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How to Understand the Focus Point for different Materials

f is focus length

f=0 focus length right matched, focus point in the surface of the metal, the strongest laser power, and weld sound clear & clean.

f>0,  focus point inside the metal.

f<0, focus point on the top of the metal.


if f=0, Extension tube just right matched.
the focus point with the smallest spot diameter, the point with the strongest energy laser beam.
When you weld thin steel require small laser spot with good focus.

if f<0: Extension tube is short.
the diameter of the laser spot is a bit bigger, shorten more away from the focus, the bigger  spot you get, which is suitable for continuous welding on thick steel with deep welding penetration, as you can see the focus length inside the metal sheet.

if f>0, Extension tube is long.
the diameter of the spot is getting bigger too, and the more away from the focus point, the bigger spot you get,  It is suitable for continuous welding of surface sealing welding with high requirement of deep penetration.


we recommend to weld thin metal sheet in the right f (focus length)

f<0 for Thick carbon steel welding.

How to adjust it to get the right focus point for welding?

Shorten the extension tube on the welding head will help you to get the right focus point.

Note:  “0” mark on the welding Extension tube is not always mean the Exact f=0, sometime f=3, or f=-2, depends on real test.

We will show you how to find out the focus point of the laser welding gun, not always f=0,  it happens like f<0 or f>0.

Let’s check the video.

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