How to Cut Carbon Steel on Fiber Laser Cutting Machine

Fiber laser cutting machine technology uses powerful laser beams to precisely cut carbon steel sheets and plates. Fiber laser cutting machines are widely used in the manufacturing industry for cutting carbon steel due to their high cutting speed, precision, and low operating costs. This article outlines the key components of a fiber laser cutting machine, the cutting process, factors affecting cut quality, methods for evaluating and troubleshooting cut quality issues, and important safety considerations.

A. Laser Source: Fiber lasers emit laser beams at around 1.06 μm wavelength in the near-infrared range. The laser power rating, typically ranging from 1 to 12 kW, determines the thickness of carbon steel that can be cut. Higher power lasers are required for cutting thicker carbon steel grades.

B. Cutting Head and Optics: The cutting head contains lenses, mirrors, and a nozzle to focus and direct the laser beam to the workpiece. Precision optics are necessary to achieve a narrow and intense laser beam for high-quality laser cutting. The cutting head is mounted on the machine’s motion system.

C. CNC Controller: The CNC controller executes pre-programmed commands to precisely control the motion system and laser during the cutting process. It integrates with CAD/CAM software to convert digital designs and cutting patterns into machine instructions.

D. Motion System: Linear motors, ball screws, or rack and pinion systems are used to accurately move the cutting head during the cutting process. The resolution and repeatability of the motion system have a significant impact on cut quality.

E. Assist Gas Delivery System: An inert gas like nitrogen or compressed air is used as an assist gas to remove molten material from the cut. The gas flow rate and pressure must be properly regulated to achieve optimal cut quality. Higher flow rates and pressures are required for cutting thicker carbon steels.

Here are the key steps to cut carbon steel on a fiber laser cutting machine:

A. Material Preparation: The carbon steel sheet is cleaned and placed on the machine bed to ensure a flat and rigid surface for cutting. For plate cutting, additional clamping or fixturing may be required to prevent movement during the cutting process.
B. Cutting Path Design: The CAD file is imported into the machine software and cutting paths are generated based on the part geometry. The cutting path takes into account factors like cut sequence, laser orientation, and pierce points to achieve the highest quality cut.

C. Select appropriate laser power. Carbon steel requires relatively high power to cut, typically 3 kW or more. Choose a power level sufficient for the thickness of the carbon steel you want to cut. More power is needed for thicker material.

D. Adjust the focus lens for carbon steel. Use a tighter focus for carbon steel to concentrate the laser energy. The specific focal length will depend on the carbon steel thickness. Shorter focal lengths are typically needed for thicker material.

E. Choose cutting parameters for carbon steel. Use a slower cutting speed for carbon steel to allow for full melting and blowing away of the material. The exact speed and other parameters will depend on the carbon steel thickness and grade. You may need to adjust parameters for clean cutting.

F. Use oxygen assist gas. Oxygen assist gas is commonly used for cutting carbon steel. It helps remove melted material from the cutting path. Use an oxygen flow rate sufficient to keep the cut clear at your chosen cutting speed and material thickness. Higher flow rates are needed for faster cutting speeds or thicker carbon steel.

G. Engage laser and cutting head. Position the cutting head over your carbon steel material and engage the laser and motion system. Monitor the cutting process to ensure high cut quality. Speed or power adjustments may be needed.

H. Follow all safety precautions. Wear proper laser safety goggles and gloves when operating the fiber laser cutter on carbon steel. Harmful fumes, sparks, and debris are generated. Use adequate fume extraction to remove fumes and keep your work area safe.

By following the proper steps to choose laser power, focus, cut parameters, and assist gas, and taking necessary safety precautions, you can efficiently and precisely cut carbon steel with a fiber laser cutting machine. With some testing, you can dial in the settings to achieve clean, high-quality cuts in carbon steel.

A. Laser Power and Focus: Insufficient laser power or improper focus lead to poor edge quality, irregular cut surfaces, and inability to cut through the material. Excessive power can cause wider kerf, dross formation, and heat damage. The laser must be properly focused and power must be optimized for the carbon steel thickness.

B. Cutting Speed: Too high cutting speeds result in poor edge quality and uneven cut surfaces. Excessively slow speeds lead to heat accumulation, melting, and wider kerf. The cutting speed must be optimized to achieve a balance between productivity and high cut quality.

C. Assist Gas: Improper assist gas selection, flow rate, or pressure prevent effective removal of molten material causing dross, striations, and irregular edges. An inert gas like nitrogen is typically used for cutting carbon steel. Flow rates and pressures must be increased for higher-power and slower cutting processes.

