1. Problems to be considered when designing injection mold:

1. Understand the flow behavior of plastic melt, consider the resistance and flow speed of plastic in the runner and cavity, and check the maximum flow length. According to the flow direction of plastic in the mold (that is, the filling sequence), the remelting problem of plastic in the mold and the original air problem in the cavity are considered.

2. Consider the shrinkage and feeding of plastics 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. Selection of pouring point parting surface.

5. Horizontal parting, core pulling and ejection of parts.

6. Cooling or heating of the mold.

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

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, which is convenient for manufacturing and assembly.

2. Typical structure of injection mold

1. Molded parts

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

2. Pouring system.

The runner from nozzle to cavity of less injection molding machine is called gating system, which consists of main runner, branch runner, gate and cold well.

3. Guide part

In order to ensure the accurate alignment of the movable die and the fixed die, the guide part usually includes: guide post (GP), positioning block and ejection guide post (EGP).

4. Parting core-pulling mechanism

Before the plastic parts with side concave or side holes are ejected, lateral parting must be carried out in order to demould smoothly. Common mechanisms are: slide block (including core-pulling slide block of female die and explosion slide block of female die), oblique pin, etc.

5. Ejection device

A device that ejects plastic parts from the mold during mold opening. Common mechanisms are thimble, pipe jacking, ejection block, oblique pin, etc.

6. Cooling and heating system

In order to meet the requirements of injection process for mold temperature, the mold is equipped with a cooling or heating system. Generally, a cooling channel is provided in the mold to heat or grease the substance.

The diameter of the water hole is φ 4 φ 6 φ 8 φ10 φ12 φ16. ※

※ "○" ring (see Figure 6)

A internal pressure type b external pressure type

Waterway form (see Figure 7)

* General zoning map (see figure 7a)

For small molds (see fig. 7b)

Deep cavity mold for finished products (see Figure 7c)

7. Exhaust system

In order to exhaust the original air in the cavity during injection, an exhaust slot is often set at the parting surface, but sometimes the exhaust volume of small plastic parts is not large, so the parting surface can be directly used for exhaust. The fit gap between the ejector pins or inserts of many molds will play the role of exhaust. (See Figure 8/9)

8. Supporting column

For larger or larger molds, support columns are added to prevent the deformation of the punch plate. Generally, the supporting column is required to be 0. 10 ~ 0. 15 mm higher than the formwork to compensate the compression deformation of the supporting column itself.

9. Return mechanism

In order to make the return surfaces of the upper and lower ejector plates have a return mechanism

In addition to the return pin (RP), the return mechanism also includes a forced pull-back mechanism and a quick return mechanism.

(1) Generally, RP is equipped with a spring (see Figure #). The function of this spring is to make the upper and lower ejector plates quickly return to their original positions under the elastic force of the spring.

Spring specifications generally choose light load or light load.

(2) Sometimes the inclined pin is broken or the thimble is broken, and a spring is added at the bottom of the return pin. The purpose is to protect the ejector pin or inclined pin, or the ejector pin and inclined pin collide with the female die surface (see Figure 2). Generally, the selected models are medium load or heavy load.

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

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

10. Standard die holder

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

(2) Die seat structure of the second flat die (see Figure 5)

Generally, a double-plate mold consists of an upper fixed plate, a lower fixed plate, a female template, a male template, an upper ejection plate and a lower ejection plate.

Sometimes there are two situations:

A In order to increase the strength of the mother template, the mother template should be thickened and the fixed plate should be omitted.

B sometimes when heating the flow plate.

3. Structure and part name of the second mold:

Four. Configuration requirements of some standard parts

※ Configuration requirements of GP

1 ? Role of GP:

1. Accurately locate the fixed side and the movable side.

2. Support the weight of the mold.

3. Protect the mold core

2? GP material SUJ2；; Heat treatment HRC60 2 (high frequency quenching).

3.GP specification and coordination requirements. (Hyperlink GP standard parts)

4.4 choice. GP diameter and position. (Diameter and location of hyperlink assembly)

5.GP configuration form and use occasion. (as shown in the figure below)

Use A-type bushing and B-type bushing. The male template is deep and large, which is convenient for taking finished products.

Generally speaking, the depth of the template decreases, and the gap between the lining die and the core is larger.

The matching length of the sleeve increases the strength of the mold and prevents the pilot injection oil stain from getting on the finished product.

Determination of 6.6. GP length. (as shown in the figure below)

It is about 15~25MM higher than the finished surface and about 10~ 15MM higher than the diagonal pin.

※ Configuration requirements of rapid prototype: (function of rapid prototype: return to push plate)

1. When the mold needs automatic production, it is generally necessary to install the spring under RP, as shown in figure 1: the spring specification is TR type. (hyperlink TR spring specification)

Note: spring installation requirements

Answer? In the state before the action, the pre-tightening force of the spring is 5 ~10 mm. ..

b？ If it is necessary to return first, the spring preload should be greater than10 mm.

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

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

3. When the mold has an inclined pin mechanism and the inclined pin breaks, a spring is installed at the bottom of RP to protect the inclined pin from breaking.

As shown in Figure 3:

4. When the mould is equipped with EGP, RP escapes from the plate. As shown in Figure 4:

3? RP material-suj2; Heat treatment HRC60 2 (high frequency quenching).

4? RP specification (hyperlink RP standard parts).

Figure 1, Figure 2 and Figure 3

※ Configuration requirements of ※EFP.

1? The role of EGP:

Guide the ejector plate to move to prevent the ejector plate from being unbalanced due to uneven stress.

2? Material of EGP su J2; Heat treatment HRC60 2 (high frequency quenching).

3? EGP specification and coordination requirements. (hyperlink EGP standard parts)

4? Selection of EGP diameter.

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

5? The assembly form and application of EGP. (as shown in the figure below)

Ordinary molds, small molds, high-temperature molds and die-casting molds.

6? When the mold is equipped with EGP, RP escapes in all templates. (hyperlink RP configuration requirements)

※ Configuration requirements of ※STP.

1? The role of STP.

1. Reduce the contact area between the ejector plate and the lower fixed plate, which is convenient for adjusting the flatness of the ejector plate.

2. Prevent the ejector plate from directly contacting the lower fixing plate.

2? STP material-S45C, heat treated at HRC 40 ~ 45.

3? STP specification (hyperlink).

4? Determination of STP position.

STP must be installed under the return pin (RP) to prevent deformation due to maximum stress. (as shown in figure 1):

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

5? Determination of STP quantity. (as shown in figure 2)

Figure 1 Figure 2 Figure 3

Length quantity

L & lt200 4 branches

200<L & lt400 6 branches

400<L 8 or above

Note: STP should be added in the middle of the large die, and the fulcrum of the lower ejector plate should be added to prevent the deformation of the top plate. (as shown in figure 3)

6? STP installation table. (as shown in the figure below):

Easy to disassemble, can be processed separately, not easy to disassemble, generally used in small size.

Large mold structures use this STP. It can be processed integrally in the mold.

Specification of ko hole ※

1? The arrangement of K.O holes is as follows:

Note: Type A K.O hole = φ 40; Type b K.O hole = φ 60

2? The center position of the K.O hole should be consistent with the center of the nozzle.

3? When the die is large and the pin is inclined, a pullback mechanism should be installed.

Verb (abbreviation of verb) three-plate mold

1. Introduction of three-plate die structure (see attached figure)

2. Opening sequence of three-plate mold

Mold closing, injection molding, pressure maintaining, mold opening, separation of B and C, separation of A and B, and separation of C and D..

3. Determine the stroke of the small pull rod

4. Determination of the stroke of large tie rod