When your CO2 laser loses power, it can cause issues with cutting and engraving, leading to poor results. Understanding the common causes and how to troubleshoot them can help you maintain your laser’s efficiency. Finding exactly where the issue is can be difficult sometimes, but there are some common culprits.
Optics (mirrors and lens)
CO2 lasers use mirrors to direct the laser beam from the tube to the material, and a lens to focus the beam. One of the first things to check and one of the most common reasons for laser cutter power loss are dirty optics. Mirrors are used to bounce laser beam that comes out of a laser tube and guide it to the lens and the material. Laser beam carries lots of heat and clean mirrors reflect most of that heat, but dirty ones absorb it and that not only reduces the laser beam power but is also heating the mirror itself and can damage it or even crack it. Same applies to lenses. Dust, stains and any kind of residue can cause heat accumulation so it is important to check your optics regularly and keep them as clean as possible as it can save you lots of headaches and some money down the road.
Fix – Start by removing any dust that accumulated on the surface with rubber blower. Avoid using shop floor air lines, as they can contain oil, water, and dust particles that can damage the optics. When handling the lenses, be careful and try not to touch the surface with your bare fingers, as the oils from your skin can smudge and damage the lens coating. It’s recommended to wear surgical gloves to prevent this. For cleaning, use acetone or IPA (Isopropyl Alcohol) with Q-tips, lens tissues, or microfiber cloths. Be careful not to scratch or drop the optics, as they are extremely fragile. Before reassembling, ensure that the mounts are also clean. Additionally, don’t forget to clean the glass at the tube exit, where the laser beam emerges.
Beam alignment
Bad alignment can also be the cause for reduced cutting power so you need to check if you laser beam is aligned correctly. Misalignment can occur if the machine is moved or bumped, so regularly check and realign the mirrors using an alignment tool. Before hitting the surface of the material laser needs to bounce off of 3 mirrors and it needs to run parallel to the axis and hit each and every one of the mirrors in the center no matter the location of the laser head. Even a slight misalignment can result in a significant power loss.
Fix -To test if your beam is aligned correctly you will need a few pieces of masking tape and some patience.
Start from the mirror closest to the laser tube. Stick the piece of masking tape in front of the mirror (over the mirror hole) but be careful not to get sticky part onto the mirror itself because it will leave a mark and some excess glue on the surface. Move the laser head as far away from the mirror as possible. Use test fire button (pulse button on some controllers) to fire you laser. Safety is important so don’t forget to close the lid and use safety glasses. Resulting burn mark should be at the center of the hole. If not, use screws on top of the mirror mount to mirror position. Once first mirror is aligned repeat the same procedure for the other 2. Here is a very good video explaining how to align your mirrors.
Focus
Laser beam coming out of a laser tube is to wide (¼ of an inch or about 6mm) to be useful for engraving or cutting. The job of a lens is to narrow down that beam and focus all that power to a point where you can get the most out of it.
Focal length will vary depending on the diameter of the focusing lens. Most of the lasers comes with some sort of a calibrator (usually a piece of acrylic) you can use to set correct focal length for you lens. This can be helpful but often not precise enough so what you’ll want to do is find the focal length for your lens and make a calibrator for it.
To do this you need to perform a ramp test which takes only a few simple steps:
- Lower you laser bed and place piece of material on it
- Elevate left or right side of the material by placing something underneath it. The goal is to set your material at an angle (30-45° or so). Make sure that the laser head is not catching the higher end of the ramp.
- Create a job which contains only one line and make sure its shorter than the length of the piece.
- Run the job. You will get a line of a different thickness. Find the place where the line is the thinnest and measure the distance from that place to the tip of your laser head. This is your focal length.
Laser bed alignment
If you are getting inconsistent results on the different parts of laser bed then most likely your bed is not perfectly aligned and the distance from material surface and laser head varies. To check if your bed is aligned correctly, move the laser head to one of the corners and use your calibrator and set the focus. Now move the laser head to the other corners and to the middle and compare focal length with your calibrator. If its not the same in all corners it means that you need to align it manually.
For laser systems with motorized bed (z-axis) you will first need to:
- Find the tensioner and unscrew it to release the belt.
- Move the belt off of the pulleys so the lead screws can rotate freely.
- Adjust lead screws until you get equal distance from head to bed in all 4 corners.
- When aligned, put the belt back on but be careful not to rotate the pulleys.
- Tighten the tensioner back on and measure the head-bed distance in all corners again.
Again this is much easier to comprehend in a video form, so here is a good video explaining this process:
Other culprits
Check the Laser Tube.
The laser tube is where the laser beam originates. Over time, the tube naturally degrades and loses efficiency, especially if it’s nearing the end of its lifespan. Typical CO2 laser tubes last between 1,000 and 10,000 hours, depending on the quality and usage. Signs of a failing tube include a noticeable drop in power and visible arcing inside the tube. If you suspect the tube is the issue, measure its output with a power meter. If the output is significantly lower than the tube’s rated power, consider replacing it.
Examine the Power Supply.
The power supply unit (PSU) is critical as it delivers the necessary electrical power to the laser tube. If the PSU is faulty or if the connections are loose, the laser will not receive enough power to operate at full capacity. Check the connections between the PSU and the laser tube to ensure they are secure. Using a multimeter, test the output voltage of the PSU. The correct voltage should match the specifications of your laser tube. If the voltage is too low, or if the PSU shows signs of failure (such as inconsistent power output), it might need to be repaired or replaced.
Check the Cooling System.
CO2 lasers generate a significant amount of heat during operation. An effective cooling system, usually involving water or air cooling, is essential to prevent the laser tube from overheating. If the laser tube overheats, its efficiency drops, leading to power loss. Regularly check the coolant level in your cooling system and ensure there are no leaks in the tubing. The water chiller should be functioning properly, maintaining the correct temperature. A rise in temperature beyond the recommended range can cause immediate and permanent damage to the laser tube.
Check the water temperature.
This can have a big influence on your laser tube power. Generally you’ll want to operate your laser tube between 16 and 24 °C. Anything higher and you will notice increased power loss, so make sure that you are not overheating the tube. Also, different fluids can also cause different problems as there are examples of people having power issues caused by using water with addition of car antifreeze. Just stick to distilled water – its your safest bet.
Smokes and fumes.
If you have a lot of smoke on the laser path it can obscure laser beam causing it to lose power. Check the fume extractor and make sure that its actually extracting most of the fumes. Clean it if necessary.
Bad wiring.
This can cause power issues especially on cheap Chinese machines since using cheap materials and cost saving all around includes wires, which are often not even soldered but just manually connected and isolated with electrical tape.
Software and Settings.
Sometimes, power loss issues are not due to hardware but to software settings. Double-check your laser’s settings in the control software. Ensure that the power and speed settings are appropriate for the material you’re working with. If the settings are too conservative, it might seem like your laser is losing power. Additionally, make sure the firmware of your machine is up-to-date, as updates can sometimes improve performance and fix bugs that might affect power output. Its a long shot, but its worth trying if nothing else provides results.
Troubleshooting power loss in a CO2 laser involves a systematic check of all critical components, from the laser tube and mirrors to the power supply and cooling system. Regular maintenance, such as cleaning and alignment checks, can prevent many power loss issues. By keeping your machine in good condition and being aware of potential problems, you can ensure that your CO2 laser continues to perform at its best. If you still encounter issues after following these steps, it might be necessary to consult a professional technician to diagnose and fix the problem.
