There are many kinds of injection molding machines, such as bulk Injection molding machine for disposable fork, lunch box and food container injection molding machine, bucket injection molding machine and so on. Do you want to know more about injection molding machines? Just read this blog!

Definition

Injection molding machine is also known as injection machine. It is the main molding equipment for making thermoplastic or thermosetting materials into plastic products of various shapes using plastic molding molds. According to the arrangement of injection device and mold locking device, injection molding machines can be divided into vertical, horizontal and vertical horizontal composite types.

Selection Guide

• Select the right type

The model and series are determined by products and plastics.

Since there are many kinds of injection molding machines, it is necessary to correctly judge which kind of injection molding machine or series this product should be produced at the beginning, such as general thermoplastic or bakelite raw materials or PET raw materials, monochrome, two-color, multi-color, sandwich or mixed color, etc. In addition, some products require conditions such as high stability (closed loop), high precision, ultra-high firing rate, high ejection pressure or rapid production (multi loop), and appropriate series must also be selected for production.

• Fit

Determine whether the "large column inner distance", "die thickness", "minimum die size" and "die disc size" of the machine are appropriate according to the die size to confirm whether the die can fit.

The width and height of the mold shall be less than or at least one side less than the inner distance of the large column;

The width and height of the die should preferably be within the size range of the die plate;

The thickness of the mold should be between the mold thickness of the injection molding machine;

The width and height of the mold shall meet the minimum mold size recommended by the injection molding machine, and it can't be too small;

• Get

Determine whether the "mold opening stroke" and "mold supporting stroke" are enough for the finished product to be taken out from the mold and finished product.

The mold opening stroke shall be at least twice the height of the finished product in the mold opening and closing direction, and the length of the vertical sprue shall be included;

The mold supporting stroke shall be enough to eject the finished product;

• Lockable

The tonnage of "clamping force" is determined by the product and plastic.

When the raw material is injected into the mold cavity at high pressure, a mold supporting force will be generated. Therefore, the mold locking unit of the injection molding machine must provide sufficient "mold locking force" to prevent the mold from being opened. The clamping force demand is calculated as follows:

Calculate the projected area of the finished product in the direction of switching die from the appearance size of the finished product;

Formwork supporting force = projected area of finished product in the direction of mold opening and closing (cm2) × Number of mold holes × In mold pressure (kg / cm2);

The pressure in the mold varies with the raw material. Generally, the raw material is 350 ~ 400kg / cm2;

The clamping force of the machine shall be greater than the supporting force, and for the sake of insurance, the clamping force of the machine shall generally be greater than 1.17 times of the supporting force;

So far, the specification of the clamping unit has been preliminarily determined and the tonnage of the model has been roughly determined. Then, the following steps must be carried out to confirm which injection unit has a screw diameter that meets the requirements.

• Full shot

Determine the required "shot volume" by the weight of the finished product and the number of die holes, and select the appropriate "screw diameter".

The number of holes the first mock exam is required to calculate the weight of finished products.

For the sake of stability, the injection amount shall be more than 1.35 times the weight of the finished product, that is, the weight of the finished product shall be within 75% of the injection amount;

• Good shooting

Determine the conditions such as "screw compression ratio" and "injection pressure" from the plastic.

Some engineering plastics need higher injection pressure and appropriate screw compression ratio design to have better molding effect. Therefore, in order to make the finished products shoot better, the injection pressure demand and compression ratio should also be considered when selecting the screw.

Generally speaking, the screw with smaller diameter can provide higher injection pressure.

• Fast shooting

Some finished products can be stably formed only by rapid injection with high injection rate, such as ultra-thin finished products. In this case, it may be necessary to confirm whether the injection rate and injection rate of the machine are sufficient, and whether it needs to be equipped with accumulator, closed-loop control and other devices. Generally speaking, under the same conditions, the screw that can provide higher jet pressure usually has a lower jet speed. On the contrary, the screw that can provide lower jet pressure usually has a higher jet speed. Therefore, when selecting the screw diameter, the injection volume, injection pressure and injection rate (injection speed) need to be cross considered and selected.

In addition, multi loop design can also be adopted to shorten the forming time by synchronous compound action.

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