Newsletter 178: Kiss-Cutting Keypad Templates, Cutting Stainless Steel Mesh, Marking Glass Mirrors

SYNRAD, INC. - http://www.synrad.com
Thursday, January 10, 2008
Issue 178

Kiss-Cutting Keypad Templates

Cutting Stainless Steel Mesh

Marking Glass Mirrors

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.

Kiss-Cutting Keypad Templates

Kiss cutting—a process where the laser cuts through a self-adhesive upper layer without cutting through the lower backing material or paper liner—is a common CO2 laser application made possible by the ability to precisely control laser energy. In galvanometer-steered (optical scanner) applications, laser control is provided by our FH Series marking heads, which generate a 20-kHz PWM frequency to obtain the highest mark quality. Additionally, FH Series marking heads provide position and resolution accuracy measuring out four decimal places to several ten-thousandths of an inch for accurate beam placement mark after mark.

The requirement for this project was to precisely kiss-cut keypad templates from sheets of laminated plastic film. Exacting power control was especially important in this application since the template design had to be completely cut out of 0.08 mm (0.003“) thick plastic without damaging the 0.04 mm (0.0015”) thick backing film.

These keypad templates were kiss-cut from sheets
of 0.003”-thick laminated plastic film using 60 watts of power at a speed of 50 inches per second in a cycle time of 0.73 seconds.

We accomplished the task using a Synrad sealed CO2 laser and FH Series marking head driven by our WinMark Pro laser marking software. A 125 mm focusing lens was installed in the marking head to create a 180-micron (0.007”) spot size with a 3 mm (0.118”) depth of focus. The keypad template, created as a .PLT (HP Graphics Language) file, was imported directly into WinMark Pro at full-size, one-to-one scale.

To kiss-cut the keypad design, we assigned the following mark properties to the imported graphic object: Power, duty cycle percentage, was set to correspond to a laser output of 60 watts, Velocity was set to 1270 millimeters per second (50 inches/second), and Resolution was set to a value of 300. At these settings, the entire design was cleanly kiss-cut, without damaging the backing material, in a cycle time of 0.73 seconds.

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).

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 Glass Mirrors

Glass marking is a proven application for CO2 lasers and mirrored glass is no exception. The silver surface is ablated and the underlying glass substrate is fractured in a controlled manner as in a normal glass mark. With this process, text and barcodes marked on the mirror’s back side are easily visible from the front.

We marked this sheet of mirror glass with an ECC200 Data Matrix code using a Firestar v40 laser, FH Series marking head and WinMark Pro laser marking software. The marking head was equipped with a 125 mm focusing lens that provides a 180-micron (0.007”) spot size and a 3 mm (0.118”) depth of focus over the extents of the mark field.

In WinMark Pro, on the Marking tab, we set a Power value (duty cycle percentage) that corresponds to 33 watts, a Velocity of 381 millimeters per second (15 inches/second), and a Resolution of 50. We then set Spot Marking Style to Yes, and entered a Spot Mark Duration of 10 (1 millisecond). On the Format tab, we set 2D Barcode Bitmap to No and set 2D Barcode Circle Radius to 50%.

This 2D code was marked on the rear (silver side)
of a glass mirror using 33 watts of power at a speed of 15 inches per second. The 15-character code
was marked in a cycle time of 1.09 seconds.

When these property values are specified, here’s what happens: The 2D Barcode Bitmap property (No) forces WinMark to mark each filled cell using circles instead of raster-filled squares. With Spot Marking Style set to Yes, the circle is marked by a series of discrete spots and as Resolution is lowered, fewer and fewer spots are used to define the circle’s circumference. At very low Resolution values (50 is the minimum value), only a single spot is marked for each circle (barcode cell). Finally, Spot Mark Duration keeps the beam on for a specific time period, which in the case of glass, controls heat input and fracturing.

Cycle time to mark the 15-character code was 1.09 seconds and we read the resulting mark on both glass and silvered sides using scanners from Microscan (Quadrus EZ) and RVSI (CM4000 vision system). When scanned from the rear (silvered side), we achieved overall AIM grades of “B” with individual grades of “A” for Symbol Contrast, “A” for Print Growth, “A” for Axial Uniformity, and “B” for Unused ECC. Although passable grades are achieved when scanning 2D codes from the front side of the mirror, Print Growth grades drop somewhat (depending on the angle of the mirror to the scanner) because the scanner “sees” the reflected image as well.

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