Assist gas

The role of assist gas in laser clean edges

September 25, 2020

Everybody likes a clean edge. Clean, precise edges can also be life-saving. And that’s exactly why laser cutting is used in creating life-saving medical devices. Laser cutting is also essential for cutting the metal bodies of airplanes and the stainless steel used in most of the equipment you find in a catering kitchen. Such precision and clean edge would not be possible without the use of assist gas in the laser cutting process. 

Assist gas is also known as cutting gas, process gas, auxiliary gas or blanketing gas. It is applied at the point where the laser beam meets the material to be cut. This compressed assist gas is supplied through an assist gas inlet leading into the cutting head; the gas fills out in the space between the focusing lens (or the protective lens, if there is one) and the nozzle outlet through which the focused laser beam is also guided.

The main role of assist gas is to expel material that builds up in the area around the kerf (cutting width). Without assist gas, there would be no clean edges. Assist gas serves many other purposes as well:

  • Protecting and cooling the focusing lens

  • Limiting the heat affected zone (HAZ)

  • Purging the beam path when using inert gas

  • Boosting the cutting power when using reactive gas
  • Types of assist gas

    The choice of assist gas depends on both the cutting process and the material being cut. Assist gases can generally be classified as inert and reactive. Nitrogen is the most commonly used inert gas in laser cutting and the top choice for cutting stainless steel and aluminum where a high-quality finish is paramount. An excellent finish means that you save money in post-processing.  

    Oxygen is the most commonly used reactive gas for laser cutting and is preferred for the laser cutting of mild steels. While oxygen’s reactivity has the effect of speeding up the cutting process, it results in an edge that needs further processing. 

    It must be noted that impurities in assist gas can significantly affect the final cut quality. When using nitrogen as an assist gas, the slightest drop in quality can lead to the discoloration and dullness of the steel. In the case of both gases, impurities can lead to lens damage and inconsistencies in the metal being cut.

    Advantages of on-site nitrogen generation

    Nitrogen is a preferred assist gas in laser cutting operations. The preference for nitrogen in operations is on account of not only its role as an assist gas but also its effect of purging the path of the laser beam as it makes its way through the plenum.

    A few set-ups rely on nitrogen supplied by third parties. Such dependence increases not only costs and safety concerns but also quality issues. Many steel fabricators looking to put in place reliable and beneficial systems prefer to generate their own on-site nitrogen supply. The cost savings from having an on-site nitrogen supply system are immediately apparent with some estimates going up to 90%. Moreover, the capital investment recovery period is about a year or less, depending on use.

    If you would like to reduce costs by producing your own nitrogen on site, explore Pneumatech’s range of nitrogen generators. Or get in touch with us right away. Call at +49 (0)2841 788 480 or e-mail to support-eu@pneumatech.com.