Originally Posted by
rayscott
Hello,
I am not sure if your lens is 20mm diameter or otherwise. It doesn't matter a lot.. except that your lens needs to be able to receive the entire laser beam. I would hope your lens is bigger diameter. As the laser tube wattage goes up, the beam diameter is also expected to be larger.
The focal length of the lens is depicted by the curvature of the lens. A 50mm lens will have more curvature than a 76.2mm lens. The actual diameter of the lens could be the same.
Your cutting application would decide what lens you want to use. I think that a 63.5mm Focal Length lens would work just fine for your needs.
I would NOT go to using a 76.2mm lens yet. It is normal that the minimal spot size gets larger as the focal length gets longer... but you need the longer focal length while cutting thicker materials.
Thank You,
Ray Scott - Rabbit Laser USA