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SYNRAD, INC. - http://www.synrad.com
Thursday, May 11, 2006
Issue 137
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Marking Painted Metal
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Cutting Mild Steel
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Cutting PVC Flex
Circuits
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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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Marking Painted Metal
Many diecast metal parts are powder-coated or painted to provide a corrosion barrier as well as an aesthetically pleasing look to the finished piece. In cases where these diecast parts are assembled into larger components, it is often useful to mark pertinent manufacturing data as parts travel though the production process. This painted surface is an ideal coating for laser marking because both laser power and mark time are significantly reduced when compared to lasing bare metal surfaces.
This application called for marking an 11-character Data Matrix code on painted diecast parts. Because of the powder-coated surface, we chose a 40-watt Firestar v40 laser, an FH Series marking head, and our WinMark Pro laser marking software for the marking setup. The marking head was fitted with a 125 mm focusing lens that provides a 180-micron (0.007”) spot with a 3-mm (0.118”) depth of focus over the entire mark field.
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The readable 3.33 mm (0.131”) 2D code was
marked on the painted metal surface using a
Firestar v40 laser and FH Series marking head.
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In WinMark Pro, we created a 2D Data Matrix code and entered an 11-digit string as 2D Barcode Text. In the actual production process, you could configure WinMark to automatically generate sequential serial numbers or read a disk file containing specific manufacturing data for each piece. The code was resized so that each individual cell measures only 0.24 mm (0.009”) square. We then set the 2D Barcode Bitmap property to “No” so that we mark each cell using unfilled vector circles instead of filled squares and entered a 2D Barcode Circle Radius of 70%. We set a marking Velocity of 635 mm per sec (25 inch/sec) on the Marking tab, set Resolution to 225, and entered a duty cycle percentage corresponding to 25 watts of Power.
Using these mark parameters on the powder-coated surface, we achieved cycle times of 0.28 seconds per part. As shown in the photograph, the 2D code has an overall dimension of 3.33 mm (0.131”) per side. Using an RVSI vision system and verification software, the marks received an overall AIM (Association for Automatic Identification and Mobility Standard) grade of “B” for axial uniformity, error correction, percent contrast, and print growth.
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Cutting Mild Steel
When cutting metal it is power density, not wavelength, that ultimately determines cutting performance. For example, with a constant beam diameter at the focusing optic, the Firestar f400 laser with an M2 value of 1.2 provides a spot size that is 14% smaller than a laser with an M2 value of 1.4. At a power level of 400 watts, Firestar’s smaller spot size equates to a power density increase of 1.43 Megawatts/cm2 at the material surface.
To demonstrate the f400’s cut quality we installed a 63.5 mm (2.5”) positive meniscus lens on our XY table. This optical setup provides a 100-micron (0.004”) spot size with a 1.8-mm (0.07”) depth of focus. Nozzle standoff—the distance from the tip of the gas jet nozzle to the steel surface—was set at 1.14 mm (0.045”) and the nozzle ID measured 0.88 mm (0.0345”). An oxygen gas assist pressure of 5.52 bar (80 PSI) through the nozzle provided a flow rate of approximately 1.33 CFM.
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The photo illustrates the narrow kerf width inherent
in CO2 laser cutting—the cut kerf in this example measures only 0.11 mm (0.0045”) wide!
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Using these settings, we cut this sample shape from a sheet of 2.6 mm (0.102”) thick mild steel using 400 watts of power at a cut speed of 1.8 meters per minute (70 inches/minute). As shown in the photograph, the edge is cleanly cut and exhibits no underside dross.
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Cutting PVC Flex Circuits
Many consumer electronic devices and even automobiles now incorporate some type of flexible printed circuitry in their design. These flex circuits can be as simple as thin ribbon conductors that replace bulky multi-conductor cables or they can be as sophisticated as complete analog or digital circuit assemblies sandwiched in multiple layers of flex material. Each of the three main flex circuit substrates have their pros and cons—polyimide has the highest temperature rating, yet is costly and absorbs moisture easily; aramid fiber has a high tear strength and costs less, but is susceptible to moisture and heat; polyester has good mechanical and electrical characteristics, low moisture absorption, and the lowest cost; however it also has the lowest maximum temperature rating of the group. In any case, all of these substrates are ideal candidates for some type of CO2 laser processing.
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Using 25 watts of power and 25 PSI of air assist,
the PVC Flex ciruit shown above produces a
clean finished cut edge.
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In this particular application, a Synrad sealed CO2 laser is used to cut individual finished circuits out of a larger sheet of the base PVC substrate. The XY table contains a cutting head equipped with a 63.5 mm (2.5”) positive meniscus lens that creates a 100-micron (0.004”) focused spot with a 1.8-mm (0.07”) depth of focus over the extents of the table.
To cut the 0.65-mm (0.025”) thick PVC circuit substrate, we set a cut velocity of 0.63 meters per minute (25 inches/minute) and applied 25 watts of power. Air assist at a pressure of 1.7 bar (25 PSI) is delivered coaxially with the beam through the nozzle to minimize melt back of the cut edges and provide a clean finished look to each circuit.
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Browse Synrad's Applications Database
Search our online library for more applications of Synrad's sealed CO2 laser technology. Sort by material, process, or industry.
http://www.synrad.com/search_apps/Default.htm
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Contact Us:
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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Copyright © 2006 SYNRAD, Inc. All rights reserved.
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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