DYNAMIC FOCUS SHIFTER (DFS)
The secret ingredient of how laser markers work on non-planar surfaces.
The Dynamic Focus Shifter bases its functionality on the presence of a third optical axis which, by moving the lens within the optical path, varies the size of the beam arriving at the focal length, leading to a variation in the plane of focus. Today there are several ways to achieve this result and we have chosen to leverage the best option.
DFS with convex lens (not used by SISMA)
The DFS equipped with a flat convex lens generates a trapezoidal working volume characterized by a limited height excursion (only a few cm) and a working base area that is larger than normal.
Generally, the largest laser spot dimension detected on the plane is considered to uniform the processing; consequently, there is going to be a greater spot with an oval component, linked to the incidence of the beam with respect to the plane.
DFS with f-Theta lens
(used by SISMA)
The DFS used in SISMA utilizes f-Theta optics, which allows for a smoother and more contained spot than alternative optics resulting in better processing quality.
The working volume, in this case, is represented by a parallelepiped with a base slightly smaller than the normal marking area. This allows for a large variation of the work surface up to 14 cm of excursion, without requiring the physical movement of the Z axis.
The SISMA DFS function allows:
- the ability to focus on a known uneven surface
- to operate on levels at different heights, without physically moving the Z axis
- to machine on cylindrical surfaces, within the permitted optical limits
Perfect centering: DFS + CVS, our integrated coaxial vision system
Our CVS vision system, coaxial to the laser beam, allows to see the marking area directly in the software.
By combining the DFS system with CVS technology, it is possible to accurately center the element to be machined, an action that is always difficult in the case of parts with uneven surfaces.
Add DFS to the configuration of your SISMA laser marker
There are a multitude of applications of DFS in laser processing.
2D marking on 3D elements
Markings on pipes, non-flat mouldable surfaces and inclined surfaces.
Multilevel 2D marking
Multi-level markings at different heights up to 140 mm (with 254 focal length) without moving the Z axis and reducing time by up to 95% for quick markings.
Texturing on 3D elements
Continuous machining on non-flat surfaces with large variations in height.
Paint removal on 3D elements
Paint removal of complex shapes, selectively removing the material with a 3D mapping pre-set in the management software.
2D engravings
The high speed of the focus excursion reduces the processing time by up to 50% in normal 2D engravings since the system does not need to physically move the Z axis.
2D engravings on 3D elements
In the engraving processes, the use of DFS allows to significantly reduce the processing execution times. The wide range in Z makes it is possible to quickly engrave work areas at different levels.
3D engravings on 3D elements
By combining engraving with non-flat surface processing, it is possible to obtain 3D machining on 3D surfaces. The processing software manages to select the combined geometries to guarantee an optimal result on the finished piece.