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SYNRAD, INC. - http://www.synrad.com |
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SYNRAD's sealed CO2 lasers are used in a variety of industrial processes including cutting, welding, drilling, and marking. This news brief showcases some of the interesting materials and products that are processed daily by Synrad's line of CO2 lasers and marking heads. |
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Although mild steel is the most common metal cut by lasers because of its cut speed and edge quality, it is also the most sensitive to the cutting setup. Controlling the metal cutting process as tightly as possible allows you to consistently achieve the best edge quality while avoiding excessive melting of the steel. In addition to choosing a CO2 laser with excellent mode and beam quality, the other important process variables include oxygen purity, gas pressure, and nozzle position. The success of exothermic processing is highly dependent on the purity of the oxygen assist gas because a significant reduction in cut speed occurs as oxygen purity decreases. Always use oxygen with a purity of 99.996% or better when cutting mild steels.
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An assist gas pressure of 5.5 bars (80 PSI) through a standard cutting nozzle (a conical or converging design with an orifice diameter around 0.035” to 0.040”) is a good starting point. This pressure creates a supersonic gas flow that provides faster cut speeds; however, the processing window becomes tighter and careful positioning of the nozzle in relation to the cut surface is required to achieve optimal cut quality. Nozzle position, or standoff, is important because the supersonic gas flow creates oblique shock waves of alternating high and low pressure areas as the distance from the nozzle increases. Through experimentation, a standoff height is quickly determined so that the nozzle tip is centered between pressure variations in order to establish a larger, more stable processing window. The photograph illustrates a typical result when cutting mild steel. We cut this section of 1018 mild steel, measuring 2 mm (0.080”) thick, using 400 watts of power at a cut speed of 3.18 meters per minute (125 inches/min). The beam was focused through a 63.5 mm (2.5”) positive meniscus lens to obtain a 100-micron (0.004”) spot size with a 1.8 mm (0.07”) depth of focus. Oxygen assist at 80 PSI was delivered coaxially with the beam through the nozzle to correctly shear the molten metal resulting in a clean, dross-free edge. This mechanism, called melt shearing, provides the characteristic pattern of vertical striations seen along the cut face where molten material is periodically ejected.
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EPDM (Ethylene Propylene Diene Monomer) rubber has many uses where resistance to weathering, ultraviolet radiation, and heat are important factors. Commonly used for decades as a low-slope industrial roofing material, EPDM is also making substantial inroads in the automotive industry because its high heat resistance outperforms natural rubber in engine bay and chassis applications requiring durable boots and seals. This application trial involved marking an easily readable identification code (with the potential to outlast the lifetime of the part) on an EPDM roofing gasket. Because the CO2 laser interaction with the EPDM provides an engraved mark with a metallic-like contrast, you can obtain similar marks on other EPDM rubber products where identification, tracking, or part numbers must appear on the part itself. |
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The marking setup included a Synrad sealed CO2 laser, an FH Series marking head equipped with a 200-mm focusing lens, and a copy of our WinMark Pro laser marking software. The 200 mm lens provides a 290-micron (0.011”) spot with a 5 mm (0.196”) depth of focus. In WinMark Pro, we created a seven-character identification string using WinMark’s built in ‘Simple’ stroke font and set a Text Height of 7.6 mm (0.3”). On the Marking tab, we set a Power (duty cycle percentage) corresponding to 10 watts, set Velocity to 381 millimeters per second (15 inches/sec), and entered a Resolution value of 300. With these settings, we obtained the mark shown in a cycle time of 0.36 seconds per part.
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Sil-Pad® is a thermally-conductive interface material developed for the electronics industry. This flexible silicone material is designed to conduct heat away from discrete components or circuit board assemblies into a thermal heat sink, heat spreader, or equipment chassis. For this application, we were asked to kiss-cut specific component shapes from the Sil-Pad. This particular thermal material is a fiberglass-reinforced silicone substrate coated with adhesive and covered by a paper liner on one side. After kiss-cutting, these pieces are peeled off the backing material and bonded to individual devices that are later installed on circuit boards. The photograph shows a shape that was laser cut to fit a TO220 transistor case. |
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Because the Sil-Pad is easily and cleanly cut without the need for assist gas, we used an FH Series marking head to steer the beam from a Firestar t-Series (t100) laser. The marking head was fitted with a 125 mm HP (high-power) lens that provides a 180-micron (0.007”) spot over an 80 mm by 99 mm (3.2” × 3.9”) mark field. To create the TO220 transistor case outline in WinMark Pro, we simply drew an 11.4 mm by 16 mm (0.45” × 0.63”) rectangle and positioned a 3.2 mm (0.125”) circle for the mounting screw hole. Alternatively, we could have just as easily imported a CAD drawing of the TO220 outline into WinMark. To kiss-cut the 10-mil (0.254 mm) thick Sil-Pad from its 7.5 mil (0.045 mm) liner, we set a Power—duty cycle percentage—corresponding to 100 watts and a Velocity of 203 millimeters per second (8 inches/second). At these parameters, parts are cleanly cut from the sheet at a rate of 1 part every 0.34 seconds.
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Search our online library for more applications of Synrad's sealed CO2 laser technology. Sort by material, process, or industry. |
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Synrad, Inc. 4600 Campus Place Mukilteo, WA 98275 Tel: 1-425-349-3500 Fax: 1-425-349-3667 E-mail: synrad@synrad.com |
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SYNRAD and Synrad product names are trademarks or registered trademarks of SYNRAD, Inc. All other trademarks or registered trademarks are the property of their respective owners. |
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