How to infer the structure of the mold based on the mold product?

 Plastic mold structure

1. Questions to consider when designing injection molds:

1. Understand the flow behavior of the plastic melt, consider the flow resistance and flow velocity of the plastic in the runner and the cavity, and check the maximum flow length. According to the flow direction of the plastic in the mold (ie, the filling sequence), consider the flow of the plastic in the mold The problem of internal re-fusion and the original air export of the mold cavity.

2. Consider plastic shrinkage and feeding during cooling.

3. Control the crystallization and orientation of plastic in the mold through mold design and improve the internal stress of the product.

4. The selection of the parting surface of the pouring point

5. The problem of horizontal parting core pulling and ejection of the workpiece.

6. Mold cooling or heating problems.

7. The relationship between the size of the mold and the injection machine used, including the relationship with the maximum injection volume of the injection machine, clamping force, and the size of the molded part.

8. The overall structure of the mold and the shape of the parts should be simple and reasonable, and the mold should have appropriate precision, smoothness, strength and rigidity, and be easy to manufacture and assemble

2. Typical structure of injection mold

1. Formed parts

The cavity is directly formed, and the part of the plastic part is usually composed of a male mold core and a female mold core.

2. Pouring system.

The runner that guides the plastic from the nozzle of the few-shot machine to the cavity is called the gating system, which consists of the main runner, the runner, the gate, and the cold slug well.

3. Guide part

In order to ensure that the movable mold and the fixed mold are accurately aligned, guide parts are set on the center surface. Usually there are: guide post (GP), positioning block, ejection guide post (EGP), etc.

4. Parting core-pulling mechanism

Before the plastic parts with outer concave or side holes are ejected, they must be parted laterally in order to be able to demould smoothly. The common mechanisms are: sliders (including core-pulling sliders for master molds, explosive sliders for master molds) , oblique pins, etc.

5. Ejection device

During the mold opening process, the device that ejects the plastic part from the mold. Common mechanisms include: thimble, ejector tube, ejector block, oblique pin, etc.

6. Cooling and heating system

In order to meet the requirements of the injection process for the mold temperature, the mold is equipped with a cooling or heating system. Generally, cooling water channels, heating or oily substances are set up in the mold.

※The diameter of the water hole is selected from Φ4.Φ6.Φ8.Φ10.Φ12.Φ16… …

※”○” ring (see picture 6)

A Internal pressure type B External pressure type

The form of the waterway (see Figure 7)

＊ Diagram for general clapboard type (see Figure 7a)

For small molds (see Figure 7b)

For molds with a deep cavity in the finished product (see Figure 7c)

7. Exhaust system

In order to discharge the original air in the cavity during the injection process, exhaust grooves are often provided at the parting surface, but sometimes the exhaust volume of small plastic parts is not large, and the parting surface can be directly used to exhaust. Many molds The matching gap between the ejector pin or the insert and the mold can play the role of exhaust. (See Figure 8/9)

8. Support column

For larger or large molds, support columns are added to prevent the deformation of the male template. Generally, the support columns are required to be 0.10~~0.15mm higher than the mold feet to compensate for the compression deformation of the support columns themselves.

9. Return mechanism

There is a return mechanism for the return surface of the upper and lower ejection plates

In addition to the return pin (RP), the return mechanism also has a forced pull mechanism, the emergency return mechanism

(1) Usually RP is equipped with a spring (see picture #) The function of installing this spring is to make the upper and lower ejector plates return quickly under the action of spring force

Spring specifications generally choose light and small loads or light and heavy loads

(2) Sometimes when the slanted pin is broken or the thimble is broken, a spring is added to the bottom of the return pin. The purpose is to protect the thimble or slanted pin, or the thimble and slanted pin will damage the surface of the female mold (see Figure 2). The selection model is general For medium or heavy loads

(3) When there is no oblique pin mechanism in the mold structure, it is generally necessary to add an ejector plate to install a forced pull-back mechanism to prevent the oblique pin from moving smoothly. For large molds, a pull-back mechanism must be added (see figure #)

(4) When there is an thimble under the slider mechanism of the mold, a quick-return mechanism is added to protect the thimble. The common quick-return mechanism is shown in the figure. (See Figure 4)

10. Standard mold base

(1). Our mold bases are all customized by outsourcing factories, so the selection and specifications of the mold bases are not very strict. (Usually our mold base specifications adopt Fudeba standard mold bases)

(2). The composition of the second plate mold base (see Figure 5)

Usually the two-plate mold consists of upper fixed plate, lower fixed plate, female template, male template, upper ejector plate, lower ejector plate

Sometimes the following two situations also occur:

a When the mother formwork is thickened to increase the strength of the mother formwork, and the upper fixing plate is omitted

b when sometimes increasing the heat flow plate

3. The structure of the second plate formwork and the names of the parts:

4. Configuration requirements of some standard parts

※GP configuration requirements

1 ‧The role of GP:

1. Make precise positioning of the fixed side and the movable side.

2. Support the weight of the mold.

3. Protect mold core

2‧GP material SUJ2; heat treatment HRC60°±2 (high frequency quenching).

