Generating nitrogen on-site for laser applications provides many benefits including reduced costs, more stable supply, uninterrupted production and improved safety.
How a laser operates
A laser is a device that produces an intense beam of coherent monochromatic radiation in the infrared, visible, or ultraviolet region of the electromagnetic spectrum, by stimulated emission of photons from an excited source. Lasers are used for many industrial manufacturing applications from the production of hi-tech computer chips to slicing thick sheet metal.
Today’s global manufacturing environment demands that suppliers meet a multitude of requirements including shortened lead times, the highest accuracy, no rejects, energy-efficiency, minimum risk with maximum up-time, all at the lowest cost. Laser applications are no exception, and as the technology evolves and develops producing more powerful, faster, and more efficient machines, keeping costs under control to ensure financial viability is a constant challenge.
How laser applications use nitrogen
As an assist gas
Oxidation occurs as a result of the application of heat in the presence of oxygen, and can produce discoloration resulting in a carbon layer forming on the cut edge. This can adversely affect the appearance of the finished product or cause adhesion problems for any coating or paint applied to the oxidized surface.
Because of its inert properties, nitrogen allows the laser to operate in an oxygen-free environment thus preventing oxidation. Additionally, the nitrogen gas pressure is used to clear the cut by blowing away the molten material, producing a clean edge. While stainless steel generally needs 99.95% pure nitrogen or better to produce a quality cut,aluminum and steel can benefit from faster cutting at nitrogen purity levels of 98%.
To purge the beam path
On many industrial laser cutting systems, specifically CO2 lasers, the beam is produced in one section and has to be directed to the point of use in another section. The laser beam is generally contained within guide-ways. The guide-ways are hollow, telescopic, tubes and flexible bellows containing lenses and mirrors to focus and reflect the laser to the target area.
To prevent the beam from distorting and to maintain power and intensity, the beam path needs to be kept clear of moisture, CO2, dirt particulate and any other contaminants that could cause it to diverge or lose power. The lenses and water cooled mirrors also need to be kept free of dirt, condensing hydrocarbons and water vapor that could otherwise cause burning and marking of these expensive components.
Nitrogen is the ideal medium to use for beam guide-way purging as it is dry, clean, oil-free and has a very low contaminant content.
Consumables, such as nitrogen used as an assist and/or purge gas, are a major source of cost and down-time for laser technology cutting equipment. In fact, nitrogen from traditional liquid and cylinder supply methods can account for over 60% of the total laser operating costs.
Sources of nitrogen
- Nitrogen can be purchased in several forms: high pressure cylinders, liquid tanks, or bulk storage vessels.
- Nitrogen can also be produced on-site using standard compressed air with an in-house nitrogen generator. An in-house generator separates nitrogen and oxygen from the air, and can often be the most efficient and economical method of supplying nitrogen.
Disadvantages of an outsourced nitrogen supply
- Relying on outside vendors can pose several challenges including uncontrollable price increases, contract negotiations, tank rental fees, adherence to OSHA requirements, hazardous material fees, delivery surcharges, and local and state taxes. Problems such as scheduling conflicts, delivery delays, and lengthy procurement processes can slow down operations.
- This all adds up to extra administrative work and higher operational costs. The delivery approach also does not fit the trend toward lean production techniques and developing fewer, more efficient supply chains.
- Precautions must also be taken when handling and storing high pressure cylinders. A dangerous situation can be created if a cylinder is dropped and a valve is broken off, potentially causing the cylinder to become a projectile.
Benefits of on-site nitrogen generation
- Lower cost - Plants producing nitrogen on-site can realize a significant reduction in gas costs as well as savings related to improved operational efficiency. Additionally, a nitrogen generator eliminates the expense and CO2 emissions associated with truck deliveries.
- Continuous supply - A typical on-site system operates on a continuous basis without the need for operator attention. No production time is wasted to change tanks.
- Less waste - The on-site system generates nitrogen at a pressure and flow rate required for the application, on demand, so no gas is wasted.
- Improved plant safety - The danger of handling high-pressure cylinders is eliminated with a nitrogen generator.
- Greater security of supply - There is no need to depend on outside vendors thereby eliminating delivery delays, long-term contracts, and uncontrollable price increases.
- Easy to install - Nitrogen generators are free-standing and are housed in a cabinet or skid-mounted, depending on the amount of nitrogen needed. Set-up is easy. Simply connect a standard compressed air line to the inlet of the nitrogen generator and connect the outlet to the nitrogen line.
To learn more about on-site nitrogen generation for laser applications, read this brochure.
This post was contributed by David Connaughton, Nitrogen Product Manager and Gas Generation Technology Blog Team Member, and Judy Silva, Gas Generation Technology Blog Team Member, Parker Hannifin.