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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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This article illustrates and explains the types of marks obtained when using a CO2 laser to mark plastic tubing manufactured from PVC, urethane, nylon, and polyethylene materials. These examples were not developed to determine maximum mark speed or optimum mark quality, but rather to demonstrate the different marking mechanisms seen when working with plastics. All of the marks produced for this application were made using an FH Series marking head fitted with a 125 mm lens that provides a 180-micron (0.007”) focused spot with a 3 mm (0.118”) depth of focus. TYGON® is a clear laboratory and chemical grade of polyvinyl chloride (PVC) tubing which produces a lightly engraved, high contrast mark. Other types of PVC tubing and PVC coated wire also exhibit high contrast marks. The contrast, or color change, seen in PVC is induced by heating of the substrate. In this example, mark speed was 762 millimeters per second (30 inches per second—IPS) using 14 watts of power. The urethane (green) tubing provides an engraved, non-contrasting mark. At a power setting of 14 watts, urethane tubing marks slightly slower than PVC at a velocity of 635 mm/sec (25 IPS). Nylon 11 (red) tubing exhibits a slight contrast caused by a combination of engraving and a light melt-back on each side of the depression. Marking speed was 508 mm/sec (20 IPS) at a power level of 26 watts. The last example, polyethylene (blue) tubing, provides a slight contrast caused by yet another type of marking mechanism – surface melting. Instead of an engraved mark due to material removal, the polyethylene tubing melts at the surface, causing a change in density and volume. This property change on the tubing surface creates a raised, contrasting mark. Mark velocity was 254 mm/sec (10 IPS) using 33 watts of power. Other dark-colored plastics such as phenolics (including Bakelite) and polycarbonates typically exhibit engraved marks; however, at very low powers—usually less than 10 watts—the surface melting mechanism can create a contrasting mark. Careful control of speed and power causes the surface to boil (instead of vaporize) and then quickly cool, which produces a raised mark. The dramatic change in density and volume causes this raised mark to appear much lighter than the surrounding darker surface.
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One of the primary uses for flame-retardant (FR) polypropylene is in the manufacture of low-cost, low-temperature electrical insulating products to replace polycarbonate, polyester, and PVC materials. In addition to its flame-retardant properties, FR polypropylene is non-hydroscopic and is now available in halogen-free formulations. Products manufactured from FR polypropylene for the electrical/electronics industry include insulating shields, barriers, enclosures, and spacers. |
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mirrors down through a cutting head. The head assembly contains a 63.5 mm (2.5”) positive meniscus lens that provides a 100-micron (0.004”) spot with a 1.8 mm (0.07”) depth of focus. To aid the cut process and protect the focusing lens, we introduced 1.4 bar (20 PSI) of clean, dry assist air into the cutting head’s gas assist port. The FR polypropylene sheet was positioned face down (paper side up) on the table so we could obtain a clean cut through the self-adhesive backing. At a power level of 200 watts, we achieved cut speeds of 5.72 meters per minute (225 inches/minute). In addition to achieving a clean cut through the adhesive paper backing, the FR polypropylene provides a cleanly cut edge (no residue or charring) with just a slight melt back on the lower edge.
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Polyetherimide, also trademarked as Ultem®, is a high-temperature thermoplastic (rated for continuous use in temperatures up to 356 °F) that features high tensile strength along with good flame and chemical resistance. Polyetherimide is commonly specified for aerospace, automotive, medical, and packaging applications. Its flame resistance combined with low smoke emission also means it is an important material for molded portions of aircraft interiors. For this application test, we were asked to demonstrate the feasibility of laser marking electrical connector housings molded from a polyetherimide formulation that includes a 10% glass fill for reinforcement. Our marking setup consisted of a 25 W sealed CO2 laser, an FH Series marking head (equipped with a 125 mm lens), and our WinMark Pro laser marking software. The 125 mm focusing lens provides a 180-micron (0.007”) diameter spot at the point of focus over a mark field measuring 85.7 mm by 105.6 mm (3.4” x 4.2”).
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In WinMark Pro’s Drawing Editor, we created a two-line, 10-character text object using the European stroke font and set a Text Height of 6.35 mm (0.25”). On the Marking tab, we set a Power, duty cycle percentage, corresponding to 25 watts and a Velocity of 254 mm per second (10”/sec). Because of the radius of the connector housing, we set our focus point midway between the upper and lower extents of the text to ensure a consistent power density across the mark. Using these settings, we achieved cycle times of 0.51 seconds per part when marking the 10-digit part code. The resulting engraved mark exhibits high contrast, due in part to the 10% glass fill reinforcing material.
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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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