Laser cutting of various materials is a common process in the manufacturing sector, but under the wrong conditions, the heat from cutting various metals will cause oxidation and/or poor cut quality of metal surfaces. Oxidation will ruin the aesthetics of the finished product. It can also impact its rust resistance and durability. Poor cut quality can lead to re-work or scrapped parts. Purging with nitrogen gas during the laser cutting process is a common method to successfully cut metal materials without oxidation and ensure a clean cut. Here’s what you need to know about the benefits of installing onsite nitrogen generators for laser cutting, and how nitrogen gas generation benefits metal fabrication operations.
Sources of Nitrogen Supply for Laser Cutting Processes
Onsite Nitrogen Generators: Nitrogen generators can be installed onsite to produce nitrogen at various purity levels and flows and provide 24/7 access to the gas for laser cutting operations. The nitrogen generator inputs compressed air and separates the nitrogen from oxygen in the compressed air stream leaving a nitrogen gas stream for process purposes.
Outsourced nitrogen supply: Nitrogen can be purchased in the form of high-pressure nitrogen cylinders, liquid nitrogen dewars, or bulk liquid nitrogen.
Types of Nitrogen Generators Suitable for Laser Cutting
Nitrogen Generator A membrane nitrogen generator filters oxygen from a dry compressed air stream through hollow, polymeric fibres to produce nitrogen gas. The purity of nitrogen can be adjusted with an onsite membrane nitrogen generator, which makes it ideal for applications such as cutting aluminum or thin gauge carbon steel where the nitrogen purity requirement is below 99%.
PSA Nitrogen Generator PSA (Pressure Swing Absorption) technology uses pressure vessels filled with carbon molecular sieve (CMS). Compressed air enters the bottom of the tower and flows up through the CMS. Oxygen and other trace gases are adsorbed by the CMS and this allows a nitrogen stream to flow out for process use. PSA nitrogen generators are ideal for applications that require purity levels of over 99%.
Laser Cutting Applications Where Nitrogen Is Used High Pressure Gas Assisted Cutting
When heat is applied in the presence of oxygen, oxidation occurs. This can produce discoloration that results from a carbon layer forming on the cut edge. When cutting a metal part with a laser, this carbon layer can ruin the appearance of the finished product or can cause adhesion issues when a coating or paint is applied to the cut surface. It can also contribute to poor cut quality.
When nitrogen is applied during laser cutting, it provides an oxygen-free environment, which eliminates oxidation. The nitrogen gas pressure is also used to clear the cut by blowing away the hot molten material and produce a clean edge. Stainless steel typically requires 99.95% nitrogen purity or higher nitrogen purities to produce a high-quality cut, and aluminum and mild steel can be cut faster and more precisely with nitrogen purity levels of 98%.
Optics Head Purge Nitrogen can be used to purge the optics head or lens of fiber lasers, which keeps it free of moisture, dirt or dust particles. Keeping the head clean protects the laser and prolongs the effectiveness of the equipment.
Beam Path Purge Many industrial laser cutting systems produce a beam in one section that needs to be directed to another section for use. The laser beam is contained within guideways, which are hollow, microscopic tubes and flexible bellows with mirrors and lenses designed to focus and reflect the laser beam to the area that needs to be cut.
Nitrogen is necessary to prevent the beam from distorting and losing power and intensity. It achieves this by keeping the path clear of moisture, carbon dioxide, dirt particles, and other contaminants. Nitrogen is the ideal medium for beam path purging, as it is dry, clean, oil-free, and inert.
Advantages of On-Site Nitrogen Generation over Outsourcing Nitrogen Supply Cost Savings Outsourcing nitrogen for laser applications can be expensive. Transporting and ordering traditional liquid and cylinder nitrogen supply can account for over 60% of the total laser operating costs. Further to this, most conventional bulk liquid supply systems for laser cutting applications use nitrogen pressure amplification system designs that create substantial nitrogen purge losses when operating. Typical purge losses can range anywhere from 5% to 20% of the nitrogen being purged.
Producing nitrogen at your own facility is far more cost-effective in nearly all circumstances. In fact, in some cases you can reduce your nitrogen gas costs by up to 80%.
Reduced Safety Concerns With your own nitrogen generator on-site, there is absolutely no risk of injury related to the transport, delivery, and installment of nitrogen cylinders. None of your workers will need to risk their safety offloading tanks from transport vehicles.
Purity Control While some applications need a nitrogen purity of 99.999%, not all do. However, when you outsource nitrogen, you pay for this level of purity regardless. Having your own generator on-site allows you to adjust the purity to meet your specific needs—if you don’t need such a high nitrogen purity, you can control the purity level and experience better savings.
Continuous Supply With an on-site nitrogen generator, you have a continuous source of the gas without the need for operator attention 24/7. There is no time wasted switching out old, empty tanks for new ones; you simply have nitrogen as you need.
Disadvantages of Outsourced Nitrogen Supply for Laser Cutting Less Control Ordering from outside vendors leaves you at the risk of price increases with minimal or no notice, contract negotiations or contract rollovers with no notice, rental fees, adherence to OSHA requirements, hazardous material fees, delivery surcharges, and more. You may also deal with scheduling conflicts, delayed or missed nitrogen deliveries and other obstacles that can slow down or even stop your operations.
More Work for You
Outsourcing nitrogen supply can add up to extra administrative work and higher operational costs for your company. Plus, outsourcing does not produce a lean production system, which can harm your reputation among other organizations who are improving their supply chains to be more efficient and environmentally friendly.
There is a higher risk of injury to personnel and damage to tanks when transporting these heavy cylinders to and from your facility. If a cylinder were to drop and the valve broke, it could become a fatal, uncontrolled projectile.
Installation of nitrogen gas generator for industrial plants