How do we understand zero focus? How do we find zero focus?

2023-03-30

In laser cutting, the position of laser focus has great influence on the cutting quality. The traditional laser cutting method is to use a laser beam to irradiate the workpiece surface, so that it evaporates and melts, thus forming the notch. In the process of laser cutting, by controlling the relative position of the workpiece and the laser focus, the metal can be vaporized, evaporated or condensed at different times to form the slit, so as to achieve the purpose of cutting.

The laser focus position refers to the position of the center of the laser beam spot, that is, the location of the focus. In high power laser machining system, in order to improve the uniformity of intensity distribution of laser beam focusing spot and the controllability of spot shape, optical path compensator is often added to laser beam to obtain uniform and narrow spot and large intensity.

A lot of laser equipment, in the process parameters of the focus set to 0 focal, but the actual laser focus does not exist zero generally has a deviation of plus or minus 2, outrageous even 3, 4 deviation, causing this situation more reasons.

We all know that focus has a great influence on laser cutting, before the process debugging, it is best to determine the position of zero focus, refer to the following figure, cutting head optical path simple diagram

The intersection point of light after the laser passes through the focusing mirror is the focus. We input different values in the focus position of the process parameters, and the focus will move up and down. When the focus is on the surface of the plate, it is zero focus, and the slit is the thinest.

The standard zero focus is 0 position, that is to say, in the process parameters, the focus position is entered 0 and the crossing point of time is just on the surface of the plate. During the process debugging, all the focus parameters are set according to 0 focus. At this time, the slit of the focus on the surface of the plate is the thinnest, and the more the focus is biased, the larger the slit is.

Now let me give you an example of how do you determine the focus of zero?

As shown in the figure above: Cut a straight line with air cutting respectively at the focal point +3, +2, + 1,0, -1, -2, -3. Let's see how the size of the slit changes. At this time, the smallest one is the focal point of 0.