Application and process of ultraviolet laser in 3D printing (SLA)

This article will guide you to understand and master the process research and application of UV lasers in 3D printing.

1. Laser and laser processing technology

(1) Laser is one of the important inventions in the 1960s. It has the advantages of good monochromaticity, directionality, strong coherence and high power density. With the development of the industry, there are more and more types of lasers. According to its wavelength, it can be divided into three categories: infrared laser, green laser, and ultraviolet laser. The application and process of ultraviolet laser are mainly introduced here.

(2) Ultraviolet laser

The wavelength of ultraviolet laser is 355nm, which belongs to the cold light source, which can be better absorbed by the material, and the damage to the material is also the smallest. The wavelength of the ultraviolet laser is short. Taking the domestic Belling 3W ultraviolet laser as an example, the pulse width is 10ns-15ns, and the action time on the material is short, which can minimize the time of thermal effect and protect the material. The spot is 0.5mm (The above data will be different for lasers of different manufacturers), the smaller the spot, the more concentrated the energy. Compared with the high thermal effect of fiber lasers and the large spot of CO2 lasers, ultraviolet lasers have unique advantages in processing some special materials.

Research and Application of Ultraviolet Laser 3D Printing Technology

UV laser

Second, the application and process of ultraviolet laser in 3D printing (SLA)

(1) Principle and mechanism of UV laser 3D printing

The ultraviolet laser irradiates the liquid photosensitive resin through the pulsed ultraviolet wave (UV), and then the scanning galvanometer scans the X-Y plane layer by layer from bottom to top, and finally solidifies and forms with high forming accuracy (±0.1mm). ), with a high degree of analog reducibility.

(2) The main parameters of UV laser in 3D printing

Since the absorption coefficient of ultraviolet light by the liquid photosensitive resin is the largest, the resin can be cured with a lower light energy density, but the absorption of ultraviolet light by the photosensitive resin follows the Beer-Lambert law, that is, the energy density of ultraviolet light increases with the transmission. The increase in depth decays exponentially. Theory and experiments show that only when the ultraviolet energy density received by the liquid photosensitive resin exceeds a certain threshold, gel will be generated (gel state is a critical state between liquid and solid), so it is necessary to continuously output more than 200mw during the curing process. The continuous UV light can cure it, but how can we achieve better curing quality?

The curing quality of the resin is mainly determined by the scanning speed of the ultraviolet laser on the liquid surface, the spot size of the laser forming and the continuous output power of the laser. The scanning speed of the galvanometer directly affects the number of pulses of the laser and the contact time of the ultraviolet laser on the surface of the liquid photosensitive resin. If the scanning speed is too fast, it may directly lead to insufficient number of laser pulses, or the final curing hardness caused by the short contact time. A series of problems such as low or curing failure. The size of the final UV spot on the surface of the liquid photosensitive resin affects the thickness of the support and the thickness of the finished product, and if the laser spot is not round, it may cause uneven energy distribution on the resin, resulting in a decrease in the final molding quality or curing line width. exception, etc. The last is the laser power. Generally, the continuous and stable output power between 350mw and 500mw is the best. If the power is too high, the resin may turn black or yellow. If the power is too low, the resin may turn white or decrease in hardness. Can cause problems such as curing line and curing depth abnormality. In summary, we need to meet the following conditions for the laser to obtain better curing quality: 1. Continuous and stable output power and above 350mw; 2. 2. Continuous and stable laser output pulse; Better laser spot quality.

The 0.5-3W air-cooled UV laser is specially launched for 3D printing and additive manufacturing applications. The single-pulse energy of this laser is >5μJ@100kHz, the repetition rate is 30-100kHz, the pulse width is <70ns@100kHz, and the beam quality is high (M2< 1.3), spot roundness > 90%, these strict parameter requirements can perfectly solve a series of problems such as insufficient hardness and color difference during the curing process, and the air-cooled cooling method makes the laser smaller and easier to integrate 3D printing the overall light path of