Use of inner-heated circular microwave spot to cut glass sheets based on thermal-controlled fracture method

摘要

Microwaves can be used to heat the inner part of glass sheets at a lower cost compared to lasers, making them more economical for use as the heat source in the thermal-controlled fracture method. Previously, only an elliptical microwave spot was used to cut glass and SiC ceramics; however, this method can only form a straight cutting path. In this study, the use of a circular microwave spot has been proposed for the first time to cut glass sheets in order to form a more complex cutting path. By using a circular microwave spot, we were able to realize both straight and curved cutting paths at a temperature lower than that employed by a laser source when generating straight and curved cutting paths. First, a model and corresponding apparatus capable of generating a 3 kW circular microwave spot with a diameter of 10 mm was developed. Then, the power density of the circular microwave spot was characterized. Unlike the circular laser spot used previously, the circular microwave spot can heat the inner parts of a work-piece more rapidly. Next, both straight and curved fractures of glass sheets were simulated and realized by using the circular microwave spot. The maximum temperature of the glass cut using a microwave was 127 degrees C, which was much lower than the maximum temperature reached with the use of a laser. Results of the simulation and the SEM analysis indicated that this peak temperature was caused by additional stress. The stress was induced by both the use of the inner-heated microwave spot and uneven absorption of the microwave owing to the different micro-composites of the glass. Lastly, the deviation between the cracking path and heated path was analyzed. The cracking path tended to deviate from the heating path where the material thinned. The simulation results indicated that the deviation was caused by the asymmetrical stress induced during the cutting process.