The right choice of laser cutting nozzle doubles the efficiency.
Although it may seem like a small and inconspicuous part, its role is not insignificant. It needs to resist the rebound of molten debris and control the area and size of gas diffusion.
Therefore, the quality of the nozzle for laser cutting head is one of the important factors that determine the quality of laser cutting. Today, we will discuss how to choose the right nozzle.
I. Is There a Big Difference Between Nozzles of Different Qualities?
Yes, there is a significant difference, as the material and precision of the nozzle play a decisive role in conductivity, thermal conductivity, difficulty of adjustment, and protection of the laser head.
A good nozzle can protect the optical lens inside the cutting head and release auxiliary gas to the surface and slit of the cutting material, guiding the gas to assist in cutting and removing the slag, leaving a clean cut.
Therefore, the quality of the nozzle directly affects the lifespan of the cutting head and the quality of the workpiece being cut.
Generally speaking, the nozzles that come with the original cutting head are priced higher, which has made third-party nozzles very popular. However, not every third-party manufacturer has the production capacity for such consumables.
In the price war of fiber laser cutters in recent years, the prices of laser cutter accessories have also been driven down. Pursuing low prices blindly and ignoring quality will result in more harm than good.
II. What Are the Consequences of Improper Selection of Nozzles?
If the nozzle design and maintenance are not appropriate, the processing accuracy may be insufficient, resulting in a reduction in the gas flow rate and unstable airflow direction, which can affect the melting of materials during the cutting process and produce molten debris. Thicker materials may even become impossible to cut.
Selecting a nozzle that is too large
Rough upper stripes with serrated edges (right)
Selecting a nozzle that is too small
III. What Are the Types of Nozzles?
Currently, there are two main types of nozzle designs: “low-speed nozzle” (gas flow rate is lower than the speed of sound) and “high-speed nozzle” (gas flow rate is close to the speed of sound).
Factors that affect the performance of the nozzle include the gas pressure in the cutting head cavity, the diameter of the nozzle, the internal shape of the nozzle, and the shape of the nozzle outlet.
The working principle of a high-speed nozzle is similar to the exhaust principle of a rocket or jet engine, which has an accelerating effect on the gas entering the nozzle. Therefore, a high-speed nozzle can produce better cutting results for viscous materials.
If a regular low-speed nozzle is used, the surface pressure of the workpiece will fluctuate significantly as the cutting height changes, which can lead to unsatisfactory cutting results.
IV. How to Select a Nozzle?
Laser cutting is currently recognized as one of the most efficient, high-quality, and precise methods of metal processing.
Various factors affect laser cutting, and the nozzle is one of them. Selecting the appropriate nozzle when cutting different materials can simplify the processing. But how can we correctly choose the right nozzle? Let’s take a look today.
The nozzle, also known as the copper nozzle, is one of the very important components in laser cutting. Located at the lower end of the cutting head, both the laser beam and auxiliary gas act on the cutting material through the nozzle. Its main function is to gather the auxiliary gas and form high pressure, releasing it onto the surface and into the kerf of the cutting material.
This blows away the parent material that has melted and vaporized during the cutting process, leaving a clean kerf. At the same time, it prevents pollutants like molten slag and dust from bouncing back up, thus protecting the internal lens.
To achieve better cutting sections, it is necessary to control the concentricity of the laser beam and the nozzle center, which is one of the important factors affecting cutting quality. Therefore, the nozzle must be coaxial with the laser beam to get better cutting sections.
When the nozzle center and the laser beam center are not coaxial, the effects on cutting quality are as follows:
- The cutting gas is sprayed from the center of the nozzle, which is the center point where the plate needs to be cut. If the laser is not at the nozzle center, there will be a deviation between the laser action point and the actual, leading to a noticeable inconsistency between the actual cutting and the expected effect.
- If the laser is not at the nozzle center, the beam will hit the inner wall of the nozzle during normal operation, which can severely burn the nozzle and affect the actual cutting effect.
To verify whether the laser beam and the nozzle are coaxial, the following steps are required for testing:
- Stick a piece of transparent tape over the nozzle opening, with the circular edge completely overlapping the tape;
- Adjust the device power to about 100W, and use the dot shooting mode to irradiate the transparent tape with the laser;
- Remove the transparent tape and observe the relationship between the circular edge and the position of the laser hole.
If the hole is in the center of the circle, this means that the laser beam and the nozzle are coaxial, and no adjustment is needed. If the hole is not coaxial with the center of the circle, or if the hole cannot be seen (the laser beam hits the inner wall of the nozzle), you need to adjust the adjustment screw on the laser cutting head. Repeat steps 1-3 until the laser hole coincides with the center of the nozzle.
Selection of nozzle type:
Nozzles are divided into single layer and double layer nozzles. Single layer nozzles have relatively slow gas flow speeds and are commonly used for cutting metals like stainless steel, aluminum alloy, and copper, often using nitrogen as the auxiliary gas.
Double layer nozzles have fast gas flow speeds, suitable for high-speed cutting, and are often used for cutting carbon steel, generally using oxygen as the auxiliary gas, and the cutting surface usually turns black due to oxidation.
