Laser Die Cutting: “Cutting Edge”; Packaging Gazette, November-December 2008

Questions and ANSWERS about Laser Cutting Labels
By Tom O’Hara, President, Spartanics (www.spartanics.com)

If you haven’t recently taken a good hard look at laser cutting technology you are probably missing out on how to move into highly lucrative niches in label products. Much has happened in the past year that allows label converters to incorporate laser cutting into their operations more effectively. Here are the key issues to consider—

Q: How do laser cutters compare to die cutters?

A: Laser cutting machines have numerous advantages compared to tool-based die cutters, mostly deriving from their absence of tools. There are no costs for tools and no production delays for time to make tools. Laser cutting machines are digital systems, meaning they can import vector-based digital images into operating software. In fact, the better laser cutting machines one can now find allow you to import images and set up jobs in just a few minutes, and then go from artwork to completed job runs in just a few hours, or even less for short runs.

Because there are no tools in laser cutting machines, it also means that you bypass many of the mechanical limitations inherent in dies that can be difficult to manage in label applications. For example, cutting adhesives is far easier with laser cutting machines because adhesives tend to literally gum up the works in mechanical cutting systems. Similarly, laser cutting machines can better handle thin substrates that are often too flimsy for mechanical dies to cut with any precision.

Laser cutting systems can readily handle special features such as perforations, creases, score lines, kiss cuts, etc. In fact, the only relevant physical limitation in laser cutting machines is the width of the laser beam, typically 210 microns in best-in-class systems.

Q: How are laser cutting machines for labels different from other laser cutting machines?

A: This past year the first laser cutting machines that were specifically designed for narrow web label applications were introduced to worldwide label converters. These laser cutting machines have smaller physical dimensions—in the area of 2.8 m wide x 1.6 m deep x 1.9 m high. The laser beams in these machines have a 210 micron spot size cutting across a 200 mm x 200 mm working field. Their software is optimized for cutting the many heat-sensitive substrates commonly used in label applications. This also allows for the automated removal of cut labels from release paper, which is difficult in inferior systems that cannot manage heat issues and therefore are poorly matched to label requirements. The difference is actually in the software controls that use advanced algorithms for controlling heat during laser cutting. The sophisticated software of these systems also enables them to combine multiple pictures (labels) with varying geometries and step ups in a single job, an important concern for efficient label manufacturing.

Q: How fast can laser cutting machines cut?

A: There are now laser cutting machines that can cut as fast as 90 m/minute web speed without sacrificing any registration accuracy. When sourcing laser cutting technology it’s very important that you focus on web speed, not just cutting speed. Today’s better quality laser cutting machines have software that optimizes cutting for web speed. This software capability also gives these laser cutters the ability to simulate jobs before they are run to determine both the web speed and production rate for a specific job.

Figures 1 and 2 show the importance of paying attention to web speed, not just cutting speed. Here, the cutting speed in both examples is identical, i.e. 0.6 seconds. However, the cutting speed that is not also optimized for web speed shown in figure 1 proceeds at approximately 9% of the web speed achieved by the laser cutter depicted in figure 2.

Q: Why do some laser cutting machines create burn through marks and pinholes at the start and stop points of cuts?

A: Burn through marks and pinholes are the telltale signs of antiquated laser cutting technology, as are rounded corners where the artwork requires sharp corners, or cuts that appear as dotted lines where there should be continuous cut lines. You just don’t find these sorts of quality problems with today’s better laser cutting machines.

Software improvements are the main source of these quality improvements, and engineers call it the “soft marking” standard. Soft marking, where the laser movements are better synchronized with artwork geometry and tightly controlled during the entire cutting sequence allow for precise cuts, even at very sharp angles and at high speeds. Soft marking is actually quite an engineering feat, and reflects the significant R&D investments for better software engineering that deliver the defect-free cutting that label applications require.

Other factors will also impact the quality and consistency of cutting. The quality of the laser source itself is important. Better lasers with 210 micron spot sizes or less will facilitate crisp cuts. Also, the type of laser tube a system uses—open or closed—has bearing on how the laser is controlled and cut quality. Open laser tube designs are inherently troublesome because every time there is a new gas bottle the ratio of gases in the mixture changes. This affects the consistency of the laser power and spot size and requires new settings in the laser cutter to compensate. It is difficult, if not impossible, to save settings that are usable from one job to the next following a change of gas bottles with an open laser tube. Sealed laser tubes, in contrast, allow label converters to keep the same settings for more than 10,000 hours and consistent quality is easier to achieve for this reason.

Q: Why are the prices of laser cutting machines, even from the same manufacturers, so variable?

A: The cost and quality of the components used in making the laser cutting machine impact its price tag. Many label converters, perhaps 80%, will be well-served by a lower cost system, that could be 20% less expensive than the high-end machines. For this reason, it’s very important to make sure that the manufacturer of the laser cutting machine you are considering for purchase can and will source components from a wide range of suppliers and is not married to particular laser sources, laser scan heads, etc. The area where there is no room for shortcuts is in the software engineering. A laser cutting machine, with or without high-end components, will either have software up to the soft marking standard or it will not.

The wattage of the laser should also be carefully considered. Most of the commercially available lasers have the best laser beam quality with full power. Generally speaking, you don’t want to get a laser where you only use 10% or so of its power.

Q: How can I make sure that a particular laser cutting machine is best-fit technology for my application?

A: A first step is always to ask the manufacturers of the laser cutting machines you are considering to create samples. If you find quality problems in the samples they provide you should definitely seek a different option. Reputable manufacturers of laser cutting machines also provide contract manufacturing services that can further provide proof of the technology-match.

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Tom O’Hara is President of Spartanics, which manufactures the family of Spartanics Fineprint Laser Cutting Systems as well as die cutting equipment, screen printing systems, and other equipment used by worldwide label converters.