Generally, under the proper driving force of the can tray, first check the TC value of the head edge width (220 ± 0.10mm), then visually check the tightness of the surrounding crimping of the can cover, and then check the appearance defects and various dimensional process requirements when carrying out the trial sealing after the second crimping. Make correct analysis and judgment on the causes of different defects before adjustment. Note:

(1) the size is measured by anatomical experiment

(2) the first crimping is the basis and premise of the second crimping, which 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 correct operation and maintenance of the operator. (to be continued)