D. Material Characteristics: Properties like material thickness, grade, flatness, and surface condition affect heat distribution and removal of molten material, impacting cut quality. Additional precautions must be taken for different carbon steel types and thicknesses. Thicker and higher-grade carbon steels typically require lower cutting speeds and higher assist gas pressures.

A. Cut Quality Metrics: Cut quality is evaluated based on parameters like dross formation, striations, taper, perpendicularity, roughness, and burr formation. Measurement methods include visual inspection, tactile evaluation, and the use of instruments like micrometers or DSLR cameras with appropriate magnification and lighting.

B. Troubleshooting Common Issues:
Problems like excessive dross, uneven edges, perpendicularity issues, and incomplete cuts can be caused by improper laser power, speed, focus, or assist gas parameters. Material condition and machine calibration issues can also contribute to poor cut quality.
•Excessive dross formation: Increase assist gas flow rate and pressure. Decrease laser power and increase cutting speed. Check for proper laser focus.
•Uneven, irregular edges: Recalibrate motion system to ensure smooth motion at optimal speeds. Refocus laser and double check power settings for material thickness.
•Perpendicularity issues: Ensure the cutting head remains orthogonal to the workpiece surface during cutting. Calibrate or service motion system if necessary.
•Incomplete cuts: Increase laser power for the material thickness. Decrease cutting speed to allow more time for heat conduction. Check for any laser power fluctuations or drops and service if required.
•Material condition: Remove any surface contaminants, rust, or burrs. Ensure the material is evenly supported and clamped. Uneven heating and inconsistent cutting may result from irregular material surfaces.
•Calibration: Periodically calibrate the laser power meter, nozzle position, cutting head orientation, and motion system to ensure parameters remain within the required tolerances for high-quality cutting.
Optimizing the laser cutting parameters, re-focusing the optics, changing the assist gas, and preparing the material are some potential solutions for improving cut quality. For persistent issues, consulting the machine manufacturer or a specialist is recommended. Routine maintenance and calibration also help avoid many problems associated with laser cutting machines.

A. Laser Safety: High-power lasers can cause harm to eyes and burns to skin, requiring the use of protective eyewear and enclosures. Laser safety training is critical for operators and maintenance personnel.

B. Material Handling Safety: Heavy carbon steel plates must be safely loaded, unloaded, and maneuvered to prevent injuries from slipping, tripping, crushing, or impact. Cranes, hoists, and fixtures should be properly rated for the weights being handled.

C. Gas Safety: High-pressure gases like nitrogen can cause asphyxiation or explosions if improperly handled or there is a leak in the assist gas delivery system. Proper ventilation, storage, line purging, and operator training in gas safety are important. Leak detection and emergency shutoff systems help minimize risks.

D. Electrical Safety: Laser cutting machines have many electrical components that can pose risks of electric shock, burns, fires, and machine damage if misused or malfunctioning. Grounding, insulation, and lockout/tagout procedures must be followed.
E. Fire Safety: The cutting process produces sparks and molten metal that can ignite flammable materials. A fire extinguisher appropriate for electrical and metal fires should be kept in an easily accessible area of the machine cell.

To adjust the focus lens for cutting carbon steel with a fiber laser cutting machine, here are the key steps:

1. Select the appropriate focal length. For cutting carbon steel, a shorter focal length lens is typically needed to achieve a tighter focus of the laser beam. The exact focal length will depend on the thickness of the carbon steel. Thicker materials require shorter focal lengths.

2. Change to the selected focus lens. If your laser cutter has multiple lenses, physically install the short focal length lens for cutting carbon steel. Alternatively, if you have an adjustable or autofocus lens, adjust the lens to decrease the focal length to the desired level for your carbon steel thickness.

3. Cut test pieces and check cut quality. Cut some test pieces of the carbon steel with the new focus lens or focal length setting. Check that the cuts are clean and complete, with minimal slag or uncut material. If the cuts are not high quality, you may need to adjust the focal length or other parameters.

4. Refine the focus and parameters. If needed, make further adjustments to the focus lens focal length or other cutting parameters like speed and power to achieve clean, quality cuts in your carbon steel. It may take some experimentation to find the optimal settings for your carbon steel grade and thickness.

By methodically selecting and adjusting the focus lens focal length, cutting test pieces, and refining parameters, you can dial in the focus and settings to cut your carbon steel cleanly and efficiently. With the proper lens focal length and parameters for your carbon steel application, your fiber laser cutter should achieve high-quality cuts.

The optimal cutting parameters for carbon steel will depend on the thickness and grade of the carbon steel, as well as your fiber laser cutter’s capabilities. Some general guidelines:

– Laser power: Use a relatively high power level, typically 3 kW or more, to cut through the strong carbon steel material. More power is needed for thicker carbon steel. The maximum power your laser cutter can output will limit the thickest carbon steel it can cut.

