Common Challenges in Laser Cut Brass and How to Fix Them

Laser Cut Brass Angles

Brass is a gold coloured metal. It features a smooth, shiny finish, making it a popular choice for a wide range of applications. It is often used in decorative pieces, engraved nameplates, and plumbing parts. 

Brass is composed of copper and zinc. By changing the ratio of these metals, their strength and properties can be adjusted. Copper is usually the primary material in the mix (Get in-depth insights about copper vs brass). Due to its polished appearance, brass is widely used for laser engraving, particularly in the creation of awards, signage, and custom products. 

Its appearance gives a premium feel. So, it’s ideal for detailed work. However, the high copper content makes brass a reflective metal, which can create challenges during laser cutting. ProleanTech’s laser cutting service helps customers get accurate and smooth parts every time. Our processes are fast, clean, and our machines work well with both metals and plastics. You can rely on our team for quick delivery and flexible order options.

This article explains how laser cutting works with brass, the type of laser best suited for the job, and the most crucial factors to achieve smooth and accurate results.

How to Cut Brass Sheet Metal?

Brass Laser Cutting

Laser Cut Brass is the process of using a high-powered laser to cut through brass by melting it along a precise path. When the brass melts, a steady flow of gas helps push the molten material out of the way. This leaves behind a clean and sharp edge.

Brass reflects a large amount of light. This makes it challenging for some lasers to cut effectively. Standard CO2 lasers usually do not work well for brass because the metal does not absorb enough of their energy. 

Fibre lasers, on the other hand, operate at a shorter wavelength. It delivers more concentrated power. Therefore, it allows the brass to absorb enough heat for smooth and accurate cutting. This makes fibre lasers the preferred choice for this material. (Also See: copper laser cutting)

What Is Laser Engraving Brass?

Laser Engraved Coins

Brass laser engraving is a process that removes a thin layer from the brass surface. It is used to create sharp and lasting patterns. It involves a fibre laser, which works well with metals due to its shorter wavelength and higher energy output. Brass absorbs laser energy, allowing it to etch detailed designs with high precision.

Unlike fibre lasers, CO2 lasers are not suitable for direct engraving on brass. The metal reflects most of the laser energy at that wavelength. So, this makes the process ineffective. 

However, CO2 lasers can still be used to mark brass. It involves applying a marking compound to the surface before using the laser. When the laser heats the compound, it bonds with the brass, leaving a dark, permanent mark. This marking does not remove any material but still creates a clear and durable finish on the surface.

Common Issues and How to Overcome Them in Laser Cut Brass

Brass sheet metal fabrication presents several technical challenges. This makes the process more demanding than with other materials. Here are the most common issues you need to be aware of: 

Custom Cut Brass Reflects Most of the Laser Energy

Shiny Brass Bar Stock 

One of the primary challenges in machining brass is its high reflectivity, particularly with respect to infrared laser beams. Metals like brass, copper, silver, and gold tend to reflect the laser rather than absorb it. 

This is primarily the case with CO2 lasers, which operate on longer wavelengths. The reflected rays may come back into the laser source itself, thus endangering the internal components of such a source and possibly even damaging other equipment.

Low Absorption Makes Cutting Inefficient

The high reflectivity of brass results in low absorption of the laser energy. Therefore, the cutting process becomes slow and unreliable. Due to the lack of heat at the surface, the laser is unable to penetrate fully into the brass, resulting in incomplete or rough cut edges.

Cutting Improves Once the Brass is Molten

Brass is easier to work with once it starts to melt. Solid brass reflects most of the laser. But having obtained the melting temperature of the brass, the reflectivity of the surface of the brass decreases, and it is then possible to get the laser energy to work in a better fashion. 

For this reason, it is advisable to start the cutting with a fast and concentrated pierce. This succeeds in quickly penetrating the solid surface and reaching the molten state beyond it, where the laser can work more efficiently.

Initial Cutting Poses a Risk to the Machine

At the beginning of a cut, when the brass is still solid, the laser may reflect energy directly back into the machine. If this exposure lasts too long, it can cause overheating or damage to the device. To reduce this risk, it is necessary to minimize the time the laser remains on the solid surface before melting occurs.

Which Laser Type Is Best for Laser Cut Brass Finish?

CO2 Laser Cutter

When it comes to cutting brass, a fibre laser is the preferred choice. This is due to its shorter wavelength and higher energy output. This makes it more suitable for reflective metals, such as brass. Compared to CO2 lasers, which struggle with brass due to poor absorption, fibre lasers provide stronger and more focused energy that the metal can absorb more efficiently.

Like other yellow metals, brass reflects most of the laser light in its solid state. This limits the energy that actually reaches the material. However, fibre lasers operate at a wavelength that brass can absorb more effectively. As soon as the surface starts to melt, reflectivity drops, and the cutting process becomes far more stable. The advantage of fibre lasers is their ability to reach that melting point quickly, allowing for faster, cleaner cuts with less risk to the machine.

What You Should Focus On for the Best Laser Cut Brass Results

To cut brass efficiently, the machinist must pay meticulous attention to a few crucial factors. Getting settings correct will not only improve the cut but will also keep the laser equipment safe. 

Here are the four elements that require more attention during laser cut brass sheet:

Power Setting

Abstract Scene of Fiber Laser Cutting Machine

Since brass requires a significantly high amount of energy to be melted, it is essential to use a high power setting. The operator should use the highest setting that matches the material’s thickness.

This helps the machine work smoothly and gives better results. For example, a thinner plate may cut well with approximately 1000 watts of power, while a thicker brass plate may require 4000 watts or more. 

A higher power setting will reduce the time spent on the solid surface. It results in a lower hazard from reflectivity.

Cutting Speed

High Speed Laser Cutting Metal

Brass cuts better at a slightly slower cutting speed. If the speed can be reduced to about 10% to 15% of the fastest recommended speed, it will help to stabilise the cut. This again leads to a continuous cutting operation rather than a cutoff. 

A cutoff operation is another challenge, as it would require the operator to restart the process and could result in injury to the machine or material, either directly or indirectly, in the future.

Focus Needs to be Precise

The laser must be aimed at the top surface of the brass. The significant concentration of the energy density at the surface is advantageous in producing molten brass cleanly and promptly. A well-focused beam also reduces the heat-affected zone. Therefore, it protects the material quality in the zone just outside the one affected by heat.

Use the Right Cutting Gas

Nitrogen is an ideal gas for use in cutting processes involving brass. This cuts the molten material without affecting the surface, ensuring it remains intact and not overly shiny or polished. On the other hand, metals such as copper may require an oxygen gas, which helps react with the surface and remove the polished-looking surface effect.

Summary

This article explained the process of laser cutting brass, covering what it is and how it works in detail. For more information about brass laser cutting, you can contact the team at Prolean.

Prolean offers a comprehensive range of metal laser cutting services. These include precise sheet cutting and other value-added options to support your prototyping and production projects. Visit our website to learn more or to request a free, no-obligation quote.