Whats the difference between 2.5D and 3D laser marking machine?

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Whats the difference between 2.5D and 3D laser marking machine?
https://www.hiteccnc.com/Latest-News/show-50-120-1.html

2D has 2 true axis of X Y axis moving.
2.5D has a 3rd axis but its of very limited utility. It uses the electric Z axis to realize the function of moving up and down
3D has 3 true and relatively equal axis of movement/control in something resembling “volume”.

2.5D working principle

The 2.5D fiber laser with 2D galvo head,which have not the Z axis mirror. It used the Motorized lifting pillar stands for the third mirror to move automatically.

Its working process is: in the process of processing, each layer is processed, the motorized lifting pillar moves, adjusts the height of the galvanometer, and then emits laser, so as to ensure that the laser spot is well focused on each layer, and finally achieve the relief effect.

2.5D laser engraving machine can finish all 2D laser work and can make 3D laser engraving on flat plate. 2.5D CANNOT make 3D engraving on curved part.

Lifting pillar of 2.5D laser machine must be motorized type. Because laser head need to re adjust the focus during engraving.
2.5d fiber laser
What a 2.5D laser marking machine can do? (youtube video link)

2.5d laser marking machine

3D working principle

3D means dynamic focusing.3D laser machine with 3D galvo head,which have three mirrors,the Z axis mirror can be moved back and forth.

The 2.5D laser with 2D galvo head,which only have two mirrors.

This is the key technology of 3D laser marking machine.

Its working process is: the joint coordination of the Z-direction dynamic axis and the XY-axis is controlled by software. With the difference of the number of processing layers, the Z-direction dynamic axis moves back and forth to focus compensation to ensure the consistency of the light spot during the whole work process.

In contrast, when the 3D galvanometer is processing relief, the Z-axis and the XY-axis are fully coordinated, which can achieve nearly microsecond forward and backward movement focus compensation, without being restricted by an external lift table, and higher efficiency and accuracy. The 3D galvanometer is more inclined to industrialized products.
2.5d &3d fiber laser

What a 3D laser marking machine can do?
https://youtu.be/kOT-rIlzWGU