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Multi-component Injection Method

06 April, 2020

Injection molding technique is the most commonly used plastic shaping method due to its suitability for mass production and enabling many different product geometries. With the advancing technology, prominence of such features as the quality of the parts and their aesthetic appearance, their durability etc. has played a major role in the emergence of technologies such as multi-component injection. Today, this one-step process, which offers compact products, reduced logistics costs and optimized production costs with the multi-component injection molding method, has become an effective solution for innovative products in almost all industries, from automotive to construction, packaging and medicine. As Alpplas, with our expertise of over 30 years, we produce solutions for our customers in every aspect of the manufacturing phase from multi-component injection applications to mold design and production to mass production.
What is the Multi-Component Injection Method?
This method is a plastic injection method that allows two or more different plastic materials to be produced within the same process. There are different injection methods according to the part design and requirements. Examples of multi-component injection methods used especially in the white goods and automotive industries are given below.
Core-Back Process: In the core-back process, the core that is pulled back on the moving side of the mold creates space in the mold cavity for the second material in the second stage of the process.

Rotary Table Process
180° Index Plate Process
In the rotary table process, which is a different form of the multi injection molding method, the moving side of the mold is rotated. The geometry of the product to be molded can only be changed by the thread of the mold. It begins by injecting the plastic melt into the primary cavity of the 2-chamber mold. Then the rotating plate is rotated 180 degrees and the primary molding is moved to the secondary cavity. Finally, another plastic melt is injected into the 2nd cavity formed inside the mold on the part formed by primary molding.
It is possible to perform more than 2 injections in the same mold according to the requirements (e.g. 3 components).

Rotary Core Process
Suitable for production processes that require the same geometry on both sides of the mold cavities. This method provides considerable freedom for part design.

Vertical Rotation Method
The mold cavity of the group of plates in the middle faces both directions. In order to use different materials or colors, the closing process takes place when the mold turns 180 ° thanks to the cores used during the first injection, and the sections left blank by the cores during the first injection are filled in during the second injection.

Transfer Method
In the transfer method, the semi-finished part that is injected into the first mold cavity is moved to the second mold cavity by a robot or by hand.
Material Selection in Multi-Component Injection
In this method, where more than one plastic is used, the interrelations of the plastics should be taken into consideration during the design phase and appropriate materials should be selected. The materials used during the process should form a chemical bond among them and stick together. Not all materials are able to bond and stick together. The Tables below show the bonding abilities of different plastic materials.
Hard Plastics

Hard – Soft Plastics

Fevzi Güler

Process Development Specialist