– Cutting speed: Use a slower cutting speed for carbon steel to allow complete melting and blowing away of the cut material. Speeds of 100-300 inches per minute are common for cutting carbon steel. Slower speeds are needed for thicker material or higher cut quality. However, the slowest practical speed should be used to maximize cutting efficiency.

– Oxygen assist gas: Oxygen assist gas is typically needed to cut carbon steel. Use an oxygen flow rate sufficient to keep the cutting path clear of melted material. Higher flow rates may be needed for faster cutting speeds or thicker carbon steel. The specific flow rate will depend on your cut speed and carbon steel thickness. Weaker oxygen flow can lead to poor cut quality.

– Focus: Use a tighter focus for carbon steel to concentrate the laser energy. The specific focal length needed will depend on the carbon steel thickness. Shorter focal lengths are typically used for thicker carbon steel. The focus must be optimized for clean cutting and to minimize the heat affected zone.

By experimenting with different power levels, cut speeds, oxygen flow rates, and focus settings, you can find the optimal parameters for cleanly and efficiently cutting your carbon steel on the fiber laser cutter. The key is to use sufficient but not excessive power and a tight focus while maximizing cutting speed for your application.

For cutting 1/4-inch (6 mm) thick carbon steel, a typical oxygen flow rate would be around 40-60 cubic feet per hour (CFH). Some key points:

– Higher oxygen flow rates around 60 CFH help keep the cutting path clear of melted material when cutting at faster speeds or higher power levels. The higher flow rate blows the molten material away more effectively.

– However, very high oxygen flow rates are not necessary and waste gas. A flow rate around 40-50 CFH is sufficient for cutting 1/4-inch carbon steel at normal speeds and power levels.

– The exact optimal oxygen flow rate will depend on your specific cutting parameters like speed and power as well as the grade of the carbon steel. You may need to test different flow rates to find the best level for your application.

– Be sure not to use an oxygen flow rate so weak that it does not clear melted material from the cutting path. This can lead to poor cut quality, wasted material, and damage to the cutting head or material. The flow rate must be sufficient to eject molten material during cutting.

In general, an oxygen flow rate of 40-60 CFH is a good place to start for cutting 1/4-inch thick carbon steel. You can then test and fine-tune the flow rate based on your cutting parameters and material to achieve clean, efficient cutting.

A good approach to testing different oxygen flow rates for cutting carbon steel is:

1. Cut test pieces at your standard oxygen flow rate. This establishes a baseline for cut quality and speed.

2. Increase the oxygen flow rate by 10-20 CFH and cut another test piece. Check if the cut quality is improved by the higher flow rate blowing away more molten material. However, watch for excess oxidation of the cut edge or wasted gas.

3. Decrease the oxygen flow rate by 10-20 CFH and cut another test piece. See if the lower flow rate still effectively clears the cutting path or if cut quality suffers.

4. Repeat steps 2 and 3 until you find an oxygen flow rate that maximizes cut quality and efficiency. The specific flow rate will depend on your cutting parameters and material.

5. Once you find the optimal flow rate, cut additional pieces to verify and fine-tune the setting. Small adjustments may be needed for consistent, high-quality results.

By systematically testing different flow rates around your initial standard and evaluating the cut quality, you can determine the optimal oxygen flow rate for your carbon steel cutting application. Testing is key to finding the best settings for your specific parameters and material.

Some common issues that can arise when testing different oxygen flow rates for cutting carbon steel include:

– Excess oxidation: If the oxygen flow rate is too high, it can lead to excess oxidation of the cut edge. The increased oxygen can oxidize more of the carbon steel, leaving a rough, discolored cut edge. Lower the flow rate if you see excess oxidation.

– Poor cut quality: If the oxygen flow rate is too low, it may not effectively clear molten material from the cutting path. This can lead to dross, slag, or other cut quality issues. Increase the flow rate if cut quality is poor to blow away more molten material.

– Wasted oxygen: A very high oxygen flow rate may not improve cut quality but will waste gas. Only increase the flow rate enough to achieve good cut quality. Too high a flow rate wastes oxygen and money.

– Variation in results: If testing conditions are not consistent or parameters are changed between tests, the results may vary. For accurate comparison, keep all testing conditions and parameters the same except for the oxygen flow rate. This ensures the flow rate is the only variable affecting cut quality.

By watching for these potential issues, you can test oxygen flow rates accurately and determine an optimal flow rate that maximizes cut quality without excess oxidation or wasted oxygen. Consistent testing approach and evaluation of cut quality are key to finding the best oxygen flow rate for your carbon steel cutting application.

