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power resonators increased the capacity of cutting systems. Upgraded drive systems with linear motors and improved beam quality boosted cutting speeds in light-gage material. Better programming software maximized material utilization, productivity and ease of use. Recently, automation in programming and material handling also improved machine utilization. The most recent innovations are the use of solid-state lasers that deliver the laser energy directly to the cutting head with an optical fi ber. Three dif- ferent laser technologies are available: fi ber, disk and direct diode. Fiber lasers can be delivered using a small-diameter fi ber core with high beam quality. The laser energy can be focused to a very small spot providing high-power density at the workpiece. Disk lasers are similar in performance.


The most recent innovations are the use of solid-state lasers that deliver the laser energy directly to the cutting head with an optical fiber.


Direct-diode lasers do not have the same beam


quality as fi ber or disk, but this is improving and they are starting to be used for laser cutting. All three forms of solid-state lasers generate energy using laser diodes. Fiber and disk lasers use diodes to excite another laser medium that generates a specifi c wave- length of light. Direct-diode lasers generate laser light directly from the diodes. The solid-state lasers are more reliable and affordable to run than CO2


lasers. For a fi ber laser, the focusability and wavelength


let machines cut very small kerf widths in thin mate- rial. Cutting with a small kerf requires less energy, and so, for a given power level, fi ber lasers can cut thin material much faster. If you bought a 2000-W CO2


laser in 2007 to clean cut 20-gage steel, the


feed rate is about 290 ipm (7 m/min). A 2000-W fi ber laser using air assist gas can cut the same material over fi ve times faster at 1615 ipm (41 m/min). Also, a fi ber machine’s lower hourly operating costs can be a game changer if you are processing thin material. Integrating lasers and material handling is also improving. Lasers are becoming more stable and able


LF6 AdvancedManufacturing.org


to run untended. Process monitoring can verify the cut- ting process and stop the laser from making scrap parts. Furthermore, there are many methods of automating the setup so untended operation is more practical. In addition to adding more power and features to


machines, many manufacturers are looking for ways to reduce lasers’ cost and complexity. Some lasers have improvements in productivity, reliability and operating costs at a price that is lower than just a few years ago. Some fi rms offer less costly machines that have less power, slower drive systems and fewer options.


Drilling With Lasers Laser drilling is a noncontact process that


removes material via photon interaction with the material being drilled. The mechanisms of removal are melting, evaporation, and ablation, sometimes in combination. Processed materials have different opti- cal (absorption at wavelength) and thermal properties (thermal conductivity, heat of melting/vaporization), which allows for selection of the correct wavelength and pulsing properties of the laser. Advantages of laser drilling over other noncon-


ventional methods include shorter processing time, less expensive fi xtures, changes to hole diameters without changing “electrodes” or other “drill bits,” changes to hole locations by programming, and the ability to drill hard and nonconductive materials. Disadvantages of laser processing include pos- sible thermal damage to material, the need for post drill processes, potentially harmful vapors and initial capital equipment costs. Like any material-removal process, optimization studies must be conducted to achieve the correct balance of cycle time, part quality, and part cost. The studies should focus on key process parameters for the material, and their effect on key quality char- acteristics of the part. Typically, wavelength, pulse width, energy/pulse and focal properties will have the biggest infl uence on hole quality. Optimal cycle time can be achieved by adjusting pulse repeti- tion rate with two important caveats. The allowable adjustment is fi nite, in that pulse repetition rate will change the laser average power, and the beam quality of many lasers can change negatively with increased pulsing. Secondly, pulse repetition rate can change the substrate temperature through sidewall conduction and cause degradation in hole quality and time.


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