Introduction
FSL confidently offers UV laser glass marking solutions that provide exceptional results. In this article, we will specifically discuss soda-lime glass, as other types of glass such as fused silica and borosilicate are less common and will be addressed separately.
Benefits
UV marking offers several advantages over CO2 glass marking. The marks are frosted white, smooth to the touch, and up to 100 times more precise than CO2 marks. This is due to the smaller spot size and higher repetition rate of UV lasers. The result is a clean, sandblasted appearance without cracking or shards. While CO2 marking is simpler and always works, its results are not as sharp or accurate as UV marking.
Key Points
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A minimum power of 5W is recommended for optimal results. Both 5W and 10W work well, while 3W is less effective.
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Successful results have been achieved using 265mm, 160mm, or 3D telecentric lenses.
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Glass is semi-transparent, meaning only a portion of the laser's energy is absorbed. To achieve the desired marking, concentrated heat must be generated to produce thermal lensing effects.
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Accurate focus is essential. Using an anodized aluminum card and the FSL focus test, determine the perfect focus within 0.5mm, then set the focal distance 2mm below the glass surface. The images below illustrate the consequences of improper focus: marks appearing subsurface, on the backside, or inconsistently, depending on the angle of the laser.
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Recommended settings: 2-3mm below focus (into the material), 100mm/sec using a 254mm lens at 1000dpi. Alternatively, use a 0.05mm wobble with 0.01mm wobble spacing at 2000mm/sec, always at 100% power and 45kHz frequency using a 355nm 5W air-cooled UV laser. Insufficient heating will cause the laser to pass through without marking the surface. However, with proper settings, the glass will look flawless when engraved with a UV laser.
We can have good focus from 307-304mm so 3mm using 254mm lens. Setting it 2mm below focus gives 1.5mm on either side for variation in glass thickness or misalignment.
Note how even 0.5mm above the focus produces undesirable subsurface marks in glass! 307.5mm part of the 3 and 5 are are on the top surface and the rest is below. At 309mm, nearly the entire image is on the back the surface. At 308.5mm the image floats mostly in the middle like it would engraved with the 3D lens but it's not as even with portion of the bottom still on the top surface.