In this tutorial, we will show you how to engrave or deep engrave metals using a MOPA laser. We will also provide time-optimized and quality-optimized laser parameters for deep engraving of metals.
Laser engraving of metals
Laser engraving on components made out of stainless steel
The process of engraving involves the removal of material from a solid surface. Because of the very high intensity of the laser, materials such as steel, titanium and (almost) all other metals can be vaporized directly. This is possible due to the high pulse power of the fiber laser (with Trotec up to 10 kW peak power) in combination with a very small laser spot diameter (with Trotec ~ 45 μm with the F-160 lens). With this method, texts, logos, serial numbers or other contents can be engraved into the material. The volume of the material is reduced and its color is changed. The resulting brown areas consist of metal oxides (or rust), which can be cleaned with a second cleaning cycle using polishing parameters. Engraving on stainless steel requires high power, low frequency (which results in high power per pulse) and marking speeds of 250 - 900 mm/sec.
Deep engraving of stainless steel
Comparison of the deep engraving results: time-optimized and quality-optimized
The laser process for deep engraving is fundamentally identical to engraving, but with more passes. In these tips we describe two different sets of parameters:
Time-optimized
Quality-optimized
Please note that the set of parameters used to achieve optimal quality (2) takes about three times as long to reach the same engraving depth. A 20 watt MOPA laser with F-160 lens is used in both cases. The time-optimized engraving results are shown at the top of the image, and the quality-optimized engraving results are shown at the bottom.
1. Time-optimized laser parameters
In the first step, deep engraving is carried out in the fastest time possible. The laser parameters are chosen so that the desired engraving depth (in this case: 200 μm) is achieved as quickly as possible. The quality of the deep engraving is not taken into consideration here. This results in a warp of up to 100 µm. The engraving depth ranges from the desired 200 μm to 240 μm.
The following parameters are used:
Power
Speed
Frequency
Pulse duration
100%
250 mm/s
60 kHz
200 ns
Focus
Filling lines distance
Passes
Engraving time
In focus
0.03 mm bidirectional
32 (for 200 μm depth)
112 seconds (5x5 mm square)
Time-optimized deep engraving under the microscope
Deep engraving on metals: laser engraved time-optimized
2. Quality-optimized laser parameters
In the second step, deep engraving is carried out with the best possible quality. The laser parameters are selected to ensure that the desired engraving depth (also 200 µm) is achieved together with the best quality. This increases the engraving time threefold, but it also means there is no warping. The engraving depth ranges from the desired 200 μm to max. 220 μm.
The following parameters are used:
Power
Speed
Frequency
Pulse duration
100%
900 mm/s
180 kHz
200 ns
Focus
Filling lines distance
Passes
Engraving time
In focus
0.03 mm bidirectional
450 (for 200 μm depth)
375 seconds (5x5 mm square)
Quality-optimized deep engraving under the microscope
Deep engraving on metals: laser engraved quality-optimized
Multiple possibilities with deep engraving of metals
We are happy to advise you.
As you can see from this example, there are many possibilities with deep engraving of metals. Different parameters can be used depending on the requirements to be fulfilled. In the time-optimized variant, a great deal of material evaporates in a few passes (at a comparatively slow speed), and the quality-optimized variant uses significantly more (and faster) passes in order to remove the material in a more uniform and controlled manner.
Our experts from the application laboratory will be happy to consult with you regarding your requirements and they will be happy to sample your materials.
