Multi-material injection molding (Multi-material Injection Molding) technology has been developed for many years and is widely used in the automotive industry, electronics, medical and other fields, and brings extraordinary economic benefits. It is a technology with development potential. Why use a multi-material solution? Due to the ever-changing market demand for plastic products; single-material, single-color, and single-function plastic products have been unable to meet consumer demand for products. For example, daily necessities, toothbrushes, razor handles, etc., require soft plastics to increase the anti-slip function; in auto parts, a small part of light-transmitting materials are required to meet the configuration of the atmosphere light in the car; pacifiers, thermos bottles, etc. in maternal and child products , Through different hardness of liquid silicone rubber (Liquid Silicon Rubber) materials to achieve compliance with health regulations and functional products. The multi-material industry has become the rising star of injection molding, and applications and demands are advancing by leaps and bounds. Among them, the multi-material injection molding process has the following advantages compared with the traditional process:
· Enhance the fit, tightness, ergonomics and other product performance characteristics of dissimilar materials
· Improve product value and appearance, increase personalized functions
· Permanent labels replace the original silk-screen printing or spraying
· Shorten product production and molding cycle and reduce costs
· The process of secondary processing and assembly after traditional injection molding is omitted.
Among them, the multi-material injection molding process has been widely defined in the industry as the next three processes.
Ø Multi-Component Injection Molding (Multi-Component)
Two different materials are injected simultaneously or sequentially through the same or different gate positions in a single mold. In the co-injection process, two materials are injected into the same tool at the same time, while the softer material migrates to the outer layer. Material compatibility is critical to this process and must be carefully controlled.
It involves injecting different materials into the mold in a specified sequence, where the geometry of the cavity may change between sequences. This process usually requires specialized equipment and tools.
Ø Over Molding
Overmolding is most common when the substrate has been cladding twice to achieve the functionality or product physical properties. The resin for overmolding must be hot enough to melt the surface of the rigid substrate, or the surface must be activated to achieve chemical bonds. When inelastic products are completely overmolded, this process is called fully encapsulated insert molding.
In response to the industry's multi-material injection molding needs, Multitech is generally summarized into two categories; they are the vertical injection molding solution (Vertical Injection Molding Solution) and the multi-injection unit solution (Figure 1). In this article, we will discuss the main axis of the injection unit (Injection Unit).