All the parameters are designed around "uniform heating and rapid cooling", but they are not isolated, but an organic whole, which must be considered comprehensively to get a perfect process.
In order to make users grasp and understand it as soon as possible, we describe the process parameters and the mechanical and electrical design that must be achieved to ensure the process realization from three aspects:
First, heat.
Uniform heating is a crucial factor for tempered glass, and the parameters related to heating include upper limit temperature, lower limit temperature, heating power, heating time, temperature adjustment, balancing device and forced convection (hot circulating air) device.
1, upper and lower temperature settings
Due to the different thickness of glass, the setting of heating temperature is also different. The principle is that the thinner the glass, the higher the temperature, and the thicker the glass, the lower the temperature. The specific data are as follows: (Table 1)
Upper limit temperature of thickness and lower limit temperature
3.2-4 mm 720-730 degrees 7 15-725 degrees
5-6mm 7 10-720 degrees 705-7 15 degrees
8 8- 10/0mm705-710degrees 700-705degrees.
12mm 690-695 degrees 685-690 degrees
15- 19mm660-665 degrees 655-660 degrees
After the heating temperature is determined, it is very important to determine the heating time, which are two closely related parameters. The principle of determining the heating time is that the thickness of 3.2-4 mm glass is about 35-40 seconds per mm, and the thickness of 5-6 mm glass is about 40-45 seconds per mm. 8- 10 mm glass with a thickness of about 45-50 seconds per mm. 12 mm glass with a thickness of about 50-55 seconds per mm. 15- 19mm glass with a thickness of about 55-65s per millimeter. Because of different raw materials, different softening points, different colors, different thickness errors and different set temperatures and powers, it is impossible for us to say the heating time so accurately, which needs to be summarized in practice by all units, especially those that have never been exposed to tempered glass before. We have an experience for reference: the glass is broken during quenching after being discharged from the furnace, indicating that the heating time is not enough; If there are ripples and pits on the glass surface, it means that the heating time is too long. Please adjust according to the specific situation.
2, the use of heating power supply
Heating power refers to the heating capacity of tempering furnace, which is generally set to 100%, which is determined during design. Due to the different heating methods of the upper and lower parts, the upper part is mainly heated by radiation, and the lower part is heated by conduction and radiation. In the initial stage after the glass enters the furnace, the lower surface of the glass is curled by heating, and the glass will gradually flatten as the upper temperature gradually radiates to the upper surface of the glass. If the glass is excessively curled in these tens of seconds, white spots or light distortion will appear in the middle of the lower surface of the glass after being discharged from the furnace. In order to solve this problem, in addition to setting a lower temperature than the upper part, the power of the lower part should be reduced to reduce the surface temperature of the ceramic roller and make the glass curl less at this stage. If you make a lot of glass after the white fog disappears, the glass may break and you can gradually power it up.
3, the use of temperature regulation
The temperature adjustment function was set by Bei Bo Company after matrix heating, and each heating control point can be adjusted independently, which is very helpful for the process adjustment of tempered glass, especially for five types of equipment, which are widely used. Because type 5 bending tempering depends on the self-weight of glass, there is no pressure forming. If the radius is relatively small, the temperature in the middle needs to be raised appropriately. If there is crack in the front end, the temperature in the front end can be raised. In addition, when magnifying large glass below 6 mm, a spherical surface may appear in the middle of the glass, which can be solved by increasing the temperature between the upper and lower parts. For another example, the upper surface of conductive film glass absorbs heat very slowly, so the lower surface absorbs heat too quickly, and there may be optical distortion in the middle part of the glass after being discharged from the furnace, which requires reducing the power at the lower part in addition to setting the temperature low. Because the aspect ratio of glass is different, the degree of light distortion will be different. To what extent should it be reduced? In continuous production, there is no optical distortion on the glass surface, and the yield of glass can reach the index. The function of temperature regulation has many functions, and the key is how to use it.
