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How to solve the problem of thick plate perforation with residue affecting cutting

When laser cutting thick plates, the residue (slag) generated by perforation affects the cutting quality is a common but optimizable problem. These residues are usually caused by improper energy control during the perforation process, mismatch of gas parameters or unreasonable process parameters. The following are the system solutions and optimization recommendations:

perforation process optimization

1. Using progressive perforation (layered perforation)

  • For thick plates (e. g.> 15mm), avoid the use of one-time high peak power perforation, and use stepped power increment or segmented perforation to gradually penetrate the material and reduce slag splashing.
  • Operation method: Set the “segmented perforation” parameter in the cutting software, first preheat with a lower power, and then gradually increase the power to penetrate.

2. Adjust the perforation parameters

  • Reduce peak power and extend perforation time: reduce splashing of molten material caused by instantaneous energy bursts.
  • Increase the perforation frequency (duty cycle): control the laser pulse energy output rhythm to avoid excessive melting.
  • Example parameter reference (using 20mm carbon steel as an example):
  • Power: 1000-1500W (adjusted according to equipment capacity)
  • Perforation time: 1.5-3 seconds
  • Pulse frequency: 200-500Hz
  • Auxiliary gas pressure: phased adjustment (see below)

 

Auxiliary gas control

1. Gas type and pressure optimization

  • Carbon steel: Oxygen (O₂) is used as the auxiliary gas, but the pressure needs to be controlled. In the perforation stage, lower pressure (0.5-1bar) can be used first, and then the cutting pressure can be switched to high pressure (1.5-2.5bar) after penetration to avoid excessive reaction of oxygen to produce a large amount of slag.
  • Stainless steel/alloy steel: use nitrogen (N₂) or air, use medium and low pressure (6-10bar) for perforation, and switch to high-purity nitrogen high-pressure cutting after penetration.

2. Gas delay and early shutdown

  • Switch gas before perforation is completed: switch to the gas parameters for cutting when penetration is about to be completed to help blow off slag in the hole.
  • Increase the gas pre-blowing time: blow 0.5-1 second before perforation to clean the hole area and cool the surrounding material.

Focus Position and Nozzle Adjustment

1. Focus position

  • When perforating, use a relatively negative amount of defocus (the focus is below the surface of the plate) to increase the aperture and facilitate slag discharge. For example, a 20mm carbon steel may set the focal point 3-5mm below the surface.
  • After penetration, adjust the focus to the best position according to the cutting requirements.

2. Nozzle selection and height

  • Use larger diameter nozzles (such as φ2.0-φ3.0mm) to enhance gas coverage and promote slag discharge.
  • Ensure that the height of the nozzle is moderate (usually 1.0-2.0mm) to avoid gas diffusion caused by too high and sputtering damage caused by too low.

Process path and programming skills

1. Pre-drilled lead hole

  • For ultra-high thickness plates (e. g.> 30mm), small diameter pilot holes can be drilled mechanically first, and then laser cutting can be started from the pilot holes to avoid direct perforation.

2. Set the perforation point offset

  • When programming, make the perforation point deviate from the actual contour line by 1-2mm, and then move from the offset point to the contour line during cutting to avoid the residue accumulation area.

3. Cutting path optimization

  • Spiral perforations or circular cutting starting points are used to spread the slag to the non-cutting area.

Equipment and maintenance inspection

1. Laser state

  • Check whether the output power is stable, ensure that the lens/protective mirror is clean, and avoid insufficient perforation caused by energy attenuation.

2. Gas purity and flow

  • Ensure the purity of the gas (especially nitrogen/oxygen), and regularly check whether the gas path is blocked or leaking.

3. The nozzle is aligned with the optical component.

  • Regularly calibrate the concentricity of the nozzle and the laser beam to ensure the symmetry of the gas flow.

Materials and Environmental Factors

1. Surface treatment of plate

  • Clean the rust layer, oil stain or coating on the surface of the plate before cutting to reduce the participation of impurities in the reaction.

2. Plate flatness

  • Ensure that the plate is flat and avoid gaps that cause gas leakage and energy reflection.

Parameter debugging process recommendation

1. First, fix other parameters, gradually adjust the perforation time and power, observe the amount of slag generated, and find the balance point.

2. Record the optimization parameters and establish the process database of different materials/thicknesses.

3. Testing and verification: several perforation tests are carried out on the waste material to confirm that the slag is reduced before formal cutting.

Summary: Quick Check of Key Points

Through the above comprehensive adjustment, the thick plate perforation residue can be significantly reduced, and the cutting quality and efficiency can be improved. If the problem persists, it is recommended to contact the equipment manufacturer for hardware testing or process support.