Challenges and Solutions to Laser Cutting Copper
Copper is a major engineering material because of its many benefits. This metal is ductile, malleable, and easy to work with. Hence, copper is indispensable in various industries from aerospace and automotive to medical and construction. However, you may experience some challenges when cutting copper using a laser beam.
Copper metal is reflective and has a high thermal conductivity. For this reason, copper laser cutting requires careful consideration and planning to get the best results. Before cutting copper with lasers, you should be aware of the challenges you may encounter. Read on to find out about the challenges of copper laser cutting and how to prevent them from occurring.
What is Laser Cutting Copper
Laser cut copper is a thermal separation process where a focused laser beam cuts through a material. The result is a clean and high-quality cut with minimal workpiece contact. The process of laser cutting copper begins with generating instructions in the form of G-code using software tools. You then produce and amplify the laser beam in a resonator. Thereafter, direct the laser beam through mirrors and lenses. Focus the laser on the surface of the workpiece. The head then moves in predetermined pathways for a cutting action.
As the laser beam comes in contact with the copper metal, it evaporates to create the desired design and pattern. Note that the laser type you use is the fiber laser. The reason behind this is the high reflectivity of copper. Copper efficiently absorbs the wavelengths from fiber lasers which allows for accurate cutting operations.
Challenges and Solutions to Laser Cutting Copper
While lasers excel well when cutting copper pieces, there are some challenges you may encounter. Let’s look at some copper laser cutting problems and how to prevent them from occurring.
High Reflectivity
The reflectivity of copper is a significant challenge you may face when laser cutting this metal. Copper metal deflects the laser beam which makes it difficult for the workpiece to absorb the energy required to cut through. This result is uneven cuts and increased production of debris. Furthermore, the reflected laser beam that bounces back can damage the laser optics.
Solutions
- Properly prepare the surface of the workpiece and apply coatings such as graphite and ceramic to reduce reflectivity.
- Adjust pulse duration, laser power, and frequency.
- Use assist gasses to reduce plasma formation.
Heat-Affected Zone (HAZ)
HAZ is a common copper laser cutting problem that occurs because of the metal’s high thermal conductivity. While this does not directly affect the cut quality, it plays a role in how customers perceive a product. HAZ describes the discoloration or darkening that affects the surroundings of the cut line. When there is an excessive heat input, the copper workpiece spreads it quickly. This thermal exposure can alter the microstructure of the material and affect how well it functions. In extreme cases, it results in grain growth and reduces the ductility of the component.
Solutions
- Modify the laser parameters based on the thickness of the part you are working with.
- Monitor the laser cutting process in real-time and make necessary adjustments.
- Ensure the assist gas is enough to provide the required cooling action.
- Carry out necessary post-formation treatment to increase the strength of the part.
Burr Formation
Copper laser cutting can also result in burr formation if one is not careful. These imperfections appear as ridges and protrusions on the cutting edge. Burrs occur when there is incomplete evaporation or if the molten metal continues to accumulate. It may be a result of insufficient laser power, focusing too far or too close to the workpiece, and using the wrong auxiliary gas. Burrs when present lowers the quality of the cut and can affect dimensional accuracy. They can be rough and spiky and can affect your safety and that of the end users.
Solutions
- Optimize the necessary laser parameters including power and speed to help achieve the required penetration.
- Use the right assist gas to remove the molten material from the cut zone and prevent accumulation.
- Properly maintain the laser cutting equipment and ensure the working time is not too long.
Dross Adhesion
Dross describes molten material that is not properly ejected or has solidified at the underside of the cut. Many factors including cutting speed, torch distance, and gas pressure influence the formation of dross. You see this imperfection appear when the speed or power is too low which causes the molten metal to solidify before it is expelled. Additionally, dross occurs when the assist gas pressure is not enough to remove the molten metal. These unwanted metal clings to the workpiece and cause rough edges and quality problems.
Solutions
- Properly focus the laser beam to ensure precise penetration and prevent the formation of excess molten metal.
- Use high-pressure nitrogen gas that matches the power of the laser beam.
- Adjust the laser speed to ensure sufficient removal of the molten copper.
- Make sure the laser nozzle is not broken or worn out.
Striations
Striations are another laser-cutting copper problem you should know. They appear as fine, parallel lines across the cut edge. Striations occur when there is instability that does not allow the metal to melt evenly. These patterns of groove, whether deep or shallow, lead to a rough surface finish.
Solutions
- Use the right laser power, feed rate, and speed to ensure that the workpiece melts evenly.
- Properly focus the laser beam and increase the focus height if necessary.
- Reduce the gas pressure and make sure the flow is steady for consistent metal removal.
Kerf Width Deviation
You can also experience kerf width deviation when cutting copper using lasers. This describes the difference between the actual cut size and the desired cut size. The kerf width you get depends on the type of laser you are using, power density, and focal length. Deviation occurs when the kerf width is not consistent throughout the cutting operation or if there is excessive material removal. This can be a result of laser beam fluctuations, problems with the beam focus, or variations in material thickness.
Solutions
- Use only high-quality nozzles and lenses to get the required spot size.
- Ensure the thickness of the workpiece is even all through.
- Avoid cutting the workpiece too slowly.
- Maintain proper focus distance.
Incomplete Cutting
Incomplete cutting is another challenge you can encounter with laser cutting copper. This happens when the laser beam does not fully penetrate or completely cut through the material. The result is areas that are unsevered. Incomplete cutting occurs when you are cutting too fast or using inadequate laser power. As a result, the laser beam passes through abruptly without performing the necessary actions.
Solutions
- Use the right cutting speed and laser power to ensure adequate penetration.
- Properly maintain the laser cutting equipment to prevent mechanical issues.
- Apply anti-reflective coatings to improve laser absorption.
- Focus the laser beam in the right spot.
Warping or Distortion
Copper laser cutting can also result in warping and distortion, especially with thin materials. This happens when there is uneven heating which can build up stress in the workpiece. These internal stresses cause the workpiece to bend inside out during the cooling phase. The part bends out of place which affects its aesthetics and functionality.
Solutions
- Use the right laser power and cutting speed.
- Properly secure the workpiece to prevent unnecessary vibrations.
- Use assist gas to aid cooling and efficient heat distribution.
- Preheat the workpiece as required.
Conclusion
Copper has a high melting point and dissipates heat quickly. Additionally, it reflects most of the laser light which can reduce cut quality. Laser-cutting copper poses certain challenges because of the properties of this metal. You can experience large HAZ, burr formation, and debris adhesion when dealing with copper metal. By understanding the challenges and solutions of laser cutting metal, you can save costs, reduce material wastage, and increase productivity.
