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Laser Systems
Are you considering buying a laser? Today's demanding fabrication industry requires more quality at faster speeds and lower operating costs. A properly-installed laser system could help meet these demands.


Arcet, through its partnership with Controls Corporation of America, can help you in the design and selection of your laser gas delivery system. To get a preview on how the process works, click here.


Here's What You Need To Know Before You Install A
Laser Gas Delivery System
Our "Ten Key Questions To Answer" introduction on the advantages of laser cutting, welding and other materials processing applications drives many companies to purchase new laser systems to best do the job.


Laser material processing has advantages over other thermal or mechanical processes because of minimum HAZ (Heat Affected Zone), minimum thermal overload and stress to parts, no mechanical contact with work peice, high processing speeds and high level of automation.


CO2 lasers require a variety of gases to perform correctly. Gases will be used for laser beam generation, purging of the laser cavity and beam delivery system, and assist gases will be necessary for cutting or welding. When purchasing a laser, here are ten questions which should be answered concerning the gas delivery systems requirements:


  1. Based on the laser processing requirements which type of CO2 laser will be purchased? What is the brand and model?


    Many different brands of lasers are available in today's market. The power rating of the CO2 lasers can range from 1kW to power in excess of 20kW. Specific applications require more laser power, and additional power can also increase processing speeds. When cutting stainless steel or in welding applications, more laser power is required to handle the application. In addition to the different power choices available, the design of the laser resonator may require either premixed laser gases or a combination of three or more gases to generate the laser beam. The laser gas delivery system is dependent on the laser manufactures' selection of laser gas. Always confirm the specifications in the installation manual for the correct purity and flow of the laser gases.


  2. Will the applications require more than one laser? If so, will the additional laser be of the same brand and model?


    In a job shop where many low volume jobs may be required, one laser may not be able to handle the wide variety of applications. When different lasers are in the same work place, care must be taken to ensure the correct laser gas is supplied to each laser. This may require additional gas delivery systems.


  3. What are the applications the laser will be expected to perform? Will it be used for cutting and welding?


    If the laser is expected to perform a wide range of cutting applications, the gas delivery system must be designed to handle the largest workload. When cutting a variety of materials of type and thickness, the demands on the cutting assist gas can vary in flow and pressure requirements. Assist gas pressures can be as high as 450 PSI (30 BAR) with flow rates in excess of 2700 SCFH (75 m3/h). Oxygen and nitrogen are the commonly used assist gases for cutting but certain materials may require argon or helium. Shielding gases for laser welding can be argon, helium or a mixture of the two depending on the materials to be welded. For multi-purpose machines the availability of the correct assist and shielding gas supply systems may avoid costly down time.


  4. What are the materials to be laser processed? Is carbon steel the primary material or will other materials also be processed?


    When cutting materials with a laser the proper selection of the assist gas can be of primary importance and the gas delivery system must be designed to support the operation. Common practice was the use of oxygen for cutting carbon steel and the use of nitrogen for cutting stainless steel, each application requiring different pressure, flows and purity requirements.


    Oxygen in higher purity (99.95%) is capable of cutting at a faster rate than standard industrial oxygen (99.5%). Some laser manufacturers, to ensure the mirror finish required on stainless steel, have required Grade 5 (99.999) nitrogen purity. Also, nitrogen has been used on carbon steel cutting when the plate needs to be painted or powder coated. The use of oxygen will leave an oxide layer on the cut edge inhibiting the finishing process. When using nitrogen the oxide will not form.


    The beam quality is of most importance when cutting stainless steel or other non-ferrous materials. The use of moisture-free nitrogen is recommended for beam delivery purge. Air delivered from a house air compressor or other system will contain a large amount of moisture. This moisture can have a detrimental effect on the beam quality producing an inferior cut.


  5. What is the thickness of the materials? What is the largest thickness to be processed?


    The thickness of the material to be processed can be directly related to the power of the laser when cutting stainless steel or other non-ferrous materials. The laser and the gas delivery systems for the assist gas must be designed for the maximum cutting capacity of the laser. When cutting stainless steel, the pressure and flow requirements may exceed the normal capacity of the gas delivery systems. A "booster" system or an additonal temporary assist gas delivery system may be required to handle the cutting of thicker stainless steels.


