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Laser Marking Glass Nail Polish Bottles
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Cutting 1018 Mild Steel
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Marking Polypropylene Pipe |
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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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Laser Marking Glass Nail Polish Bottles
Marking or coding glass bottles for various consumer products is a frequent CO2 marking request that we receive in our Applications Lab. Because of the very small size of these bottles, and the curvature of the mark surface, extra care must be taken in lens selection. Long focal length lenses have large depths of field that compensate for large curvatures; however, they also have larger spot sizes, making it difficult to achieve fine mark detail. On the other hand, short focal length lenses have small depths of focus, which limits marking to a small area of curvature (to prevent slight fading of the mark), but these lenses have small spot sizes that are perfect for marking fine detail.
For this particular application, the request was to mark a small 8-character alphanumeric date code on the outer rim of a glass nail polish bottle. We set up the test using a Synrad 10 W laser and an FH Flyer marking head equipped with a 125 mm focal length lens. This choice provided a focused spot size of 180 µm (0.007") on the glass surface, which was required to mark the small text size requested for the date code. This lens selection provides a 3 mm (0.118") depth of field that allowed us to mark the eight characters in fine detail without exceeding the depth of focus.
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We marked this 8-character date code, consisting of 0.15" high text, on a glass nail polish bottle using 10 watts of power at a speed of 5 inches per second. Each bottle was marked in a cycle time of 0.34 seconds per mark.
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The mark file, created in WinMark Pro, consisted of 3.8 mm (0.15") high stroke text (our Simple font) with a mark Velocity set to 127 millimeters per second (5 in/sec) at a Power level corresponding to 10 watts. In addition, the Text Radius property was set to -127 mm (-5.0"). This negative value corrects a slight downward warp of the text string due to the lip around the neck of the bottle. The resulting date code produced by these settings was completed in 0.34 seconds. The contrast produced by the mark is fairly low with a semi-transparent look; it does not detract from the overall 'look' of the product, but is still easily readable by the human eye.
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Cutting 1018 Mild Steel
Although mild steel is the most common metal processed 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, nozzle diameter, and nozzle position.
Oxygen purity-
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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This 0.080" thick mild steel plate was cut at a speed of 125 IPM using 400 watts of power. Note the vertical striations and clean, dross-free edge.
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Gas pressure/nozzle diameter-
An oxygen assist 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 combination of gas pressure and nozzle diameter 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 standoff-
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 (0.36" diameter) 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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Marking Polypropylene Pipe
Polypropylene (PP) piping is used in diverse fluid-handling installations ranging from potable water and purified water systems to acid waste and chemical systems. PP pipe is ideal for high temperature applications where polyethylene (PE) and PVC pipe are not rated for use. Extruded PP pipe is seamless and chemically inert. When multiple sections or branches of pipe are fusion welded together, the assembly becomes a continuous piece with a zero percent leakage rate.
For this application, we were asked to mark manufacturing data on 2-inch nominal O.D. UV resistant polypropylene pipe. Our marking setup consisted of a Firestar t80 laser, FH Flyer marking head, and our WinMark Pro laser marking software. Because of the large mark required, we fitted the Flyer head with a 370 mm lens that provides a 540-micron (0.021") diameter spot over the extents of a mark field measuring 241 mm by 297 mm (9.5" x 11.7").
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We achieved contrasting, engraved marks on polypropylene pipe using 80 watts of power at a speed of 12 inches per second. This large- area mark, measuring 0.75" by 11.5", consists of 64 TrueType font characters with a detailed logo and was created in 8.69 seconds.
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The mark file covers an area measuring 19.1 mm by 292.1 mm (0.75" x 11.5") and consists of manufacturing data including company name and location (using a custom TrueType® font), logo, and patent/part numbers. The company name/location text object measures 14.2 mm (0.56") high while the smallest part number text measures 6.1 mm (0.24") high. The logo measures 19.3 mm high by 19.8 mm wide (0.76" x 0.78").
At a power level of 80 watts, we achieved engraved marks with good contrast at a Velocity of 305 millimeters per second (12 inches/second) in a cycle time of 8.69 seconds per mark.
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FH Flyer / Fenix Flyer Technical Updates
Synrad Technical Updates keep you informed of recent developments related to FH Flyer Marking Head or Fenix Flyer Laser Marker products. Sign up to receive these bulletins automatically via email at http://www.synrad.com/FH_Flyer/flyersupport_subscribe.htm
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Contact Us:
Please do not reply directly to this newsletter. E-mail questions or comments to synrad@synrad.com
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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