Derrick Peterman, Northern California Sales Engineer, Ophir-Spiricon
Surprisingly, many laser machine shops suspect a problem with their laser, but simply “live with it” and suffer low yields and longer manufacturing times as a result. In other cases, the laser machining system’s field service technician may be dispatched to solve the problem. Despite the considerable expense of these field service calls, machine shops rarely use any measureable metrics to see if the service technician has actually improved the laser.
It turns out that reliable metrics can be performed on kW CO2 lasers using easy to use diagnostic equipment that reduces on-site service time while improving customer satisfaction. This application note will discuss results we found measuring output beam power in multikilowatt CO2 laser systems and how this affected cutting speed.
Cutting speed is most directly related to laser power. The higher the power, the faster the cutting speed. In one CO2 laser machining system we evaluated, the system was manufacturing good parts, but working slowly. Operating at its full power setting, which the manufacturer claimed was 4 kW, the system should have been cutting the customer’s 0.375 inch thick Aluminum sheets at a rate of 25 inches a minute. Instead, this system was only cutting 15 inches per minute, so each part took nearly twice as long to complete. Looking at the company’s labor costs, this resulted in an additional unit cost of $50 for a part made several times each day. After analyzing the output power of the system laser, it was easy to see why.
At full power, the laser was actually producing 1.8 kW instead of the rated 4 kW. For the power measurement, we used an Ophir 10k-W-BB-45 thermopile sensor to analyze the laser output. With this sensor, the beam is simply directed into the sensor and an internal cone prevents the laser light from reflecting around the shop; this avoids potentially dangerous conditions.
At kilowatt powers, the sensor requires water cooling to keep from overheating. However, a simple scheme using a 5 gallon bucket of tap water and a recirculating garden fountain pump was sufficient to keep the sensor cool for measurements under a couple minutes.
Thermopile power sensors are designed to accurately measure power regardless of the beam size and position of the beam on the sensor. They are easily calibrated to power standards traceable to National standards laboratories, such as NIST, for a high level of accuracy. They respond to changes in beam power within three (3) seconds, making them ideal for active adjustment of laser power during an optimization process.