4. Thermal balance device
It is a device that uses compressed air to form convection in the furnace, which can manually adjust the pressure as needed, accelerate heat dissipation and balance the temperature.
5. Forced convection (hot circulating air) device
Forced convection (hot circulating air) device is the latest device for users to choose. Its function is to strengthen convection in the furnace and shorten heating time. It is an ideal equipment for off-line tempering Low-E glass.
6. Temperature-related glass defects and their correction methods.
(1), wave reinforcement
If the set temperature is too high and the heating time is too long, the glass will appear waves. This is because the heating of the glass has exceeded the critical point and the glass has begun to soften. If this defect occurs, it can be solved by shortening the heating time.
(2) Pitting
Too long heating time will also cause pits on the lower surface of glass. There are two kinds of pits, one is dense orange peel, which is caused by long heating time. (Especially for thick glass with a thickness of 12mm or more, some units set the heating time for a long time in order to keep it unbreakable. ) can be adjusted according to the situation. The other is individual star-shaped pits, which are caused by the unclean surfaces of the feeding table and ceramic roller table, or the broken glass of the air grid roller table is not cleaned up.
③ White fog
White fog is a white mark in the middle of the lower surface of glass, which generally appears in the first few furnaces of initial production. This is due to the high surface temperature of ceramic roller. In the first few tens of seconds before the glass enters the furnace, the lower surface of the glass is directly subjected to heat conduction and its four corners curl, so the contact surface between the glass and the ceramic roller becomes smaller and the friction force with the ceramic roller increases. With the decrease of the surface temperature of the ceramic roller, the friction force disappears. We can set lower temperature and power at the initial stage of production. In addition, production should continue, and the furnace should not be idling. If it is not produced temporarily, you can turn off the heating switch to prevent white fog.
(4), bending
When we produce tempered glass, if there is bending, it is usually solved by adjusting the wind pressure or blowing distance, which is very effective and fast. But some operators don't understand that the temperature difference between the top and bottom can also cause the glass to bend. Assuming that the blowing distance is equal to the wind pressure of the grille section, if the four corners of the glass bend upward, it means that the lower temperature is too low. On the contrary, if the four corners of the glass bend downward, it means that the lower temperature is too high. If it is necessary to adjust the temperature to level the glass, it can be solved not by one or two heats, but by several heats.
(5) Sphere
This is when making thin glass below 6 mm and the layout is relatively large. You can increase the vertical temperature in the middle through the temperature adjustment function, sometimes it needs to be increased by about 30 degrees. (increasing from both longitudinal sides of the second row to the middle).
An excellent operator should understand the relationship between temperature and optical properties: high temperature and long heating time will lead to high yield, but poor optical properties; On the other hand, the temperature is low, or the heating time is short, and the optical performance is good, but the yield is low. This requires us to sum up carefully and find the best effect.
Temperature has a great relationship with the particle size of tempered glass; Under the condition of equal wind pressure, the particles are small at high temperature and large at low temperature.
Second, cooling.
Parameters related to cooling: quenching air pressure, quenching time, cooling air pressure, cooling time, delayed blowing time, fan waiting frequency, fan propulsion time, discharging speed and other mechanical guarantees related to cooling: blowing distance between upper and lower air grids, height of air duct deflector, and air inlet flow adjusting bolt.
1. Quenching air pressure refers to the air pressure required for glass tempering. The principle is that the thinner the glass, the greater the air pressure, and the thicker the glass, the smaller the air pressure. The wind pressure in northern glass tempering furnace is set by computer to change the opening of air inlet, and its value is a percentage. The unit with fan frequency converter can change the fan frequency by computer to achieve the required wind pressure, and its value is also a percentage. The theoretical wind pressure required for rapid cooling of glass with various thicknesses is as follows (Table 2 unit: Pa).
