How Does Laser 3D Printing Precisely Sculpt Models?

When 3D printing is mentioned, you might first think of plastic filament stacking. But there's a laser 3D printing technology-stereolithography (SLA) based on high-speed galvanometer scanning-that can create delicate models as if "sculpting with light," while avoiding the "match-head" defect. How does it balance high precision and efficiency?

Unlike ordinary fused deposition modeling (FDM), which builds objects by stacking molten plastic filaments, SLA uses liquid photosensitive resin. An ultraviolet laser cures the resin where it hits, and a galvanometer-acting like a "light pen"-controls the laser to draw each layer's outline, which is then stacked to form the model. The high-speed galvanometer and intelligent control system are the keys to making the laser "draw fast and accurately."

The galvanometer is the "precision navigator" of laser 3D printing. Composed of mirrors and scanning motors, it controls the laser to scan rapidly in the X and Y directions-faster and more stable than early XY-axis moving platforms. However, at high speeds, galvanometers can exhibit lag, such as "rounding" corners, and changes in speed can cause uneven resin curing, resulting in the "match-head" effect.

The solution is to add an intelligent control scheme to the galvanometer:

• Use a speed planning algorithm to calculate the maximum speed for different corners (about 750mm/s for 180° corners, up to 2500mm/s for 20° corners), allowing precise corner traversal.
• Adjust laser power in real time with speed to ensure uniform resin curing energy and avoid abnormal solidification.
• Reading 3D model files efficiently is also crucial. Files like Gcode and SLC can be hundreds of megabytes, making direct reading slow and previewing specific layers difficult. Researchers use segmented multi-channel caching-splitting the file, parsing in parallel, and using binary search to quickly locate target layers-greatly improving efficiency.
• After parsing the contours, the ray casting algorithm is used to distinguish inner and outer contours (odd intersections mean inner contour, even intersections mean outer contour). The order is adjusted according to rules and a "contour tree" is built to prevent the laser from "drawing the wrong boundaries."

Today, SLA technology can print highly detailed models, from small dental models to large industrial parts, and is used in jewelry making, industrial prototyping, and medical restoration. It is not just "stacking materials" but "sculpting details with light and algorithms", promising more high-precision, personalized products in the future.