Laser cutting machine nozzle loss of several common cases

In fiber laser cutting, the nozzle is an extremely critical and vulnerable consumable. Its loss directly affects the cutting quality, gas consumption and production costs. Common nozzle loss mainly has the following several situations:

Physical impact and wear (This is the most common and direct cause of wear and tear.)

1. Collision with plate: in the process of feeding and blanking, perforation (especially slag splashing during blasting and perforation of thick plate), or machine tool positioning/edge finding, the end face of nozzle directly impacts on the plate, resulting in deformation, scratch or notch.

2. Collision with fixture: During the movement of the cutting head, due to the wrong programming path or the zero drift of the machine tool, the nozzle may hit the fixture.

3. Long-term wear: Even if there is no violent collision, in the long-term high-speed cutting process, the high-speed flow of cutting gas (especially with tiny metal particles) will continue to scour the inner wall of the nozzle, resulting in the gradual expansion of the aperture, out of round, affecting the gas flow field.

Consequences: The cutting gas flow field is disordered, resulting in rough cutting surface, hanging slag, increased burrs at the bottom, and even unable to cut through.

Slag splashing and clogging

During the cutting process, molten metal spatter adheres to the inner wall or end face of the nozzle.

1. Inner wall adhesion: When cutting galvanized sheet, stainless steel or coated sheet, the viscous slag generated is easy to splash and adhere to the inner wall of the nozzle hole, gradually accumulating to reduce the aperture and asymmetric airflow.

2. End face adhesion: The slag accumulates on the lower end face of the nozzle, which changes the distance from the nozzle to the plate (nozzle height) and affects the gas dynamics effect.

3. Complete blockage: In severe cases, the slag may completely block the nozzle, and the airflow is interrupted, resulting in instantaneous cutting failure and may burn the nozzle.

Consequences: unstable cutting, poor section quality, frequent suspension of cleaning, reduce production efficiency.

Thermal Damage and Ablation

1. High temperature ablation:

• Perforation ablation: When penetrating thick plates, high-power laser acts on a point for a long time, generating extremely high heat and reverse splashing molten metal, which will directly ablate the lower end surface of the nozzle and the edge of the inner hole.
• Plasma ablation: When the cutting parameters (such as air pressure, power, speed) do not match, a high-temperature and high-density metal vapor plasma cloud may be formed above the incision. The plasma cloud will absorb the laser energy and spread upward, directly ablating the inside of the nozzle, and selecting irreversible damage.

2. Thermal deformation: Working in a high temperature environment for a long time, the nozzle material may undergo microstructure changes or deformation, especially the nozzle with poor quality.

Consequences: the nozzle aperture becomes larger or irregular in shape, the gas focusing ability is permanently reduced, and the cutting ability is drastically reduced.

Improper installation and use

1. The installation is not vertical/loose: the nozzle is not tightened or is not concentric with the cutting head, resulting in gas leakage and eccentric flow field. Slight looseness will also increase wear in cutting vibration.

2. Select the wrong nozzle type or size:

• Aperture mismatch: Use large-aperture nozzles to cut thin plates (insufficient gas pressure, energy diffusion), or use small-aperture nozzles to cut thick plates (insufficient gas flow, poor slag discharge).
• Wrong type: The double-layer nozzle is used when using a single-layer nozzle, which affects the cutting stability and anti-reflection protection of highly reflective materials (such as aluminum and copper).

3. Cutting parameter setting error:

• Too high/too low air pressure: too high air pressure may cause airflow disturbance, too low can not effectively discharge slag and cooling.
• Improper setting of nozzle height (Z axis): too close to the plate is easy to collide, too far away is poor gas protection effect.

contamination and corrosion

1. Gas pollution: the use of cutting gas (oxygen, nitrogen, air) is not pure, containing oil, moisture or solid particles, these pollutants will accumulate in the nozzle or the nozzle corrosion.

2. Environmental dust: The environmental dust in the workshop is large, and the dust is sucked into the cutting head and attached to the nozzle and lens.

How to reduce nozzle wear and extend life?

1. Standard operation:

• Perform sound edge-finding and elevation procedures to ensure a safe distance.
• Use reasonable power and blasting height (if any) during perforation.
• Take it gently, use special tools and ensure tightening and centering during installation.

2. Optimization of process parameters:

• According to the material and thickness, scientifically select the nozzle type and aperture (general principle: small holes for thin plates, large holes for thick plates; single layer for oxygen cutting, double layer for nitrogen cutting).
• Optimize the combination of air pressure, power, speed, nozzle height and other parameters to avoid excessive slag and plasma.

3. Strengthen maintenance:

• Regular inspection: check the nozzle end face and aperture every shift or when changing materials, and use a centering rod (centering instrument) to ensure concentricity.
• Regular cleaning: use special nozzle holder cleaning tools and soft materials (such as wooden toothpicks, non-woven fabrics) to clean the inner hole and end face, it is strictly forbidden to use metal tools to hard scrape.
• Timely replacement: once the nozzle is found to have visible damage (notch, oval, rough inner wall), or the cutting quality continues to be unstable, it should be replaced immediately.

4.Security of the working environment:

• Use high purity, dry cutting gas.
• Keep the cutting area and sheet relatively clean.
• Ensure the stability of the machine tool guide rail and reduce the jitter of the cutting head.

Summary: Nozzle loss is the result of a combination of factors. Through standardized operation, process optimization, fine maintenance and selection of high-quality consumables, abnormal losses can be minimized, and production costs can be effectively controlled while ensuring cutting quality.