The types of plastic molding methods and the production of polymer products, in general, are very wide, each of which has its own advantages and disadvantages and specific applications.
In this article, we are trying to introduce the types of plastic molding methods. By presenting each one, you will know the advantages and disadvantages of each of them.
Before introducing these methods, it is necessary to know what molding means!
The molding process uses pressure and temperature to fill the empty space of the pre-designed and made mold. This substance is called a “matrix”.
A raw material that is flexible (such as plastic, glass, or ceramic) is pressed until it hardens and gains sufficient strength.
The advantage of molding is its high speed, diversity, and high efficiency.
The introduction of the types of plastic molding methods
By using a variety of plastic molding methods, products produced in various industries can be used. These materials have high quality and stability.
In general, there are 5 types of plastic molding methods, which are as follows:
- Compression molding
- blow molding
- extrusion molding
- injection molding
- rotational molding
In the following, we will explain more about each of the mentioned items.
Compression molding of plastic molding methods
In this method ( which is one of the types of plastic molding methods ), raw liquid plastic is placed in a heated mold. Then the mold is closed and pressed to take the desired shape.
Since a lot of heat is involved in this process, the final product is very concrete.
Before the final product is taken out of the mold, the cooling operation is done and then the product is taken out of the mold.
In fact, if we want to describe it more fully, the raw material is heated and turns into a molten form. Then these materials are poured into the cavity of the mold. Then the upper part of the mold (which is called the upper jaw) is placed on the lower part (lower jaw) and the mold is closed.
In addition to temperature, pressure is also involved in this process. The simultaneous combination of these two factors leads to the cooling of the material.
This method is one of the types of plastic molding methods , very similar to the metal casting method, with the difference that molten plastic is used instead of molten metal.
In using this method, a series of points must be observed, which include the following:
In order to heat the mold for the melting process, the lowest amount of energy and cost-effective heating method should be used
Saving the time needed to heat the material
Providing a suitable and fast cooling system
The advantages of compression molding:
Using the compression method has a clear advantage, which is cost savings. In the following, we refer to its other benefits:
Ability to produce long pieces
Long life of molds
The possibility of doing the molding process manually and automatically
Common applications of compression molding:
One of the most effective applications of this method is when it is used to replace broken metal pieces.
The reason for using plastics produced by this method is that a lot of heat is involved in their production. Therefore, these materials have high strength.
Since this material is plastic, it is a cheap and sturdy alternative for replacement.
In this method, the row material is directed to the mold through a plastic tube and with airflow, and as a result, the final product is obtained with the desired shape.
This method is very suitable for producing hollow and simple materials with thin walls and includes 3 stages injection, blowing, and ejection.
That is why it is used in the production of plastic bottles. Although this method is not used in making products with complex shapes.
This method is considered a quick and economical method.
It is interesting to know that two methods called Extrusion Blow Molding and Stretch Blow Molding are used in the molding industry, which we will explain a little about in the following:
Extrusion Blow Molding:
In this method, the primary material, which is molten plastic, is extruded from the upper side of the mold. Then the mold is closed.
After the mold is closed, compressed air is blown into it.
The extrusion method is divided into continuous and alternating.
Stretch Blow Molding:
This method is similar to the air injection molding method and its application is the mass production of bottles.
Unlimited high-volume parts can be produced by this method.
One of the disadvantages of this method is that it has a high cost and its devices occupy a large volume.
Common applications of blow molding:
Usually, blow molding is used in the manufacture of products such as plastic bottles and fuel tanks.
Extrusion molding of plastic molding methods
In this method, melted plastic is transferred through a tube. The final product is a long product.
The shape of this mold, through which the plastic passes, is the shape of the final product.
This method is considered one of the cheap methods of plastic molding methods because the equipment is very simple.
Common applications of extrusion molding:
This method is mostly used to produce hollow products such as pipes.
It is also used to produce T and U-shaped slots, but it cannot be used to make products with complex shapes.
Injection molding is one of the most widely used types of plastic molding methods. Because you can produce products with different dimensions and shapes with it.
As the name suggests, in the injection method, molten plastic is injected into the mold and after the cooling process, it is separated from the mold.
It is clear that the more complicated the shape of the mold, the more difficult the plastic injection process will be for all parts of the mold.
It is necessary to know that the type and quality of plastic used are also very important in this method.
Common applications of injection molding:
This method is a common method among plastic molding methods, which is used in the production of bulky plastics (for example, plastics used in the automotive industry).
The more flexible these products are, the more they will be used in the engineering, design, and decoration industries.
Among the polymers that are usually used in injection molding are thermoplastics, some thermosets, and elastomers.
These materials can be considered input materials in the form of combination and alloy. In fact, this causes the properties of the manufactured product to change.
The devices used in this method are divided into different tonnages according to the force applied to the clamp plates.
Note that if the target plastic is dry, more injection pressure is required.
Rotational molding of plastic molding methods
Rotomolding is one of the most popular methods of plastic production.
In this method, which is another type of plastic molding methods , plastic in powder form is poured into a mold and then the whole mold rotates around two perpendicular axes which are inside a furnace. This rotation makes the plastic stick to the mold wall.
Then the cooling operation is done and after that, the formed product is separated from the mold.
rotational molding applications :
The most common use of this method is making large and hollow products. The types of products that are made using this method include kayaks, car parts, water and chemicals storage tanks, etc.
In this article, 5 important and practical methods were introduced to you for plastic molding.
These methods included the following:
Each of the above has a series of advantages, disadvantages, and uses, and all kinds of plastic products in different dimensions and sizes can be produced by using these methods.
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