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FLEXO Magazine : November 2009
www.flexography.org NOVEMBER 2009 FLEXO 49 Another constraint is that there are always areas beyond the reach of the other laser scan head, as shown in Figure 24, which means that you must contend with the difficulties of stitching two objects together that have been cut by different scan heads. This always means some compromise in quality, because different scan heads will have different tempera- tures, resulting in different drifts during operation. Realisti- cally, there are very few laser cutting applications that are forgiving enough for the quality issues that such stitching en- genders. It is not only applications with stringent cut-to-print registration requirements that are challenged by stitching the cut images from each of the dual scan heads. For example, if there is an offset of the two cut parts by more than +/- 0.1mm this can create a knick during waste removal due to the mis- alignment during stitching. Thus, the higher cost of double scan head systems is not justified, especially if one compares these systems to single scan head laser cutters that are designed for cutting at higher speeds. Double scan head systems often cannot use the 200 to 210-micron spot size lasers that avoid the excess heat known to cause problems such as burnthroughs, adhesives sticking to release papers, etc. Moreover, the costs for higher wattage single scan heads is considerably less than the dual scan head designs, yet the production speed they afford is typically the same or a bit faster. INTEGRATION AND PRODUCTION OUTPUT The quality improvements that are possible when high- resolution camera systems communicate to scan head control software to determine required X/Y offsets is only one example of the benefits of systems integration in top-quality laser cutting machines. The extent of systems integration in one or another laser cutting system can largely determine how user-friendly they are and has great bearing on the pro- duction outputs that can be achieved. For example, older sys- tems required users to obtain a separate camera system, and required operators to master the camera control software. In contrast, today 's better quality laser cutting systems come with cameras fully integrated with the laser software. Opera- tors do not have to learn setup of a separate camera system, as this is now done directly from the laser control software, and in the best-in-class systems only takes three simple steps. The better quality laser cutting systems with full integration of all systems components are, in fact, the only laser cutting machines one can find in the market today that work seam- lessly with variable images from digital printers. These laser cutters allow one to create laser jobs with multiple pictures with different geometries and different step-ups. This is only possible where there is ongoing communication between the FIGURE 22. Combining two large heads FIGURE 23. Combines two small heads FIGURE 24. Yellow is cut with either the upper or lower scan heads TECHNOLOGIES & TECHNIQUES
Sustainable Fall 2009