Synrad Applications News

SYNRAD, INC. - http://www.synrad.com
Thursday, December 10, 2009
Issue 227

Laser applications at a glance

Laser Marking Glass Lenses
Cutting Stainless Steel Mesh
Marking Rubber and PVC-Coated Wire Insulation

Laser Marking Glass Lenses


Cutting Stainless Steel Mesh


Marking Rubber and PVC-Coated Wire Insulation

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.


Laser Marking Sensitive Glass Lenses

Glass marking is a common application for CO2 lasers because glass absorbs the 10.6µm CO2 wavelength very well. The process heats the glass substrate, so for very sensitive glass applications, extra care must be used to ensure that the glass isn't destabilized by tiny micro-fractures produced by the marking process. Fortunately, Synrad's WinMark Pro Laser Marking Software provides many options to control and optimize marks to reduce heat input and micro-fracturing.

For this application, we were asked to mark glass lenses with a 16-character alphanumeric 2D code containing serial number and date code data. The 2D code format is an excellent choice to hold this type of information because 2D codes can contain a very high data density while covering only a small area on the edge of the lens; this capability was critical to this application so that the performance of the lens is not reduced.

    


Close-up of 2D code marked on glass lens

This 6 mm x 6mm 2D code contains serial number and date code data. It was marked in a cycle time of 0.53 seconds using a 25W laser and FH Flyer Marking Head.

For these tests, we used a Synrad 25 W laser and an FH Flyer marking head equipped with a 125 mm focal length lens and controlled by Synrad's WinMark Pro software. This setup produced a focused spot size of 180 mm (0.007") on the glass lens surfaces. The mark file consisted of a 6 mm x 6 mm (0.24" x 0.24") 2D code with a mark Velocity set to 508 millimeters per second (20 IPS) and the Mark Passes property set to 3. In addition, the 2D Barcode Bitmap property was set to No and the 2D Barcode Circle Radius property was set to 10%.

This careful selection of marking properties eliminates micro-fracturing of the glass lenses after marking. Performing multiple high-speed mark passes allows heat to dissipate quickly into the surrounding glass substrate, whereas a single slow mark pass tends to heat the glass more, which produces larger fractures. In addition, by setting the 2D Barcode Bitmap property to No, individual cells of the code are marked as small, unfilled circles instead of being marked with the default raster scan fill. Marking the 2D code cells as unfilled circles eliminates overfilling (print growth errors) and reduces heat input.

The resulting 2D code produced by these settings was completed in a cycle time of 0.53 seconds per lens. The cells of the code still appear as filled cells due to the small cell size and the reduced circle radius. These codes were scanned and achieved "A" grades when a dark surface was placed behind the lenses and the lighting was optimized to eliminate reflected glare from the lens surface.


 

Cutting Stainless Steel Mesh

Woven stainless steel mesh is used for a variety of applications depending on the mesh count, which is the number of openings per linear inch. This 120-mesh sample consists of 0.07 mm (0.0027") diameter wire woven in a plain square weave to create a 145-micron (0.0057") opening. Stainless steel 120 mesh is often used in gas diffusion, for filtering hydraulic fluids or fuels, and for separating and classifying solid particles. As a point of reference, the mesh filter in your kitchen faucet is typically 60-mesh material.

To cut this stainless steel mesh, we set up our XY table with a 63.5 mm (2.5") positive meniscus lens, which provides a 100-micron (0.004") spot and a 1.8 mm (0.07") depth of focus. Air, at a pressure of 2.8 bar (40 PSI), was selected as the assist gas instead of oxygen to prevent overburning of the fine mesh. With this cutting setup, we achieved cleanly cut edges using 100 watts of power at a speed of 7.62 meters per minute (300 inches/minute).

    

Cut Stainless Mesh Sample

We achieved cleanly cut edges on this fine woven stainless steel mesh using 100 watts of power at a speed of 300 inches per minute.

 



 

Marking Rubber and PVC-Coated Wire Insulation

There are almost as many types of electrical wire insulation as there are uses for wire and cable. Nylon, polyimide, silicone rubber, PTFE, XLPE (cross-linked polyethylene), PVC, and polypropylene are a few of the more common insulation coatings applied to wire. In particular, silicon rubber and PVC (or PVC-coated) insulation provides a great surface for obtaining high contrast CO2 laser marks.

To mark the wire samples shown, we set up a Firestar t-Series laser and FH Series marking head equipped with a 125 mm HP (high power) focusing lens. The 125 mm lens provides a 180-micron (0.007") spot size with a 3 mm (0.118") depth of focus. Using one of WinMark Pro's built-in stroke fonts, we created a 21-character part number with an actual Text Height value of 0.062" for the small diameter wire and a height of 0.077" for the larger diameter wire.

    


Laser Marked Wires

High contrast marks were obtained on this silicon rubber coated wire (small) and PVC coated nylon wire (large).


The 16 AWG (small) wire has a silicon rubber coating and was marked at a Velocity of 80 inches per second (IPS) with 32 watts of power. Cycle time to mark all 21 characters was 0.14 seconds. The 10 AWG (large) PVC-coated nylon wire was marked at a Velocity of 50 IPS using 60 W in a cycle time of 0.19 seconds.




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http://www.synrad.com/search_apps/Default.htm


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