"Double Seaming - efficiency"

Kirin had contacted Quality By Vision (QBV) to assist in the analysis phase. Various parts of Kirin's seaming procedures were reviewed, and the test results concluded that different seaming heads reacted differently over time, and that high variances in stop rates between the different seamer heads were a drain on efficiency. All the seamer heads were adjusted to the same specifications using the standard techniques.

The company recorded the number of stops per head over a period of time and found substantial variations: while some heads required more frequent stops, others could go on producing good seams without needing any readjustments. The end result was that the seamer had to be stopped whenever any of the heads went out of alignment, and soon after it would have to be stopped again when another head started producing out-of-specification seams.

Stop rates also tend to reduce a seamer's lifespan. A seamer, just like an aeroplane, tends to develop failures primarily during "lift-off" and "landing" because these procedures exert more pressure on it than during the "flight" itself. A seamer with fewer stops will have a longer lifespan. In short, reducing the number of seamer stops is of critical importance to both efficiency and performance.

At this point, QBV started working to isolate the issue. As cans are fed into seamer heads randomly, the ends and cans themselves could not be the source of the problem. In fact, only a small number of factors could cause such a phenomenon.

The first suspects were slight differences between roll profiles. The brewery had already purchased a laser profiling system (inROLL 9000) to inspect their rolls, and concluded that the new roll and chuck profiles between the heads were virtually identical and could not be the source of the variation between the seamer heads.

Pressure exerted on each can from below was also checked, as were the motion of the rolls. None of these could account for the variations.

Finally, the conclusion was reached that the technique currently being used for initially positioning the first and second operation rolls against the chuck was the source of the problem.

The technique used today to position the rolls usually involves two parts. Firstly, the operator uses feeler gauges for thickness adjustment. Then the operator can use a special gauge for the vertical alignment of the roll (there are several different ways to perform this). The combination of the two techniques provides a way to position the rolls in position. However, due to the inaccuracies in the technique, seam inspection is then used as a corrective means, a procedure that requires extensive skill from the operator.

This technique presents a few problems. The technique is slow, and only an expert can calibrate a seamer, while two different experts will usually adjust a seamer differently. Seamer adjustments require heavy testing (teardown or seam inspection) after which readjustments may be required, and there is no way to produce a calibration document that proves that the seamer was properly adjusted at a particular date and time. Finally, no record is currently maintained whether or not the roll alignment was done properly, nor is there a possibility of comparing the clearance before and after the alignment.

Solution

QBV approached the problem by inventing a new method of measuring clearance values. The new technology (patent pending) utilizes a computerized optical measurement, which measures the clearance values directly within the seamer.

Such a device means that adjustment is fast and accurate, and anyone can perform the adjustment high expertise levels are a bonus, but not a requirement. Also, variations in adjustment between operators will be negligible. Once the rolls are in position, extensive seam testing is superfluous, and the system can produce accurate reports that track the position of the rolls in a seamer at a particular date.

Furthermore, analysis can help the company find the best position for the rolls. There are less mistakes than with feeler gauges, and both first and second operation rolls can be adjusted during scheduled downtime and less so during production runs. Finally, less seamer stops mean a longer lifespan for the rolls, chucks and even the seamer itself.

The clearance gauge is inserted into the seamer during routine seamer stops, after roll/chuck changes and after Q/A tests (like seam inspection) indicate a problem.

Once a problem in a seamer is detected, the seamer must be stopped and the appropriate head must be readjusted. Any adjustment requires retesting, after which additional adjustments might have to be made. This can take a while, during which time cans are not being produced. Incorrect clearance values can also damage the seamer and erode the rolls/chuck due to friction. As rolls and chucks deteriorate, they can break or simply compromise the quality of the seams.

The objective is to find the perfect "sweet spot", an optimal point where the seams are perfect and the seamer can go on running for the longest amount of time. With today's setups, finding the optimal position of the rolls is difficult, and positioning heads in that optimal position is even more intricate.

The situation is exacerbated for companies who need to have the same seamer produce seams for more than one type of can. When rolls have to be frequently exchanged, in order for the seamer to produce another product, the roll installation procedure can be a lengthy and expensive process unless a quick method for adjusting rolls is used.

In some cases, producing first operation seams (for first operation teardown tests) can be tedious, as it may require second operation rolls to be physically taken off the machine. For those seamers, removing the second operation rolls can often prove to be impractical during lengthy production runs.

As a result, second operation rolls are adjusted in order to compensate for issues that are actually produced by incorrectly positioned first operation rolls. This creates imperfect seams and the variations between the heads are increased.

Correlating the seam shapes to the clearance values is an interesting exercise. An effect called "springback" causes the seam to spring back into position after its shape is formed. As a result, heads with significant differences between the roll and chuck distances can often produce similar looking seams. Seam thickness, for example, may not vary much between the heads, although the position of the rolls for these heads might vary greatly.

The clearance gauge provides a critical tool that can assist companies to increase both production speed and production quality. The future holds promise for such a tool, and by ensuring clearance values, the number of destructive tests may be reduced as the unit can reduce seam failures over time. This can provide an affordable alternative to x-ray for companies seeking to improve quality using less destructive means. By checking the parameters affecting the seam, as opposed to checking the seam itself, companies will have better control over the seaming process.

As the research continues, the clearance gauge will help QBV have a clearer understanding of the types of seaming failures that are all too common today.

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