Seamer problems & solutions
common double seamer problems
Many common seamer problems are not handled correctly due to the inability of operators to locate the exact cause of the problem. This can be wastful in time and stop manufacturing while the technician attempts to correct the problem on the seamer.
Damaged chuck or roll
When the initial position of the roll or chuck is incorrect, starting up the seamer can often cause the rolls and chuck to grind one against the other. The result of such work can be unpredictable and can cause a variety of problems depending on the location of the crack or damage.
Toolings must be perfectly shaped in order to create a good seam. Here are some examples of actual chucks and rolls that were damaged and left unnoticed in the double seamer (these were found using Quality By Vision's Clearance gauge). In many cases, a simple seamer roll height gauge is insufficient to solve this issue.
The damage in this case is so substantial that it can actually cause a mis-seam (Also called "false seam"):
In some cases, a corner of the chuck or roll can be damaged in one point, which can cause scuffing, wrinkle (tightness issue), sharp seam or various other problems. A cracked chuck can cause the double seam thickness to vary and even cause a bump that can compromise the integrity of the can's vaccum hermetic seal.
This type of broken corner can cause material to accumulate at the corner - thus causing problems such as a "sharp seam", which can cause cuts to the person handling the can.
Incorrect roll and chuck placement
The most common problem is incorrect relative placement of one or both of the rolls against the chuck. In most cases, using of techniques like feeler gauges (sometimes called filler gauges) and seamer roll height gauge are incapable of telling the whole story. Minor problems in the first operation will often require big adjustments in second operation in order to correct. Often, the result of such incorrect placement can be leaks, wrinkle (tightness) issues.
The most often mistake is overly tight second operation. While it seems logical that tighter seams would produce a more secure, closed seam, there are many factors that can cause this to be incorrect. In some cases, spring back can cause the seam to behave like a spring and the tighter the setting, the seam can actually open up more.
In the above case, the roll is way too close to the chuck (as evident by the damage it had caused to the chuck). Overly tight seams can cause the seam to become fragile and more prone to break.
On the other hand, loose or incorrect clearance values can cause the seam to be too loose and can increase the seamgap (metal pickup can become a problem) or freespace.
bad adjustments in first and second operation are the primary cause of problems in the seam, including wrinkle issues, bad freespace, incorrect BH Butt, Cover hook and body hook values.
Roll and chuck design
Correct roll and chuck design is critical to form a successful double seam. In most cases, operators place rolls and chucks blindly into the double seamer without any acceptance testing. Profile checking with tools like inROLL HR can help detect problems like this one:
The image above is a scan of the roll profiles for each of the heads in a 12 headed seamer. In this case, the rolls were installed on the seamer without acceptance testing. The rolls appeared identical, but that particular head produced incorrect mis-shaped seams. In such case, no amount of adjustments will produce a good seam, any efforts are destined to fail and will just waste precious production time.
Roll and chuck erosion
Given enough time and cans, even the most durable rolls and chucks can start to "wear and tear".
This type of erosion will cause the chuck (or roll) to become mis-shapen and to essentially change their design. A wrong profile will simply cause the resulting seam to be incorrect!
Erosion in some places on the chuck can cause the chuck to slip, skip or skid during the seaming process, potentially missing some of the areas around the can and potentially producing cans that are not properly sealed!
Bearing and bushing
The rolls and chucks in the double seamer often use expensive ball bearings (in many cases, ceramic bearings are used to help reduce the chance of breakage). If one or more of the ball bearings break inside the bearing, this can cause the roll to become loose and can cause various problems like occasional bad seams, open seams, wrinkle (Shaking).
A similar but slightly different problem can be caused by loose bushing lever. This can become loose during cleanup or maintenance and can cause an endless number of problems during the seaming process. In fact, it can make the entire seaming process unpredictable and unreliable, making a bad seam every so often.
Lifter pressure and position
The lifter pressure and position are critical to the correct placement of the can against the end during the double seaming process. Incorrect pressure or position can lead to a mis-seam (false seam).
Luckily, this is a very easy adjustment to ensure, using a pressure gauge and a hight meter (or johnson gauge), this setting can be easily adjusted. In addition to making sure that these two values are within specification, it is also critical that the lifter height and pressure be set identically for all the heads across the entire seamer.
Conclusion
Double seamer problems are more common than most operators believe. They are the unavoidable result of working blind and placing rolls and chucks into the seamer without much control or monitoring over their condition or placement position.
While seamer manufacturers design the seamers to operate within very tight specifications, it is very common for operators to "fix" incoming issue, such as tin plate thickness, end measurements such as diameter, curl length, flange etc. by readjusting the roll position, causing by that the seamer to operate out side of its "safe zone" of operation, causing problems as described above.
Trying to fix this will often result not only in loss of precious production time but can often lead to other problems. An open seam can be the cause of several problems, tightning the roll against the chuck can cause the seam to break, springback or cause unwanted tightness (wrinkles) issues and leaks.
Another potential probglem caused by the clash between the needs and requirements of the maintenance technicians and QA personel. While Q/A personel would like to see the seams as close to specifications as possible, The maintenance technicians are mostly concerned with getting back to manufacturing as soon as possible. The resulting compromise can cause incorrectly set up seamers to start producing in production.
Tools like the Clearance Gauge, can help resolve this potential problem by setting up the seamer both accurately and quickly. Issues such as described above will easily be found without having to tkae apart the seamer (e.g., bearing issues). Roll and chuck deformation, damage and erosion can be found during setup. All heads are set identically and right in the middle of the spec, minimizing the influence of incoming material fluctuations on the seam.
The images above were taken from real customers with real problems that were fixed using the Quality By Vision double seamer clearance gauge.