- April 02, 2009, By Mike Bacon, Spartanics www.spartanics.com
Label converters that last looked at laser cutting machines as recently as early 2008 are likely mistaken about what is and is not possible with laser cutting technology. The sophistication of scan head control software, the quality of the laser scan heads that can be purchased at a particular price point, and the systems integration of laser cutting machine components have transformed the possibilities for laser cutting. Today’s best quality laser cutting machines for label applications can achieve web speeds as fast as 90 mpm with cut-to-print accuracies that far exceed earlier generation technology.
However, some new features for laser cutting machines are ideal for label applications while others have potential to add cost with little return. Here are some questions/answers to consider when you are revisiting laser cutting technology to determine best-fit options for your label application.
Q: Will today’s laser cutting machines make tool-based die-cutters obsolete?
A: There will always be a need for both tool-free (laser) cutting and tool-based cutting (rotary dies, steel rule dies, and hard tool dies) http://pffc-online.com/die_cut/ . Material thickness and material handling considerations sometimes make laser cutting preferable (e.g., for very thin flimsy material) and sometimes make more traditional die-cutting the better option (e.g., for very thick polycarbonates that may be discolored by laser cutters).
Because setup time with laser cutters is negligible, and there is no delay or cost for tool making, they have an obvious niche in fast turnaround short-run jobs. However, now that laser cutters achieve web speeds of 90 mpm, and probably will be even faster by next year, the lines are beginning to blur as to whether tool-based or tool-free cutting is the better option. Laser cutting is also the only option for labels with intricate die-cut patterns that are often beyond the limitations of mechanical dies. Practically speaking, the width of the laser beam, which is 210 microns or less in laser cutting machines optimized for label applications, is the only dimensional constraint on cutting. If artwork involves many small angle cuts, you probably want to use a laser cutter.
Q: Which laser cutting control software improvements are most important to label converting?
A: The better laser cutting machines for label converting are optimized for high-speed removal of labels from release paper http://pffc-online.com/tapes/paper_release_liner_reclamation/ . Inferior laser cutters do not use laser sources of sufficient quality to avoid excess heat during cutting nor do they have the control software that ensures that lasers do not overheat. Without the algorithms for controlling heat during laser cutting, one finds that the adhesive layers melt, causing release paper and labels to adhere and making high-speed extraction of labels impractical, if not impossible.
More sophisticated software engineering also means higher quality cuts, and this is especially important to some of the more cutting-edge label designs with unusual and intricate geometries. You still can find laser cutters in the market that leave burnthrough marks and pinholes at the start and stop points of cutting! These are signs that the laser cutter manufacturer is using generic laser control software and has made minimal or ineffective investments in software engineering. These issues have caused many converters to give up searching for laser cutting solutions, and we concede that if you see this, the best advice is to walk away.
Q: How can you tell if the software engineering of the laser cutting machine is up to the label application requirements?
A: There are a few telltale signs that should clue you in quickly as to the quality of software engineering in a particular model/brand of laser cutting machine. The above-mentioned pinhole/burnthrough marks are a strong indication of obsolete technology. To spot this problem requires that samples to be run, or better yet, use of contract manufacturing services as proof of technology-application compatibility.
There are some questions to ask upfront, even before obtaining samples, which may help sort out if the laser cutting machine is even worth testing.
One, ask if it can combine multiple pictures with varying geometries and step ups in a single job. This is often critical to efficient label converting operations, and laser cutting machines that do not have this capability and instead require many more serial job setups are not only inefficient but red flags that generic laser control software is being used.
Second, ask if it is possible to change laser settings on the fly while cutting. If the answer is no, consider it another red flag that inferior software controls the cutting and that there is little thought toward systems integration.
Third, does it automatically determine the job step up and the position to start cutting?
Fourth, does it include job simulation software to determine web speed and production rate?
Fifth, is there consistent cut-to-print registration at top speeds?
And last but not least, look at how automated the job setup is. Can you save all job parameters in one file and call up repeat jobs with a few keystrokes? If yes, it’s a good sign; if not, it’s a clear warning of less-sophisticated software engineering.
Q: Are there other ways to quickly tell if a model/brand of laser cutting machine is appropriate for labels, besides looking at control software capabilities?
A: Actually, today’s laser cutting machines that are optimized for labels do look different. They have smaller narrow web dimensions—e.g., 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.
Also, the better laser cutting machines for label applications, especially those with more demanding quality requirements, will use sealed laser tubes and avoid open laser designs. Although open unsealed lasers are getting better in quality, they are still rarely up to the demands of most label applications.