3mm 4mm 5mm 6mm 8mm10mm12mm15mm19mm
16000 8000 4000 2000 1000 500 300 200 200
Due to the different altitude, air density, ambient temperature and wind direction in different countries and places, the actual wind pressure is different from the values in Table 2 and needs to be adjusted to meet the requirements of particle size.
2. Quenching time refers to the time required for glass tempering (Table 3 unit: second).
3mm 4mm 5mm 6mm 8mm10mm12mm15mm19mm
3 - 8 10 - 30 40-50 50 - 60 80 - 100 100- 120 150 - 180 250-300 300-350
3. Cooling wind pressure and cooling time refer to the wind pressure required for cooling glass after rapid cooling, and its function is only to cool the glass to the required temperature. The setting principle is that the cooling wind pressure of thin glass is less than that of quench air, and that of thick glass is greater than that of quench air.
(Table 4 Unit: Pa)
3mm 4mm 5mm 6mm 8mm10mm12mm15mm19mm
1000 1000 1000 1000 1500 1500 2000 2000 2000
(Table 5 Unit: seconds)
3mm 4mm 5mm 6mm 8mm10mm12mm15mm19mm
20 30 50 60 80 120 180 250 300
Because the glass is only cooled, the setting of cooling air pressure and cooling time is not strict, but it should be noted that if the glass spontaneously explodes more, the quenching air pressure should be reduced. If the air pressure is already very low, but there are still many spontaneous explosions, besides the high content of nickel sulfide in the raw materials, it is also necessary to check whether the quenching time is too short. If there are multiple stations, there will generally be a special cooling section, and the cooling time and cooling air pressure may not be set.
4. The delayed blowing time is a parameter set separately for bending glass. It cannot be blown immediately after the glass is taken out of the furnace, but only after the glass is formed. It has a lot to do with the shape and particles of glass. The lag time is long. When the glass is soft, it will take a long time to reciprocate in the grille, and the radian is good, but the glass is damaged more and the particles are poor. This requires the organic combination of these two parameters to find the best point.
5. The waiting frequency of the fan and the lead time of the fan are the parameters of the frequency converter with the fan.
When the glass is heated in the furnace, the fan doesn't need to run at high speed, so the frequency can be set lower, and the speed can be increased to the required level before the glass is discharged. The setting principle is that the waiting frequency of glass thickness is lower, and generally the waiting frequency is lower than the working frequency 10- 15 Hz. The lead time of the fan is the time required to raise the waiting frequency to the working frequency, which is about 10 Hz, 15-20 seconds. If the waiting frequency is set low, the lead time of the fan will be longer. If the waiting frequency is set high, the forward time of the fan can be shorter, which can save power consumption.
6. Tapping speed is also a parameter closely related to cooling. Its function can not be ignored, especially for type 5 equipment. In order to reduce the explosion, the discharge speed is generally adjusted to 600.
7. The distance between the upper and lower air grates has a great relationship with the granularity and smoothness of glass. Under the condition of constant wind pressure, the denser the grille, the better the particles. Generally, the bending of flat glass is basically solved by adjusting the distance of the upper wind grid. (Table 6 Unit: mm)
3mm 4mm 5mm 6mm 8mm10mm12mm15mm19mm
12mm15mm 20mm 25mm 30mm 40mm 50mm 60mm 70mm
Because the distance is difficult to adjust, the small bend tempered grille can be summarized as (Table 7 unit: mm)
3.2mm 3.5mm 4mm 5mm 6mm 8mm10mm12mm
15mm15mm15mm 20mm 30mm 30mm 30mm
Because the radius is different, if the distance is too close, there will be scratches on the upper surface of the glass, just adjust the distance of the upper wind grid.
8. The air duct deflector is a mechanism for adjusting wind pressure, which is arranged in the center of the upper air duct and the lower air duct. Downward is windy above, upward is windy below.
9. The intake flow adjusting bolt (installed on the piston rod of the intake butterfly valve) is used to adjust the intake flow. The works of two fans should be equal. If there is any difference between the two fans, it can be used to adjust the consistency. If one of the fans has high pressure and high current, lower the adjusting bolt of this fan until the two fans are consistent.
