A normal question from customers, they wonder how to operate the machine well with the right approach. Why is the cutoff effect bad? Is there a problem with the focal length? We will clearly present in this blog on how to fine tune the focus.

Definition of focus position

The distance from the focal point to the top surface of the cutting workpiece. The position of the focal point on the workpiece is generally called the positive focal point. And the position of the focal point under the workpiece is generally called the negative focal point.

Positive focus cut

That is, the cutting focus is on the workpiece, the focus position above the cutting material. For cutting oxygen with carbon steel, it is appropriate to take a positive approach. The bottom groove of the workpiece is wider than the groove of the upper surface, which is beneficial for the discharge of slag and oxygen to the bottom of the workpiece to participate in the complete oxidation reaction. In a certain focus range, the higher the positive focus, the larger the plate surface dot size. The more sufficient preheating and heat supplement around the cutting seam, the smoother and brighter the carbon steel cutting surface is.

Negative focus cut

That is, the cutting focus is below the workpiece. In mode, since the focus is far from the cutting surface, the cutting seam is wider than the cutting point on the workpiece surface. And the required cutting air flow is large and the temperature is sufficient. When cutting stainless steel, it is suitable to adopt negative focus cutting, smooth cutting surface and good section.

For plate piercing before cutting, due to a certain piercing height, a negative approach is adopted for the piercing position, which can ensure the minimum spot size and the maximum energy density of the piercing position. Also, the deeper the drilling position, the greater the negative focus.

Zero focus cutoff

That is, the cutting focus is on the surface of the workpiece, which is generally relatively smooth near the cutting surface of the focus, while the bottom surface away from the cutting focus appears rough.

The positive and negative selection of laser cutting focus is not determined by the cutting plate material (stainless steel, carbon steel).

But by the cutting method (oxidation cutting, melting cutting).