“9.1.2 Partial qualification…qualification may be performed daily, weekly, monthly or every three months.” Now we can answer the original question. For full qualification (system calibration), you are obliged to use the best available measurement technology and devices, where the calibration of the devices is traceable to the National Institute of Standards (NIST). The devices in this package can typically produce a report of all the recorded measurements. This laser beam metrology package costs approximately $25,000 to $45,000. What measurements can you perform and how accurate are these measurement devices? 1. Laser power (P) to the accuracy of ± 3%. 2. Energy per pulse (E) to the accuracy of ± 3% (E = average P/pulse rate). 3. Focused beam diameter (do) to the accuracy of < 10 microns. 4. Focal distance of the final optics to within ± 0.003 in. (± 0.080 mm). 5. Pulse shape and pulse width (t) to within 5-microsecond accuracy. 6. Spatial profile (uniformity of…), unfocused, collimated, to within ±10%. For daily partial qualification, less accurate devices may be able to identify the critical characteristics of the laser beam sufficiently. Some of these devices may not produce a report, but are very easy to use. The last time I compiled this information for a client, the cost of this quality entry-level laser beam metrology package was under $3000. What is the accuracy of the devices in an entry-level package? Compare the following information to the specifications of the more expensive devices. 1. Laser power (P) to the accuracy of ± 5%. 2. Energy per pulse (E) to the accuracy of ±5%. 3. Focused beam diameter (do) to the accuracy of 99% of No. 3 (Ref. 1). 4. Focal distance of the final optics to within ± 0.005 in. (± 0.127 mm). 5. Pulse shape and pulse width (t) to within 5-microsecond accuracy. 6. Spatial profile (uniformity of…), unfocused, collimated, to within ± 20%. A company that uses lasers to manufacture products should have at least one of the higher-level measurement packages and several sets of the entry- For info, go to aws.org/adindex NOVEMBER 2016 / WELDING JOURNAL 25
Welding Journal | November 2016
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