Stainless Steel - Material Analysis Stainless Steel Engraving vs. Tempering

Stainless steel is lasered with a fiber or fibula laser. So far we have mainly used it for engraving. Due to a small order to laser a WMF coffee can, we wanted to try out the parameters for "tempering engraving".

The main difference between engraving and tempering is the removal of material. After engraving you can feel the result. Tempering takes place mainly on the surface and has the following advantages:
- Little or no susceptibility to corrosion
- shorter marking times

In contrast to engraving, the focus of the laser is often shifted slightly when it is started. In order to find the best possible parameters and to test their results, we carried out a small series of tests with a stainless steel business card.

Technical parameters for the series of tests for tempering stainless steel

Material: stainless steel
Performance: 100% - 20%
Speed: 16%
Frequency: 30 - 240khz
Passes: 1 - 2
Focus shift: 0 - 2 mm
Air cooling: 0
Mode: Grid
Laser: Fiber 20W
Resolution: 400 - 3600 DPI
Font: ITC Officina Sans
Duration: 13 -68 seconds

series of measurements:
We carried out 13 engraving tests with the following settings.
(Power / Speed / Frequency / Sweeps / Focus / Resolution / Duration)

01. 100% / 16% / 30khz / 1 / 0 400dpi / 5sec
02. 100% / 16% / 80khz / 1 / 0 1200dpi / 12sec
03. 100% / 16% / 80khz / 1 / 0 3600dpi / 34sec
04. 100% / 16% / 80khz / 1 / 2 3600dpi / 34sec
05. 100% / 16% / 80khz / 1 / 1 3600dpi / 34sec
06. 100% / 16% / 80khz / 2 / 1 3600dpi / 68sec
07. 100% / 16% / 20khz / 1 / 1 3600dpi / 34sec
08. 100% / 16% / 160khz / 1 / 1 3600dpi / 34sec
09. 100% / 16% / 240khz / 1 / 1 3600dpi / 34sec
10. 80% / 16% / 240khz / 1 / 1 3600dpi / 34sec
11. 60% / 16% / 240khz / 1 / 1 3600dpi / 34sec
12. 40% / 16% / 240khz / 1 / 1 3600dpi / 34sec
13. 20% / 16% / 240khz / 1 / 1 3600dpi / 34sec

Hints:
In principle, we only ever change one parameter in a series of measurements in order to be able to trace changes in the result back to a change in one parameter.

Result:
The first three engravings took place without shifting the focus, which is why a significant amount of material was removed. Here you can see what influence the resolution has on the surface of an engraving.

In step 4 we set 2mm focus shift, which was clearly too much because you can hardly see anything of the engraving.

From attempt 5, all further tests were carried out with a focus shift of 1mm, which already resulted in a rich black on the first attempt. We then varied the frequency, which only marginally affected the result. Higher frequencies resulted in cleaner, deeper blacks.

In the last test steps we reduced the energy and found that the result does not really differ whether you engrave with 100, 80, 60, 40 or 20% of the possible power.