There are several intrinsic problems with an open laser tube design. CO2 is usually one of several gases in a laser tube, with helium, nitrogen, and hydrogen making up the balance. The proportion of each of these gases in the mixture will affect the laser power. This ratio is apt to shift in an open laser tube design. With open tube designs there is a requirement to frequently change one open laser tube CO2 tank for another. This makes it is nearly impossible to save settings because there almost always is a difference in gas mixture ratios from one CO2 tank to another. These shifting ratios affect how the laser powers and the quality of its cut.
To achieve the same quality cut, operators will need to fuss with adjustments every time they switch tanks, and even then, there will likely be variations. In contrast, the sealed laser tubes are not as likely to change in gas ratio composition and only require replacement every 10,000+ hrs of operation. This translates into a much better ability to control cutting and to get a consistent result.
Q: Is it simply a matter of the higher cost laser cutting machines being the best ones?
A: Not really. Nearly four times as many label converters—but not all—will be well-served by lower cost systems if they have the requisite improvements in software engineering. If you have determined that the software engineering is indeed expert, the next step is to ensure that your source for laser cutting technology is not married to particular component suppliers.
You can expect a cost difference of up to 20% between laser cutting machines made from high-end components and those that are made of components of a lesser quality.
The wattage of the laser and associated costs should be considered carefully. Many of the commercially available lasers have the best laser beam quality with full power. For lasers of that type, if you end up using only 10% or less 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-W 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. On the other hand, a label converter making many throughcuts, including more difficult to cut release paper, that also wants to achieve high cutting speeds, would need that 300-W laser.
The lower cost laser cutting systems may use sensors for registration, or in more demanding applications use the sophisticated camera technology to deliver the very tight tolerances in cut-to-print registration that are typical of high-end systems. If these camera systems are fully integrated with the laser scan heads, they are able to apply the offset values to keep cuts to a precise registration. Here, too, it is not only the quality of the camera but the underlying software engineering that has great bearing on the tolerances that are achieved at varying speeds. But whether or not sophisticated camera technology is used is important to consider because if your plant’s particular label applications do not require them, it will help cut costs of the laser cutter.
Q: What kinds of production speeds can be expected in laser cutting machines that are best fits for label applications?
A: There is both a general and very specific way to answer this question since job throughput has several determining factors. The better quality laser cutting machines now available have built-in job simulation software made possible by many of the same algorithms that enable them to optimize cutting sequences for maximum web speed. The manufacturer of the laser cutter should be able to take your label artwork, input details regarding the material, and material thicknesses you are cutting and give you detailed projections of what to expect. That job simulation capability also will be available to production managers if and when that laser cutter is purchased.
Generally speaking, web speeds of 90 mpm or better are now doable by today’s best-in-class laser cutting machines for label applications. This will vary to some extent with the complexity of label design and material/thickness being cut.
It is important not to 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 production. Until recently, delivering faster cutting speeds was the best that laser cutting machines could do. Now, the state-of-art algorithms in today’s better quality laser cutting machines take speed to the next step by figuring in the adjustments in the cutting sequence that would need to be done that take web speed into account. If the web is moving from right to left, this means, for example, that the geometry details on the far left need to be cut first and that the way in which the scan heads are moved will depend on the web speed being used. This is shown in Figure 1, where the cutting sequence also is optimized for web speed, not just cutting speed, such that a 350% faster web speed is achieved. If you think about this, you soon realize that optimizing for cutting speed alone can actually result in slower web speeds. That’s why it’s important to ignore claims regarding cutting speeds. Focus instead on demonstrations of the ability of the system software to optimize for web speed.
In real-world plant conditions, the ease-of-use features of the laser cutting machine have great impact on production rates. Setup should be possible in a few minutes, with the ability to seamlessly import any vector-based drawing into the laser cutting machine. Automated stops with fault conditions such as full rewinder rolls are also big boosts to production.
Figure 2 summarizes many of these pointers on distinguishing between laser cutting machines with obsolete, generic designs from both lower-cost and high-end laser cutting machines suited for most label applications. For a more detailed discussion of how to source best-fit laser cutting technology, write to LaserCuttingTechnologyGuide@spartanics.com for a copy of a white paper entitled “How to Match Today’s Laser Cutting Technology to Application Requirements.”
Mike Bacon is VP sales and marketing of Spartanics which manufactures the family of Spartanics Finecut Laser Cutting Machines as well as die-cutting equipment, screen printing systems, and other equipment used by worldwide label converters, among others. Spartanics is headquartered in the US and maintains a sales and service office in Hanover, Germany. He can be reached at firstname.lastname@example.org or 847-394-5700.