How to control the cutting quality of laser cutting machine

1.The effect of cutting speed on cutting quality

For certain laser power density and material, cutting speed corresponds to an empirical formula, as long as the above access threshold, material cutting speed is proportional to the laser power density, increase power density can improve the cutting speed.

The power  besides  related to the laser output power,  also related to the beam quality mode.

In addition, the characteristics of beam focusing system, namely the size of the light spot after focusing, also have a great influence on laser cutting.

The cutting speed is inversely proportional to the density of the cut material.

When other parameters remain the same, the factors that improve the cutting speed are: improve the power (in a certain range, such as 500 ~ 2 000W);

Improved beam mode (e.g., from high to low order to TEM00);

Reduce the size of the focusing spot (such as focusing on short focal length lens);

Materials (such as plastic, plexiglass, etc.) that can be used to cut off the initial evaporation.Cutting low-density materials such as white pine, etc.

Special for metal materials, in the case of other process variables constant, laser cutting speed can have a relatively adjusting range and stays a satisfactory cutting quality, the adjustment range when cutting thin metal is a slightly wider than thick.

Sometimes the cutting speed is slow, which can lead to the discharge of the hot melt material to the surface, making the cut surface rough.

 

2.The influence of focus position adjustment on cutting quality

Because the laser power density has great influence on cutting speed, the selection of lens focus is an important problem.

The light spot size of the laser beam is directly proportional to the focal length of the lens, and the light beam is very small after focusing on the short focal length lens.

The power density in the focus is very high, which is beneficial to the cutting of materials.

However, its disadvantages are that the focus is very short and the balance is small, which is generally applicable to high-speed cutting thin materials.

Because long focal length lens has wider focal depth, as long as it has sufficient power density, it is suitable for cutting thick workpiece.

After determining which focal length lenses are used, the relative position of focus and workpiece surface is important to ensure the quality of cutting.

Due to the high power density of the focal point, most of the time the focal point of the cutting is just at the surface of the workpiece, or below the surface.

During the whole cutting process, it is important to ensure that the relative position of the focus and the workpiece is stable.

In some cases, the heat of the lens is caused by the cooling of the lens, which causes the focal length to change, which requires the focal position to be adjusted in a timely manner.

When the focus is in a better position, the slot is smaller and more efficient, and the better cutting speed can get better cutting results.

In most applications, the beam focus is adjusted to just under the nozzle.The surface spacing of the nozzle and workpiece is usually about 1.5mm.

3.Influence of auxiliary gas pressure on cutting quality

In general, the material cutting needs to use auxiliary gas, which mainly involves the type and pressure of auxiliary gas.

Usually, the auxiliary gas and the laser beam are ejected, protecting the lens from contamination and blowing the bottom slag of the cutting zone.For non-metallic materials and parts of metal materials, use compressed air or inert gas to deal with melting and evaporation materials while inhibiting excessive burning of cutting areas.

For most metal laser cutting is the use of reactive gas (O2) as long as it is, the formation and hot metal oxidation exothermic reaction, this part of the additional heat 1/3 ~ 1/2 can improve the cutting speed.

The gas pressure size is an important factor in ensuring the auxiliary gas.

When cutting thin material at high speed, high gas pressure is required to prevent the backside of the incision from sticking slag (the hot glue to the workpiece can also damage the cutting edge).

When the thickness of the material is increased or the cutting speed is slower, the gas pressure should be reduced properly.

In order to prevent the plastic cutting edge cream, it is also better to cut the pressure with lower gas pressure.

The laser cutting practice shows that when the auxiliary gas is oxygen, its purity has obvious influence on the cutting quality.

A 2% reduction in oxygen purity would reduce the cutting speed by 50% and lead to a significant reduction in the quality of the incision.

4.Influence of laser output power on cutting quality

For the laser of continuous wave output, the laser power size and mode will have important influence on cutting.In practice, high power is often set to achieve high cutting speed or to cut thick materials.

But the beam mode (where the beam energy is distributed across the cross section) is sometimes more important, and when it comes to output power, the patterns often get slightly worse.

It is often found that high power density and better cutting quality are obtained in the focus area under the lower power condition.

The mode is not consistent throughout the effective working life of the laser.The condition of optical elements, the subtle changes in the mixture of the laser work, and the fluctuation of the flow of flow will affect the model organization.

To sum up, although the factors affecting laser cutting are more complex, the cutting speed, focus position, auxiliary gas pressure and laser power and mode structure are four important variables.

In the process of cutting ,if you find cutting quality  gets worse, you can check and regulated in time.

 

Anne

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Email:xintian121@xtlaser.com