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Cutting is an essential basic process in glass production and deep processing. During the operation, it is usually necessary to meet the quality requirements of accurate size, flat and vertical cross-section, and no edge chipping. As the market demand becomes more and more diversified, the requirements for glass size are also stricter. For example, the accuracy needs to be controlled within ±0.5mm, and some even only accept a positive tolerance of 0-0.2mm. Therefore, how to improve the cutting quality of glass is a problem that enterprises have to think about.

Glass cutting method:

The most common glass substrate cutting method is to use a diamond grinding wheel or a carbide wheel to scratch the glass surface and then break it by breaking the edge.

Picture 1 The mechanical cutting method

Picture 1 The mechanical cutting method

This method is relatively simple and easy to operate, but after the scribing and breaking process, due to the generation of residual stress and micro-cracks on the glass edge, subsequent processes such as cleaning, grinding, and heat treatment need to be added. During the cleaning process, tiny debris may cause certain damage to the glass surface.

As people have higher and higher requirements for glass cutting quality and glass cutting yield, traditional mechanical cutting methods have been unable to meet production needs. In the past five years, some laser cutting glass equipment for the industry has appeared in the industry, and processed glass has some advantages over traditional cutting methods.

There are two main methods for cutting glass by laser, one is the fusion cutting method and the other is the crack control method. Among them, the crack control method is widely used, and the cut-glass has a straight slit, no debris, and few problems such as micro-cracks.

Picture 2 The working principle of the crack control method

Picture 2 The working principle of the crack control method

Regardless of the cutting method, it is necessary to continuously optimize the cutting process to improve the cutting quality of glass, specifically. Starting from the cross-cutting machine, the following aspects can be considered:

1. Improve the quality of cross-cutting

1.1 The thickness of the product should match the cutting wheel and cutting pressure

The cutting wheel should be adjusted according to the required thickness of the glass. The thicker the glass, the greater the angle of the cutter wheel and the cutting pressure. The thinner the glass, the smaller the angle of the cutter wheel and the cutting pressure. The pressure of the small-angle cutter wheel should not be too large, otherwise, the skin will be easily broken during the glass cutting process; the pressure of the large-angle cutter wheel should not be too small, otherwise, the problem of shallow or no knife marks will occur. With the proper cutter wheel angle and cutting pressure, the knife marks should be smooth, uniform, continuous, free of planning scratches and flying chips.

1.2 Adjust the drop point, lift point, toolbar stroke, etc. of the cross-cutting knife

The function of the cross-cutting machine is to cut the glass horizontally so that the glass can be broken horizontally and the separation is accelerated. The usual practice is to set the knife lift or drop point in the inner tooth mark, which can not only protect the cutting knife but also ensure the uniformity and continuity of the cutting knife mark.

The stroke of the cutter bar should not be too high or too low. If the stroke is too high, the knife marks will be discontinuous, which will cause continuous breaking or not straightening.

The cylinder pressure on the tool holder needs to be adjusted according to the glass of different thicknesses. Generally, the cylinder pressure pointer is between the yellow area and the green area, and the air pressure is not easy to be too large.

1.3 Control the horizontal breaking time

The advance or lag of the breaking time determines the breaking action time of the breaking roller. The parameter setting must ensure that the glass is just broken when the cross-cutting knife mark reaches the top of the breaking roller. After the glass is broken, it will fall synchronously with the breaking roller. The breaking time should be adjusted according to different thicknesses.

In addition, because the knife mark is not at the highest point of the breaking roller, usually the breaking action of thin glass should be advanced, and the breaking action of thick glass should be delayed. During the adjustment process, it should be adjusted according to the actual breaking position.

Figure 3 The glass cross cutting machine

Figure 3 The glass cross cutting machine

2. Control of tin backing process

The glass comes out of the tin bath and is cooled by the annealing kiln and transported to the cold end cutting area. During this process, due to the influence of the stability of the equipment and the adjustment of the process, the warpage of the glass ribbon is often formed. Especially in the production of thin glass, the deformation is particularly strong, and a drum-like sound can be heard in the annealing furnace. The unevenness of the glass ribbon will seriously affect the cutting accuracy, which puts forward strict requirements on the control of the tin withdrawal process. Although the glass warpage cannot be completely solved at present, it can be improved by ineffective means. The longitudinal cooling gradient is reasonable, to ensure that the plate surface tends to be flat when the glass ribbon is transferred to the cutting area, and the fluctuation of the glass ribbon is reduced within a certain range, to reduce the influence of the glass ribbon on the cutting accuracy.

Figure 4 The float glass production line

Figure 4 The float glass production line

3. Stable air source and reduce friction

If the air source is unstable, the up and down of the tool holder will be affected. To ensure that the cross-cutting machine has sufficient air source pressure, the cross-cutting machine can be equipped with a separate air storage tank, and the air outlet is equipped with a pressure-stabilizing valve to ensure that the outlet pressure is stable and the pressure entering the cylinder is stable. At the same time, try to shorten the distance between the gas storage tank and the head of the cross-cutting machine to reduce the loss of gas, to ensure that the pressure on the cylinder of the cross-cutting machine head frame is balanced and stable, to improve the telescopic speed and response time of the cylinder, to ensure The drop point error is small, to reduce the cutting error and improve the accuracy of the cross-cutting machine.

4. The shorten the signal response time

To improve the knife drop response time of the cross-cutting machine and reduce the influence caused by the unstable air source, the cylinder can be replaced with an electric cylinder. Under the same environment, the electric cylinder can ensure stable output pressure and distance, and at the same time, the response speed of the electric signal is faster than that of the pneumatic signal. The response time is shortened, the accuracy of the up-and-down position of the tool head frame will be greatly improved and improved, and the accuracy of the corresponding drop point will also be improved, thereby improving the cutting accuracy.

Summary: The above are the factors that need to be considered in glass cutting. In actual production, only by fully understanding the factors affecting glass cutting and making corresponding adjustments in time can the accuracy of glass cutting be improved.

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