A visual seam defect is a type of defect which you can see outside of a can’s seam. Visual seam defects include cut seam, droop, false seam, incomplete seam, cut-over, sharp seam, and vee. A packager should inspect visual seam defects on a can before starting the packaging process. Cans are considered acceptable if they are free of any visual defects.
To help you a bit in determining a visual seam defect on your can and how to solve them, we created this short guide. In today’s discussion, we are going to discuss the 6 common visual seam defects, their possible causes, and their solutions. Let us start with how a defective double seam can affect the packaging process.
Effects of a Defective Double Seam
A can’s seam is unacceptable if it contains visual defects and defective or unacceptable can seam can:
- Prevent an airtight seam
- Cause spoilage to the product inside
- Become dangerous to the health when bacteria enter the container via the defective double seam. This bacteria can cause foodborne botulism.
Common Double Seam Defects, Their Possible Causes, and Solutions
The double seam defects we will mention in our discussion are just some of the most common ones. You can find a more complete list of visual double seam defects here.
#1 Cut Seam
This seam defect happens when the seam is extremely tight. It causes fractures to the can seam’s outer layer.
Possible Causes and Solutions
- Too tight 1st and 2nd seaming rollers.
- Loosen the 1st and 2nd seaming roller operations.
#2 Droop
This is an overhang in the normal seal’s bottom which gives the seam’s bottom edge a scalloped appearance. It may happen at any part around the double seam. However, a droop is mostly found where the can’s seam crosses the can body’s side seam in 3-piece cans.
Possible Causes and Solutions
- Too great pressure in the turntable.
- Decrease the pressure in the turntable. Check the spacers if the number is appropriate for your can’s size.
- Too loose first roller operation.
- Tighten the first roller operation.
- Trapped food in the seam.
- Clean the can’s edge thoroughly before resuming the seaming process.
- Dented or bent cans.
- Inspect your cans for any defects before using them.
- Worn out 1st seaming roller.
- Replace 1st seaming roller.
#3 False Seam
This is a very serious can defect which can cause food leakage from the container. You can see it on the can’s outside portion through close inspection. The can’s edges and the lid will be pushed towards the can but no hooks are formed.
Possible Causes and Solutions
- Damaged or bent can edges or lid.
- Inspect the lids and cans for any damage before you use them.
- Overfilled can and/or trapped food in the seam.
- Check the can’s fill and clean the can’s edge thoroughly before resuming the seaming process.
- Too loose 1st seaming roller operation.
- Tighten the 1st seaming roller.
- Too tight 2nd seaming roller operation.
- Loosen the 2nd seaming roller.
#4 Incomplete Seam
In this double seam defect, the seam will be unfinished or some parts around the finished seam will be loose.
Possible Causes and Solutions
- Too low or too high pressure from the turntable.
- Check instructions on your can sealer regarding the recommended number of spacers for your can’s size.
- Worn seaming chuck.
- Replace the seaming chuck.
- Seaming rollers do not rotate freely.
- Oil, repair, or clean the seaming rollers.
- Grease or oil is present on the turntable and/or seaming chuck.
- Clean the turntable and/or seaming chuck.
#5 Cut-Over and Sharp Seam
This is a sharp seam edge that you can usually feel by running your fingers around the lid seam’s inside portion. It can indicate a cut-over defect in which there is a fracture in the seam. Cut-over and sharp seam defects have similar possible causes and solutions.
Possible Causes and Solutions
- Too tight 1st and/or 2nd seaming roller operations.
- Loosen 1st and/or 2nd seaming rollers.
- Trapped food in the seam.
- Clean the can’s edge thoroughly before resuming the seaming process.
- Too great pressure from the turntable.
- Decrease pressure on the turntable. Check the spacers if the number is appropriate for your can’s size.
- Worn chuck head and/or seaming rollers.
- Replace the chuck head and/or seaming rollers.
#6 Vee
This is a pointed and sharp overhang found on the normal seam’s bottom edge. When your can has vees, it means that the edges of the can body and the lid did not interlock correctly.
Possible Causes and Solutions
- Too great pressure in the turntable.
- Decrease the pressure in the turntable. Check the spacers if the number is appropriate for your can’s size.
- Too loose first roller operation.
- Tighten the first roller operation.
- Trapped food in the seam.
- Clean the can’s edge thoroughly before resuming the seaming process.
- Too tight 1st seaming roller operation.
- Loosen the 1st seaming roller.
- Worn 1st seaming roller.
- Replace 1st seaming roller.
Conclusion
When finding a solution for visual can defects, you should always read the instructions on your can sealer first. Your machine usually comes with details regarding these issues.
Moreover, do note that you cannot correct seams that failed the visual inspection of defects through a second run on the can sealer. What you can do is to correct the problem in the can sealing machine itself. Also, you need to pack the product inside the defective can into a different container. Then, the container must be reprocessed based on the recommended instructions accordingly.
One possible solution to prevent visual seam defects is having a reliable tin or aluminum can sealer manufacturer. They can help you create your ideal machine that will match your cans and packaged products. Through this, you can reduce problems in the packaging process and eliminate unnecessary mistakes.