Technological requirements of laser cutting thick stainless steel plate

1. Nozzle selection Nozzle diameter laser cutting thick stainless steel plate

The nozzle diameter determines the gas flow shapegas diffusion area and gas flow rate into the notch, which affects the stability of melt remova and cutting

The larger the air flow into the notch,the faster the speedand the proper position of the workpiece in the air flowthe stronger the ability of jet to remove melt.

The thicker the stainless steel,the larger the nozzle should be used.

The larger the setting of the proportional valve and increase the flowthe pressure can be ensured and the normal section effect can be cut.

Nozzle specifications

The specification of the nozzle here mainly refers to the end aperture

Taking Precitec's cuttina nozzle as an exampleits aperture ranges from 1.5mmto 5.0mm

The selection of aperture is mainly related to cutting power

The greater the powerthe more heat generatedand the greater the amount of gas required.

When we cut the plate below 3mm,the nozzle with 2.0mm aperture is generally selected

When cutting 3mm to 10mm platesselect 3.0mm nozzle;

When cutting plates above 10mmnozzles of 3.5mm and above are required.

Single-layer nozzle or double-layer nozzle?

Generally speakingdouble-layer nozzles are used for oxidative cuttingauxiliary gas is oxygenand single-layer nozzles are used for melt cutting(auxiliary gas is nitrogen.

However some lasers have special instructions whether to use single layer or double layer. In this caseoperate according to the laser instructions.

2. Auxiliary gas selection and gas purity

Various auxiliary qases such as oxygennitrogen and airare often used in stainless stee

laser cutting

Different gas types have different cutting effects.

Oxygen is black sectionthe air is light yellow and nitrogen can keep the primary color of stainless steel from being oxidized

Nitrogen is the preferred auxiliary gas for stainless steel cutting

Recommended oxygen and nitrogen purity:

The ordinate is the gas flow test value the abscissa is the adjustment setting,different

gas pressure changesand different colors represent the test conditions of different nozzle diameters.

It can be seen from the graph that the flow is determined by the set gas pressure and nozzle diameter which is a linear positive correlation.

3. Focus position

In order to ensure the cutting effect and protect the nozzle from damage a coaxial test needs to be conducted before cutting to ensure that the nozzle is coaxial with the laser output beam.

Focus position test method

Stick the transparent tape paper on the end face of the nozzle outletadjust the laser

output power for drillina. opserve whether there is a centrahoe on the transparent tape

paper and the position of the central holeand synchronously adjust the adjusting screw on the mirror cavity handle until the hole punched by the laser on the transparent tape paper coincides with the center of the nozzle.

The focus is different, and the thickness,material and quality can be cut are also different.

Cutting different materials and thicknesses need to be adjusted into different focus.

Before cutting,measure the actual zero focusand test and analyze the cutting process parameters based on the zero focus

Negative defocus is the main process selection direction for stainless steel cutting

4. Influence of laser frequency adjustment and pulse duty ratio on cutting quality Influence of frequency change on the cutting of stainless steel thick plate:

The frequency decreases from 500-100hzthe cutting section effect becomes fine and the stratification is slowly improved

When the frequency is set to 100Hzit cannot be cut and the blue light is reflected

Find out the best frequency range through the change of frequency

In order to ensure the best cutting sectionthe perfect matching of pulse times and single pulse energy must be ensured.

Influence of pulse duty cycle change on stainless steel thick plate cutting

The pulse duty cycle of 45% is the critical value

Continue to reduce the duty cycle,and the undercut mark appears on the lower surface

When the duty cycle increases to 60%the section becomes roughthe stratification is obvious,and the cutting surface turns yellow.

The pulse duty cycle refers to the proportion of beam irradiation time in each pulse.

Frequency is the number of times peak power occurs in a pulseand duty cycle is the ratio of peak power to low power in a pulse