Hyperboloid glass is more common in our daily life, such as cars or airplanes are used as hyperboloid heat bending glass as windshield glass. The shape of the glass is achieved by hot bending technology. To get hyperboloid glass, through the laminated hot bending technology, it is the use of more than two pieces of single glass hot bending → laminated glass. Laminated hot-bending glass can ensure the good fit and optical quality between the glass, and the accuracy and shape of the glass are also guaranteed.
The processing method of laminated heat bending glass has the same as that of ordinary glass processing, but also has different places. Its heating method is as follows:
1. Die heat storage stage: the heating element is rationally arranged in the furnace space to ensure the uniformity and balance of the temperature in the heating furnace.
2. Heating stage: when the temperature reaches 300 degrees Celsius, restart the other groups of heating elements, the left, middle and right sides of the glass should be heated at the same time, to ensure the stable heating rate of the hot bending furnace, must not be heated hastily.
3. Hot bending stage: when the glass is between 420-630 degrees Celsius, it maintains the state of viscoelastic body, and the rheological model is more complex. When the deformation temperature of the glass is close, several groups of heating elements can be closed to keep both sides of the glass surface heated, and the influence of the glass weight on the glass surface can be reduced by the temperature gradient.
4. Annealing stage: after the heat bending glass forming, the heating element in the hot bending furnace, do not immediately take out the glass, but let the glass stay in the forming room for a period of time, the length of time according to the glass specifications, shape, thickness, state and so on, will also be determined according to the operator's experience to judge, there is no fixed formula to calculate.
In the process of hot bending, single glass is affected by multiple factors such as elasticity, heat conduction, viscosity, specific heat and density, among which elasticity and viscosity are crucial, and temperature is the main factor that determines the viscosity, elastic constant and shape accuracy of glass optical quality. Therefore, in the process of heat bending glass, temperature is the key and the way to determine the quality of glass.