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Custom Blow Molding: Know Your Method Options

When it comes to custom blow molding, there are various method options to consider. That said, it’s helpful to learn the details about all of them. Read more below.

Custom Blow Molding: Know Your Method Options - KB Delta

The adoption of custom blow molding in PET bottle manufacturing is needed to create uniform or conforming hollow shapes in plastic bottles that are meant for carbonated drinks.

To be specific, just imagine and think of this PET bottle as a balloon (in its stereotype) design that gives room for a hollow extension or expansion of the bottle shape or tube sides.

Do you get a satisfactory blow molding and high impact PET flakes? Well, it is not that easy as it looks. So, kindly read on.

The process of manufacturing PET bottles, jars, or containers from the scratch and at a maximum capacity without enveloping the peaks of demand most of the time is what we will be emphasizing, sooner.

You will also get to know that the available choices for the custom blow molding processes called the ‘integrated’ for the making of PET bottles present no difficulties.

Although, the decision of which mold blowing processes to be used can be quite complex. However, below are the two stages of PET bottle making processes that will assist you in choosing the perfect one for your mold application.


The Two Types of Custom Blow Molding Processes

The production of PET bottles entails the process of mold injection preforms, stretching, and blowing of extruding mold into the bottles. These operations can be executed using two processes and they include:


  • The single-stage PET bottle making process
  • The two-stage PET bottle making process



The Single-stage PET Bottle Making Process

In a single-stage PET container production, the whole process starting from the raw material down to the finished bottle will be carried out using a single machine.

Also, note that the PET preforms will not be produced as an intermediate semi-product that will later be re-heated for custom blow molding. Instead, the still-hot mold injection preform will be moved into the blow molding section directly.

Besides, be enlightened that the preforms are molded out of a plastic pelletized material before they are immediately stretch blow molded. This applies to all range of plastic materials capable of molding and not just PET.

Essentially, this single-stage process core attributes make the PET integration suitable for molding non-standard shapes too. Non-standard shapes like the oval shapes, off-center containers, etc. that are mostly used in the cosmetics industry.


The Two-stage PET Bottle Making Process

In an attempt to know your method options in custom blow molding, you must note that the two stages PET bottle or container making process is also known as the Re-heat stretch blow molding (RSBM).

This two-stage or RSBM process of making PET bottles or other resins can be executed in two distinct steps. During the first step, the injection machine is going to produce a semi-finished product known as the preforms.

Here, the preform neck will be at the finished stage but the length and diameter will be smaller than the jar, container, or bottle into which is going to be produced.

The second stage of this RSBM process is very simple and straight-forward. The preforms only need to be heated and then, blown into the finished bottle or containers.

Truthfully, if you want to make a custom blow mold PET bottle that will be virtually lightweight, unbreakable with perfect clarity, then this two-stage or RSBM process is recommended.

This is so because the material used undergoes significant changes that reflect in the PET molecular orientation greatly. The two-stage PET bottle making process is often used for the production of beverage bottles.

It also has greater flexibility suitable for customized articles as well as large-scale container production. Today, 80% of all beverage bottles are produced using this two-stage technology.

By and large, having discussed the single and two-stage PET manufacturing processes, you should know your method options and which will be suitable for you.

But then, take notice that both PET making processes have their various advantages as well as shortcomings, none is 100% perfect.


Other Custom Blow Molding Processes

Other than the above blow molding processes discussed, there are other infamous processes too that are capable of creating the hollow in the bottle part.

These other processes include injection blow, injection stretch, and extrusion blow molding. Each of these uses different methods to realize its desired shape.

Let’s take a look at them one after the other.


  • Injection Blow


The injection custom blow molding is not often used in plastic production as the other available options.

As with the extrusion blow molding, the polymer will be heated till it melts, and only then will it be pushed down into a manifold responsible for injecting the liquid via nozzles into the cavity with a core pin.

The mold will form the exterior part or shape of the object and such is called the pre-mold. The mold will then be removed after it must have cooled down.


  • Injection Stretch


The injection stretch is very similar to the injection blow process just that this particular process can be used to make different bottle or jar shapes, offering several options compared to other methods.

That being said, note that the preforms in the injection stretch process are seriously heated before being blown to form the hollow or ballon area.

In the same vein, the core rod will be used to stretch the plastic interior to form the desired shape. Typically, this can be completed using the single or two-stage PET making processes too.


  • Extrusion Blow Molding


With the extrusion blow molding process, the plastic will be heated to its melting point after which it will be forced into a shallow tube known as parison.

The parison will then be placed into a mold (metal and not plastic) for it to be cooled. During this process, air will be simultaneously blown into the hollow tube, which will inflate through the mold to form its desired shape.

After the mold must have cooled down, it will be opened so that the part can be retrieved.

The mold sides will control the “ballon” or “hollow” shape for a complete uniform production component.



It will be right to say that selecting the perfect custom blow molding for PET bottle or container manufacturing process is a usual concern for almost all clients.

However, productivity, product application, machine footprint, efficiency, and environmental impacts are the key factors to be considered to know the ideal custom blow molding method options.


Custom Blow Molding: Know Your Method Options - KB Delta

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