One of the most repeated demands during the last year is the possibility to create an easy open with double or triple lines, that means to have a separation that varies from 1 mm to 3 mm (0.039 in to 0.12 in). The main purpose of doing this application is to ensure that the easy open perforation of the front will match with the easy open of the back when creating the stand-up pouch or the final shape of a concrete packaging. If the process and application required while creating this stand up pouch is not precise, the line of the front won’t fit and won’t be at the same height that the line of the back. Currently, the most common trend in order to achieve this demand is to split this line into 2 or 3 in order to increase the likelihood of matching the easy open of the front with the easy open of the back.
Regarding space and investment, is not reasonable to install 12 different laser heads to create so many lines. That is so; the most realistic, efficient and profitable solution is to split the laser from one head into various lines.
That is why in Comexi, our preferred choice, is to achieve it by a multiline removable optics. With this system the customer only needs to acquire a special optic that will divide the laser on those jobs that might require it. Later on, the customer only has to take this special optic out of the laser to return the equipment to its normal mode run, without the beam being divided. This manual operation is also the quickest one because it only takes 5 minutes.
Another way to achieve this demanded packaging solution is to divide the laser beam with mirrors, usually called beam splitter. Compared to the other system, this is a fixed solution. It means that once you choose this system the laser will always be divided but it has also a main advantage: the space you save when having a lot of tracks that require multiple lines.
At Comexi slitting line, our standard configuration has 4 laser heads. So we can easily create 4 tracks with double or 4 tracks with triple lines at the same time using the proper multiline removable optics. Laser heads minimum separation must be 170 mm (6.7 in) so you can see that the maximum number of heads also depends on the space. Sometimes you can put some lasers (half of them) in one bridge and the others (the other half) on the following bridge. However when a job requires a big number of multiple lines – like 16 tracks with double lines- it is not possible to achieve it with the current module with 4 laser heads and multiline optic lenses. In this case, the solution will pass from dividing each laser head into 2 beams with beam splitters. Then, we would add 1 multiline optic lens in every beam splitter so we would obtain 16 different laser beams. In this case, it would be also recommended to install 300W laser heads instead of the regular 100W laser head in order to give each laser beam enough power.
In this sense, it is suggested not dividing laser with mirrors with more than 2 laser beams because of the problems for working cross direction, calibration and loss of power.
Dividing the laser with laser beam splitter means having a perfect calibration with the mirrors used for this system. This operation is achievable with good results when we divide the laser in 2 different beams. When having 3 or more different beams, is complicated to control that each of them work the same way, with equal power.
Moreover, every division of the laser would carry out a loss of power. Therefore, by dividing 100W into 2 laser beams, both lasers will not have 50W. The first one would be working at 50W, but the second laser beam will have a power loss of about 3 or 5 percent. So if we divide 100W in more than 3 laser beams the difference of power can be really serious comparing the first beam with the fourth or the fifth beam.
Comexi's Slitting Brand Manager