SYNRAD, INC. - http://www.synrad.com  
Thursday, February 2, 2006
Issue 130

Cutting Alumina Ceramic

Marking Coated Paper

 Marking Powder-Coated Aluminum

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 Cutting Alumina Ceramic

As more and more products are manufactured using alumina ceramic materials, it has become crucial to fabricate ceramic parts as fast as possible while eliminating the fracturing that often occurs when traditional cutting methods are employed. CO2 lasers are widely used in these cutting or scribing operations because the laser responds precisely to pulsed or modulated input signals. Careful matching of cut speed to the pulse frequency and duty cycle of the laser’s input signal serves to minimize heat input into ceramic materials, allowing you to obtain clean cuts without inducing fractures.





This 1-mm thick fired alumina ceramic plate
shows the edge quality achieved by gating
the Firestar f201 laser with 800 µs wide pulses
at a frequency of 1.2 kHz.

For this application, we setup our XY stage with a Firestar f201 laser and directed the beam through a 63.5 mm (2.5”) positive meniscus optic. The resulting focused spot has a diameter of 100 microns (0.004”) and a 1.8 mm (0.07”) depth of field. In addition, high-grade clean dry air at a pressure of 5.5 bar (80 PSI) was delivered coaxially with the beam to enhance the cut process. While cutting, we gated the f201 laser with 800 microsecond pulses at a frequency of 1.2 kHz. Using these parameters on the 1 mm (0.04“) thick fired alumina sample, we were able to achieve cleanly cut edges using 200 watts of average power at cut speeds of 1.02 meters per minute (40 inches/minute).

 


Marking Coated Paper

Laser marking coated paper or cardstock-based packaging is perfect for food, cereal, film, pharmaceutical, and health care products because the 10.6-µm carbon dioxide wavelength fully ablates the inked coating down to the paper surface leaving a crisp, clean, high-contrast mark.

For products where lot numbers or expiration dates are mandated, laser marking during the actual packaging process eliminates the need to manage an inventory of pre-printed materials. Further savings are realized because laser marking does not require the consumables and maintenance overhead associated with other marking or labeling processes such as inkjet and thermal printers where make-up ink and transfer tape are reoccurring costs. Because our WinMark Pro laser marking software is easily configured to generate sequential numbers and date codes, the process of marking serial numbers, expiration dates, lot numbers, and batch codes is done without operator invention.







We used a 125 mm focusing lens with a spot
size of 180 microns (0.007”) to mark coated
paper products using 10 watts of power in a
cycle time of 0.15 seconds per mark.

The photograph shows an example of a serialized laser mark on inked paper. Our mark file was created with a single nine-character text string where the first four digits were set to increment serially from 0001 through 1000 while the remaining text was fixed. To do this, we created a text string using WinMark Pro’s built-in Simple stroke font at a Text Height of 4.75 mm (0.1875”). Auto Text Type was set to Serial Number Text and we configured the Serial Number Mask property so that only the first four digits are serialized. At a power level of 10 watts and a mark velocity of 40 inches per second (IPS), we achieved cycle times of 150 microseconds (0.15 s) per mark. Based on the distance between marks on consecutive packages, we could mark over 370 packages per minute in this application. Much higher line speeds are possible by simply increasing laser power and mark speed.


Marking Powder-Coated Aluminum

Although bare aluminum is reflective at CO2 wavelengths, coated aluminum provides an excellent mark surface and is a large part of the market for CO2 laser marking. In many cases, the process of treating aluminum parts with a paint or anodize coating to prevent corrosion is already factored into the manufacturing operation so no additional costs are incurred.

This example was done to test the feasibility of replacing an inkjet marker with a laser marking operation. To do this, we setup an FH Series marking head with a 125 mm lens to obtain a 180-micron (0.007”) spot over a maximum mark field of 85 mm × 105 mm (3.4” × 4.2”). We then created a 25-character, two-line text string in WinMark Pro using the Simple stroke font and set a Text Height of 4 mm (0.155”). To mark the part number, we choose a Velocity of 381 mm/sec (15”/s) and a Power (duty cycle percentage) corresponding to 25 watts.







Using 25 watts of power, we were able to mark
a 25-character text string in a cycle time of
0.44 seconds per part.
The accompanying photo shows the difference between a permanent CO2 laser mark and the existing inkjet mark (partially visible on the left). The cycle time required to mark this particular powder-coated part with 25 watts of power was 0.44 seconds.


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