10, glass defects related to cooling and correction methods
(1), bending
This is a common defect in manufacturing flat glass. As mentioned earlier, temperature can also cause bending. Assuming temperature equilibrium, if the glass bends downward, the cooling rate of the upper part is faster than that of the lower part. If the glass bends upward, the cooling rate of the lower part is faster than that of the upper part. Generally, when the glass bends downward, the height of the grille will increase, and when it bends upward, it will decrease.
(2), Fried mouth
When making flat tempered glass with large thickness, the heating time of the glass is long enough, but when blowing, the front end of the glass begins to crack first, and then breaks or splits in two. This is because of the large layout and slow discharging speed, which leads to inconsistent cooling before and after glass breaking. Generally, it can be solved by accelerating the furnace speed.
(3) Self-explosion
General self-explosion refers to the self-explosion of tempered glass after a long period of time, which is a characteristic of tempered glass, but what we are talking about here is the self-explosion of glass at the end of blowing. In addition to raw materials, the quenching pressure is too high, or the quenching time is too short and the cooling pressure is too high, which can be solved according to the specific situation, but attention should be paid to whether the glass particles meet the requirements.
Third, molding.
The parameters related to molding are: arc changing speed, grid entry distance, effective length of air grid, rapid cooling reciprocating speed, side roll pressing time, upper pressure roll action time, positioner action time, upper wind grid pre-lifting time and glass length.
1, variable arc speed
It refers to the speed at which the glass turns from flat after entering the grille, and its setting principle is as follows:
Require small radius, thin glass and faster speed; A larger radius and a slower glass thickness are required. Generally, SM 2 equipment should not exceed 350, and SM 5 equipment should not exceed 400.
2, the distance into the grid
It means that after the glass is discharged from the furnace, the front end of the glass reaches the position of the air grid.
3. Effective distance of grille
Refers to the distance between the position where the rear end of the glass reaches and the front end of the glass after the glass enters the grille.
4, quenching reciprocating speed
Refers to the speed at which the glass swings in the grille. The principle it sets is that the glass is thin, the radius is small and the speed is fast; Glass has a large radius and a slow speed. However, it must be noted that if the quenching reciprocating speed is fast, the rear end of the glass may run out of the grille, and the effective distance of the grille must be properly adjusted.
5. Edge rolling time
Is a parameter of SM 2, which refers to the action time of the press rollers at both ends of the grid. When the glass is discharged from the furnace, it reaches the front 1 press roller, which is pressed by the air cylinder, but the glass must also run to the back end to press the back end of the glass to eliminate the straight edge. Because the arc length of the produced glass is different, it takes a period of time for the glass to return from front to back, which is the edge roller time. Only by pressing both ends of the glass can air be blown, otherwise the glass will break. Especially SM 2-25 equipment.
6, the upper pressure roller action time
Because the application range of SM 2 small bending section is relatively large, which can reach the radius of 450, in order to make the shape meet the requirements, the method of back pressure forming is adopted. When the glass is discharged from the furnace, it is formed by pressing the glass by an upper pressure roller. Generally, if the radian is above the radius of 1000, no pressure is needed, and the pressure roller is self-weight. If the radius is below 1000, pressure can be used, which requires a pressing time, that is, the action time of the upper pressure roller. Generally speaking, it can be set to be approximately the same as the quenching time.
7, locator action time
Because the glass is narrow and long, after heating from the feeding platform to the heating furnace for a period of time, the glass will go to the air grid at high speed when discharging, which is easy to produce deviation and often warps the glass. In order to solve this problem, a positioning device is installed in the grille, which can adjust the glass and eliminate warping. Its setting principle is: the glass swings backwards after it is discharged from the furnace, and then it can fall.
