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Ophir Photonics Group 3050 North 300 West
North Logan, UT 84341 Tel: 435-‐753-‐3729
www.ophiropt.com/photonics
Tutorial: The Importance of CO2 Laser Optimization By John McCauley, Midwest Sales Manager, Ophir-Spiricon The New Year is a time to look back on the past year and contemplate how to do things better. It’s a time to make New Year’s resolutions in an effort to be a better person and do things better. One of the most common and popular New Year’s resolutions is the renewed commitment to losing weight. As many of us are all too familiar with, that means eating better and getting involved in a regular exercise routine. One of the advantages of losing weight in the 21st Century is the technology at our fingertips that helps us reach those goals. From the sciences behind how the body uses the food we eat, to the plethora of Smartphone apps that help us measure and track our results, it seems like losing weight would be an easy task. So why is it not? For a moment, let’s discuss the importance of data measurement. The case might be made that one of the primary reasons that someone doesn’t lose weight is because they don’t keep track of their results and/or make adjustments based on those results to achieve the goals that they’ve set for themselves. And why is that? Let’s be honest. Isn’t it because we won’t like what the measurements are telling us? Worse, how successful would a weight loss program be if we didn’t take measurements at all? What if we never stepped on a scale, but just said to ourselves, “I think I feel thinner today.” Or, what if we wait for that next dreaded doctor’s visit to record the weight? What if someone attempting to lose weight never counts and tracks the daily calories they take in? Or never wear a heart rate monitor to determine how many calories are burned during an exercise session? How successful would that particular weight loss program be? Your laser can be one of your most valuable investments. But as anyone working with lasers knows, it can also be a source of frustration when it comes to optimizing it for your manufacturing processes. In a perfect world, a laser user would put their system(s) on autopilot, perform their routine scheduled maintenance, and continue to make money day in and day out. And in a perfect world, we could all maintain the same metabolism rates at
Ophir Photonics Group 3050 North 300 West
North Logan, UT 84341 Tel: 435-‐753-‐3729
www.ophiropt.com/photonics
Figure 1: Electronic Laser Analysis System
Inefficient Laser Cutting
40 years old that we enjoyed in high school. But because it’s not a perfect world, we go on diets and keep closer eyes on our laser systems. It’s safe to say that every laser user, along with their superiors, wants the laser system to operate as optimally as possible. When these systems aren’t optimized, time and money is lost through lower cut speeds, increased dross on the edges of the cuts (resulting in personnel spending time removing the dross), and more frequent down time due to maintenance. So, it might be very surprising to learn that these same laser users often times don’t use the latest in measurement technologies to learn as much as they can about their laser system(s). Thermopile Measurements and Mode Burns The most commonly used approaches include simple thermopile measurement devices for measuring laser power and acrylic blocks for measuring the laser’s beam shape at the workpiece. A mode burn into acrylic usually consists of a shape produced from beam-‐on time to about a second and a half after the beam has been turned on and that it is. The problem with these approaches is that they only give single data points on how the laser is performing over a just a few seconds. Contrast that with today’s laser measurement technologies. Water-‐cooled thermopile power measurement sensors, along with camera-‐based CO2 beam analyzers, allow the laser user to observe trends in laser power, beam size, pointing stability, and beam shape in real-‐time. These techniques allow for a more comprehensive understanding of how a laser is behaving over longer periods of beam-‐on time and give the user a better way of troubleshooting problems that arise with the laser system. Like a routine doctor’s visit, some laser users rely on visits from either OEM or independent technicians to provide information about their laser systems’ performance. The levels of service and the advice given on how to continue maintaining their systems can be very highly regarded, often based on years of experience. However, most of these technicians still use the same rudimentary laser measurement techniques. And the visits certainly don’t come without a hefty price. So why is measuring a laser over several seconds (compared to just the few seconds after the laser is turned on) important? Here are some examples to illustrate.
Efficient Laser Cutting
Ophir Photonics Group 3050 North 300 West
North Logan, UT 84341 Tel: 435-‐753-‐3729
www.ophiropt.com/photonics
Figure 2b: Stable Laser Power Figure 2a: Unstable Laser Power
Figures 2a and 2b show the average power measurements of two different CO2 lasers. The measurements were taken with an Ophir 10kW water-‐cooled thermopile sensor sending data to a Juno USB device interfaced to a local laptop. You’ll notice that the graph in Figure 2a shows a laser that ramps up in power, peaks at about 2.3kW and then starts to drift downward. It was thought that this laser had a damaged output coupler. Contrast that graph with the measurement illustrated in Figure 2b which shows a laser that ramps up to the power that was programmed and holds that power throughout the duration of the measurement.
Would a simple thermopile power measurement device giving one single number for the output of the laser’s power show the problem with this laser? Figures 3a and 3b show the beam profiles of two different CO2 lasers. The profiles were taken with a Spiricon ModeCheck beam analyzer which analyzes the beam real-‐time (with new data points 15 times per second!) and shows the beam profile from the beam-‐on time to several seconds after the beam was turned on. Figure 3a illustrates a laser whose profile showed an off-‐balance energy distribution in addition to a drastically increased beam diameter over the first few seconds (approximately 5 seconds) after the beam was turned on and stabilized into the beam shape similar to what is seen in the last frame.
Figure 3a: Profiles from Unstable CO2 Laser
Ophir Photonics Group 3050 North 300 West
North Logan, UT 84341 Tel: 435-‐753-‐3729
www.ophiropt.com/photonics
Figure 3b: Profile from Stable CO2 Laser
Contrast that with the laser that is profiled in Figure 3b. This laser shows a balanced energy distribution and remains consistent from beam-‐on time to several seconds laser. Would an acrylic mode burn help diagnose the problem that the laser in Figure 3a is having? Similar to someone trying to lose weight without using a scale, a laser user that does not include periodic laser measurements cannot fully understand how the laser system is behaving. And not fully understanding the performance of the laser system will ultimately result in the system’s unnecessary loss of time and money. Only through the application of modern-‐day, real-‐time laser measurement technologies can a laser user completely analyze their laser’s performance and better maintain their laser system over the years. And this is the maintenance routine that is going to best protect one of your most valuable tools. Can you think of a better New Year’s Resolution? Ophir Photonics Group http://www.ophiropt.com/photonics Copyright © 2014, Ophir Photonics Group.