1.What Is Injection Molding?
Injection molding is to inject the plastic melt into the closed mold cavity at high speed under high pressure, and get the plastic product with the shape of the mold cavity exactly after cooling and shaping.
Injection molding must meet two necessary conditions: first, the plastic must be injected into the mold cavity in a molten state; The second is that the injected plastic melt must have sufficient pressure and flow speed to completely fill the mold cavity. Therefore, injection molding must have the basic functions of plastic plasticizing, melt injection and pressure holding molding.
(1) Plasticization process In the plasticization process of injection molding, the solid plastic through the transmission of the rotating screw, constantly moving forward along the direction of the screw groove, after heating, compaction, shear mixing of the screw thread and other effects of heating into a uniform density, viscosity and composition and temperature distribution of viscous plastic fluid. The heat required for plasticizing solid plastics mainly comes from the heating of the external cylinder to the plastic and the friction shear heat of the injection screw to the plastic. In the plasticizing process, whether the temperature of the plastic melt meets the injection requirements and whether the temperature distribution is uniform is an important parameter to measure the plasticizing function of the injection molding machine, and the plasticizing function refers to the amount of molten plastic that the injection molding machine can provide in a unit time.
After the solid plastic is plasticized into melt, it is pushed to the head of the screw by the constantly rotating screw and stored in the storage area at the front end of the barrel. The plastic melt in the storage area has a certain pressure, and the pressure of the melt acts on the screw to push the screw to overcome various resistance and retreat. The screw stops rotating after retreating to a certain distance, the plastic melt volume (called the injection amount) in the storage area is determined, the plasticization process is ended, and the injection process is entered.
(2) The plasticized plastic melt in the injection process is stored in the storage area of the barrel. When injected, the screw moves axially. Under the action of the injection pressure of the screw, the plastic melt flows through the nozzle installed in the front end of the barrel and is injected into the mold cavity at a certain rate.
(3) The plastic melt injected into the mold cavity during the cooling and setting process overcomes various flow resistance and fills the mold cavity. The plastic melt filled with the mold cavity is subjected to huge pressure from the mold cavity, which is driven by the plastic melt flow back to the barrel; Moreover, due to the cooling effect of the mold cavity, the plastic melt produces cooling shrinkage, at this time, the injection screw continues to provide pressure to keep the plastic melt full of the mold cavity without backflow, and the plastic melt is appropriately added to the mold cavity to fill the shrinking space in the mold cavity until the plastic melt gradually cools and solidifies into the product.
2.What Is Injection Mould(Tooling)?
injection mould(injection tooling) is a tool for injection molding, is a common molding industrial production. Injection mould is a process in which a plastic, such as a plastic particle or a plastic fiber, is heated to a molten state and then the molten plastic is injected into a mould by an injection molding machine, such as a plunger or screw injection molding machine, which is cooled and formed into a product of the desired shape and size.
Injection moulds usually consist of the following parts:
A.Mould body : The mould body is the main part of the injection mould, usually made of materials with high hardness and wear resistance (such as steel, copper, etc.) to ensure the service life of the mould.
B.Injection(Feeding) system : includes a main channel, a flow channel and a gate for transferring the molten plastic from the injection molding machine to the mould cavity.
C. Cooling system : used to cool molten plastics for rapid curing.
D. Ejector system : including ejector pins, blocks, top plate, etc., used to ejector the molded product from the mould.
3.How to make a injection mould?
A. Mould design
The first step of mould manufacturing is design. In the mould design, we first need to determine the mould type according to the shape and requirements of the injection parts. Then, according to the shape and size of the injection parts, as well as the type and nature of the injection materials needed, the mould structure is designed. Finally, the material selection and heat treatment design are carried out to ensure the quality and performance of the mould.
B. Numerical control machining
CNC machining is a very important part of mould manufacturing. CNC machining can realize high-precision and high-efficiency parts manufacturing, which is particularly important for mould manufacturing. In CNC machining, milling, cutting, drilling and other processing methods are usually used to realize the machining and manufacturing of moulds.
C.Precision grinding
Precision grinding is one of the key steps of mould manufacturing. Precision grinding can help grinding the various parts of the mould, and ensure its dimensional accuracy and surface roughness, while also increasing its sealing performance and wear resistance, improve the service life of the mould.
D.Electric discharge machining
Edm is an efficient non-contact processing method, which can achieve metal melting and cutting through the discharge phenomenon, and is also very important for mould manufacturing. Edm is usually carried out in parts of the mold with high requirements for internal, external profile and dimensional accuracy. Edm can improve the accuracy and surface finish of the mould, and reduce manufacturing and processing costs.
E. Assembly and debugging
After the mold manufacturing is completed, assembly and debugging are required. The assembly process needs to check the various parts of the mould to ensure its correctness and fastness. In the debugging process, it is necessary to carry out injection molding test, simulate the production environment, and test the performance and reliability of the mould. Through proper adjustment and precision test, the stable operation of the mould can be guaranteed.
Injection mould manufacturing is a very complex process that needs to go through multiple steps to complete. From mould design to CNC machining, precision grinding, EDM and assembly and debugging, all aspects need to ensure the accuracy and efficiency of manufacturing. Only through strict inspection and testing, can we ensure the quality and performance of injection moulds.