The design experience data of the core size in mold design

1. Core thickness

The thickness of the core needs to consider the basic thickness required after adding the cooling water pipe, and the thickness to maintain the strength of the mold core. The main consideration for the strength of the mold core is to be able to withstand the injection pressure, so that the mold will not be deformed due to the injection pressure, and the product will not produce flash. Mold core strength design needs to take below factors into consideration:

a. Injection pressure

b. Product projected area

c. Product height

d. Product thickness

e. Product appearance

f. Product projection appearance

g. Total number of mold cavities.

2. Mold core safety size design

The number of mold cavities and runner configuration, the safe distance between mold cavities, and the safe distance between mold cavities and the edge of the mold core are as shown in the figure below

The safety distance Sa & Sb can resist the lateral force exerted by the injection pressure on the side wall of the mold core during molding.

● Product (part) width + 2 Sa = core width

● Product (part) length + 2 Sb = core length

1. Mold core safety size reference table

Note: When designing the mold, the designer will be required to take the size of the mold core as an integer, so the safety distance is not a fixed value; it can be adjusted according to the size of the product (part).

4. Mold core safety size setting

l 1. When designing a mold, first estimate the size of the mold core, and then estimate the size of the mold base .

l 2. The key point of estimating size is how to judge the safe distance. The choice of safety distance has a great influence on the mold cost.

l 3. Determine the size and thickness of the core according to the size and characteristics of the product and the preparation of the product. According to the width of the core, it must be placed between the two mold feet. The length of the core should not exceed the distance from the return pin to determine the size of the mold base.

5. Estimate the thickness of the mold core from the product size.

6. Determination of the height of cavity

The mold cavity does not burst, it can pass water and the screw should be as thin as possible, and the mold core should be as conservative as possible to prevent deformation.

Note: 1. The height of the core: from the lowest gate position to the bottom of the core Y=X+(10-20)

2. The cavity and core of precision frames generally take integers

3. The cavity can be as low as possible, and the core can be thicker

7. Factors considered in the selection of mold core.

       Generally speaking, after the projected area of the product (including the mold cavity) is determined, the projection width plus 20mm ~ 50mm on one side is the recommended size of the mold core. After knowing the size of the mold core, the width of the mold core + (0~10) which is about the distance between the mold feet, and the size of the mold base is determined accordingly.

        The key point of considering the size of the mold base is whether the mold base will cause structural deformation due to excessive injection pressure during the molding process. Therefore, when the product is thin and the number of mold cavities is large, the size of the mold core should be larger (such as 50mm for one side of the projection). If the product is thicker and has a single cavity, the mold core can be closer to the size of the product (such as 25mm for one side of the projection).

 3. If the mold base has mechanisms such as sliders or lifter pins, the dimensions of the sliders and lifter pins must be taken into consideration.