Since the British Pilkington Company announced successful research on float glass processing technology in 1959, the float glass process has gradually become the main forming processing technology of flat glass. Float glass has the advantages of high surface quality, simple process, wide glass plate, etc. At present, more than 80% of flat glass is made by the float process. At present, the defects of float glass mainly include tin printing, scratches, air bubbles, etc. Reducing or preventing the occurrence of these defects is of great significance to the development of float glass. Jinan LIJIANG Glass analyzed the scratch mechanism and proposed two process principles to prevent scratches by enhancing the scratch resistance of the glass and reducing the relative speed difference between the glass and the roller. Jinan LIJIANG Glass analyzed the causes of roll deformation and bending through gravity, manufacturing, and temperature. This study mainly focuses on scratch defects, and analyzes the effects of cold end roll perpendicularity defects and bending deformation defects on scratches.
Figure 1 The tempering furnace rubber roller
2. The roller is defective
2.1 The tempering glass roller produces bending deformation defects
The manufacturing process of the tempering glass roller generally adopts the centrifugal casting process. When the molten steel composition is not uniform, the centrifugal casting machine rotates unevenly or the temperature control is not good, it may cause the roll to find bending deformation. During use, the temperature of the glass plate is different in different sections, and the uneven heating of the rollers in different sections may cause the rollers to bend and deform.
2.2 The tempering glass roller produces perpendicularity defects
The tempering glass rollers are supported on the support frames at both ends through the outer spherical bearing with the seat, one end is the driving end, which is connected with the transmission shaft through the bevel gear, and the other end is the driven end, which rotates with the driving end. The conveyor roller is long and requires high installation accuracy. During the installation process, due to the error in the installation position of the bearings at both ends, the verticality error of the roller occurs.
3. The influence mechanism and theoretical calculation of roller defects on scratch characteristics
First, a coordinate system needs to be established. It is assumed that the forward direction of the glass ribbon is the positive direction of the longitudinal Z axis, the vertically upward direction is the positive direction of the vertical Y axis, the forward direction of the glass ribbon is facing, and the leftward direction is the positive direction of the X axis. The necessary condition for scratches is the relative speed of the roller and the glass plate, resulting in relative sliding, which will lead to scratch defects when the contact pressure is large. In the actual production equipment, an apron is set on the roller to contact the glass plate. Since the analysis is about the influence of the roller defect on the scratch, the apron is in an ideal state, so it is now simplified as the roller is directly in contact with the glass plate. Assuming that there is a protruding defect point on the surface of the roller, the surface of the glass plate is an ideal plane, the verticality error of the roller is α, and the angle formed by the cross-section of the roller when the glass plate contacts the defect point is θ, as shown in Figure 2.
Figure 2 The contact range between the glass plate and the defect point
Analyze the relative motion relationship between the defect point and the glass plate.The moving speed of the glass plate V0 is
In the formula: 3 is the rotational angular velocity of the spoke, and the curve is the outer circle half of the spokepath. The moving speed direction of the glass plate is the positive direction of the longitudinal Z axis.
The movement speed of the defect point V1 is
In the formula: h is the radius of gyration of the defect point.
The movement speed direction of the defect point has a large component on the lateral X-axis
The direction is the positive direction of the horizontal X-axis.
The movement speed direction of the defect point has a large component on the longitudinal Z axis
The direction is the positive direction of the longitudinal Z axis.The component size of the moving speed direction of the defect point on the lateral X-axis is
The direction is the positive direction of the vertical Y axis.
The generation of scratches on the glass plate is only related to the relative speed of the transverse X-axis and the longitudinal Z-axis.
The length of the scratch in the transverse X-axis direction is
The length of the scratch in the longitudinal z-axis direction is
4. The scratch feature simulation analysis
4.1 SolidWorks Modeling
Now, according to an actual cold-end production process, the glass ribbon speed is 13 m/min, the outer radius of the spoke is r0=72.5 mm, the length of the spoke is 4750 mm, and the width of the glass plate is 4250 mm. It is assumed that the contact angle θ0=9° when the defect point starts to contact the glass plate.The defect point gyration radius H=73.5 mm was established through SolidWorks, the spoke perpendicularity error a was 0.1°, 0.2°, 0.3°, 0.4°, 0.5°, 0.6° and the spoke perpendicularity error was α=0.2°, the defect point
The gyration radius rl is 72.75 mm, 73 mm, 73.25 mm, 73.5 mm, 73.75 mm, and 74 mm, a total of 12 three-dimensional models under defect conditions. Now take the 3D model of the defect point with a radius of gyration H=73.5 mm and spoke perpendicularity error α=0.2° as an example.
4.2 Adams motion simulation
Import the established 3D models into Adams for motion simulation, and create a marker! points on the spokes to simulate defect points, create moving pairs on the glass plate, and create rotating pairs on the spokes.
From the linear velocity of the glass plate v0=13 m/min=216.667 mm/s, the radius of the spoke is r0=72.5 mm, it can be known that the angular velocity of the spoke (0=2,9885 rad/s =l11.229 mm/s, the period of the spoke T =2.1024 s when the contact angle is 18°, the contact time is 0.1051 s. Therefore, set the rotating auxiliary driving function to -9 d+171,229 d*time and the moving auxiliary driving function to -216.667*time. The simulation termination time is set to 0.1051 s, Set the number of simulation steps to 100 steps, click to run the simulation, and get the simulation result. By creating the movement trajectory of the marker l point in the analysis result relative to the glass plate, multiple spatial coordinate points of the movement trajectory can be obtained.
4.3 Matlab draws the scratch curve
The scratch curve can be obtained by inputting the X coordinate and Z coordinate of the space coordinate point of the market trajectory obtained by the motion simulation in Adams into Matlab for drawing. The scratch curves are shown in Figure 3 under six working conditions where the radius of gyration at the defect point is mouth=73.5 mm, and the spoke perpendicularity error α is 0.1°, 0.2°, 0.3°, 0.4°, 0.5°, and 0.6°.
Figure 3 The scratch features under different perpendicularity errors
It can be seen from Figure 3 that with the increase of the perpendicularity error, the scratch curve gradually becomes flat from vertical, and the curvature of both ends of the scratch gradually increases. This is because with the increase of the perpendicularity error, the speed of the defect point in the transverse X direction increases, resulting in an increase in the length of the scratch in this direction and an increase in the degree of curvature of the curves at both ends. The perpendicularity error at the spoke is α=0.2. , the radius of gyration 1 of the defect point is 72.75 mm, 73 mm> 73.25 mm, 73.5 mm, 73.75 mm, and 74 mm under six working conditions, the scratch curve is shown in Figure 4.
Figure 4 The scratch features under different radius of gyration
It can be seen from Figure 4 that with the increase of the radius of the gyration of the defect point, the scratch curve gradually changes from flat to vertical, and the curvature of both ends of the scratch gradually decreases. This is because as the radius of gyration of the defect point increases, the relative velocity in the longitudinal Z-axis direction increases, resulting in an increase in the scratch length in this direction and a decrease in the curvature of the curves at both ends.
The problem of scratches on float glass is an urgent problem that needs to be solved at present. Reducing or preventing the occurrence of scratches has great economic benefits for enterprises. In this article, through the comparison and analysis of scratch characteristics under the tempering glass manufacturer different working conditions, specially glass producing by the tempering glass furnace, it is found that the perpendicularity defect of the spoke and the bending deformation defect of the spoke has a significant impact on the scratch characteristics, and the corresponding change rules are summarized to analyze the causes of the scratches. It is of great significance to prevent scratch defects.