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8 Tips to Choose the Right PET Injection Molding Machine

Aug 11.2022

pet injection molding machine

PET injection molding machine is an injection molding machine designed according to the characteristics of PET materials and products. The modern plastic bottle industry is constantly changing, and the market requires efficient, hygienic, versatile and flexible PET preform injection molding machines to meet the production requirements of manufacturers. As a professional PET injection molding machine manufacturer, we will give you 8 tips to choose the most suitable PET injection molding machine for your business.


1. Screw.

For screw aspect ratio, special PET screw is designed. Generally, the aspect ratio of plastic screw is about 18-22. The aspect ratio of PET screw is generally above 1:24. The larger the aspect ratio, the better the plasticizing ability.


2. Mold space.

Judging by the size of the mold, the inner distance of the large column, the thickness of the mold, the minimum size of the mold and the size of the template are suitable to confirm whether the mold can be placed. The width and height of the mold should be smaller than or at least one side is smaller than the inner distance of the large column; The width and height of the mold should preferably be within the size range of the template; The thickness of the mold should be between the thickness of the injection molding machine; The width and height of the mold should be Complies with the recommended minimum mold size for PET injection molding machines. 

PET injection molding machine

3. Product take-out space.

It is determined by the mold and the finished product whether the mold opening stroke and the mold supporting stroke are sufficient for the finished product to be taken out. The mold opening stroke must be at least twice the height of the finished product in the direction of opening and closing the mold; the mold supporting stroke and mold supporting force must be sufficient to eject the finished product. 


4. Clamping force

The tonnage of the clamping force of the machine is determined by the product and the plastic. When the raw material is injected into the mold cavity at high pressure, a mold-pulling force will be generated, so the clamping unit of the injection molding machine must provide enough clamping force to prevent the mold from being stretched. The clamping force requirement is calculated as follows:

Calculate the projected area of ​​the finished product in the direction of the opening and closing die from the appearance size of the finished product;

Supporting mold force = the projected area of ​​the finished product in the direction of opening and closing the mold (cm2) × the number of mold cavities × the pressure in the mold (kg/cm2);

The clamping force of the machine needs to be greater than the clamping force of the die, and for the sake of safety, the clamping force of the machine usually needs to be more than 1.17 times the clamping force of the die. 

Preliminarily determine the specifications of the clamping unit and roughly determine the tonnage of the PET machine, and then the following steps must be performed to confirm which injection unit has a more suitable screw diameter. 


5. Injection volume

Determine the required "shot volume" and select the appropriate "screw diameter" from the weight of the finished product and the number of cavities. The number of mold cavities (one mold several cavities) should be considered when calculating the weight of the finished product; for the sake of stability, the injection volume should be more than 1.35 times the weight of the finished product, that is, the weight of the finished product should be within 75% of the injection volume. 


6. Forming effect

Conditions such as "screw compression ratio" and "injection pressure" are determined from PET plastic. PET plastic needs good plasticizing ability and suitable screw compression ratio design to have a good molding effect. Therefore, in order to make the finished product injection better, the plasticizing demand and compression ratio must also be considered when selecting the screw.


7. Increase the storage motor

PET plastic is easy to stick and the molding temperature is high, which requires a large screw torque, and a storage motor that is two or more stages larger than ordinary machines is often selected to meet the needs of the machine.


8. Increase the power system.

The storage motor increases the screw speed and reduces the speed of the screw. When the storage motor is enlarged, the power system is also increased to ensure more stable operation of the machine and shorten the product cycle time. There are some special issues that may also have to be considered:

In some special cases, the customer's mold or product may have a small mold but a large amount of shots, or a large mold but a small amount of shots. In this case, the standard specifications set by the manufacturer may not be able to In line with customer needs, there is a mismatch in injection volume and volume.

In this case the following two occur:

  • Using the original standard clamping unit with a smaller injection screw
  • Use the original standard clamping unit with a larger injection screw.

Of course, there may be several levels of difference between clamping and injection. 

In addition, it is necessary to consider the mold waterway to improve the cooling efficiency of the mold. The PET mold is equipped with a special PET water dividing block.


PET injection molding machine, as an important injection molding machine category, is very competitive in the market. There is no doubt that choosing the right PET injection molding machine has a huge impact on your business. Hope this article is helpful to you.

LOG Machine is a leading PET injection molding machine manufacturer in China, if you have questions or are looking for a suitable injection molding machine, please contact us!

Read More:

How to select a Plastic Injection Molding Machine

2022 Top 30 Chinese Injection Molding Machine Manufacturer Brands: Ultimate Guide

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