Core Technology of Three-dimensional Dynamic Focusing Laser Marking Machine: Laser Scanning Galvo Mirror

The laser marking process is a widely used new technology that uses a laser beam with an appropriate energy density to scan the target surface, which results in a physical or chemical change in the material and produces a trace on the surface to form the marking. It is characterized by wide application scope, fast marking speed, stable performance, high quality, low operating cost, low environmental pollution, and easy computer control. It has become one of the important application areas of lasers.

The galvo mirror scanning laser marking technique is based on the control of the deflection angle of two high-speed galvo mirrors

The galvo mirror scanning laser marking technology of the XY galvo scanner marks the surface of the workpiece by controlling the deflection angle of two high-speed galvo mirror mirrors through focusing on the surface of the workpiece. Compared with traditional marking technology, it has the advantages of wide application scope, no mechanical deformation of the workpiece, no pollution, fast marking speed, good repeatability, high degree of automation, and is widely used in industry, defense, scientific research, and many other fields. High-speed and high-precision galvo mirror marking has become the development direction of the current marking industry.

The traditional galvo mirror marking control system is connected to a single-chip control board through the serial port and ISA bus of a PC, which is simple in interface, convenient in connection, low in development cost, but cannot meet the real-time requirements of modern numerical control systems due to low transmission speed. In the field of laser marking control technology, some new explorations have been carried out: a new way is proposed to control the galvo mirror marking control system using high-speed data transmission and processing capabilities, to achieve precise control of marking control, improve control efficiency, and ensure system real-time performance.

This kind of system has low cost and fast scanning speed, but the scanning field size and spot quality are severely limited by the lens design. Different from the front focusing scanning system, in the three-dimensional dynamic scanning system, the scanning galvo mirror is placed behind the focusing mirror. Its focusing mirror system consists of a movable beam expander and a focusing mirror group. The laser beam enters the beam expander first and then the focusing mirror group, and then reflected by the scanning galvo mirror, and finally reaches the focal plane. By moving the beam expander along the optical axis direction with a transmission device, the distance between the beam expander and the focusing mirror group can be changed, thus changing the position of the focusing spot in two-dimensional or three-dimensional space, called "three-dimensional scanning". The focusing surface of this system is a curved surface, and the flat field can be achieved by micro-adjusting the distance between the beam expander and the focusing mirror group with the rotation of the scanning galvo mirror.

The advantages of the three-dimensional dynamic scanning galvo mirror system

• A smaller focusing spot can be obtained compared with the front focusing system.

• The uniformity of the focusing spot can be improved.

Among various marking methods, galvo mirror marking has become the mainstream marking method at present due to its wide application scope, ability to perform vector marking and mark dot matrix characters, adjustable marking range, and fast marking speed. It is considered as the development direction of future laser marking.

The principle of galvo mirror scanning online laser marking

The laser beam output from the laser passes through the X-axis scanning galvo mirror, the Y-axis scanning galvo mirror, and the flat field focusing mirror, and converges onto the workpiece surface of the production line. By controlling the rotation of the X-axis and Y-axis scanning galvo mirrors, the laser beam can be arbitrarily moved in the X-axis direction (parallel to the production line direction) and the Y-axis direction (perpendicular to the production line direction) on the material surface to produce the corresponding marking.