Main Techniques and Benefits – Blog CLR

multi-material injection molding (overmolding) is one of the most widespread manufacturing technologies plastic components. The procedure is based on the Injection of two or more materials in a single mold and process. In this article we analyze the different techniques as well as the advantages they can offer for the production of personalized pieces.

What multi-material injection molding processes are there?

  • interval injection molding

    Among the various injection molding techniques, interval injection molding allows great advantages since it achieves chromatic effects through the synchronous activation of two injection units on the surface. It’s worth noting that there is no limit to the component colors.

  • “Sandwich” injection moulding

    It is a process involving a superficial element, just like interval injection molding where in order to obtain a three-layer structure it is necessary to use an interval unit. On the other hand, this technology uses two injection units connected to a nozzle, which are used to inject two materials into the mold.

  • over injection

    In multi-material manufacturing process, It is common to machine or cast a part and then inject another material. In the overmolding process, we carry or overmold a hard or soft polymer onto a base material (substrate), which can be a metal or plastic component, thus achieving a strong bond between the overmolded polymer and the plastic or metal substrate. What’s interesting about that overmoulding Technology is that through a unique manufacturing process we get a hybrid material.

Brass-Plastic Over-Injection
Brass plastic overmolding

In addition, in relation to chromatic effectswe can find:

  • marbling

    This process achieves multiple chromatic effects on the surface. It is worth noting that there are no limits in terms of colors and chromatic effects. These, in turn, cannot be reproduced.

  • core back

    On the other hand, if you want to create simple geometries, this is the core back method suitable. It is characterized by being the simplest multi-material injection method and suitable for repeated injection with a single cavity. In addition, it allows displacement of the cavity. This cavity is expanded by using a sealing slide to inject the second component.

On the other hand, All of the above technologies are complemented by three more techniques where separate parts are taken for later assembly:

  • rotation technique

    As the name suggests, it is based on a horizontal rotation. This transfers benefits to a second station. But are they demolded?

    At this stage they are not fully demolded; that is, they stay in the shape that is rotated. For this reason turning devices are required inside or outside the mould. You should also keep in mind that the rotation cannot be complete, but only 180° on a bowl or insert in the mold. It is also known as rotating index plate injection.

  • assembly technology

    A combination of all the above methods. This technique combines all the procedures where assembly was present in the injection molding process. In this phase we can work in two well-defined ways. On the one hand, after the injection phase, the assembly phase takes place in the tool. On the other hand, two mutually incompatible components are added, which prevents the injection process itself from creating a permanent connection.

What are the advantages of multi-material injection molding?

  • Increased production
  • Increases the value of the product
  • Innovation and improvement of aesthetic design and product
  • Increase in mechanical properties
  • Reduction in parts assembly, allowing for a cheaper product
  • High personalization of the final results

Do you have questions about multi-material injection molding? at CLR we have a Track record of over 40 years shows great skill in designing specific shapes for this technology. Always looking for something higher precision and homogeneity, CLR offers parts that combine plastic with brass, rubber or steel. Learn more about our injection molding machines and don’t hesitate to download ours guide about the processes used to manufacture mechanical parts.

Mechanical part production