Overmolding, also known as multi-shot molding or soft-touch molding, is a high-performance, integrated injection molding process used to combine two or more different plastic materials into a single, functional component. As multi-material technology and mold-making capabilities have evolved, Overmolding has been widely applied across custom plastic parts, medical device molding, plastic parts manufacturing, and medical plastic molding, becoming a key technique in precision manufacturing.
Overmolding is a process where a rigid plastic or metal substrate is first injection molded, followed by an overmolding step where one or more layers of elastomers or functional plastics are molded over or around it. For custom plastic parts, Overmolding brings several benefits:
Function Integration: Rigid structural support and soft protection within the same part
Enhanced Appearance and Comfort: Soft-touch layers improve ergonomics and anti-slip performance
Reduced Post-Processing: Eliminates gluing, assembly, or secondary bonding steps
Optimized Cost: Lower per-unit cost in high-volume production compared to manual assembly
In mass production, Overmolding utilizes several types of automated systems to achieve continuous, efficient, multi-material injection molding:
The most common industrial solution, ideal for large-scale plastic parts manufacturing:
The mold consists of two cavities: one for base material and one for overmolding
The mold rotates 180° after each injection cycle to switch between cavities
Dual injection units operate alternately, ensuring high efficiency and low energy consumption
Final parts are completed within a single mold, significantly improving cycle time and consistency
Perfect for medical plastic molding applications requiring high precision and complex geometry:
Robotic arms or automatic loaders transfer the base component to a second mold
Accurate overmolding is performed in the second cavity
Both molds may share the same injection machine or cooling system
High precision and flexible production, suitable for mixed production lines
Used in high-end industrial scenarios like complex medical device molding or advanced electronics:
Two injection machines each inject different materials
Robots manage the automatic transfer and overmolding
MES systems enable traceability and defect control
Widely applied in production lines for premium custom plastic parts
Overmolding originated in the mid-20th century alongside two-shot injection molding technology. It gradually developed in Europe and North America as a key method for integrating complex functions into single components. Its use in medical manufacturing began in the 1990s, when advanced medical-grade materials and mold precision enabled its adoption.
Today, Overmolding is widely used in medical devices, personal care instruments, and biocompatible components. Many global medical plastic molding companies now incorporate Overmolding as a core production capability.
Overmolding involves a multi-step injection molding workflow. The main steps include:
First Injection (Substrate Molding)
A rigid material (e.g., PC, ABS, PA66) is molded to provide structural support.
In-Mold or Robotic Transfer
The molded part is rotated or transferred to the overmolding station.
Second Injection (Overmolding Material)
Soft materials (e.g., TPE, TPU, silicone) are injected to form outer layers or seals.
Cooling, Ejection & Inspection
The part is cooled, ejected, and inspected for dimensional accuracy and bonding strength.
Mold design for Overmolding is more complex, requiring multi-cavity layouts, precise alignment systems, and dual-material runner control. These are essential in high-end plastic parts manufacturing projects.
Overmolding serves numerous precision industries. Here are common use cases:
Surgical handles, anti-slip grips, hemostats with overmolded areas
Soft-seal connectors for catheters
Integrated housings for ventilators and injection systems
Analytical device parts with color codes and flexible seals
Industrial buttons, waterproof switches
Oil-resistant handles, power tool grips, flashlight housings
Dual-layer insulation for electronic connectors
Gear shifters, soft-touch door handles
Remote control and appliance bezels
Shock-absorbing housings for high-end electric tools
Overmolding enables significant breakthroughs in materials integration and structural design, especially for custom plastic parts, medical plastic molding, and medical device molding. At Vanmodel, we offer advanced injection platforms, custom mold development, and strict quality control to deliver efficient, reliable Overmolding solutions.
Contact Vanmodel today to receive professional Overmolding consultation and a personalized quote.
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