1.Focus point on the surface of the material
This method also calls 0 focal length, in this method, the focus point close to the surface of the material. In this way, the smoothness of the upper and lower surfaces of the material is different. The near-focus cutting surface is more smooth. The lower surface away from the focus point is more rough. You should use this mode according to the process requirements of the upper and lower surfaces in the actual application.
2. Focus point inside the material
This method also calls positive focal length. When the material you need to cut is stainless steel or aluminum, you should set the focus inside the material. However, as the cutting surface is far away from the surface of the material, the cutting edge width is larger than the focus point on the surface of the material. Meanwhile the cutting gas in this method need to be more stronger. The temperature need to be enough. The cutting perforation time is slightly longer. Therefore, you should use this mode when the material you choose is mainly stainless steel or aluminum material and hard material.
3. Focus point on the material
This method we also calls negative focal length. Because the cutting point is not on the surface of the cutting material nor inside the cutting material, but rather above the cutting material. This method mainly used for cutting thick materials. Why focus on the top of the cutting material? Because the thick plate needs a large cutting width. Otherwise the oxygen delivered by the nozzle is very likely not enough. And lead to lowered the cutting temperature. However, the cutting surface in this method is rough and not practical for high precision cutting.