Sapphire laser cutting machine is a high speed and high quality cutting method. Cutting sapphire chips not only has the characteristics of fast processing speed and good cutting quality, but also can cut many graphics. Sapphire is a hard and brittle material, and general mechanical processing will make it easy to produce cracks, fragments, delamination, edge collapse, edge fracture, tool wear and other defects. Because of its good chemical stability, traditional chemical processing methods are difficult to process sapphire. Therefore, the appearance of sapphire laser cutting machine is particularly important.
Because of the uniqueness of sapphire, when we operate the sapphire laser cutting machine, we should also pay more attention to the problems. Here is a group of tests to identify the precautions of the sapphire laser cutting machine:
First, the principle of QCW sapphire cutting is shown in the figure below. The laser is transmitted to the collimating mirror through the optical fiber and then passes through the focusing mirror. After obtaining the focus spot in the focal plane, it acts on the sapphire surface to achieve cutting; The automatic control system controls the mobile platform to move in X and Y directions. QCW quasi continuous fiber laser is used to cut optical grade sapphire substrate, with thickness of 0.52mm and diameter of 5mm.
The applied pulse width is 0.15~0.18 ms, the wavelength is 1064 nm, and the spot diameter is 15 μ m. The repetition frequency is 0~5 kHz, and the variation range of energy density is 0~2.4 ×  105J/cm ²、 The cutting speed varies from 0 to 50 mm/s. Nitrogen is used as the auxiliary gas for processing, and the nozzle diameter is 0.5-1 mm.
Selection of knife starting line position: first, set the knife starting line position in the sapphire cutting software. We can change the angle Θ (angle between tool starting line and material edge) to change the position of tool starting line. And observe and analyze the influence of the position of the starting line on the cutting quality Θ。 15 °, 30 °, 45 °, 60 °, 75 ° and 90 ° are selected for the test, and the length of the starting line is 0.3mm.
Cutting results and analysis: from the photos of cutting samples, it can be seen that: 1. The edges of the cut sapphire are smooth, basically free of slag and burrs; 2. The cutting surface has almost no slope, and the taper is within 100; 3. The cutting edge of the front side of the sapphire is better. The size of the edge collapse is smaller than the size of the back side, and the size of the back side is also controlled at 10 μ M below.
Therefore, a very important factor affecting the amount of sapphire edge collapse is the laser energy density. The larger the laser energy density is, the more obvious the edge collapse on the back of the sapphire is, and the larger the size of the edge collapse is. Therefore, while ensuring that the sapphire can be cut through, reducing the laser power will improve the edge collapse on the back of the sapphire to some extent. However, the smaller the energy is, the more serious the slag is on the back, and it is not easy to remove. If the laser energy is properly increased, the molten material on the back of the sapphire can become powder, which can change the cutting effect on the back of the sapphire.