What is a plastic injection mold?
Plastic injection mold is a type of mold whose output product is of the plastic family. Like pens, vacuum cleaners, toys. These templates are usually the most used templates in the world and have high quality and beauty. The components of these templates are: blind and Kuwaiti, shoe, fly, bridge, hot runner and fly sprue. The devices that are used to produce plastic parts from these molds are known as plastic injection machines. These devices have different types such as 100 grams, 50 grams, one kilogram and more.
The history of the emergence of plastic injection mold
Plastic injection molding was first used by billiard ball manufacturer John Wesley Haight in 1868. He used celluloid injection into a primitive plastic injection mold to make billiard balls. Then, by upgrading the celluloid, he prepared it for processing and making the final shape. John and his brother also unveiled the first plastic injection machine in 1872.
This machine had fewer components than its current type and used a piston to enter the material from a hot cylinder into the plastic injection mold. In 1964, James Hendry invented the first spiral injection machine and thus revolutionized the plastic molding industry. These molds are considered one of the best and most appropriate methods for mass production due to their excellent performance, especially the high speed of parts production.
Types of plastic injection mold
Plastic injection molds are generally divided into two types:
Classification of molds in general
Plastic injection mold with cold runner
Plastic injection mold with hot runner
Construction of molds
In terms of construction, these molds are divided into two categories:
Two-plate injection molds: in a two-plate mold, the channel is placed between the two matrix plates and the spike. Is. Three-sided plastic injection molds: in these molds, the number of plates and the dividing line of the molds are determined based on factors such as: the shape of the plastic parts, the number of holes in the mold, the type of material used, the type of injection machine, and the type of air outlet system. .
Division based on the number of cavities
Single-cavity injection mold
The single-cavity plastic injection mold is economical and cheap. These templates have a simple design and take little time to make. This type of mold is used in the production of limited plastic parts.
multi-hole injection mold
This type of mold is used when The number of manufactured products should be large. Especially in cases where the parts have a small size, the method of designing and making a multi-hole injection mold can be used.
Molds
After preparing the template theoretically, i.e. by using the map and formula, it is time to make it in-depth. Of course, before construction, there are steps such as choosing materials and mold materials. The choice of metal in any application depends on the cost of making the desired part, its characteristics and access to the metal. In general, the technical characteristics of the parts are different. In the case of a part, its strength may be important and in the case of other parts, its appearance is an important condition.
Steel that is used for plastic molds must be able to cover a lot. Therefore, it should have a high percentage of chromium. Steel is suitable for these types of molds due to the smoothness of the plastic part and the easy separation of the part from the surface of the mold. The amount of the quality of the parts is somewhat indicative of the number of holes in the plastic molds.
The basis of the work of plastic injection devices
In general, the basis of the work of plastic injection machines is as follows: melting the resin, injecting it into the molding system and finally removing the part. This cycle lasts between two seconds and two minutes. Each plastic injection mold consists of two components: Cavity and Core. The part is finally formed by placing the plastic melt between the cavity and the core and the cooling process. When the mold is closed, the molten resin is injected between these two pieces with high pressure. The area between the cavity and the core is called muscle. The number of built-in holes are different depending on the shape of the requested part inside the mold.
Factors affecting the life of plastic injection molds
The life of the plastic injection mold depends to a great extent on the behavior of the user and consumer of the mold. Of course, if we assume that the selection of the mold material and the design of the molds have been done appropriately and completely correctly. It is a very important point to design a multi-cavity mold, as well as to choose a feeding and opening system that fits the geometry of the part. The most important issue is accuracy when using molds in mass production. Depending on the complexities of the mold and also depending on the mechanisms used in the design and production of the plastic injection mold, programs for maintenance and repairs are prepared by specialists. It is important and any failure to carry out these programs will cause irreparable damage to the mold. Another problem is the disturbance in the normal process of heat transfer in molds, which causes wear and tear of its components. Correct cleaning of the air exit paths also helps us in better maintenance of molds. Also, lubrication and greasing of the moving parts of the mold prevents wear between the moving parts of the mold. In cases where oil or grease does not reach these levels, lubricating sprays can be used.
