Laser Die Cutting: “Configuring a laser die cut system”; Labels&Labeling; November 2008

Matching Laser Cutting Technology to Label Application Requirements
By Tom O’Hara, President, Spartanics

It was only a few years ago that laser cutting was a relative novelty in the label converting industry. That is no longer so, and there is now a dizzying array of laser cutting equipment system components to choose from. The challenge to label converters making first investments in laser cutting technology is to source machines that are well-matched to label requirements and to avoid the many models of laser cutters with obsolete software and other out-of-date design features that one can still find in the marketplace. At the same time, one needs to avoid extra costs, which can be as much as 20% more, for higher end components that are not required for the great majority of label applications. In this article we will give a brief overview of some of the most important concerns when matching laser cuttingtechnology to label application requirements.

Configured for Narrow Web Applications

The first question one should ask is whether a particular model of laser cutting equipment is configured and designed for narrow web applications. Those that are have a 200 mm working field and a smaller spot size of 210 microns that is ideal for cutting crisp and sharp complex designs, even in the thin and heat sensitive substrates used in most label applications. Narrow web laser cutting machines are not only smaller than other laser cutters, but are precisely engineered to work seamlessly in-line with digital printers. This includes modifications to operating software, beyond the smaller physical dimensions that are apparent in narrow web laser cutting systems.

Optimized for High Speed Automatic Label Removal

For nearly every label converter, any laser cutter model that makes the automated removal of cut labels from the release paper difficult is not worth the bother. Inferior laser cutters do not use laser sources of sufficient quality to avoid excess heat during cutting. The better quality laser cutting systems that one needs to use in label applications generally have highly controlled laser with a smaller spot size of 210 microns and the requisite superior laser control software that allows one to do cutting without overheating. Without the advanced algorithms for controlling heat during laser cutting, one finds that the adhesive layers melt in way that makes release paper and labels stick together instead of coming apart when they are supposed to. This makes these poorly controlled laser cutters inappropriate for any label application involving adhesives and release paper.

Controlled Laser Power from Sealed Laser Tubes

The quality requirements of nearly all label applications require the better cutting control afforded bylaser cutting machines configured to use sealed laser tubes. Unlike flow-through open designs, the sealed laser tubes keep a relatively constant mixture of gases and that in turn allows consistency in both the laser power and the spot size of the laser. In open laser tube systems the ratio of gases in the CO2 laser (i.e. mixture of hydrogen, nitrogen, helium, and carbon dioxide) is more variable and also requires you to change the gas bottle quite frequently. Every time there is a new gas bottle it means there is a new gas ratio mixture requiring new settings on the laser cutter. It is difficult, if not impossible, to save settings that are usable from one open laser tube to another. Sealed laser tubes, in contrast, will allow one to keep the same settings for more than 10,000 hours that each sealed laser tube lasts. Consistent quality becomes far more doable.

Optimized for Web Speed, Not Cutting Speed

It is important to not be confused by various manufacturers’ claims on cutting speeds, as this is not particularly relevant to the actual web speed in most applications, which is the all important consideration in actual label production. Figures __, __, __ and __ showing a scalloped edge design created with older technology that cannot optimize for web speed and the same scalloped edge design created by today’s better laser cutters that CAN optimize cutting sequences for web speed. Note that the marking speed (a.k.a. cutting speed) is 0.6 seconds in both cases. However, the cutting sequence that is not optimized for web speed proceeds at approximately 9% of the web speed shown in Figure __, where the cutting sequence is optimized for web speed.

This optimization of web speed is done automatically by the software in today’s better quality laser cutting machines, and does not require operator training or input.

Selecting System Components

You can expect a cost difference of up to 20 % between laser cutting systems made from high-end components and those that are made with components of lesser quality. As a manufacturer of both high-end and more affordable laser cutting systems, Spartanics estimates that nearly four times as many label converters–but certainly not all– will be adequately served by lower cost systems. It is important to know that your source for laser cutting technology is not married to particular component suppliers. Best-match components for particular applications (laser source, laser scan heads, etc.) can be sourced worldwide. Lower cost systems can produce high quality outputs IF the underlying software engineering and systems integration are expert.

Knowing your real quality requirements is the first step in zeroing in on whether your operation is better served by low cost or higher quality laser cutting systems. However, there is a baseline of quality that should ALWAYS be achieved such as avoiding burn-through marks and with a crisp narrow cut as the cutting occurs. If a laser cutting system presents burn-throughs it usually reflects a poorer quality of software engineering to operate the laser power and especially at the start and end of a cut. The soft marking capabilities of today’s better quality laser cutters should be considered as a non-negotiable feature, whether a system is high-priced or low-priced. There are systems at all price levels that can and cannot achieve this level of quality and thorough investigation is required.

The wattage of the laser should be carefully considered. Most of the commercially available lasers have the best laser beam quality with full power. If you end up using only 10% of the laser power from your laser source you can expect significantly diminished laser beam quality. For example, a label converter making kisscuts with easy-to-cut materials that has a 300 watt laser in their cutting system may be using only a small portion of available laser power and would be better suited by a lower watt laser. In contrast, a label converter making many throughcuts, including more difficult to cut release paper, which also wants to achieve high cutting speeds would need that 300 watt laser.

The above is a short list of criteria that one needs to first address when sourcing laser cutting technology. For a more detailed discussion, please contact us!

 

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