Checking And Adjusting Coaxiality in Laser Cutting

Achieving stable, high-quality laser cutting depends on more than just power, speed, or focus settings. One of the most easily overlooked yet crucial factors is coaxial alignment—the alignment of the laser beam center with the nozzle center. Poor coaxial alignment can lead to inconsistent cuts, excessive slag, kerf offset, and even frequent nozzle damage.

What is coaxial alignment in laser cutting?

Coaxial alignment means that the center of the laser beam is perfectly aligned with the center of the nozzle orifice, and both share the same central axis with the auxiliary airflow. In other words, the laser beam, nozzle orifice, and cutting airflow should be on the same central axis when they leave the laser head.

When all three are aligned, the laser energy and gas pressure will be symmetrically distributed at the cutting edge, ensuring a smooth and uniform processing. If the three are not aligned, the gas will shift laterally, the molten metal will not be able to escape smoothly, and the cutting direction will become unstable.

Why is coaxiality so important?

Even if your power, focus position, and cutting parameters are set correctly, poor coaxial alignment can ruin the entire cutting result. Here are the most common defects caused by coaxiality misalignment:

2.1   Poor cutting edge quality

• A large amount of slag appears on one or both sides of the workpiece

• Other sides remain clean

• Rough or uneven edges

This situation occurs because the airflow direction is deviated, preventing the molten metal from being removed evenly.

2.2   Excessive burrs and slag

Coaxiality deviations can hinder the flow of the assist gas, causing molten material to adhere to the cutting edge.

2.3   Cut Offset and Contour Deformation

When the laser beam does not enter the material perpendicularly, it can cause:

• Tilted cuts

• Insufficient dimensional accuracy

• Part deformation

2.4   Nozzle overheating or burning

When the spark is deflected, it may directly strike the nozzle tip, shortening the nozzle's lifespan and potentially damaging the protective lens.

2.5   Reduced cutting stability and increased operating costs

In the long run, coaxiality deviations can lead to:

• More scrap material

• More rework

• More frequent nozzle replacement

• Reduced overall equipment efficiency

For any production environment—especially medium-to-high power cutting—maintaining precise coaxiality is not an option, but a fundamental requirement.

Coaxiality Inspection and Adjustment Steps (Step-by-Step Guide)

Step 1: Attach transparent tape to the nozzle.

Cut a small piece of transparent tape and carefully attach it to the nozzle opening. Ensure the tape surface is clean and completely adhered.

Step 2: Set the focus to 0 and fire a short pulse.

Set the focus position to 0 mm, press the "Laser" button (manual pulse mode), and fire a single low-energy pulse. This will burn a mark onto the tape.

Step 3: Check the laser spot position

Remove the tape and observe the burn mark location:

• Ideal situation: The laser spot is exactly in the center of the nozzle's circular opening.

• If off-center: This indicates that the coaxial alignment is not satisfactory and adjustments must be made.

Step 4: Laser Coaxial Alignment

Adjust the beam to the center position using the adjustment screws (usually two Allen screws located on the laser head):