A bottle for a hand sanitizer, a deodorant, an orange juice and for cosmetics such as toner or lotion. I have just mentioned several products that are in my sight around me. These bottles all have a common characteristic. Do you have any idea of what the characteristic they are sharing might be? They are all bottles with small entrances and are empty inside. It would be easier to understand if you think of a cylinder since they are alike. In this article I would like to explain about a method called ‘Blow Molding’, which is used when manufacturing a product that is empty inside like a hand sanitizer. I’m sure you would be able to fully understand, even the parts that were confusing, after reading this article.

As you can see from the name of the method, ‘Blow Molding’ is a way that you blow air inside and make the product. In this process the two words that you might hear most frequently will be ‘Parison’ and ‘Preform’. Blowing air into melted plastic, in order to harden it as the shape of the frame, is the main process of ‘Blow Molding’. The melted plastic that you use before injecting air is what we can call ‘Parison’ and ‘Preform’.

There are largely three types of ‘Blow Molding’. ‘Extrusion Blow Molding’, ‘Injection Blow Molding’ and ‘Injection Stretch Blow Molding’. The difference between the three is whether you use the extrusion method or the injection method. 

The most general way of manufacturing, Extrusion Blow Molding

‘Extrusion Blow Molding’ is the most commonly used method of ‘Blow Molding’. It starts with putting ‘Parison’ into a cold mold. After closing the mold and injecting air inside, the ‘Parison’ starts to attach to the surface of the mold and hardens into that shape. When it is hard enough and shaped well, the method finishes by taking the product out of the mold.

Since this method is mostly used, it has a low production unit price. Moreover, another advantage is that this method is suitable when manufacturing bottles with handles. Most of the polyethylene bottles, which include bottles that contain milk or yogurt, are made in this way.

High unit price, therefore suitable for mass production, Injection Blow Molding

‘Injection Blow Molding’ is used when producing a large amount of glass or plastic bottles. Among the three methods introduced, this one is the least used. However, it is extremely automated, so handwork is not needed in the finishing process. What was called ‘Parison’ in ‘Extrusion Blow Molding’ is called as ‘Preform’ in this method. Also, because the mold is not cold it is hardened with the air injected rather than the temperature of the mold. Other than that, most of the process is similar with ‘Extrusion Blow Molding’ that it puts air inside the ‘Preform’, waits until it hardens and takes it out. 

Due to the hardening process, which uses the temperature and the power of air, this method is suitable when making low storage products. It is also noticeable that it has a high production speed even though the cost is slightly high. Therefore, ‘Injection Blow Molding’ is usable when producing portable hand sanitizer bottles. 

Lengthening horizontally and vertically, Injection Stretch Blow Molding

‘Injection Stretch Blow Molding’ is a method that combines the two previous ones. It lengthens the ‘Preform’ vertically once and then injects the air in order to inflate it horizontally. The ‘Preform’ can reach the bottom so it is fit for manufacturing tall and deep bottles. The ‘Preform’ that stretches less is thin, while the part that stretches more is thick, in order to make the thickness identical when the manufacturing is done (It is the same for ‘Injection Blow molding’).  An advantage of this method is that the final product is durable. Which is why it is used to produce PET bottles, for juice or soft drinks, that we can often see around us. 

‘Injection Stretch Blow Molding’ is divided into two stages. A single-stage process, which does the process of injecting and blowing in a single machine, and the two-stage process, which does both processes separately. The single-stage process has a difficulty in changing the shape of the machine. This infers that the design of the product that can be made is limited. 

However, it is useful when producing a small number of products in a short time. Unlike the single-stage process, the two-stage process separated the process. In result, various designs can be produced in a large scale. 

Bonsystems Global is a company in South Korea professional of providing service to other manufacturing companies. We are able to provide a large number of 500ml PET bottles, gun spray bottles, and flip cap type bottles etc. to companies who are having difficulties in importing plastic bottles from overseas. 

If there are any questions related to the hand sanitizer bottles using ‘Blow Molding’, manufacturing cosmetic bottles, or purchasing any of the products, feel free to contact us on our website or just send us an email, and we would be glad to give you a specific answer to any of your questions.