How are glass bottles made?

- May 09, 2020-

How are glass bottles made?

Glass production process includes: batching, melting, forming, annealing and other processes.

They are introduced as follows:


1.

Ingredients, according to the design of the material list, weighing all kinds of raw materials in a mixing machine mixed evenly.

The main raw materials of glass are: quartz sand, limestone, feldspar, soda ash, boric acid and so on.

 


2.

Melt system, will match the raw material through high temperature heating, the formation of uniform bubble-free glass liquid.

This is a very complex physical and chemical reaction process.

The melting of glass takes place in the melting furnace.

There are two main types of melting furnaces: one is the crucible kiln, in which the glass material is held inside the crucible and heated outside the crucible.

Small crucible kilns hold only one crucible, and large ones can hold as many as 20 crucible.

Crucible kilns are interstitial-type, and only optical glass and colored glass are produced by crucible kilns.

The other is a pool kiln, in which the glass material is melted and the open flame is heated on the surface of the liquid glass.

Most of the glass temperature of the melted in 1300 ~ 1600 ゜ c.

Most are heated by flame, but some are heated by electric current, which is called electric melting furnace.

Now, the pool kiln is continuous production, the small pool kiln can be several meters, the large can be as large as more than 400 meters 2.

 


3.

Forming is the transformation of molten glass into solid products with a fixed shape.

Forming takes place at a temperature range. It is a cooling process in which glass first changes from a viscous liquid to a malleable state and then to a brittle solid.

Forming methods can be divided into artificial forming and mechanical forming.

 


A.

Artificial forming.

(1) blowing, with a nickel-chromium alloy blowing pipe, pick a ball of glass in the mold to turn while blowing.

It is mainly used for forming glass bubble, bottle and ball.

(2) pull, after blowing into a small bubble, another worker with a top plate stuck, two people blowing while pulling mainly used to make glass tube or rod.

(3) press, pick a mass of glass, cut it with scissors so that it falls into the concave mold, and then press it with a punch.

Mainly used to form cups, plates, etc.

(4) free forming, pick materials with pliers, scissors, tweezers and other tools directly into crafts.

 


B.

Mechanical forming.

Because manual forming labor intensity, high temperature, poor conditions, so, in addition to free forming, most have been replaced by mechanical forming.

Mechanical forming in addition to pressing, blowing, drawing, and (1) calendering, used to produce thick plate glass, engraved glass, wire glass, etc.

(2) casting method to produce optical glass.

(3) centrifugal casting method, used to manufacture large diameter glass tubes, utensils and large capacity reaction POTS.

This is done by injecting the molten glass into a high-speed rotating mould. The centrifugal force causes the glass to cling to the mould wall, and the rotation continues until the glass hardens.

(4) sintering method, used to produce foam glass.

It is in the glass powder to add foaming agent, in the metal mold with a cover to heat, the glass in the heating process to form a lot of closed bubbles this is a good insulation, sound insulation material.

In addition, the forming of plate glass has vertical lead method, flat pull method and float method.

Float method is the method that lets glass liquid flow float on the surface of molten metal (tin) to form plate glass, its main advantage is glass quality is high (level, smooth and clean), pull speed is fast, yield is big.

 


4.

During annealing, the glass undergoes drastic changes in temperature and shape during shaping, which leave thermal stress in the glass.

This thermal stress will reduce the strength and thermal stability of glass products.

If it is cooled directly, it is likely to break during the cooling process or during storage, transportation and use (commonly known as cold explosion of glass).

In order to eliminate cold burst, glass products must be annealed after forming.

Annealing is the process of holding or slowly cooling the glass within a certain temperature range for a period of time to eliminate or reduce the thermal stress in the glass to the allowable value.

 


In addition, some glass products can be hardened in order to increase their strength.

Including: physical hardening (quenching), for thicker glasses, table glass, automobile windshield, etc.;

And chemical rigidization (ion exchange), used for watch glass, aviation glass, etc.

The principle of hardening is to produce compressive stress on the glass surface layer to increase its strength.

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