The collimation focusing head can be divided into high-power and medium low power welding heads according to the application scenario, with the main difference being the lens material and coating. The phenomena exhibited are mainly temperature drift (high-temperature focus drift) and power loss. A collimating and focusing head with generally good temperature drift can be controlled within 1mm; Almost exceeding 2mm; Power loss mainly refers to the power loss caused by the laser entering the welding head from the QBH head and then protecting the lens from below. The main energy is converted into lens heating, which generally requires less than 3%, some can reach 1%, and some can exceed 5%. Therefore, these two are actually key indicators for collimating and focusing heads. It is best to measure them yourself before use or request the manufacturer to provide relevant reports to ensure that the product meets the requirements of industrial production on site.
Classification of collimated focusing heads – functional classification
According to whether it has swing function and whether it is a single or double mirror, it can be divided into ordinary collimating and focusing head, single pendulum head, and double pendulum head. It mainly targets different scene requirements, and the trajectory of the double pendulum will be more and complex than that of the single pendulum.
According to the matching laser system, it can be divided into: (1) dual band composite head (red blue, fiber semiconductor, etc.), (2) composite swing head (single swing), and point loop head.
(3) Point ring welding head is a relatively new type of welding head that can shape high-power laser beams into circular or point ring shapes through beam shaping, balancing energy distribution. It feels similar to turning high-power lasers into circular light spots, but it is different. Compared to circular shapes, the center energy of point ring heads is insufficient and their penetration ability is limited. However, this simple way of achieving laser energy distribution similar to circular light spots through point ring heads can achieve low-cost and low splashing effect. In the welding of steel, it has the unique advantage of gas. Due to the enlargement of light spots and the uniformity of energy density, it may be prone to false welding on high reflective materials (aluminum, copper).
Collimated focusing lens
For the lenses used in laser transmission systems, their materials can be divided into two types: transmissive materials and reflective materials; The collimating focusing lens and protective lens shall be made of transmissive materials. Requirements: the material shall have good transmissivity to the working wave band, high operating temperature and low thermal expansion coefficient. Generally, the collimating focusing lens shall be made of fused silica; The protective lens is made of reflective material, commonly K9 glass. Reflective optical elements are made by coating a thin film of high reflectivity metal material on polished glass or metal surfaces, and reflection does not have dispersion. Therefore, the only optical characteristic of reflective optical materials is their reflectivity of various colors of light. The coating material requirements for optical lenses are: 1. Stable reflectivity of light; 2. High thermal conductivity; 3. High melting point; In this way, even if there is dirt on the coating layer, excessive heat absorption will not cause cracking or burning.
The combination of collimation and focusing mainly affects the spot size: The spot size of the laser beam is an important parameter that affects the quality of scanning welding, especially the spot size focused on the surface of the workpiece directly affects the power density of the laser beam. When the scanning laser power is constant, a smaller spot size can achieve a higher power density, which is beneficial for welding high melting point and difficult to melt metals. At the same time, it can obtain a larger aspect ratio and meet certain special welding requirements. When the melting point of the welding base material is low, or when there is a certain gap between two plates during welding, a larger spot size is often chosen to achieve better welding results.
The collimation focal length is generally between 80-150mm, and the focusing focal length is generally between 100-300mm,; It mainly depends on the processing distance and spot size (energy density), as well as the tolerance of the spot to the weld seam gap (if the spot is too small, the gap will leak light if it is too large, and the gap is generally not greater than 30% of the spot diameter).
Pre use testing of collimating focusing head: transmittance testing; Temperature drift test
Post time: Mar-25-2024
