Cut a good workpiece with a laser cutting machine

        Since the laser power density has a great influence on the cutting speed, the choice of lens focal length is an important issue. After the laser beam is focused, the spot size is proportional to the focal length of the lens. After the beam is focused by a short focal length lens, the spot size is smaller, and the power density at the focal point is higher, which is beneficial for material cutting; but its disadvantage is that the focal depth is short and the adjustment margin is small. Generally more suitable for high-speed cutting of thin materials. Since the long focal length lens has a wider focal depth, as long as it has sufficient power density, it is more suitable for cutting thick workpieces.

       After determining which focal length lens to use, the relative position of the focal point and the surface of the workpiece is particularly important to ensure the cutting quality. Due to the high power density at the focal point, in most cases, the focal point is just at the surface of the workpiece during cutting, or slightly below the surface. In the whole cutting process, ensuring the constant relative position of the focus and the workpiece is an important condition for obtaining stable cutting quality. Sometimes, the lens is heated due to poor cooling during operation, which causes the focal length to change, which requires timely adjustment of the focus position.

      When the focus is in the right position, the slit is small, the efficiency is high, and the cutting speed can obtain good cutting results. In most applications, the beam focus is adjusted to just under the nozzle. The distance between the nozzle and the surface of the workpiece is generally about 1.5mm.

In the process of laser application, problems such as focusing are often encountered. There are three common easy methods to determine the focus position:

     (1) Printing method: The cutting head is moved from top to bottom, and laser beam printing is performed on the plastic plate, with the smaller printing diameter as the focus.

     (2) Inclined plate method: Use a plastic plate placed obliquely at an angle to the vertical axis to pull it horizontally, looking for a smaller spot of the laser beam as the focus.

    (3) Blue spark method: remove the nozzle, blow air, and hit the pulse laser on the stainless steel plate to make the cutting head move from top to bottom until the blue spark is the focus.