100 mm lens Approx 2" process field |
160 mm lens Approx 4.5" process field |
254 mm lens Approx 7.5" process field |
330 mm lens Approx 9.5" process field |
420 mm lens Approx 12" process field |
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100mm Beam is the sharpest like a surgeon's scalpel, but depth of focus is very small |
160mm Best all around for marking and deep engraving metals using a 20 watt pulsed fiber laser and higher. |
254mm Larger lens is better for marking many plastics, since plastics have a low melting point. Deep engraving is Ok using a 50 watt pulsed fiber laser or higher. 10 and 20 and 30 watt pulsed fiber lasers may not overcome reflectivity of some shiny metals Good lens for marking surgical tools that need to survive passivation Good for marking anodzied aluminum |
330mm Deep engraving using higher powered pulsed fiber lasers. Good lens for marking surgical tools that need to survive passivation Good for marking plastics Good for marking anodzied aluminum |
420mm Good for marking anodzied aluminum Good for marking plastics Best focus range |
Focus Range 100mm | Focus Range 160mm | Focus Range 254mm | Focus Range 330mm | Focus Range 420mm |
.020" (.5mm) | .080" (2mm) | .240" (6mm) | .43" (11mm) | .64" (16mm) |
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1. Focusing on the top of a material is OK IF the material is thin. Thin is relative and depends on the laser used, wattage of laser, material, material thickness and lens size 2. Extreme example: Using a flatbed CO2 laser, a 1.5" lens and 1/2" acrylic, the material may cut through if using high enough power but expect the bottom .25" to be rough looking (chatter). 3. Expect a non flat material edge due to the laser's natural taper, as shown above |
1. Focusing below the material surface is helpful when cutting thicker materials. Focus depth is limited and will vary per lens. 2. In the previous example, simply by raising the table or lowering the laser head (depends on the laser being used) can use more of the lens' natural focus range. This will help with the "chatter" at the bottom and help keep a flatter material edge. If chatter is not eliminated then a larger lens can be used since it will have a better focus range - but be aware! at the cost of energy loss - so prepare to set the speed slower! Also, be aware the cut's line width (Kerf) will also be wider. (more material will be removed because the larger lens focused spot will be larger. 3. I typically like to re-focus halfway between the material top and the middle, especially using thicker material. 4. Higher laser wattage helps to overcome focus issues. Higher wattage is a major consideration when purchasing the laser. |