Cost-effective option for laser cutting

The situation

High quality gases

Common assist or auxiliary gases that are used for laser cutting are nitrogen (N2) or oxygen (O2). Crucial points that make you select the approppriate gas are the wished result, the thickness of the material that is going to be cutted and the cutting speed which is desired. Usually they are delivered in bottles and in very high quality. Nonetheless the number of on-site gas generators running 24/7 hrs. is rising for big machines .

These processes are quite expensive as those gases represent the absolute majority of the whole operating costs.

Common application scenarios

N2 and O2 in comparison

N2 - Nitrogen

Surface has direct welding, coating and strong corrosion-resistant properties
Suitable for non-ferrous metals like stainless steel, aluminium (alloys), brass, galvanized sheets
No oxide layer on the cut edges which results in a clean oxide-free edge (non-oxidative cutting)
Consumes a lot of N2 (reduced efficiency due to no reaction heat of N2)

O2 - Oxygen

Suitable for carbon steel and also low pressure cutting
Chemical reaction of Q2 accelerates cutting process
For deep & precise cuts (minimal heat-affected zones)
Not suitable for materials like stainless steel or aluminum, as it can lead to oxidation and deteriorate the quality of the cut edges
Oxide films, hardening of material, black or yellow colorization

The alternative

Compressed air as assist or auxiliary gas

Advantages while using

No changing of bottles = no down time , no additional supply chain, less costs
Good for acrylic and plastics
Air assisted cutting is approx. 20% faster in alloy and stainless steel
Very cost-effective option - largely depends on energy costs as m³ of N2 is at least three times more expensive than m³ of compressed air (some regions factor >10!)
'Retrofit' - shift to compressed air as assist gas rather easy
no electricity needed for compressed air treatment

Application take-aways

Contains approx. 80% of nitrogen (N2) already
Contains approx. 20% of oxygen (O2) already
Lower cutting efficiency than O2 but higher than N2
Most efficient for material thicknesses < 2mm
When replacing the assist gas, laser cutting machine manufacturers know best which qualities and operating parameters are required - settings will be somewhat in the middle of O2 and N2 cutting mode

Suitable use cases

Cooling: of laser generator and other components
Cleaning: generally during cutting, removing residuals
Air curtain: protecting lense and laser precision
Power source: to move pneumatic cylinders/ switches

Typical operating system

If compressed air is used for lascer cutting, a compressor is typically located nearby the laser cutting machine. The compressor must be equipped with solid dryers and filters.

Compressed gases are introduced into the cutting head through a gas delivery system, consisting of tubes, hoses and nozzle. Within the cutting head the gas flow is directed precisely to the point where the laser beam interacts with the material.

Pressure

Pressure is a very important gas parameter and the laser cutting machine does not like pressure fluctuations. Pressure is typically maintained in the range of 4-7 bar (60-100 psi) for creating an effective air curtain. In smaller compressed air systems also air curtains of below 2 bar (29 psi) are used. If the compressed air is used to assist cutting, higher pressures are required (up to 16 bar/ 232 psi).

Flow rate

The flow rate of the compressed air is adjusted for the desired air curtain. Therefore it can vary and depends on the laser cutting machine's requirements. The typical flow rates range lies between 100-300 l/min (3-10 cfm). In compariosn big machines need up to 4000 l/min (141 cfm) when used for cutting.

In general the pressure dew points are very low between -40°C to -60°C (-40°F to -76°F) ; rarely -20°C (-4°F)

Furthermore we are talking about class 1 or 2 according to ISO 8573-1 in particulates and residual oil.

Success stories

Retrofit

From nitrogen to compressed air

A customer wants to use compressed air instead of nitrogen. After evalutaing the situation on-site and considering all needed parameters, we came to the conclusion that we are able to meet the desired requirements. Furthernmore the customer decided to install flow measurement as well to observe different gas consumptions.

Compressed air best practice I

Technical design matters

The customer was using compressed air already as assist gas but made bad experience: damaged mirrors, lenses and laser heads lead to enormous costs in replacement. After considering the requirements at the cutomer's place, it was clear that the existing compressed air treatment was only generic but not adequate for the application. The debris of the desiccant dryer and oil vapor polluted the mirrors and ruined the laser beam. The improvement with a better after filtration was done quickly.

Compressed air best practice II

The difference of drying

This time a refrigeration dryer was installed and did leave a lot of condensate water inside the pipes. Due to the requirements of the customer, a membrane dryer was recommended also as an appropriate filtration. Since then the customer has a stable pdp of -12.4°C , no condensation and no problems with pollution in his compressed air system.

Our expertise

Your case

Since laser machine is complex , it is possible that the integration and operating parameters differ between machines. Following the size of the machine (e.g. laser power, cutting speed, etc.) the treatment components can’t simply be scaled up.

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