Are you looking for a new injection molding machine for the company's new products, or want to upgrade the injection molding machine in your factory, but you don't understand a bunch of proper terms on the Internet? What is "mold opening stroke"? What is the "Tie-bar"? How to judge whether the "screw diameter" is suitable for your product? In this article, we have sorted out 8 key points and selection suggestions for you to teach you how to select the injection machine correctly, so that you can purchase accurately and save costs. The following are our key points:
 

Key 1: The nature of the injection product

There are certain ideas for plastic injection products, which can be simpler and clearer when choosing an injection molding machine. If you have any questions when purchasing an injection molding machine, you can directly ask the supplier of the machine according to the requirements of the product. You can provide ideas to discuss the actual product that is injected with the injection machine company. If there is no actual injection product, there will be more communication problems. For example, does the company have set the product to be produced with a plastic injection machine? Is it a general household item? Or are there special-purpose parts? Does the injection product have requirements for temperature, light transmission, softness, or weight? Should the product material use thermoplastic plastics (such as ABS, PE, PP, engineering plastics) or thermosetting plastics (FRP, LSR)? Is it necessary to make high-precision and high-density products to meet the needs of the product (such as automobiles, communications)? Should the product color be used for single-color injection or two-color injection? These are the questions that we often encounter from customers, so you must clearly understand your needs, and then determine the nature of the product is one of the very important homework.
 

Key 2: Mold size, product size

If we just want to shoot a small plastic doll, the size of the mold will naturally be smaller, but if we want to shoot a trash can today, the mold will be much larger. It can be known from this that if the product to be injected is larger, the mold will be larger, so the injection molding machine must be larger. In addition to understanding the size of the product to be developed, it is also necessary to know that the size of the mold that each injection machine can use is different. Therefore, instead of calculating the approximate size of the mold by yourself, it is better to consult a number of mold factories to understand the size of the mold, and then determine whether the inner distance, mold thickness, and size of the machine can be placed according to the mold size.
<Extended reading: What is the Corinthian Pillar? 〉
 

Key 3: Mold opening stroke

Generally speaking, a mold is divided into two parts: a male mold and a female mold. The product structure and appearance geometry we design is to design a film cavity in the male and female molds, and then inject the plastic materials into the film cavity. Here, after the plastic material is injected, the "mold opening" will be performed, which means that the male mold will be opened backwards, and then the finished product will fall out from the female mold, which is "demolding". The maximum distance that the male mold can be separated from the female mold is called "mold opening stroke". When purchasing an injection machine, in addition to the product size mentioned just now, how long the length of the mold opening stroke is, it is also a very important point, otherwise it may happen that the product cannot be taken out after injection into the mold.
 

Key point 4: Clamping force

After the injection machine injects the plastic into the mold, in order to keep the shape of the finished product, it will maintain a certain pressure on the product, and the plastic itself will also give a reaction force to the outside. Therefore, in order to prevent the mold from being completely opened and the phenomenon of supporting the mold, the clamping unit of the machine will give "clamping force". The clamping force can also be calculated according to the product area, size, material and other factors. However, if you want to know how much clamping force your product needs, it is recommended to consult a professional to avoid insufficient clamping force calculations. There may be burrs and glue overflow to the injected products.
〈Extended reading: Is there any relationship between the flash of the product and the strength of the template? 〉
 

Key point 5: Injection volume

The injection volume will vary with the weight of the product, the material, the number of cavities of the mold, etc., but usually the larger the weight and volume of the product, the larger the tonnage of the machine, otherwise it may not be able to manufacture. This is related to the "screw" in the machine. The screw is horizontal in the machine. It pushes the melted plastic material to the injection port before injecting the plastic. It also melts, compresses, and mixes the plastic in the process. The longer the diameter and stroke of the screw, the larger the volume of the finished product that can be injected. So when choosing an injection machine, not only need to look at the tonnage of the injection machine, but also pay attention to the diameter of the screw by the way.
〈Extended reading: What are injection molding machines? What are the types? 〉
 

Key point 6: Screw compression ratio

We just mentioned the screw in the injection machine, and explained what its work is. Let's explain the work of each section of the screw more clearly. The screw is divided into three sections. The order from feeding to injection is: feeding section, compression section, discharge section.

• Feeding section: the plastic pellets that have not been melted are transferred to the compression section, where some plastic pellets will be slowly melted.
• Compression section: plastic is compressed and mixed.
• Discharge section: the plastic will be completely melted, and the temperature and particle mixing should also be completely uniform.

The screw compression ratio stated in the title is about the groove depth of the feed section/the groove depth of the discharge section. There is no best number for screw compression ratio, because each type of plastic has different properties, so you should seek professional manufacturers to evaluate the compression ratio production to have the best production quality.
 

Point 7: Injection speed

When the injection machine is producing thin-shell products, the injection speed of the injection molding machine must reach a certain value before production can be produced to avoid the failure of production due to cooling when the filling is completed. In addition, it should be noted that the higher the injection speed, the mold exhaust and the higher the accuracy requirements, the overall planning is required.
 

Key 8: Other requirements for finished products

We often hear that customer products have relatively high standards for appearance, function, quality, etc. or other applications and requirements, such as gloss, surface brightness, fire rating, environmental protection rating, etc. Some factors are quite related with the plastic material, but some are also related to whether the injection machine itself can support this function, so if you have requirements for product quality, it is recommended to ask first to see if the injection machine can meet your needs. We are committed to helping customers solve problems and tailor-made professional companies for customized injection molding machines. If you have any questions, please feel free to ask.

Conclusion

The above 8 points are the key considerations when choosing an injection molding machine. Of course, there are many considerations and attentions in the injection molding process, such as mold making and plastic selection. The customers often encountered affected the finished product because of the wrong shape or material selection of the product itself. Later, after repeated communication to modify the mold in the injection machine, or to change the material to solve it. We are a professional injection machine expert who has been operating for many years in the local area. We care most about is the "quality" of the product. If you want to learn more about our expertise, please continue to pay attention to our blog. We are happy to share more about plastic  knowledge of injection molding to everyone.