What information about injection molding machines need to be known when designing molds

Update:09-07-2021
Summary:

In order to ensure that the mold designed by the master […]

In order to ensure that the mold designed by the master matches well with the injection machine, it is necessary to check the relevant information between the injection machine and the mold, and then carry out the mold design and select the injection machine number.

The mold data to be checked include injection volume, injection pressure, clamping force, installation size, mold opening stroke and ejection device. (Junior designers must take it seriously)

Inspection of injection volume

Whether the mold cavity can be filled, it is necessary to know the maximum injection volume allowed by the injection molding machine. If there is a partial lack of material in the product, the most likely cause is insufficient injection volume. Therefore, when designing the mold, you should ensure that the total melt volume required by the mold is within the actual maximum injection volume of the injection machine, which is equivalent to 80% of the rated injection volume of the injection molding machine. Therefore:

NM1+M2 ≦ 80% m

M1-the quality or quantity of a single product

M2-The mass or volume of the plastic required by the gating system

M-the maximum injection volume allowed by the injection machine (grams or cubic centimeters)

N-number of cavities

Note: n is related to factors such as plasticizing speed, maximum injection volume of injection molding machine and clamping force, product accuracy, production economy and other factors. Generally speaking, for every additional mold cavity, the dimensional accuracy of the product will be reduced by 4%-8%, and the cost of the mold will increase. For example, gears or blades can only be designed at most 1*2.

Injection pressure check

This is to verify whether the maximum injection pressure of the injection molding machine can meet the molding needs of the plastic part. The injection pressure required by the product is determined by the injection machine type, nozzle form, plastic fluidity, gating system and negative flow force of the mold cavity. If the injection pressure is insufficient, short shots will form.

Generally speaking, for products, whether the injection pressure is sufficient can be controlled organically by the machine regulator, and should not be adjusted too much to prevent insufficient gate or mold strength from being damaged by pressure or mold separation

Check the clamping force

During injection molding, the projected area of ​​the injection product on the PL surface is the main factor affecting the clamping force, which is proportional to the projected area. If the clamping force provided by the injection molding machine is not enough, the parting surface of the mold will not be closed tightly, and the adhesion will not be sufficient, which will directly form burrs or overflow. The tonnage model of the injection molding machine is determined by the clamping force. How to calculate the tonnage required for the clamping force of the injection molding machine can be calculated according to the formula:  F1=(n A1+A2) P

A1-The maximum projected area of ​​the product, total length * total width, unit: cm2

A2-Projected area of ​​gating system unit:

Pressure coefficient (high pressure: 0.75 tons/square centimeter, general pressure: 0.5 tons/square centimeter)

F1-resin pressure unit: ton

f1≦80% f f-Injection molding machine clamping force

Installation size check

In order to ensure the smooth installation of the mold, it is very important to check the installation dimensions of the mold on the injection molding machine. In this link, designers often ignore this problem, because they rely too much on computer operations, resulting in molds that cannot be tested on time.

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