Multicomponent injection molding offers new possibilities for plastics processing, that is, combining different materials or colors in a single molding. Production can be completed in one process without the need for additional assembly or post-processing steps. Multicomponent injection molding Forming is a fully automatic process with a high degree of flexibility and is particularly suitable for mass production.
The final molded part can have a variety of functions and characteristics. Using this process, it is possible to produce colored parts that are highly resistant to pressure, heat, or chemicals.
The concept of multi-component injection molding covers multiple independent processes. The common point of these processes is the simultaneous injection of a corresponding number of different materials into the mold using two or more injection molding devices, and the final product is produced through a series of steps. The final parts do not require subsequent processing. Can be used directly.
According to the gate number, it can be divided into two groups:
Uses a single gate system, including sandwich and alternate injection molding processes.
The multi-gate system can be initially divided according to the core-pulling and transfer process. The transfer process consists of transferring from the robot system between two standard machines, transferring in a specific multi-component machine through the rotation of the robot system and the mold. Rotation includes rotation of the movable mold half through the rotating device, rotation of the mold inner member and rotation around the vertical axis (GRAMTM process).
Application advantages:
Advantages of multi-component injection molding: In multi-component injection molding, the components of the molded part are completely separated. All components are visible on the surface, reflecting the appearance and function of the part.
For example, keyboard buttons, flagged switches, or handles with soft areas for added comfort. In addition to the ability to produce injection-molded parts in multiple colors or materials in one process, there is no need for additional assembly or subsequent processing. The continuous improvement of technology can also bring the benefits of continuous growth.
Injection molded parts are resistant to external influences (such as mechanical, thermal or chemical effects) and are achieved through appropriate material combinations and high bond strengths. Adhesion of two-component bonded surfaces can be achieved through chemical bonding or mechanical bonding. Links to achieve. If chemically compatible materials are used, permanent molecular binding can also be achieved through melting or welding processes.
Two-component injection molding:
The automatic two-component injection molding mold has a two-stop type. The molded parts are pre-injected and then the production of the parts is completed through another injection molding stage. The pre-manufactured parts are produced in the first cavity. Then the mold is opened, and the entire movable mold half is rotated 180 ° Rotation of the prefabricated cavity to the final injection position. Then, by adding a second material, the prefabricated part is made into the final part. The mold cavity can be rotated in the same direction or alternately rotated in different ways. The final part is demoulded. Afterwards, the empty cavity is ready for the next prefabrication.
In order to demold the part independently of the production process, a demoulding station is integrated into the two-component molding. Then, the mold rotates clockwise. There is an opening on the side of the third station, from which the robotic system grippers can reach and close. The mold, which releases the part and its gate, is placed on a conveyor belt for further processing.
Three or more components injection molding:
The molding process of three or more components can be realized by various methods. The following describes two possible methods.
Two-station mold:
The setting of the two-station mold can be done in a manner similar to the setting of the three-component mold described above. In the first process step, three or more (up to five) components are injected at the same time to produce the prefabricated parts. Then, the entire half-surface mold is rotated 180 and moved to the second position. At this time, other materials are used to injection-mold the preform to produce the final part.
Another method is that in the correspondingly configured molds, the parts can basically be combined in a production step with up to five surface elements made of other materials/colors. Therefore, the inserts in the mold can be driven by the rotation pattern and electric The rotating device rotates between three stations.
Four-station mold:
For example, multi-layer plastic parts can be produced using a four-station mold. When using recycled materials and barrier layers, this method is easy to implement. The innermost layer is produced at the first station. Then, the mold is rotated 90°; One station. At this time, the second component is used for injection molding of the first component. Then, the mold half continues to rotate to the third station, and finally rotates to the fourth station for the final stage of production.
At this time, the protective outer layer or the surface of the molded part is injection molded on the part. After the cooling stage, the final multilayer part is released from the cavity. In the continuous cycle, each time the mold is opened, Produce a final molded part.
Alternate injection molding, alternate injection molding alternates the same plastic components of two different colors into the same cavity.
Before entering the mold, both colors are placed in a special mixing nozzle. The two-color components are mixed to form a color effect. The two colors can be purposely mixed and configured. In the alternate injection molding process, two injection devices are used in special Alternating injection device (with mixed nozzles) joined together.
Sandwich injection molding:
The sandwich injection molding process injects a core material into the outer skin. The process takes place in a cavity in two or three steps.
First, the material of the stroke surface is injected into the cavity part. Then, the core component is injected through the first material into its inner center. Finally, the first component is sealed at the gate position. This prevents The core material appears on the surface, and at the same time, the second component in the gate system is removed to prepare for the next injection of the first component.
Assembly injection molding:
With a rotary mold, components that need to be assembled after injection molding can be separately formed on a two-component machine and then assembled in the mold. The example of the seal assembled in the cable duct illustrates how the assembly process can be performed in the mold. Two separate The components are first molded at the respective mold station.
Then, after opening the mold, the first element is transferred to the second station by rotating the insert, and then placed on the second element core. The assembly of the two parts is realized by the core punch. Therefore, it can be saved. To go to the next step, you do not need to use complex automation solutions.
to sum up:
Multi-component injection molding will become more and more important in the future. Especially the function of making hard and soft combinations, the development of this technology is only just beginning. With assembly injection molding, reasonable integration of various functional elements can be realized in the near future. , gradually replace the coupling process.
Technologies that have potential for future growth include the use of shrinkage behavior of the material for directional separation of components, or the manufacture of collective circuits through metal-plastic combinations.