What is a glass hot thermal bending bent furnace?

1. What is thermal bent glass?

Thermal bent glass is made by using the annealing process and heat transfer principle of glass, using hot bending furnace equipment, zone control method, regulating the temperature of the heating area and the temperature and pressure parameters of the furnace cavity, using specialized steel molds, and adopting a combination of heating rod centralized local heating and pressing (or supporting) operation. After partial or complete hot bending treatment of the float glass raw material, it is annealed and cooled, Thermal bent glass is a type of glass that is formed by pressing and deforming it according to customer requirements when it is heated up to near the softening temperature. Thermal bent glass can be divided into mountain type, fan type, sheet type, angle type, S-type, and double right angle type according to the shape of the product. Thermal bent glass can be shallow bent and deep bent according to the degree of bending

Shallow bends are commonly used in building decoration, car and ship windshields, glass furniture decoration series such as TV cabinets, wine cabinets, coffee tables, etc; Deep curved glass can be widely used in horizontal refrigerators, display counters, sightseeing elevator corridors, glass ceilings, ornamental aquariums, etc. The process equipment of curved glass is simple, the product has high added value, and the application decoration effect is good. It has broad market prospects and development space

2. Process flow control of glass thermal bending furnaces

The production of thermal bent glass involves sending glass and molds together into a hot bending furnace for bending and forming, followed by annealing and cooling. According to the bending form, it can be divided into gravity method and molding method. The former is a more traditional hot bending production process, which involves placing glass on an open mold with the same curvature as its product and heating it to the glass softening temperature according to the usual method. Under the action of gravity bending, the glass forms a product with the same curvature as the mold, Very suitable for bending shallow bent products with different curvatures, but with significant errors; The latter uses an electric heating element to heat to a temperature lower than the softening deformation temperature of the glass, then turns on the heating rod to concentrate heating on the bending part, and cooperates with the pressing and supporting roller operations to bend the glass into shape. This method is suitable for various forms of bending and the bending of specific complex shaped products, and can produce high-quality and high-precision curved glass products

Prepare the original glass sheet and conduct monthly testing to ensure that there are no obvious surface quality defects. Based on the shape of the product and considering the net size of the hot bending furnace cavity and the condition of the mold, reserve a certain amount of cutting amount and optimize the cutting of the original sheet reasonably. After grinding the edges (usually in the height direction), washing, and drying, use it as the original glass sheet for the upper furnace. For multi-layer curved glass, sprinkle a uniform and appropriate amount of talcum powder on the inner and lower surfaces of the glass, place the glass horizontally on the mold, align the center after calibration, Together, the glass is transported into the hot bending furnace for hot bending treatment. When it approaches the softening temperature, the heating rod is turned on to concentrate heating on the bent part, and hot bending temperature control and rolling operations are carried out. After the glass is bent into shape, it is gradually cooled and cooled. After obtaining the bent finished product, it is inspected, cut, ground, drilled according to customer requirements, and then cleaned with detergent or washed with warm water. After strict inspection according to technical standards, it is directly packaged and stored in the warehouse.

In addition, thermal bent glass can also undergo other cold processing treatments such as sandblasting and hollow, or heat treatment treatments such as interlayer and coating. After final inspection, the product is packaged and stored in the factory

The process characteristics and main technical indicators of thermal bent glass:

The finished product has no mold scratches;

In addition to unidirectional bending, various forms of bending can also be carried out; The product has good annealing performance and can be subjected to cold processing after bending; Fit<4mm, non straightness<3%.;

The maximum deep bending radius R is 30mm~200mm;

The processing glass shards range from 3mm to 19mm, corresponding errors

The difference range is 0.2mm~0.6mm

3. Classification of glass thermal bending furnaces

Glass hot bending furnaces can be divided into four types based on fuel methods: coal-fired, oil fired, gas fired, and electric fired. Structurally, they can be divided into cyclic, reciprocating, and single chamber furnaces. Coal fired glass hot bending furnaces are now rare due to their difficult temperature control, complex structure, and easy surface contamination of glass products. Oil fired and gas fired glass hot bending furnaces, if assisted by electric heating, have lower energy consumption indicators than electric fired ones, but due to their complex structure, It is also rarely used. Gas fired glass hot bending furnaces have the advantages of simple structure, convenient temperature control, easy operation, and no pollution to glass products, and are widely used

