Chapter 5 Solutions to Production Process Problems of Tempered Glass

1、 Confirmation items before production:

1. Confirm that the drive air supply is normal and the pressure changes between 6kg/cm2 and 8kg/cm2.

2. Confirm whether the driving air has been removed from the moisture contained by the air dryer.

3. Confirm whether the furnace temperature has reached the working temperature and must be kept warm for at least 20 minutes. Maintain a clean environment around the machine and clean the entrance workbench. (Special attention should be paid to the cleanliness of the entrance workbench to prevent dust from entering the furnace when the glass enters, which may affect the quality of glass production.)

4. Set working parameters based on the thickness, processing status, and edge grinding quality of the produced glass.

5. Activate the blower and set production parameters.

6. Enter the furnace in a simulated manner 2-3 times. During the simulated operation, please confirm whether the blower operates normally, whether the reinforced air pressure setting is correct, and whether there are any abnormal sounds or noise during machine operation.

7. Usually, simulation operations can be used to test the normal operation of the machine and quickly increase the furnace temperature to the working temperature.

8. Formally arrange and enter production.

2、 Precautions during production:

1. Check the glass for defects such as bubbles, scratches, notches, and poor edge grinding during film arrangement; Pay special attention to the arrangement of glass sheets, as poor arrangement can easily cause uneven temperature in the furnace, affecting the quality of glass production. In severe cases, it will significantly reduce the success rate of glass strengthening. (For the arrangement method of glass, please refer to the example of glass arrangement)

2. Do not fill the furnace during the first sheet production, as sudden and significant sheet changes may cause insufficient reaction speed in the heating zone. Therefore, if produced at normal heating time, the glass may crack in the strengthening zone due to insufficient temperature. We strongly recommend that operators adopt an asymptotic sheet arrangement method, such as increasing the sheet arrangement in the first furnace to 40%, increasing the sheet arrangement in the second furnace to 60%, and continuing to increase the sheet arrangement in the third furnace to 80%, in order to gradually increase the sheet arrangement until the furnace is full. This method not only improves the success rate of glass strengthening, but also has a significant effect on the uniformity of temperature inside the furnace.

3. After three or four consecutive non full furnace production, proceed with full furnace grate production.

4. During full furnace production, special attention must be paid to the temperature changes inside the furnace. Timely adjustment of the temperature setting for each group of electric heating can make full furnace production smoother and more stable.

5. When arranging glass sheets, it is necessary to ensure a uniform load. The distance between the front and rear sheets should be at least 50mm, and the distance between the left and right sheets should be at least 30mm. If the gap is too large, it is necessary to arrange the plates alternately from left to right and from front to back, and pay attention to the temperature changes in the furnace at any time.

6. Pay attention to the changes in wind pressure values at all times and make timely adjustments to ensure that there are no significant differences in the quality of the produced glass.

7. If the glass breaks in the furnace (due to improper position and size of glass drilling or poor annealing of thick glass, it is easy to cause cracking in the furnace), production should be stopped immediately and the broken glass should be cleaned. After the furnace cools down, the surface of the roller should be cleaned to avoid glass chips left on the surface of the roller, which may affect the quality of the produced glass.

III Glass breaks in the strengthening zone

Reason:

The original quality of A glass board is poor, with bubbles, missing corners, cracks, uneven thickness, poor quality of grinding and drilling, or impurities in the glass.

Insufficient temperature or uneven heating of B glass.

Improper clearance between C glass sheets caused collisions in the strengthening area of the glass.

Adjustment method:

Pay attention to the quality of the glass raw material and the processing quality of the previous process.

Increase the heating time of the glass and confirm whether the temperature conditions are correct and whether the arrangement method will cause uneven temperature in the furnace.

Confirm whether the glass arrangement method and spacing are correct.

The heating time for large pieces of glass (single piece fully loaded) must be increased, and the temperature and power of the upper and lower main heating furnaces should be appropriately extended by 5-10%.

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Glass with white lines

Reason:

The surface of the A roller is overheated.

The surface of the B roller is not clean or too rough and dry.

The interval between C and furnace is too long.

The swinging speed is too fast in the early stage of D.

Adjustment method:

Reduce the furnace temperature setting by 5-10 ℃ or change the process,

B Stop the furnace, clean and maintain the roller.

C Shorten the interval time.

D reduces the initial swing speed.

Lower temperature too high: Adjust the lower temperature setting value while reducing the lower set power.

The white line usually occurs in the first few heats after the furnace is opened.

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4、 Strengthening of Special Glass

The following are our suggestions for the precautions that should be taken during the production of some special glass. These suggestions are provided to operators as a reference for production data.

4.1 Glass with holes and gaps

For the relevant regulations on the position and size of glass holes or notches, please refer to the size regulations when glass has holes or corners. If the hole position is close to the corner at the edge of the glass, and its distance is shorter than the recommended size when the glass has holes or missing corners, the glass at the corner is prone to cracking during heating and forming defective products, and the broken glass will fall into the furnace. If the number of drops is too large, it is easy to cause the uniformity of the temperature in the furnace to deteriorate, and in severe cases, it can even cause a short circuit in the lower electric hot wire. If a notch is cut at the narrowest point of the glass at this time, it can reduce the risk of glass breakage during heating.

When strengthening glass with holes, the heating time must be increased by 2.5% to 3% compared to flat glass of the same material; When strengthening glass with holes and notches, the heating time must be increased by 5% to 6%; However, this is only a rough number, as the main factor determining the increase in heating time is the processing quality of holes and notches.