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Important factors and steps in the selection of injection molding machines

by:Vowin Rapid Prototyping     2023-02-12
1. Important factors in the selection of injection molding machines

Generally speaking, most customers who have been engaged in the injection molding industry for many years are able to judge and select a suitable injection molding machine for production. However, in some cases, customers may need to decide which specification of injection molding machine to use, or even There may be only the characteristics or ideas of the product, and then ask the manufacturer whether the machine can be produced, or which model is more suitable. In addition, some special products may need to be equipped with special devices such as pressure accumulators, closed loops, injection compression, etc. to increase production efficiency.

The important factors that usually affect the selection of injection molding machines include molds, products, plastics, molding requirements, etc. Therefore, the following information must be collected before making selections: mold size, weight, special design, etc.; types and quantities of plastics used; injection molding finished products The appearance size, weight, etc.; molding requirements, such as quality conditions, production speed, etc.

2. Injection molding machine selection steps

After obtaining the mold, product, plastic, and molding requirements, you can follow the steps below to select a suitable injection molding machine.

1. Selection of injection molding machine

The model and series are determined by the product and plastic. Since there are many types of injection molding machines, it is necessary to correctly judge which type of injection molding machine or which series the product should be produced at the beginning.

2. Determine the size of the mold

Shanghai Mulan Injection Molding Factory judges from the size of the mold whether the inner distance of the Green column of the machine, mold thickness, mold size and mold plate size are appropriate, so as to confirm whether the mold can be placed. The width and height of the mold must be less than or at least one side less than the inner distance of the Green column; the width and height of the mold should be within the size range of the mold plate; the thickness of the mold should be between the thickness of the injection molding machine; the width and height of the mold It is not enough to keep the staff who are in line with the reading plan machine's suggestion too small.

3. Determine the product ejection

Mold and finished products determine whether the mold opening stroke and the supporting mold movement are enough to make the finished product.) The opening stroke must be at least greater than the two grids of the finished product in the direction of the switch root and the length of the vertical sprue must be included; The mold stroke needs to be enough to eject the finished product.

4. Determine the clamping force

The clamping force is determined by the injection molded product and the plastic. When the raw material is injected into the mold cavity at high pressure, it will generate a force to support the mold. Therefore, the clamping unit of the injection molding machine must provide enough locking force to prevent the mold from being stretched. The calculation of the clamping force is as follows: calculate the projected area of ​​the finished product in the direction of opening and closing the mold from the appearance size of the finished product; Usually it is more than 1.17 times of the support force. So far, the specifications of the clamping unit have been preliminarily determined, and the tonnage of the injection molding machine has been roughly determined. Next, it must be confirmed which injection unit has a screw diameter that meets the requirements.

5. Determine the injection volume

Determine the required injection volume and select the appropriate screw diameter based on the weight of the finished product and the number of mold cavities. The number of cavities needs to be considered in calculating the weight of the finished product; in order to ensure stability, the injection volume must be more than 1.35 times the weight of the injection molding finished product, that is, the weight of the finished product must be within 75% of the injection volume.

6. Determine the screw form

The conditions such as screw compression ratio and injection pressure are determined by the type of plastic. Some engineering plastics require higher injection pressure and appropriate screw compression ratio to have a better molding effect. In order to make the finished product injection better, Shanghai Mulan Injection Molding Factory also needs to consider the demand for injection pressure when selecting the screw. and compression ratio issues. In general, a smaller diameter screw provides higher injection pressure.

7. Determining the Injection Rate

That is, the confirmation of the injection rate. Some injection molding products require a high injection rate to stabilize the cause, such as ultra-thin products. In this case, it may be necessary to confirm whether the machine ground is sufficient, whether it needs to be equipped with a pressure accumulator, a circuit control and other loading capacity. Generally speaking, under the same conditions, the screw that can provide higher injection pressure usually has a lower injection rate, on the contrary, the screw that can provide lower injection pressure usually has a higher injection rate. Therefore, when selecting the screw diameter, the injection volume, injection pressure and injection rate need to be considered and traded off. In addition, multi-loop design can also be used to shorten the molding time with synchronous compound actions.

8. Determine the match between the mold clamping part and the injection part

Shanghai Mulan Injection Molding Factory, under some special circumstances, the customer’s mold volume is small but the required injection volume is large, or the mold volume is large but the required injection volume is small. In this case, the injection molding manufacturer pre-sets The standard specifications may not be able to meet customer needs, but the so-called 'size matching' must be carried out, that is, 'big wall small shot' or 'small wall big shot'. The so-called 'big wall and small injection' refers to the original standard clamping unit with a smaller injection screw, on the contrary, 'small wall and large injection' means the original standard mold clamping unit with a larger injection screw. Of course, it is also possible that the mold clamping unit and the injection unit differ by several levels in terms of matching. After the above steps, in principle, the injection molding machine that meets the needs can be determined.

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