Introduction of Multi-component injection molding
In the field of plastics technology, multi-component injection molding is a manufacturing procedure that is utilized in situations when injection-molded components have to be composed of two or more different types of plastic. As an illustration, this is the case if the plastics that are utilized merely differ in color, for instance in order to accomplish a certain design scheme. Nevertheless, this method can also be utilized to blend elements that are wholly distinct from one another. It follows that these characteristics can be specifically mixed with one another in many different ways.
Several different methods are included under the umbrella term of multi-component injection molding. The following paragraphs will describe two of these processes. A minimum of two distinct melts are merged with one another, being as follows:
- Multi-component injection molding using the overmolding process and in
- Multi-component injection molding using Sandwich molding process
The following summary provides an additional breakdown of distinctions between multi-component injection molding.
Multi-component injection molding using the overmolding process
The translation of this method is something like “overspraying”. This already constitutes the heart of the manufacturing process. This entails over-injecting a previously created injection molded object with a second melt during the next production stage. Depending on the plastics used, this technique can yield the following product groupings, among others:
- Injection moldings with several colors, which are made up of a variety of colored plastics that share the same structure as the base material. Examples of such items are caps for cosmetic goods and telephone buttons that come in a variety of colors and are fitted with backlit symbols.
- Joint connections that are movable and made of various types of plastic (for example, the arms of dolls, hinges, and other similar pieces of equipment)
- Connections that are said to be hard-soft. Most of the time, they are constructed out of rigid polymers that have a layer of elastic material. (for example, plugs manufactured with an injected seal or transport rollers that have a running surface that is soundproof)
The procedure of overmolding can only be carried out with the assistance of specialized tools and machines. There must be at least two injection units that are capable of being controlled independently of one another, and these machines must be fitted with them. A significant number of them are already developed for a matching application, which is also applicable to the control system that is related with it.
Multi-component injection molding using the sandwich molding process
During the process of overmolding, two thermoplastics are injected either against each other or on top of each other. When it comes to the sandwich molding process, the situation is quite different. When doing this particular sort of multi-component injection molding, a consistent structure is established over the cross-section of the item that is being molded by injectioning.
It is made up of an outer layer and a core component that is located in the middle. In the injection mold, also known as the cavity, the constituent components are initially injected into the mold in sequential order. The core, also known as the interior of the finished injection-molded item, is formed by the layer of melt that is injected last. The phenomena that is referred to as swelling flow is the reason for this observation.
It is therefore essential for the swelling flow and the laminar flow to be present in the sandwich molding process in order to ensure successful multi-component injection molding. Assume the following in order to accomplish this: In a cylinder, two melts of different colors are stacked one on top of the other on successive layers.
From this point forward, a piston is used to press them into a second cylinder. The result would be a structure similar to a sandwich. This is due to the fact that the plastic melt adheres to the walls of the construction. It is possible to further increase the effect that has been described by freezing the plastic melt on the cold equipment wall.