3. GP specifications and matching requirements. (Hyperlink GP standard parts)

4. Selection of GP diameter and location. (Hyperlink GP diameter and location)

5. GP configuration form and usage occasions. (As shown below)

Use A-type bushings Use B-type bushings, the male template is deep and large, and it is easy to take out the finished product

In general, the depth of the template is reduced, and the gap between the core of the mold and the master mold is large.

The matching length of the sleeve increases the strength of the mold and prevents the guide oil from staining the finished product

6. Determination of GP length. (As shown below)

About 15~25MM higher than the finished surface, about 10~15MM higher than the brace pin

※Requirements for configuration of RP: (the role of RP: to return the ejector plate)

1. When the mold needs to be automatically produced, springs are generally installed under the RP, as shown in Figure 1: the spring specification is TR type. (Hyperlink TR Spring Specifications)

Note: spring installation requirements

A‧In the state before actuation, the spring preload is 5~10MM.

B‧If it needs to return first, the spring preload should be more than 10MM.

2. When the mold has an oblique pin mechanism and the oblique pin is not broken, no spring can be installed under the RP to prevent the finished product from being damaged.

The tilt pin is pulled back. As shown in Figure 2:

3. When the mold has an oblique pin mechanism and the oblique pin is broken, a spring is installed at the bottom of the RP to protect the oblique pin against the broken surface.

As shown in Figure 3:

4. When the mold is equipped with top plate guide pillars (EGP), RP escapes between each plate. As shown in Figure 4:

3‧RP material------SUJ2; heat treatment HRC60°±2 (high frequency quenching).

4‧RP specification (hyperlink RP standard).

Figure 1 Figure 2 Figure 3

※EFP configuration requirements

1‧The role of EGP:

Guide the movement of the ejector plate to prevent uneven ejection due to uneven force on the ejector plate.

2‧EGP material------SUJ2; heat treatment HRC60°±2 (high frequency quenching).

3‧EGP specifications and matching requirements. (Hyperlink EGP standard part)

4‧Selection of EGP diameter.

The diameter of EGP is the same as that of RP.

5‧Assembly form and application occasion of EGP. (As shown below)

General molds Small molds High mold temperature and die-casting molds

6‧When the mold is equipped with EGP, RP escapes on each template. (Hyperlink RP configuration requirements)

※STP configuration requirements

1‧The role of STP.

1. Reduce the contact area between the ejector plate and the lower fixed plate, and easily adjust the flatness of the ejector plate.

2. Prevent the ejector plate from coming into direct contact with the lower fixed plate.

2‧STP material-----S45C, heat treatment HRC40°~45°

3‧STP specification (hyperlink).

4‧Determination of STP position.

A STP must be installed under the return pin (RP) to prevent deformation due to the maximum force. (Figure 1):

B STP avoids interference with other parts, such as SP, EGP, K.0 hole and pipe jacking.

5‧Determination of the number of STPs. (Figure 2)

Figure 1 Figure 2 Figure 3

L Length Quantity

L<200 4 sticks

200<L<400 6 pieces

400<L 8 or more

Note: Large molds need to add STP in the middle to increase the fulcrum of the lower ejector plate to prevent deformation of the top plate. (Figure 3)

6‧STP installation form. (As shown below):

Easy to remove, can be processed separately, not easy to remove, generally used in small

Large molds are built using this STP. It can be processed in one piece in the mold.

※Specification of KO hole

1‧The floor plan of K.O hole is as follows:

Note: Type A K.O hole=Φ40; Type B K.O hole=Φ60

2‧The center position of the K.O hole should be consistent with the center of the sprue.

3‧When the mold is large and the pin is inclined, a pull-back mechanism should be installed

Five. Three-plate mold

1. Introduction to the structure of the three-plate formwork (see attached photo)

2. The mold opening sequence of the three-plate mold

Clamping Injection molding Pressurization Mold opening B and C separate A and B separate C and D separate.

3. Determine the stroke of the small tie rod

4. Determine the stroke of the large tie rod