Some good ways to determine the optimal oxygen flow rate for cutting carbon steel include:

Cut test pieces at different flow rates and compare cut quality. This direct testing is the most effective way to find the best flow rate. Cut test pieces at a range of flow rates and evaluate the cut edges for quality, oxidation, and dross. The flow rate that produces the cleanest cuts with minimal oxidation and dross is optimal.

Start at a standard flow rate and adjust based on cut quality. If cut quality is poor at the standard flow rate, increase the flow rate in increments until the cuts are clean. If excess oxidation occurs at a high flow rate, decrease the flow rate until the oxidation is minimized while still achieving good cut quality.
Consider the carbon steel thickness and cutting speed.

In general, higher flow rates are needed for faster cutting speeds or thicker carbon steel to effectively clear molten material. The flow rate must be sufficient for your cutting parameters, so take the thickness and speed into account when determining an optimal flow rate range to test.

Monitor gas usage and costs. While cut quality is the priority, be aware of the gas costs at different flow rates. Only increase the flow rate enough to achieve good cut quality and minimize wasted oxygen. An optimal flow rate will balance cut quality and efficiency.

By using these methods to directly test and evaluate different oxygen flow rates, you can find the best flow rate for your carbon steel cutting application that produces clean cuts, minimizes oxidation, and avoids wasted gas. Determining the optimal flow rate may take some experimentation, but with systematic testing and evaluation you can find the best setting.

Some common oxygen flow rates for cutting carbon steel on a fiber laser cutter include:

– 1/8-inch (3 mm) carbon steel: 30-50 cubic feet per hour (CFH)
– 1/4-inch (6 mm) carbon steel: 40-60 CFH
– 3/8-inch (9 mm) carbon steel: 50-80 CFH
– 1/2-inch (12 mm) carbon steel: 60-100 CFH

These are just general guidelines. The optimal oxygen flow rate will depend on your specific cutting parameters like speed and power as well as the grade of your carbon steel. Higher flow rates may be needed for faster cutting speeds or higher power, while lower rates could be sufficient for slower, lower-power cutting. Testing is important to determine the best flow rate for your application.

In general, thicker carbon steel will require higher oxygen flow rates to effectively remove molten material from the cutting path. But excessively high flow rates should be avoided to minimize wasted gas. By testing, you can find the flow rate that achieves the best cut quality for your carbon steel thickness and cutting parameters.

Some common cutting parameters for cutting 1/8-inch (3 mm) thick carbon steel include:

– Laser power: 3-4 kW
– Cutting speed: 200-400 inches per minute (ipm)
– Focus setting: 0.020-0.040 inch (0.5-1.0 mm) focal length
– Oxygen assist gas: 30-50 cubic feet per hour (CFH)

These are just general guidelines. The optimal parameters will depend on your specific fiber laser cutting machine and the grade of your carbon steel. You may need to test different settings to find the combination of power, speed, focus, and oxygen flow rate that cuts your 1/8-inch carbon steel cleanly and efficiently. In general, higher power and tighter focus with slower speeds and sufficient oxygen flow are needed for quality cutting of this thickness of carbon steel.

Some common grades of carbon steel used in laser cutting include:

– A36: A low-carbon steel with good weldability and formability. It has a carbon content of 0.26% and is a common structural steel.
– A572: A high-strength low-alloy steel with a carbon content of 0.23%. It is stronger than A36 steel and is also used for structural components.
– A516: A steel for pressure vessels with a moderate carbon content of 0.27-0.31%. It is designed for good weldability and has high strength and durability.
– 1020: A mild low-carbon steel with 0.18-0.23% carbon. It is a inexpensive steel with good machinability and weldability.
– 4140: A chromium-molybdenum alloy steel with 0.38-0.43% carbon. It is heat treatable with high strength and toughness and good wear-resistance. It is often used for axles, shafts, and machinery parts.

These are some of the more common grades of carbon steel used for laser cutting. In general, lower-carbon steels with less than 0.30% carbon content have better weldability and formability, while higher-carbon and alloy steels provide more strength. The optimal steel grade will depend on the application and requirements.

In summary, fiber laser cutting machines use high-power lasers to precisely cut carbon steel.

When the machine components are properly selected and maintained, the cutting process is optimized, and all safety precautions are followed, these systems can achieve high-quality cuts in carbon steel efficiently and cost-effectively. Understanding the machine setup, cutting process parameters, troubleshooting common issues, and safety considerations is key to operating a fiber laser cutting machine successfully for cutting carbon steel.

With their versatility, precision and rapid cutting capability, fiber lasers have become an essential tool for manufacturing industries that work with carbon steel.