Double 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. This can be very time-consuming as manufacturing is stopped 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 area, 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 vacuum hermetic seal.
This type of broken corner can cause material to accumulate at the corner, causing problems such as a “sharp seam”, which can injure the person handling the can.
Incorrect roll and chuck placement
The most common problem is incorrect relative positioning 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 the seam. Often, the result of such incorrect positioning can be leaks and wrinkle (tightness) issues.
The most common mistake is an 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 a mistake. 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 far too close to the chuck (as evident by the damage 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 seam gap (metal pickup can become a problem) or free space.
Bad adjustments in first and second operation are the primary cause of problems in the seam, including wrinkle issues, bad free space, 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 such as the 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-head 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 a case, no amount of adjustments will produce a good seam and any effort is 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 in 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 produce 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 such as bad seams, open seams, wrinkle (Shaking).
A similar but slightly different problem can be caused by a 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.
Lifter pressure and position
The lifter pressure and position are critical to the correct positioning 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 can be adjusted easily by using a pressure gauge and a height meter (or Johnson Gauge). 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 on the seamer.
Double seamer problems are more common than most operators believe. They are the unavoidable result of guesswork and placing rolls and chucks into the seamer without much control or monitoring over their condition or 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 the seamer to operate outside 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 also to other problems. An open seam can be the cause of several problems, tightening the roll against the chuck can cause the seam to break, spring back or cause unwanted tightness (wrinkles) issues and leaks.
Another potential problem caused by the clash between the needs and requirements of the maintenance technicians and QA personnel is that while Q/A personnel 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 is most often less than ideal.
Tools, such as the Clearance Gauge, can help resolve this potential problem by setting up the seamer both accurately and quickly. Issues, such as described above, can be easily resolved without having to take apart the seamer (e.g., bearing issues). Roll and chuck deformation, damage and erosion can be found during setup. All heads can be set identically and at nominal values, 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 Quality By Vision’sClearance Gauge.