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Main factors affecting sealing quality
The failure of can sealing is mainly manifested in the quality of the seal, in addition to some problems in the transportation process of the can body and the lid, such as scratches on the can or the lid, and the appearance of the can and the lid. The quality of the seal mainly has the following aspects: the three requirements of the double crimping mechanism (sealing roller, chunk, tray), manufacturing, installation and commissioning problems; the original and auxiliary materials (cap, tank body, sealant) ) For the problems that often occur in actual production, the following aspects are analyzed from the causes of the problems.
(1) Sharp seam and cut-ower
The sharp edge on the inside of the crimp top is called the sharp edge.When the sharp edge reaches the tinplate. The degree of fracture is called cut-ower. Cut-ower is a serious curling defect, also known as curling edge, fin, thin edge, etc.
Cause analysis: the indenter is worn or the sealing roller is adjusted to a higher position than the indenter; the second sealing roller is adjusted to be tighter; the distance between the indenter and the tray is too small or the tray pressure is too large; the indenter moves axially; the tank body The flanging is too large; there is too much sealant in the cover.
(2) Fake roll (false seaming) Fake roll refers to the folded cover hook that presses the folded body hook, but the crimps that are not engaged with each other are essentially
It is because the curled body hook and the cover hook are not engaged, which is a serious curling defect.
Cause analysis: the flange damage (bending deformation) caused during the transportation and transfer of the can body; the shape of the can body flange is unqualified (such as a mushroom shape); the round edge of the can lid is defective or damaged; the can lid is not sealed when sealing Align the can body.
(3) Knocked-down flange refers to the can body being severely bumped against the edge of the can or lid when sealing the can.
The lids of the cans are not hooked with each other, and there is an obvious phenomenon of the can body flanging at the lower part of the hemming, which is a serious hemming defect.
Cause analysis: damage to the flange caused during the transportation and transportation of the tank body; the shape of the tank flange is unqualified (such as mushroom shape);
The edge is damaged or the round edge is too large; the lid is not aligned with the can body when sealing.
(4) Jumped seam (jumped seam) Jumping seam refers to the fact that because the seam at the welding seam is thick, the sealing roller is skipped when passing through the seam of the tank body. Failed to press crimp. The tightness of the seal at the jump seal is insufficient, which is a major crimp defect.
Cause analysis: The speed of the can sealing machine is too fast; the buffer spring of the second sealing roller is too soft, and the seams of the can body are too thick.
(5) Incomplete hemming (slip)
Incomplete hemming refers to the fact that the can lid is slipping on the indenter or the sealing roller is not rotating during the sealing process.
The phenomenon that the partial hemming is not completely compressed due to good reasons, also known as slip seal, is a major hemming defect. Its characteristic is that part of the curl has normal thickness, and part of it is super thick (loose). May be accompanied by rounded wrinkle deformation of the countersunk wall caused by indentation slippage. The first crimping seal shows signs of teeth along the periphery of the can. The second crimping seal makes the crimping incomplete (loose), and may also be accompanied by crimping and abrasion.
Cause analysis: the pressure of the tray is too small, the size of the tank cover and the indenter is small or the taper is not suitable; the indenter is worn; the distance between the indenter shaft height and the tray is too large; the tray spring fails; the indenter or tray has oil; pressure The head has axial movement, and the positioning is not allowed to be changed or adjusted incorrectly.
(6) Hemming "tooth" (, pp) Hemming "tooth" refers to the bad sealing of the can, the cover hook and the body hook are not partially overlapped, and the lower edge of the hemming. The V-shape and protrusion are the main defects.
Cause analysis: The sealing curve of one sealing wheel is not ideal; the pre-sealing machine or the head sealing roller is adjusted too loosely; the sealing wheel is worn; the second sealing wheel is adjusted too tightly, which will exacerbate tooth defects; the design of the lid shape is not ideal (such as The rubber bearing surface is too straight); the lid has crumpled edges on the rubber bearing surface, or there is too much sealant in the lid; the tray pressure is too high, the tank can be filled too much; the sealing wheel bearing is not flexible. miscellaneous.
(7) Because of the poor sealing of the iron tongue or lip, the tongue-shaped part that affects the appearance is obviously exposed at the lower edge of the curl, which is called the iron tongue or lip.
It is called folds (defects between folds and wrinkles are called folds), which are the main defects.
Cause analysis: The cause of the "tooth" is roughly the same.
(8) Hemming (cut seam) Hemming refers to bad can sealing, and the outer iron sheet of the hemming is broken, which usually occurs at the seam of the tank body.
This is a major defect. The bottom cover is broken or cracked at the hem of the arc.It is often difficult to detect without magnification. The curl that reveals the traces of the two rollers should be carefully checked, especially in the seam of the tank or where there are draped lips. Cracked double line.
Cause analysis: the two sealing wheels are adjusted too tightly; the lid material is defective; the sealant inside the lid is too much; debris is caught in the curling edge;
The sealing wheel is adjusted too tightly, causing the lid to be folded too long.
(9) The overlap rate does not meet the requirements. The qualified overlap rate should be greater than 50%, a minor defect between 35% -49%; a major defect between 5% -34%; and less than 5%. Serious flaws.
Cause analysis: The undercut depth of the indenter is too large, which will cause the cover hook to become smaller; adjusting the seal wheel too loosely will also make the cover hook smaller; the tray pressure is small, and the amount of flanging will make the body hook smaller; the second seal wheel Excessive width of the sealing curve will cause the crimp width to increase, resulting in a decrease in the overlap rate.The sealing position of the road sealing wheel is higher than the adjustment of the indenter, resulting in a decrease in the width of the crimp. The width is uneven.
(10) Tightness (wrinkle degree) does not meet the requirements The qualified tightness should be greater than 50% (wrinkle degree <50%), at 33.3%
A minor defect is between 49%; a major defect is less than 33.3%.
Cause analysis: One sealing wheel curve is unreasonable, and the adjustment of the sealing wheel is not suitable; one sealing wheel curve is severely worn; the shape of the rubber bearing surface of the tank lid is unreasonable (too flat or round edge shape is not ideal) or the rubber bearing surface of the tank lid is wrinkled; Wheel bearings are not flexible.
(11) Hemming damage Hemming damage refers to the damage to the outer surface of the hemming part or the loss of the coating during the process of hemming and sealing.
Cause analysis: the curve of one sealing roller is unreasonable; the smoothness of the sealing surface of the first and second sealing roller is low; and the adjustment of the first and second roller.