8. Pre-lifting time of upper air grid
The upper wind grid and the lower wind grid in the small bend change arc together. After the arc changes, its chain is loose. When the wind blows out and the lower grille is leveled, it will flatten the glass and break it. This requires an action of putting the chain away in advance, which is the pre-lifting of the upper wind grid. The principle of time setting is: small radius, long time, large radius and short time, but don't take the chain too tightly, especially when the radius is small.
9, glass length
This is a parameter that must be set for small bending multi-station equipment. The position of glass in the furnace depends entirely on the length of glass. If the length of the glass is set longer, the reciprocating distance of the glass in the furnace will be shortened, and the effective distance of the grating will be shortened after being discharged. It should be set according to the actual length of the glass.
10, common defects of small bend tempered glass are:
Straight edge, unstable radian, too deep indentation, etc. In order to let users quickly understand the application of various parameters, we specially list the manufacturing methods of small curved glass for users' reference.
Adjustment method and application of compression bar parameters on sm _ 2 small bending section
The small bending section of Luoyang northern glass adopts back pressure method to meet the needs of production. It is characterized by a wide range of applications and can be used as R450 glass with various radians. However, some units are not skilled enough in the adjustment method of the upper pressure bar and the application of various parameters. Now, the adjustment method of the pressure bar on the small bending section and the application of various related parameters are listed for users' reference:
1. Adjustment method of the upper pressure bar: put two long bars with the same thickness as the glass to be produced on both sides of the small bend, drop the upper wind grid and flatten it, check the pressure of the upper pressure bar and adjust it to 0.5 kg, then adjust the conical wheel of each pressure bar one by one until the pressure bar can be rotated by hand, but it feels heavy. Everyone has this feeling. After only one adjustment, do not measure the screw length outside the tapered wheel, and then adjust the screw length evenly. This is a misunderstanding, because screws are not benchmarks. The work of adjusting the compression bar is a meticulous work and must be serious.
2. Use of the pressure of the upper strut: If the glass curvature r is below 1000 or the glass is thick, the pressure can be used, which is generally about 2kg, and it is not necessary to be too large. If the pressure is too high, the optical properties of the glass surface will be affected. The key to eliminating straight edges depends not only on pressure. If r is above 1000 mm, there is no pressure, only by the weight of the compression bar.
3. Selection of positioning: The function of positioning is to prevent the long and narrow glass from tilting due to deviation in long-term operation. If the arc length of the glass is below 600 mm, the third type can be used; if the arc length of the glass is above 600 mm, it is best to use 1 air knife as the positioning, so that the glass can have enough reciprocating distance in the grid. If the clearance of the upper pressure bar is well adjusted, the longer the reciprocating distance, the better the curvature of the glass, and the straight edge will be reduced or eliminated accordingly. The action time of the positioner can be set. The principle is that the glass can fall and move in the opposite direction when it reaches the locator after baking. Just correcting the glass.
4. Determination of entrance distance: After using the positioner, the entrance distance is a very important parameter, which must be adjusted to make the glass move in the opposite direction as soon as it reaches the positioner. Never let the glass move forward after touching the locator, which will not only bend the locator, but also make the straight edge of the glass protrude forward, which can reach 4-5 mm seriously. The gap between the pressure rods above the positioner should be increased accordingly to prevent the positioner from bending forward when rotating. The parameter closely related to the distance into the grille is the effective length of the grille, which determines the reciprocating distance of the glass in the grille. We should make full use of the length of the grille. However, if the reciprocating speed of quenching is relatively fast, the glass may swing out of the grille, and the effective length of the grille needs to be adjusted to control the reciprocating position of the glass.
5. Setting of 5.Biow delay time: it is a key parameter of bending glass, which is closely related to the particle size of glass. Because the glass is not blown immediately after it is discharged from the furnace, it must be blown after the glass is formed, but at this time, the temperature of the glass will drop rapidly at a speed of about 20-30 degrees per second. If the blowing delay is too long, the glass will break during the blowing process. Especially for 3.2 mm, 3.5 mm and 4 mm glass, in order to meet the requirements of good radian without affecting the requirements of glass particles, the setting of delayed blowing time should be: when the glass reaches the locator, it is better to move backwards and then blow when moving forward.
