Why is there a crack at the front end of the curved/arc edge of tempered glass and what are the solutions?

The arc edge cracks of bent/curved tempered glass usually occur during the bending and tempering process of thick glass with small radius, especially at the front end of tempered glass processed by soft shaft bent glass tempering furnace, this problem is more common.

There are several possible reasons and the solutions for this situation:

1.The main reason for this problem is that the front-end cooling is too fast. To solve this problem, there are two common methods:

1.1. Place a guide glass at the front end. We mean, when you produce the curved tempered glass, you can put one small piece of glass at the front side.

1.2. Increase the chamfer of the lower edge of the front end for the curved tempered glass.

2. The arc length of tempered glass is too long, so the over long part could be not cooled by the quenching section. Therefore, a small amount of explosion cracks/marks usually appear on the edges. At this point, we should adjust the curvature of the bent quenching section and correct the glass position in the bent quenching section.

3. When there are cracks on the arc edge of the bent tempered glass; We should reduce the tempering air pressure of the curved quenching section, appropriately shorten its blowing delay time, and reduce the arcing-changing speed.

4. When the glass is tempered inside the curved/bent quenching section, if the tempering air/wind pressure is set too high, it will cause cracks to appear on the arc edge of the tempered glass. At this point, we should appropriately reduce the air pressure according to the actual situation.

5. Cracks on the curved edges of bent glass may also be caused by insufficient heating of the glass edges in the heating furnace, resulting in excessively low edge temperatures when it comes out from the furnace; At this point, the set temperature of the glass edge should be increased to ensure sufficient and effective heating of the glass edge, which can solve this problem;

6.If the arc changing speed of bent quenching section is too fast, it will also cause cracks to appear on the arc edge of the tempered glass; At this point, we should modify the arcing speed parameter of the bent quenching section on the tempering process parameter page of the control software.

7. If the blowing delay time during tempered cooling is too long, it will cause cracks on the curved edge of the bent glass; Modifying process control parameters and appropriately shortening the blowing delay time is an effective solution to this problem;

8. If the pre-processing of the glass edge is not done well during the cold processing stage, it will cause cracks to occur at the arc edge of the glass during tempering; So we should firmly ensure that glass that does not meet the process requirements does not enter the furnace;

9. In the air ducts of bent quenching section of the glass tempering equipment, the open & close device is not tightly closed, resulting in air leakage, which leads to a low air pressure and causes cracks on the curved edge of the bent tempered glass; At this point, the leakage point of the circuit breaker should be determined and sealed.