A growing number of manufacturers and fabricators are turning to lasers to boost production and enhance metal processing services. These cutting machines are ideal for meeting shortand long-run production requirements while providing the flexibility to adapt to any economic changes on the horizon. Reliable, fast and versatile, lasers use less energy, process thick material and cut complex shapes with precision.
Regardless of type, size or brand, lasers represent a serious investment, so it’s important to fully maximize their features and capacity. To get the most out of your equipment, it is critical to understand the three key pillars of laser cutting production: process operation, program operation and machine operation.
Process operation
It’s important to follow the manufacturer’s recommended startup steps. Make sure to consider the material type, thickness and assist gas being used. Also, check that you are using the correct nozzle as directed from the material library.
Materials: The manufacturer provides the machine with default process parameters or material libraries that match common production material types and thicknesses. These libraries are a good starting point for cutting each of these materials, but variations in material quality and specific part geometry can require fine tuning. The fine-tuning parameters are located within the process parameters file.
Beam adjustment: For some CO2 lasers, beam size, focus, assist gas pressure and feed rate are adjusted to improve the cutting performance. Fiber lasers may have beam profile, but often this is not adjusted in normal setup. Instead, focus, assist gas pressure and feed rate are used. The adjustment is made to one parameter at a time in small increments.
Start with beam size for CO2 lasers (that have the adjustment) and focus for fiber lasers. After cutting a test part with default parameters, increase or decrease the cut beam size or cut focus parameter and determine if the adjustment improves the part cut quality. Part quality is based on edge uniformity and dross with dross being the material that is attached on the part’s bottom edge. The goal is uniform striations and no dross.
If after your initial adjustment the cut quality is worse, take the setting back and past the original setting. Once a trend of part improvement is found, continue with incremental adjustments until the part quality goes from good to better and then starts to decline. It is helpful to label the parts with the parameter value to create a record of parts to allow for future settings. It is important to note that these parameters set up a bell curve where a given parameter value that is too low or too high will make the cut worse.
This method is repeated for focus and assist gas. The feed rate is the speed the laser processes the material. The default process parameters have a posted feed rate. This is the maximum speed that production parts should be cut. After the beam size (CO2 ), focus and assist gas, if the part quality is within specification and feed rate is at the default posted value then proceed to cutting a large test part; the large test part will test if the optics have thermal issues (dirty).
Troubleshooting: A large test part also forces the motion control system to cut at close or equal to the posted feed rate. If the large test square cuts within specification, then proceed to production parts. If the large test part failed, check optics for cleanliness and re-check the cleanliness of the nozzle.
Verify the lens centering and recalibrate standoff. If the optics and other setup steps are fine, then a reduction in feed rate may be required. Reduce by increments of 5 percent of the original speed. If the test parts do not contain satisfactory cut quality, be sure to verify process parameters, including material type and thickness. Contact the manufacturer for assistance from service and applications department if the problem persists.
Program operation
Even the most sophisticated cutting systems only do what they are programmed to do and lasers are no exception. Ensure that the CNC program is derived from a quality drawing file and parts are programmed with the correct lead-in, geometric and design details.
Crashes: During the cutting process, it is not uncommon for cut parts to tip and protrude above the cutting surface. This can result in crashes as the laser head traverses across the material during the cutting process. Such collisions damage the laser, resulting in repair, replacement or extensive downtime. Proper feature and part avoidance should be included in any laser nesting software. This correctly positions the lead-ins in the parts to prevent the laser head from having to traverse over a tipped part. Lead-ins are the initial cut that starts before the part specific geometry – like an entry ramp to a highway.
Nesting: Similarly, nests should be generated with quality nesting software. Tight part placement reduces scrap while maximizing throughput. Nesting software features, such as common line cutting and bridge cutting, not only speed production but also save material costs.
Troubleshooting: If the large test part cuts with proper quality after parameter adjustment and the production part does not – especially in the straight geometry – then it’s likely the part program is suspect.
Explicit feed rates, incorrect lead-in length and feature avoidance layout could all be suspect. Try a different program with the same material and assist gas and look for differences between the test part settings and the production part settings inside the CNC program.
Machine operation
Each piece of equipment on the shop floor is designed to operate optimally when properly maintained and used as intended. And there are several areas to consider for optimizing the performance and longevity of your fiber or CO2 laser.
Inspection and maintenance: It’s important to maintain a dust-free cutting environment. Keeping optics clean and free from contamination is important to maintain accuracy. A fume collection system collects and removes fine laser dust on and around the cutting table.
Check your fume collection system regularly to be sure it is working properly.
To maintain the proper focus of the beam into the material, the height sensing system positions the laser cutting head safely above the material during the cutting sequence. If the height varies or is unstable, poor-quality cutting will result.
Also be sure to check your motion control system regularly. Repeatability and accuracy are important to ensure quality and precision. Repeatability errors, lost motion from mechanical wear and encoder positioning electrical issues can all adversely influence motion control. Periodic checks by maintenance personnel or laser operators helps ensure that the cooling system is operating properly. Similarly, the CO2 laser light source requires internal optics inspection at regular intervals while fiber lasers have less servable components.
Assist gases: Assist gas is the lifeblood of a laser. The laser light does the job of heating the material to a plasma or vapor state, but assist gas provides the pushing force to remove the molten metal. Nitrogen and oxygen are the most common types of assist gas. Oxygen is exothermic and adds heat to the cut and is required for thick mild steel cutting. Nitrogen is endothermic and removes heat from the cut. Nitrogen is better for small features and cuts thin materials significantly faster than oxygen.
Air-generated assist gas is gaining popularity due to low maintenance costs, but it does require a separate high-pressure, high-purity generation system. This system will have an upfront cost.
No matter what assist gas is used, it’s important that the gas is pure and operates at correct flow and pressure. Contact the laser manufacturer or gas supplier for answers to any questions you may have.
The bottom line is, like any piece of equipment, it’s critical that maintenance and preventive maintenance are performed following the laser manufacturer’s recommended schedule.
Troubleshooting: Diagnosing cutting issues can sometimes be difficult. Begin by considering the material that is being processed. Make sure that the material is of good quality and the right type and thickness for laser applications. Ensure jobs are being run based on the appropriate material, thickness and assist gas.
There are ways to identify if a problem resides with the laser. For example, if the large test part and the production part do not cut with satisfactory quality after correct parameter adjustment, then the issue lies with the machine. On a fiber laser, this is likely an optical contamination issue, and corrective steps should begin with an optical inspection.
Lasers are one of the most widespread and versatile forms of metal cutting, offering solutions for precise and complex geometry. While they are an asset to any fabrication environment, a lack of proper attention given to equipment upkeep and operation will result in a waste of energy and raw materials.
Process, program and machine operation are the three pillars that maximize laser cutting speed, quality and efficiency. Take the time to learn and implement these areas and you will begin seeing a measurable and sustained return on your laser investment.