In order to make the particle size meet the requirements, the quenching swing speed can be accelerated, and if R is small, the arc striking speed should be accelerated.
Speed). We should understand that when the glass is in a soft state, the longer it takes to go back and forth in the grille, the better the radian. It is impossible to change the shape of the glass after blowing (if the reciprocating speed of quenching is accelerated, the glass may swing out of the grid with the same effective length and need to be adjusted properly). Of course, if the glass thickness is greater than 6 mm, the delayed blowing time can be appropriately extended. Because the thickness, shape and size of the glass produced by each unit are different, it is impossible to determine the specific time here. All units need to explore and form the best process parameters.
6. Setting of compression time of compression bar: This parameter needs to be set after the compression bar is used. If you can only make one product in one furnace, the cold air blowing for a few seconds can stop the pressing time of the layering. If the product can be loaded with multiple pieces continuously, the pressing time should be set longer to prevent the glass from colliding with each other due to high wind pressure.
7. Setting of arc forming speed: This parameter must be set before arc adjustment. The principle is that the smaller the R, the faster the speed, but generally do not exceed 400. The greater the r, the slower the speed. If the arc speed is set after arc adjustment, the radian of the glass may be different from that of the grille.
8. Relationship between temperature and radian: Some units reflect why the radian and straight edge of glass are good at the beginning of arc adjustment, but after a period of time, the radian will become shallow and straight edge will appear. In fact, at the beginning of arc adjustment, the temperature in the furnace is relatively high and the glass burns soft. After a period of time, the temperature in the furnace is relatively low and the glass will change. If the requirements for radian and straight edge are high, the heating can be increased appropriately.
9. The charging interval (f) is a parameter that must be set for multi-stations. Its calculation method is: the quenching time is multiplied by n, and the sum of them is subtracted from the heating time, and then the reversal time of the two ceramic rollers is reduced by about 20 seconds. Divided by n, the interval of entering the furnace is (for example, 4 mm glass heating time is 220 seconds, quenching time is 30 seconds, multiplied by 3 (stations) equals 90 seconds. It should be understood that the more average tapping time of each furnace glass, the better its suitability.
10, several problems need to be paid attention to: if the curvature of glass is found to be irregular, we should pay attention to whether the roller gap is too small or the pressure is too high. If the curvature of the glass front end (furnace head) is good, and then the furnace tail has a straight edge and is long, you should pay attention to whether the reciprocating distance is too short, the lag time is too short or the gap between rollers is too large. If it is the front end (straight edge) of the glass, we should pay attention to whether the distance from the furnace is too long or the working time of the positioner is too long (often a few millimeters more will cause the straight edge to protrude forward, especially the narrow and long glass in the shower room). If the ruler is too long and needs to be adjusted, it should be understood that the two rollers should be adjusted. Some units only adjust the pressure roller near the positioner, and the effect is not obvious. You should pay attention to where the glass is when it blows back and forth in the grille. This is the pressure roller that needs to be adjusted. If a locator is used and the glass is still tilted, pay attention to whether the distance into the grid is too short and the locator has no effect. In addition, if the upper pressure roller does not need pressure, the position of the glass should be in the center of the grille when the grille is opened to avoid slight scratches on the two straight edges of the glass. If it is not in the center, the quenching time can be shortened or extended 1-2 seconds.
1 1. Some companies report that it is very troublesome to readjust the gap of the pressure bar when the glass thickness changes. We suggest that you can make some special gaskets, the diameter is 30mm, the inner hole is 12mm, and a groove is as wide as the inner hole and the thickness is 2mm. When you finish 4mm, if you want to make 5mm, you can push the tapered wheel in and insert the gasket into the screw. If it is 6 mm, just insert another piece. This method can greatly improve efficiency.