3.1 Circular glass hot bending furnace

In order to reduce the footprint, the circular glass hot bending furnace generally adopts an up and down cycle in production. The upper part of the hot bending furnace is divided into preheating zone 1 and preheating zone 2, and the hot bending zone, annealing zone, and lower part of the hot bending furnace are all cooling and annealing zones. Each zone is composed of an independent kiln car

The glass is loaded from the product discharge area, rises to the upper layer of the hot bending furnace, and the kiln car is pushed in. In the preheating area, the glass is preheated to 400cC-450 ℃ and enters the hot bending area. The glass starts hot bending at around 600 ℃ and then enters the cooling and annealing area. The kiln car descends to the lower layer for annealing at around 400 ℃, and the glass annealing is completed at around 70 ℃

The circular hot bending furnace has the advantages of small footprint, low energy consumption, and large output. However, due to the cyclic operation, the process system needs to be consistent and suitable for mass production of products, such as automotive windshields. However, the one-time investment is large and requires a large amount of electrical power

3.2 Reciprocating glass hot bending torch

The reciprocating glass hot bending furnace has 5 stations, 3 stations, etc. For example, a 5-station furnace has 2 loading and unloading areas, 2 preheating areas, 1 hot bending area, and 2 shuttle cars. The glass enters the hot bending area after preheating to around 400 ℃ in the preheating area, then retreats to the preheating area to cool down, and another car enters the hot bending area. This cycle repeats. The 3-station furnace does not have 2 preheating areas, but also 2 kiln cars. The glass in the hot bending area rises directly from room temperature to the hot bending temperature according to the temperature system, After the hot bending is completed, the temperature drops to 250-300 ℃ before returning to the loading and unloading area. The reciprocating hot bending furnace can adapt to different glass products and does not require a continuous temperature system. However, the sealing degree is not as good as that of a single chamber furnace, and the structure is also more complex than that of a single chamber furnace.

3.3 Single chamber glass hot bending furnace

There are two common types of single chamber hot bending furnaces: drawer type and lifting type, which are also the most commonly used in the current market

Due to the small batch size and wide variety of specifications of architectural glass, using a single chamber hot bending furnace is the most economical and convenient. A single chamber hot bending furnace only has one workstation, and glass heating, hot bending, and annealing are all completed at this workstation

The advantage of a single chamber hot bending furnace is that it can adapt to various specifications of products without requiring a continuous process system. Each furnace formulates corresponding process parameters according to the different products;

The single chamber glass hot bending furnace is simple to manufacture, easy to handle in structure, well sealed, and relatively low in energy consumption. The disadvantages are low efficiency and long hot bending cycle

As the name suggests, the structure of a drawer type single chamber furnace is like a drawer, but currently, most single chamber hot bending furnaces have kiln cars that have only the bottom and front face, with both sides and inner ends sealed by the kiln body, and observation windows open on the kiln body

The kiln car is actually a flat car with only a front face, which provides great convenience for the loading and unloading of glass products. Therefore, the single chamber hot bending furnace has the largest bendable glass specification among all hot bending furnaces

The four sides and upper part of the lifting single chamber hot bending furnace body are fully sealed, and there is a certain height of space at the bottom of the furnace. Glass enters from the bottom of the furnace. The bottom can be lifted, and the hot bending mold passes through the external track to the hot bending platform, rises to the hot bending position, and the glass products exit in reverse order. The biggest advantage of this hot bending furnace is that it utilizes space, saves space, and the biggest disadvantage is that it is difficult to load and unload glass and products, especially human plate glass

There is also a type of combustion electric single chamber hot bending furnace, with a fixed bottom and a reciprocating furnace body. There are adjustable furnace doors at both ends of the furnace body. Undoubtedly, this structure requires a large investment, and the upper power cord also needs special treatment