How to Determine CO2 Laser Lens Focal Length |

How to Determine CO2 Laser Lens Focal Length

How to Determine CO2 Laser Lens Focal Length

Hello guys, welcome to MimoWork. Many people often are confused with the focal length adjustment when using a laser machine. To answer the questions from clients, today we will explain the specific steps and some attention to how to find the right co2 laser lens focal length and how to adjust it.

What is focal length for the CO2 laser machine

For laser machine, the term "focal length" usually refers to the distance between the lens and the material being processed by the laser. This distance determines the focus of the laser beam that concentrates the laser energy and has a significant impact on the quality and precision of the laser cutting or engraving.


Operation Method - Determining CO2 laser focal length

Step 1: Prepare Materials

Let’s look at the laser engraving machine and start our tutorial today. To focus the laser all you're gonna need is two pieces of cardboard. I'm gonna use one piece of cardboard as the wedge, simply because I have it kicking around, but you can use whatever you have like a rubber wedge.


Step 2: Find the CO2 Focal Length

The lens in your laser head focuses the laser beam down into a fine point, kind of like a triangle. This is the point where the laser light concentrates with the most powerful light energy.The focal length can be quite different, depending on the type of lens you have in your laser head. So I'm gonna go ahead and show you how to find the particular focal length. To start all you  need to do is make sure that one piece of cardboard is on an angle, as you can see I've used one scrap to wedge my cardboard. now  can engrave a straight line on your piece of cardboard with the laser. when that's done, take a close look at your line and find the point where the line is the thinnest. Mine looks the thinnest right about here, now you want to move your laser head over that point you just marked. Using the focal ruler to measure the distance between the smallest point you just marked and the tip of your laser head. This is the right focal length for your particular lens.

For the focal ruler, you can always make your own with your laser engraving machine. If you want to get the design file of the focal ruler for free, leave your comments below and send us an email.

Back to the laser machine, As you can see I got 5 millimeters with mine, which means to focus my particular laser, my laser head needs to be 5 millimeters away from the material.

Step 3: Double Confirm the Focal Length

So I’m going to shoot laser to the cardboard at different height. In this way, I can compare the actual burning marks to find the correct focal length . Put the cardboard scrap evenly on the working table and move the laser head over it at 5 millimeters high. Next, press the “pulse” button on your control board to leave burning marks. Repeat the same procedure, change the laser head at different height and press the pulse button. Now, we can compare the burning marks and we find the smallest spot is engraved at the height of 5 millimeters. You can choose either method to find the correct focal length.

Video Demonstration | how is the focal length of a lens determined

Some Suggestions

How to set appropriate CO2 laser focus distance?

For laser cutting

When cutting materials, we usually suggest adjusting the focus spot slightly below the material to get the best cut. For example, you can adjust the laser head 4mm or even 3mm above the material. In this way, the most powerful laser energy will be concentrated inside the material, better to cut through the thick material from the top to the bottom.

For laser engraving

But for laser engraving, you can move the laser head above the material surface a little bit higher, like 6mm or 7mm away. In this way, you can get a blur engraving result and enhance the contrast between the carving effect and raw materials.

How to select the right laser lens?

We also suggest you to choose a suitable lens based on materials and requirements. Shorter focal length like 2.0" means a smaller focal spot and focal tolerance, which is really suitable to laser engrave high DPI picture. For laser cutting, a longer focal length can guarantee cutting quality with a crisp and flat edge. under the circumstances, 2.5" and 4.0" are more suitable choices. Remember the longer focal length has deeper cutting distance. I list a table here regarding the focal lens choices.

how to choose suitable laser lens for your application
co2 laser machine lens

Any questions about how to choose suitable co2 laser lens for your application

For laser cutting thick material

Another method to find co2 laser focus

For thick acrylic or wood, we suggest the focus should lie in the middle of the material. Laser testing is necessary for your different materials. How thick acrylic can be laser cut? High power and lower speed is usually a well-advice choice, for a more detailed procedure you can inquire us!

Learn more about how is the focal length of a lens determined

Post time: Sep-04-2023

Send your message to us:

Write your message here and send it to us