Laser technology has come a long way since the introduction of the first laser in 1960. Nowadays, it is considered one of the best marking solutions for engraving metals, as it provides high-contrast, high-quality identifiers in all types of production lines.
Manufacturers seeking to engrave identifiers such as logos, serial numbers or data matrix codes on metal parts turn to fiber laser marking.
As a laser system manufacturer, we know what it takes to engrave metals efficiently. Here are our top considerations when laser marking metal.
- Choose the right type of laser
- Gather information on the metal you’re marking
- Optimize the laser power for your cycle time
- Choose the right laser marking process
- Consider post-process treatments
- Minimize the quantity of encoded information
- Manage dust generated during metal engraving
Different types of lasers emit light of a specific wavelength based on their gain medium. With fiber lasers, the gain medium is an optical fiber; with CO2 lasers, it’s CO2 gas. The wavelength is important because it affects how energy is absorbed by the metal.
In general, metals react well to fiber lasers because most of them absorb its wavelength efficiently. It’s therefore a good idea to choose a fiber laser when engraving these metals. CO2 lasers are rarely a good choice because their wavelength is not absorbed well (they are good at marking organic materials such as plastics and wood, though).
Each metal has different requirements and reacts differently to the laser beam, so it’s crucial to understand the metal you intend on marking.
Here is a list of specificities for common metal materials and alloys:
- Aluminum: Aluminum absorbs fiber laser light efficiently and can be marked at high speed.
- Steel: As a hard material, steel cannot be marked as fast as softer metals. White markings can be created faster than black markings. If white contrasts well with the bare metal color, it should be used to speed up the laser process.
- Stainless steel: The chromium oxide layer on the metal surface must usually remain intact to prevent rusting. In these cases, annealing is the recommended laser process, especially in the medical and food & beverages industries.
- Anodized aluminum: Permanent markings can either be created on the anodized layer or before the anodization process. To read identifiers through the anodized layer for example, deeper markings are required.
- Copper: Copper does not absorb fiber laser light as efficiently as other metals, which means high-speed markings are not possible.
- Lead: Lead is easy to mark at high speed, as it is one of the metals that absorbs fiber laser light the most efficiently.
The laser power of a pulsed laser represents the average amount of energy it releases over time, with high energy peaks represented by pulses. High power lasers can release a higher number of pulses in the same amount of time, which allows them to engrave metals faster. At Laserax, we offer up to 1000W of laser power to meet the most demanding marking times.
You can find examples of marking speeds for specific applications below:
- Laser marking performance on aluminum
- Stainless steel marking times on batteries
- Deep engraving speed on aluminum and steel
While high-power lasers are faster, they’re also more expensive. You should choose the laser power that meets your cycle time while minimizing costs. Strategies can be used to minimize the laser power and diminish costs. Here are some of them:
- Laser engraving machines can include features such as a rotary table to shorten the cycle time.
- Unessential information can be removed to reduce the size of the identifiers.
- The laser configuration (parameters and optical components) can be optimized for faster marking.
In addition to optimizing your marking process, Laserax looks at your complete manufacturing process to find the best solution for your application.
Some laser processes remove material from the surface, while others discolor the surface through a chemical reaction. For this reason, certain metals require a specific laser marking process.
Here is how different processes affect the metal surface:
- Laser etching: As the fastest marking process, laser etching is the recommended method when high-speed marking is a priority. This process creates a raised mark on the surface of the metal.
- Laser engraving: Slower but sturdier, laser engraving ensures you get permanent marks even if your workpieces undergo surface treatments or are exposed to high abrasive wear. When laser engraving metals, the laser beam digs into the material, much like laser cutting.
- Laser annealing: This process is used to protect the bare metal or its protective coating. Unlike the other options, it does not remove material from the metal surface. Instead, it discolors the metal through a chemical reaction (passivation) happening under the surface.
- Deep engraving: Deep engraving is slower than other processes because it removes more material. It is often used to produce deeper and aesthetic markings such as logos, stamping plates, and mold inserts.
If the metal surface you’re engraving is subjected to post-treatments in your manufacturing process, laser marking will require more time. This is because post treated metal parts usually require deeper engravings to remain readable.
To keep up with your cycle time, the laser power can be increased, or a rotary table can be installed to engrave parts while other parts are loaded.
Laserax has developed laser marking processes that make codes more resistant so that they maintain traceability through post treatments like shotblasting, e-coating, powder coating, and heat treatments.
Here is an example of patented shotblast resistant laser engraving:
If you’re marking for traceability, data matrix codes and QR codes are great options since barcode readers can read them more reliably than serial numbers. They can also encode more information within a smaller area.
These codes are made of black and white modules, or cells, arranged in a square or rectangular pattern. For example, a barcode could be 18 modules wide and 18 modules high (18x18).
Codes with more information need more modules, which leads to larger codes or smaller cells. This can lead to two problems:
- Larger codes require more marking time or more laser power.
- Cells that are too small are harder to read for barcode readers and may affect the reliability of your traceability.
If your traceability requirements are flexible, it is best to minimize the amount of information you encode. This will help you meet your cycle time or diminish the power needed for the laser, lowering its cost.
For example, if you go from a 100W to a 50W laser, you could save several thousands of dollars. Going from 20 characters to 8 characters could go a long way.
When laser engraving metals, the metallic dust released in the air can affect the performance of the laser. Some processes generate more dust than others because they remove more material.
For example, deep laser engraving is the process that generates the most dust, and laser annealing generates none.
To make sure dust is managed properly, you should choose features based on the amount of dust generated:
- Air knives, or air blowers, can be installed to blow dust away from the lens, preventing dust accumulation.
- A dust extraction unit is needed to keep the air clean and prevent dust accumulation in the laser marking machine.
- The laser head can be designed with the right environmental protection to make sure it is dust and liquid resistant.
We hope this article helps you choose a laser system for your metal marking needs. Proper considerations can save you a great deal of time and money.