In this tutorial, we will show you how to laser engrave or deep engrave metals using a MOPA laser source. We also provide you with time-optimised and quality-optimised laser parameters for deep engraving of metals.
Laser engraving of metals
Laser engraving on components made out of stainless steel
Laser engraving involves removing the material from a solid surface. Due to the very high intensity of the laser, materials including steel, titanium and (almost) all other metals can be vaporised directly. This is made possible due to the high pulse power of the fiber laser (Trotec lasers have up to 10 kW peak power) in combination with a very small laser spot diameter (Trotec ~ 45 μm with the F-160 lens). With this method, text, logos, serial numbers and other contents can be laser engraved into the material. The volume of the material is reduced and its colour is changed. The resulting brown areas consist of metal oxides (or rust), which can be cleaned with a second cleaning cycle using polishing parameters. Laser 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 laser engraving stainless steel
Comparison of the deep engraving results achieved using time-optimised and quality-optimised parameters
The process for deep engraving is fundamentally identical to regular laser engraving, however, deep engraving requires more passes. There are two different sets of parameters:
Time-optimised
Quality-optimised
Please note that the set of parameters used to achieve optimal quality (2) takes about three times as long to reach the same laser engraving depth. A 20 watt MOPA laser with F-160 lens is used in both applications. The time-optimised engraving results are shown at the top of the image, while the quality-optimised engraving results are at the bottom.
1. Time-optimised laser parameters
Firstly, deep laser engraving is carried out in the fastest time possible. The laser engraving 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 laser engraving depth ranges from the desired 200 μm to 240 μm.
The following parameters are used for the laser engraving:
Power
Speed
Frequency
Pulse duration
100%
250 mm/s
60 kHz
200 ns
Focus
Filling lines distance
Passes
Laser engraving time
In focus
0.03 mm bidirectional
32 (for 200 μm depth)
112 seconds (5x5 mm square)
Time-optimised deep laser engraving under the microscope
Deep engraving on metals: Laser engraved with time-optimised parameters
2. Quality-optimised laser parameters
In the second step, deep engraving is carried out with the best possible quality, using the quality laser engraving parameters. The laser parameters are selected to ensure that the desired engraving depth (also 200 µm) is achieved together with the best quality. The laser engraving process takes three times as long using these parameters, however there is no warping of the material. The laser engraving depth ranges from the desired 200 μm to max. 220 μm.
The following laser engraving parameters are used:
Power
Speed
Frequency
Pulse duration
100%
900 mm/s
180 kHz
200 ns
Focus
Filling lines distance
Passes
Laser engraving time
In focus
0.03 mm bidirectional
450 (for 200 μm depth)
375 seconds (5x5 mm square)
Quality-optimised deep laser engraving under the microscope
Deep laser engraving on metals: Laser engraved quality-optimised
Multiple possibilities when deep engraving metals
We are happy to advise you.
Laser application lab
Deep laser engraving metals offers many possibilities. Different laser parameters can be used depending on your requirements. In the time-optimised example, a great deal of material evaporates in a few passes (at a comparatively slow speed), and the quality-optimised variant uses significantly more (and faster) passes in order to remove the material in a more uniform and controlled manner, negating the possibility of the material warping.
Our experts are happy to advise you if you have any questions about deep laser engraving metals. Contact us today for a sample.