Selection of nozzle size:
The size of the nozzle opening determines the gas flow speed acting on the cutting material, thus affecting the removal of the molten material. The larger and faster the airflow entering the kerf, the stronger the ability to blow away the molten material.
In theory, the thicker the plate, the larger the nozzle should be used. However, the larger the aperture of the nozzle, the greater the chance of molten material splattering upwards during cutting, which shortens the lens life.
Deformed nozzles or nozzles with molten droplets will affect the cutting effect. Therefore, the nozzle should be handled with care to avoid impact or deformation, and any molten droplets on the nozzle should be cleaned up promptly.
Factors to consider when selecting a nozzle:
There are several factors to consider when selecting a nozzle:
Processing needs: Single-layer nozzles used in laser equipment are mainly used for cutting stainless steel and aluminum plates with nitrogen, while double-layer nozzles are mainly used for cutting carbon steel with oxygen.
Material: Nozzles are commonly made of two materials, purple copper and brass. Purple copper has better conductivity and thermal performance than brass.
Size: The aperture size of the nozzle determines the gas flow rate and the shape of the gas field. Generally, when cutting sheets below 3mm, it is recommended to use a nozzle with a diameter of 1mm, and for 3mm or more, a nozzle with a diameter of 1.5mm is recommended. For cutting over 10mm, a nozzle with a diameter of 2mm or above is recommended.
Processing accuracy: A good laser head nozzle should have a concentricity of 0.03mm, while nozzles with a size of 1.0mm or less should have a concentricity of 0.02mm or better. Nozzles with high-precision concentricity not only reduce the initial debugging during the processing, but also effectively avoid damage to the laser head caused by the high-energy laser hitting the inner wall of the head.
V. Introduction to Common Nozzles
There are several types of nozzles commonly used in industrial applications. Here are some of the most common ones:
Single-Layer Nozzle
Features: Conical inner wall with high gas flow rate for slag blowing.
Purpose: Melting cutting of materials such as stainless steel and aluminum plate.
Double-Layer Nozzle
Features: Double-layer composite nozzle with an added inner core on the basis of a single-layer nozzle.
Purpose: Double-layer 2.0 or larger for carbon steel sand cutting
High-speed Double-Layer Nozzle
Features: The nozzle has a pointed shape, and the three holes on the edge of the inner core are larger than those of a regular double-layer nozzle.
Purpose: It is mainly used for high-power, high-speed, and high-quality cutting of carbon steel up to 20mm thickness with a smooth and bright surface finish.
High-speed Single-Layer Nozzle
Features: The nozzle has a pointed shape, with a conical inner wall that features a stepped design.
Purpose: It is mainly used for high-power, high-speed cutting of carbon steel with a thickness above 20mm, resulting in a smooth and bright surface finish. It is also suitable for oxygen-focusing cutting applications.
High-speed Single-Layer Nozzle
Features: The nozzle has a pointed shape with a conical inner wall and a larger nozzle orifice area.
Purpose: It is mainly used for high-speed cutting of carbon steel with a thickness above 20mm, resulting in a smooth and stable cutting performance with better cutting quality.
Boost Nozzle
Features: Improved from a single-layer nozzle, the nozzle has a step layer at the nozzle orifice.
Purpose: It can be used for high-power cutting of stainless steel and carbon steel with nitrogen or compressed air at low pressure.
VI. How to Install and Adjust a Nozzle?
Nozzle Installation Steps:
- Unscrew the old nozzle.
- Install the new nozzle and tighten it with appropriate force.
- After replacing the nozzle, recalibrate the capacitance.
As an example, for a BLT 12kW laser cutting head with a focal point paired with a nozzle (0 focal point must be calibrated):
- Double-layer 1.2E nozzle: for cutting 3mm-12mm carbon steel plate, focal points between 5-11.
- Double-layer 1.4E nozzle: focal points between 9-14.
- Double-layer 1.6E nozzle: focal points between 11-16.
- Double-layer 1.8E nozzle: focal points between 13-18.
- SP single-layer 1.2 nozzle: focal points between 8-13.
- SP single-layer 1.4 nozzle: focal points between 10-15.
- SP single-layer 1.6 nozzle: focal points between 12-17.
- SP single-layer 1.8 nozzle: focal points between 14-19.
It is important to properly install and calibrate the nozzle to ensure optimal performance and cutting quality.
VII. Recommendations for Common Nozzles
| Laser | Cutting thickness (bright surface cutting of carbon steel with oxygen) | Suggested nozzle |
|---|---|---|
| Low power laser (≤6000W) | 16-20mm | 1.4D-1.6D general conical nozzle |
| High power laser (≥6000W, using Raycus 12kW as an example) | 3-12mm | 1.2E dual-layer high-speed nozzle |
| 12-14mm | 1.2B-1.4E dual-layer high-speed nozzle | |
| 16-20mm | 1.4E-1.6E dual-layer high-speed nozzle | |
| 22-35mm | SP1.4-SP1.8 single-layer high-speed nozzle or 1.4E-1.8E dual-layer high-speed nozzle | |
| 35-40mm | SP1.6-SP1.8 single-layer high-speed nozzle or 1.6E-1.8E dual-layer high-speed nozzle |
The quality of nozzles on the market varies greatly. It is recommended to carefully distinguish them according to the above content and purchase through regular channels.
