We are going to see Stepwise Glass bottle manufacturing process in this article. We use glass bottles in everyday life. Glass is a ceramic material.
Glass bottles are manufactured by melting sand and blowing the molten viscous material into required shape using a mould and then cooled.
The process may looks simple, but multiple technologies are used to get a defect-free glass bottle in the glass bottle manufacturing factories. Diving into this article to understand the details of the techniques and principles used in the manufacturing process.
The glass bottle manufacturing process has ten steps in the process from the beginning to the end. We now look into each step in details.
Raw Materials Preparation:
- The primary raw materials are used in manufacturing glass bottles are Sand, Soda ash, Limestone And Cullet.
- Sand is the body former which gives the strength to the glass once it is made. Usually, the percentage of silica or sand varies based on the type or usage of the glass bottle. The percentage of the Silica is 70% plus or minus 10%. The melting point of the glass is inversely propositional to the silica content present in the composition. Initially, silica is crushed and grounded to fine particle size and then stored in storage hopper. The size of the quartz is reduced up to 50#.
- Soda ash is used as a fluxing agent. Which helps to lower the melting point of the silica present in the glass.
- Cullet means the recycled glass. One of the best property of the glass is it can be recycled. 10% to 20% cullet is added in the composition based on the property required for the glass. Culets may be a defect piece from the production process or maybe a recycle from the real world market. Both ways the Glass is recycled to avoid any damage to the environment. Cullets are initially stored and then broken into smaller size materials using the crushers. From the hopper, size reduced recycled glass material is carried to another storage hopper using belt conveyor. Manually foreign elements will be removed, and magnets are used to remove the iron in this conveyers.
- Colour glass will be produced by adding an oxide to the compositions.
- The glass bottle production process is a continuous process so batching also done continuously to feed the furnace. The continuous feed of raw material to the furnace is done by belt conveyer until the furnace beginning.
- Raw materials are proportionally fed into the hopers and then mixed and unloaded and transferred to the furnace.
- In the conveyor again magnet is used to remove any iron materials present in the conveyor.
- Iron is the foreign contamination that should not be allowed in the raw materials. Because metal will not burn off and creates specks in the clear bottle. Any other organic matter will be burned at the initial melting process. Also, the air bubbles can be cleared at the later stage of the melting.
- The mixer of raw materials will be added to the furnace like a batch. The reason is to make sure the composition of the mixer is the same for all the products.
- Every batch of the raw materials fed into the furnace will be heated and melted, and continuously send to the next process.
- The peak temperature of the glass melting furnace can vary based on the composition. It usually ranges from 1400 degree Celsius to 1600 degree Celsius.
- There are three things process happens inside the furnace. They are as follows: 1) Melting 2) Clarification or Soaking 3) Cooling
- The first stage is melting; during this stage, the raw materials are heated and melted to get viscous mass. The process starts with water evaporation and proceeds to organic matters burn off, and silica transformation and then the composition begins to melt.
- The glass bottle melting furnace is made of silica-based refractories to avoid any contamination of the raw materials. To maintain the excellent firing curve and to get the better fuel efficiency, the Air and fuel ratios will be adequately monitored.
- The atomization of fuel in the burner helps to get the higher fuel efficiency. These controllers are the cost-effectiveness of the process. Because the most significant contributor to the glass manufacturing cost is the fuel used in the process. Around 40% of the total cost of the glass is contributed by the fuel used.
- The modern furnace does the job efficiently to get the best fuel efficiency. The controllers are done automatically, and any failure in the machinery the alarm will go off.
Soaking or clarification:
- A part of the composition may not be melted because of the rapid heating, so to make sure everything is melted the composition is maintained at peak temperature for 3 to 8 hours based on the composition.
- Moreover, the air bubbles formed in this stage are allowed to pass through the melted glass. Trapped air will create a defect in the product. So during the soaking time, it is essential to remove the air bubbles present inside the molten glass.
The Molten glass is cooled to lower temperature to make the viscous condition. Because if the glass is fluid like condition is difficult to blow into the required shape. Once it is cooled, it will become a viscous state then it is sent for the feeders.
- The next stage of the glass bottle manufacturing is to feed the glass blowers.
- Feeders do this process. Feeders have openings at the bottom of the furnace end.
- Low shear panels control these openings. This shear panels continuously cut the molten glass to get the required quantity of viscus mass for blowing.
- The amount of mass passed through the opening can be controlled by the speed of the sheer panels. The rate of the shear panel is controlled when required for different sizes of the glass bottles. If need a big size glass the sheer panel speed will be less and vice-versa.
- The cut glass mass is called as garbs; The garbs forms elongated shape during the cut from the furnace.
- The garbs are ready for the next process and now it one step away from to get the shape. The next step is blowing.
- The forming machine will transfer the garbs into containers.
- The air is blown through the forming machine when the garbs are placed inside moulds.
Now the hot air is blown into the garbs to form the shape of the mould. Hot air is used to avoid sudden colling or sudden thermal shock to the glass.
- The formed shape is released from the mould. And Then based on the shape required a second part may be attached when at this temperature. After this temperature, we can’t join anything to the glass body. If you need to anything to the body, then you need to melt the bottle again.
- In this stage, the bottle cap sealer line is marked or joined to the body.
- Once the shape formation is complete, then it is sent for the next stage called Hot end coating.
Hot End Coating:
- A Thin layer of tin is applied in the process. The coating is used to give the better strength for the glass bottle.
- The application of the tin coating to the body of the glass bottle is made at around 350-degree Celsius.
- When the glass container is formed, the outside surface cools more rapidly than the interior side, causing stress in the glass.
- To avoid this problem, the annealing process is carried out. During the annealing process, the inside and outside of the bottle are cooled evenly to avoid any stress creation.
Cold end Coating:
- A thin layer of polymer is applied to the glass container. The temperature of the polymer coating lies around 100-degree Celsius.
- This layer is given to the glass container to provide a scratch resistant to the outer surface of the bottle.
- All glass containers are checked for any foreign contamination in the glass and air bubbles in the glass.
- The inspection is done at multiple levels. Both automatic and manual checkings are done to ensure the product quality is perfect for the customers.
- Some of the things checked during are the size of the product, the shape of the product, cracks in the body, pinholes and contamination and air trapped inside the bottles. These are the major defects in the glass bottles during the production process.
- All this inspection is done in the continuous conveyor where the bottles are passes, and multiple inspectors are checking the defects.
- Once the classification is done the good products are sent to the next stage for packing.
Defected bottles are sent to the recycling and used as cullet in the batch composition.
- Also, all the defects are recorded to give feedback to the production to reduce the defects.
All the good bottles are packed based on the customer requirement. Usually, glass bottles are wrapped in a cardboard box which has multiple segments separated by corrugated sheets. Packing is done by automation to avoid any damage during preparation.
Now we have seen the entire production of the glass bottle manufacturing process. The process is nearly the same in all factories. Only difference based on the automation or manual involvement in the production. But, the overall glass manufacturing principle, is the same. We try to cover the topic as much as possible; we hope you have got the information you are looking for. Comment below to ask any questions related to the glass bottle manufacturing process. We will answer it.
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