When using a 12kW Fiber Laser Cutter it is best to adjust focus positioning, focus & focal adjustment, oxygen pressure and cutting speed for optimal results. Below is a case study on cutting 40 mm Carbon Steel

Power: 12000w
Nozzle selection: double 1.6
Cutting focus: 14.2
Cutting speed: 0.25m/min
Duty cycle: 100%
Frequency: 5000Hz
Cutting height: 1.2mm
Cutting air pressure: 50kpa

laser cutting height effects

Laser cutting height

Three cuts were made using 0.8 mm clearance, 1.2 mm clearance, and 1.5 mm clearance, with no other parameters adjusted.

Here we can clearly see that 1.2 mm clearance produces the best cut.

Oxygen pressure

Three cuts were attempted using 40 kpa, 50 kpa, and 60 kpa.

At 40 kpa, the pressure was insufficient to cut through the material.

With 50 kpa, we achieved a perfect cut.

And at 60 kpa, the pressure is too high and over-burn slag generates across the bottom.

laser cutting oxygen pressure

Fiber Laser cutting speed

Here, speeds of 0.15m/min, 0.25m/min, and 0.35m/min were compared.

At 0.15m/min, we can see the deep grooves in the cut edge caused by the laser being in contact with the material for too long.

At 0.35m/min, we can see the slag that accumulates as there is insufficient time for it to be blown away by the assist gas.

0.25m/min produces the surface quality required.

Focus position

Focus of 12, 14.2, and 14.5 were tested.

Setting the focus to 12 is shown to be too small by the long deep grooves produced.

A focus of 14.5 resulted in the improved texture, but burn residue across the bottom.

14.2 was determined to be the optimal focus.

larger positive focus results in smoother and brighter cuts in carbon steel

positive focus in laser cutting results in smoother brighter cuts

Tips for cutting thick carbon steel plates with a 12KW laser:

Optimal Nozzle Size

When cutting thick carbon steel plates, it is recommended to use full power and small nozzle cutting. This approach ensures a smooth cutting surface with minimal taper. Generally, a smaller nozzle diameter with faster airflow speed provides better molten material removal. It is also suitable for cutting thin plates. However, when cutting thick plates, a larger nozzle diameter with slower airflow speed is preferred. Using a larger aperture nozzle to cut thin plates at high speeds can cause residue. Thus splashing and potentially damage the protective lens.

Adjusting the Light Spot

The primary challenge when cutting high-power carbon steel thick plates is nozzle heating. Therefore, it is crucial to accurately adjust the light spot to the center of the nozzle for optimal output.

Finding the Right Focus

To achieve a smooth cutting surface, it is advisable to choose a smaller nozzle size and a larger positive focus. However, excessive focus adjustment can lead to nozzle heating, resulting in unstable cutting. It is essential to eliminate external factors first and then determine the maximum focus value that the nozzle size can withstand before making adjustments.

By following these tips, you can effectively cut thick carbon steel plates using a 12KW laser, ensuring high-quality results and stable cutting performance

laser cutting selecting nozzle and focus

Choose the correct nozzle and focus

When cutting carbon steel thick plates, the preferred method is to use oxygen and a positive focus approach. As the thickness of the carbon steel increases, it is important to adjust the focus accordingly. The thicker the material, the larger the positive focus should be, resulting in a larger spot on the surface of the sheet.

In order to achieve optimal cutting results, it is recommended to use a larger nozzle size ranging from D1.0mm to D2.0mm. This allows for efficient material removal and ensures a smooth and precise cutting process.

Nozzle Temp and Focus

In order to maintain stable processing conditions, it is crucial to prevent the nozzle from overheating and experiencing further temperature increases. To achieve this, it is important to carefully select appropriate nozzles and focal positions based on the thickness of the carbon steel being cut.

Laser cutting engineers have conducted tests on high-power lasers that emit continuous full-power light under various combinations of nozzles and focal points. These tests aim to assess the heating conditions of the nozzles and determine the optimal settings for different carbon steel thicknesses.

laser cutting nozzle temps and focus

Centering the Nozzle on the machine

To ensure optimal cutting quality, it is essential to set the focusing lens in a way that aligns the focused laser beam precisely at the center of the nozzle hole. Ideally, the deviation of the focused laser beam from the center of the nozzle should not exceed +0.002″.

When the laser beam is not properly centered within the nozzle, it can have a significant impact on the cutting quality. In such cases, the quality of the cut may vary depending on the direction of cutting. In extreme scenarios, the material may not be cleanly cut or properly separated in certain directions, while achieving good cuts in others.

During torch cutting of carbon steel, if cutting is performed in a direction opposite to the eccentricity (non-centered position), sparks may form on the surface of the sheet. This occurrence highlights the importance of maintaining proper alignment and centering of the laser beam within the nozzle to ensure consistent and high-quality cutting results.