  6. How many days a week and hours per day will the laser be on line?


    Many customers run their lasers round the clock to take advantage of their laser's superior efficiency and production capacity. The longer the up time of the laser, the greater the consumption of both laser and assist gases. The gas delivery system must be designed properly to meet the demands these longer production times require.


  7. Are there any space limitations for the installation of the gas delivery systems?


    When large volumes of gases are required for the assist or process gases, the installation of a permanent cryogenic supply system may be the most cost-effective method suited for the job. "Bulk" installation requirements for space, access for refill by the gas supplier and certain zoning requirements must be addressed when considering this type of installation.


  8. Can the gas delivery system be customized to meet the changing requirements of the processes?


    When and if the requirements of the processes change, will the existing gas delivery system handle the new demand? Has the gas delivery system been designed to handle the existing workload and can it be easily updated to handle increased capacity? The addition of more lasers will place more demands on the system. An upgrade in laser power can also change the requirements of the gas delivery systems. Additional lasers may require additonal volumes of gases. An increase in laser power may demand an increase in pressure and flow requirements.


  9. Will an alarm notification be required to warn of depletion of gas supply?


    The worst thing that can happen in the laser material processing application is the depletion of either the laser gases or the assist gases during operations. If the laser gas supply is deleted, the machine will automatically shut down and the work piece may need to be scrapped. The installation of a manifold gas delivery system with a low-level pressure alarm notification is suggested to avoid the shut down of the laser. Assist gases normally will be supplied in "bulk" delivery system. The use of alarms for these systems is also recommended to maintain the processing time of the laser.


  10. What piping requirements are required to meet the specifications of the installation?


    The piping system must be designed to maintain the purity of the gases supplied and also to the handle the flow and pressure requirements for the cutting assist gases. The presence of moisture and hydrocarbons can be detrimental to the laser gas supply. The installation of stainless steel tubing with compression tube fittings is recommended to maintain the integrity of the laser gases. The proper size of the assist gas lines to avoid flow restriction is necessary. Piping of 1/2" or larger is recommended.
Contact Arcet for recommendations on the correct installation of the laser gas delivery systems.


Typical Assist Cutting Gas Requirements*

Type of MaterialThickness    Gas    Pressure    Flow
    mm            PSI**    SCFH
Carbon steel5.0    Oxygen    52    92
Stainless Steel5.0    Nitrogen    180    918
Aluminium5.0    Nitrogen    185    847
                               
Carbon Steel10.0    Oxygen    9    32
Stainless Steel10.0    Nitrogen    210    2380
Aluminium10.0    Nitrogen    290    1213
                               
Carbon Steel15.0    Oxygen    9    131
Stainless Steel15.0    Nitrogen    261    3032
Aluminium15.0    Nitrogen               
                               
Carbon Steel20.0    Oxygen    9    131
Stainless Steel20.0    Nitrogen    348    4042
Aluminium20.0    Nitrogen    NR    NR

* Will vary as to laser power and nozzle selection
**Pressure required at nozzle, allow for pressure to drop in machine



Typical Laser Gas Requirements*

Type of GasPurity    Maximum    Maximum    Flow Rate
                               
HeliumGrade 4.6    5 PPM**    1 PPM**    .50-.70
    99.999%                       
NitrogenGrade 5.0    5 PPM*    1 PPM*    .21-.30
    99.999%                       
Carbon DioxideGrade 4.5    5 PPM*    1 PPM**    .04-.06
    99.995%                       
                               
Premix-3 Gases                           
He/N2/C0299.990%    5 PPM*    1 PPM*    1.414
40%/55%/5%                           
                               
Premix-4 Gases                           
He/N2/C02/C099.990%    5 PPM*    1 PPM**    0.0625
28%/60%/8%/4%                           
                               

See laser manufacturer's specifications




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