injection mold. Turn the inside of the circle upside down

Design of the whole inner circle inverted injection mold

1.The introduction

All kinds of plastic internal thread covers, tubular joints and structural plastic parts usually have the whole inner circle inverted button, which is a kind of products with the characteristics of the whole inner circle inverted button, and the inner wall has the whole circle side convex or side concave, as shown in the figure. Injection molding such as plastic parts must consider the reverse position of the demoulding, demoulding can be used in the current mode of forced demoulding, and two-step core-pulling demoulding. And each of the above has advantages and disadvantages, for example, when the reverse depth is large can not be forced stripping. This paper discusses how to use core-pulling method to realize the smooth demoulding of plastic parts inside the circle.

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2.Plastic parts requirements

In this paper, the polarization cover plastic parts as an example, introduced the characteristics of mold design, material for POM, shrinkage rate of 1.018. As we all know, POM material is the hardest in plastics, so the design of forced demoulding mould cannot be considered. Please refer to the drawing of polarizing cover mould.

Requirements of polarization cover plastic parts for molds:

1)the diameter of the plastic part mouth is large, followed by a full circle of inverted button, forming a closed ring.

2)obvious strain is not allowed at the inverted buckle of the whole circle, and forced stripping is not allowed.

3)there can be clamping wires inside the plastic part at the inverted buckle of the whole circle, but no more than 6~8 wires, the less the better.

4)the whole circle of inverted buckle can not walk on the front.

5) the demoulding of the mold must be solved on the machine, and cannot be solved manually outside the machine.

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3.Analysis of key points of mold design

We do mold design all know, usually, the product buckle inside do inclined top, product outside buckle do slide (also can inclined top), if the product all around have inverted buckle, and cannot do strong take off, how should we design? Out of the inverted button, in the final analysis of the mold design or rely on the inclined top or slider, the product design scheme according to the different combination of inclined top and slider has a variety of design methods. Famous foreign standard parts manufacturers such as DME and HASCO have introduced the standard parts that solve the inside inversion many years ago. Due to the high price of DME telescopic core and the long supply cycle due to the need to customize the drawing, it is only used when customers require it in practice.

The polarization cover plastic parts use self-made parts to solve the problem of mold design, the specific points are summarized as follows:

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1.Mold placement:

The plastic part size involved in the whole circle inverted button mold is small, but because of the difficulty of mold design and processing, higher requirements for the precision of mold processing, so the general use of 1 out of 1 mold structure. The main difficulty of machining is reflected in the linear cutting accuracy of t-groove inclination. Because of the inclination in both directions, the precision of slow-moving wire cutting is very important. Due to structural reasons, non-standard die blank is adopted. The die design exported to the United States is followed, and the standard parts adopt DME standard.

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2.Glue feeding method:

For circular products, multi-point inner glue can ensure the roundness of plastic parts without affecting the appearance of plastic parts. The die is designed with a latent gate, and the runner needs to be set on the top of a larger slider or slope.

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3.Lateral parting and core-pulling mechanism design:

According to the structural characteristics of the plastic parts, two layers of inclined internal sliders were designed, which were shown in section e-e and section d-d respectively. Under the action of inclined guide column, four large sliders in section d-d first moved toward the center and came out inverted, and then four small sliders came out inverted under the action of t-groove.

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4.Mold positioning and guidance:

Besides the guide column and guide sleeve, the cone positioning block is also designed.

5.The moulds of plastic parts are pushed out by push plate, while the nozzle material is pushed out by thimble. 

In this case, because there is only a small glue position in the back model cavity of the plastic part, the plastic part basically has no holding force after being inverted and demoulded, which is very easy to demoulder. Therefore, it can be used to reverse the whole circle and reverse the whole circle with two internal sliders. Imagine if the plastic part of the overall shape of the ball, the mold in the reverse buckle at the same time also need to take into account the top out, then change a small group of internal slider into the inclined top, plastic part of the demodulation problem will be solved.

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6.Cooling and water transportation design: injection mold

Mold components need to be designed with adequate water transport to maintain sustainable operation.

7.The slide block and inclined roof steel are all made of H13, heat treatment HRC48~52 and nitriding. The slide bar is made of o-1 steel and heat treated HRC54~56.


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