Die structure and principle
1. Overview of molds:
"Mold is the mother of industry" this sentence has been familiar to us, the importance of the mold is increasingly recognized by people, mold design and mold manufacturing technology has made great progress.The innovative design of mold processing technology, the wide application of all kinds of new mold materials, the standardization and specialization of mold parts, etc., all force us to design faster, more accurate to adapt to the development of the mold exhibition.The improvement of speed requires that the design stage can be delivered to the post section in about 3 days; the improvement of precision requires that the processing method of each part should be considered clearly in the design process, and the processing method with high precision and low processing cost should be adopted as far as possible.The increase in accuracy and speed goes hand in hand.The increase of speed inevitably requires the increase of precision; the increase of precision inevitably drives the increase of speed.
2. Basic composition of plastic mold:
The plastic mould consists of seven systems: guide system, supporting system, forming parts system, gating system, cooling system, ejecting system and exhaust system.For the mold composed of the above systems, the plastic enters the mold cavity through the pouring system through the sprue, and is cooled by the cooling system after filling and holding the pressure. After the cold solidification of the finished product, the molding parts are ejected out by the ejecting system to complete a molding cycle.
3. Mold closing guide system:
Mold closing guide mechanism in the plastic mold, mainly used to ensure that the two parts of the male mold and the mother mold or other parts of the mold between the accurate match, to ensure the shape and dimensional accuracy of plastic products, and avoid the collision and interference of various parts in the mold.The basic requirements of designing die closing guide mechanism are accurate positioning, accurate guidance, and sufficient strength, stiffness and wear resistance.The guide mechanism has a guide pillar guide mechanism and a cone (face) positioning mechanism.
4. Supporting system:
In the plastic mold, the male and female templates, upper and lower fixing plates, die feet, support columns (SP), stop pins (STP) and other parts are called supporting parts.The supporting parts and the die closing guide mechanism are assembled together to form the injection mold frame.The function of the mould frame is used to install and fix the various functional structures in the injection mould. Therefore, when designing the injection mould, it is necessary to ensure that all kinds of supporting parts have enough strength and stiffness.Male and female templates in the mold to install and fix the molding parts, die closing guide mechanism and ejecting demoulding mechanism and other functional mechanisms.The upper and lower fixed plate supports the male and female formwork and the parts installed on the male and female formwork, and can be used to install the mold on the molding machine.The mould foot and the supporting column (SP) pad are between the public formwork and the lower fixing plate, which can form the movement space of the ejecting and demoulding mechanism.The stop pin (STP) adjusts the smoothness of the ejection stripper.
5. Molded parts system:
Molded parts system is mainly to make the finished product can smooth injection molding, get the ideal product and design.At present, the common situations are as follows:
A mechanism for handling the external inverted hook of finished products (slider mechanism)
A mechanism for handling the internal inverted hook of finished products (inclined pin mechanism)
6. Gating system:
After the plastic particles are fused, they are ejected from the nozzle of the injection molding machine and flow through the channel in the mold before reaching the mold cavity.The basic principle of gating system design is to improve the molding speed and shorten the molding cycle while satisfying the quality of plastic products
7. Cooling system:
Mold cooling system includes: cooling water channel, mold temperature controller and heating components, etc.Set the function of cooling waterway:
A. Control the mold temperature to improve the quality of injection parts, mainly in the following aspects: surface finish, residual stress, crystallinity, thermal bending.
B. Shorten the molding cycle. 80% of the molding cycle should be used for cooling. A well-designed cooling system in the early stage of the mold is very necessary to improve the production efficiency.
C. Cooling large sliding parts to avoid sticking in the working process.
8. Ejection system:
Product ejection is the last link in the process of injection molding, when the product is solidified in the mold, it needs a set of effective way to ejection from the mold, the quality of ejection will finally determine the quality of the product, therefore, the ejection of the product is not to be ignored.And in the top out can not make the product deformation, top white, rupture and other damage to the phenomenon of products.Such a device is known as a push-out system. There are several types of push-out systems:
9. Exhaust system
, the structure of the exhaust function in the process of plastic injection mould cavity filling, in addition to the original air cavity, and plastic containing water at injection temperature evaporation of water vapor, plastic local overheating decomposition of low molecular volatile gas, plastic additives volatile (or chemical) produced by the gas and thermosetting plastic hardening of the release of gas.If these gases can not be discharged from the mold cavity, it will affect the quality of the molding and demoulding.Therefore, in the design of cavity structure and gating system, we must consider how to set the exhaust system, in order to ensure that the product is not due to poor exhaust quality problems.
Form of exhaust groove
The exhaust groove is best processed into a curved shape, and its section is gradually increased from fine to coarse.This reduces the kinetic energy of the plastic solution when it escapes from the vent, and also reduces the flow rate of the plastic solution when it escapes from the vent to prevent industrial accidents.
Opening position of exhaust groove
Generally, it needs to be determined after the mold test, but for large molds, it is often necessary to open a good exhaust groove before the mold test, and then adjust after the mold test.
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