Marking and Cutting Leather

Decorating leather products is another consumer market that is well-suited to CO2 lasers and marking heads. The laser’s 10.6-micron wavelength beam reacts with the leather to produce a customized hand-tooled look in only seconds. Leather shoes, belts, handbags, and jackets are some of the many items that are marked using CO2 lasers and marking heads. In addition to marking, decorative patterns and shapes are easily cut into the leather simply by increasing laser power or reducing optical scanner velocity.

To mark and cut the oval leather pendant with the dove image shown in the photo, we set up a Firestar t100 laser and FH Flyer marking head. The Flyer head was equipped with a 200 mm lens that provides a 290-micron (0.011”) spot with a 5 mm (0.118”) depth of focus across the mark field.

Using WinMark Pro, we began by importing a stylized drawing of a dove that was drawn in a vector graphics format. After sizing and positioning the image, we set a Power (duty cycle percentage) equal to 90 watts and a marking Velocity of 3048 millimeters per second (120 inches/sec).

This pendant was marked and cut from a sheet
of 0.052” thick leather using 90 watts of power
in an overall cycle time of 2.33 seconds. The
image was marked at a speed of 120 inches
per second (IPS), while the shape was cut out
at a velocity of 5 IPS.

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We engraved this contrasting 2D code on a
ferrite insulator core at a speed of 18 inches
per second using 25W of power in an overall
cycle time of 0.48 seconds.

Drilling Small Holes

CO2 lasers excel at drilling small holes (small defined as less than 250 microns or 0.01" in diameter). Small holes are drilled directly without trepanning, resulting in reduced cycle times. Direct drilling also highlights one of the unique characteristics of lasers - the focused spot from a single laser can produce a range of hole sizes in a range of different materials due to a phenomena called “tip processing”.

The term "tip processing" means that only the central part of the Gaussian beam is used for drilling (or marking). As the circular diameter of the Gaussian beam decreases, the power density level at the outer edge increases, which corresponds to an effective beam diameter. Every material has a threshold of power density required for processing—marking, cutting or drilling. Below this level the material is unaffected, hence the term "tip processing".

Ultimately, the wavelength of the laser determines the minimum focused spot you can achieve. For a Synrad laser, the 10.6-micron CO2 wavelength can easily achieve spot sizes as small as 100 microns (0.004“) without the addition of specialized optics. With a properly sized expander/collimator and an aspheric lens; however, spot sizes down to 25-30 microns (roughly 2.5 times the CO2 wavelength) are possible. With a smaller effective diameter beam, power density is concentrated in a smaller area resulting in a smaller heated area.

In the case of the polyacetal nozzles shown in the photograph, a burst or train of pulses from the laser delivered a precise amount of energy into the material. The final hole diameter depends on where that energy level matches the threshold of the material on the beam's Gaussian profile. Additionally, the number of pulses, pulse duration, and pulse frequency enter into the equation. Alter the number of pulses to make small increases in hole diameter; change pulse duration and/or frequency to create larger holes.

In the case of the polyacetal plastic shown
here, nozzle diameters ranged from 75 microns
to over 300 microns. This variety of hole
diameters is due to two features of the laser:
(1) the Gaussian mode of the beam, and (2) the
fine energy input control.










As shown in the illustration above, the method
of drilling a hole smaller than the spot size is
to precisely control the laser's energy input in combination with a high threshold material.