DDM Laser

Light Amplification by Stimulated Emission of Radiation

Appendix

PROBLEMS AT THE FOCUS IN C02 LASER PROCESSING SYSTEMS

THE NOZZLE ASSEMBLY AND ASSIST GAS
The nozzle and assist gas conditions have as much influence on the laser cutting process as the optics!

  1. Check that the focus point is at the required distance below the nozzle tip. In typical cutting operations this will be perhaps 2-5mm, but this distance may be greater in the cutting of thick section metals. Large changes in localised gas pressure can occur along the axis away from the nozzle tip. This effect must be taken into account when replacing a lens, perhaps from an alternative supplier, if minor re-focusing is needed.

  2. Is the nozzle aperture size correct for the required operation?

  3. Is the nozzle condition adequate? Badly worn nozzle tips can lose processing efficiency.

  4. Check that the nozzle aperture is not clipping the beam. If clipping is occurring the nozzle tip will get hot after a few minutes of operation of the laser.

  5. Check that the correct amount of assist gas is emitted from the nozzle tip, and not leaking elsewhere in the focus head assembly.

  6. Check that the type and purity of the assist gas is appropriate to the process (especially when cutting with oxygen).

  7. If using gas bottles, check that the bottle is not nearly empty. Occasionally contamination has been noted towards the end of a bottle supply.

  8. Is the nozzle set at the correct ‘stand-off’ distance from the workpiece?

  9. Is the assist gas dry and clean (not depositing moisture or other contamination onto the lens)?

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