In Mold Assembly: High-Performance Manufacturing with Advanced Embedding Technology

The Definition of In Mold Assembly

In‑mold assembly (IMA) is a multi‑shot injection molding process in which pre‑fabricated metal inserts—like terminals, busbars, or lead frames—are placed in the mold during the first injection (“pre-mold”). In the second (and any subsequent) shot, molten plastic flows around and fully encapsulate these inserts, locking them permanently in place within the part. By embedding conductive or structural elements directly into the plastic during the initial molding cycle, IMA eliminates all the time-consuming pick-and-place and manual fastening steps required in traditional post-molding assembly.

 

 

The Difference Between Typical Assembly and In Mold Assembly

Type/Item	Typical Assembly	In Mold Assembly (IMA)
Process Flow	Parts are produced individually, then joined in secondary process.	Molding and assembly occur in one operation.
Production Speed	Lengthy secondary processes extend cycle times.	Eliminates secondary steps, dramatically shortening cycle times.
Accuracy	Manual placement or separate‑assembly tolerances can introduce variation.	Precise, repeatable component placement controlled directly within the mold.
Component Strength	Joints and adhesives can create weak points.	Overmolding binds parts into a unified, durable structure with fewer potential failure sites.
Cost Efficiency	Higher labor costs, material waste (e.g. adhesives), and extra equipment needed.	Fewer process steps reduce labor, cut material waste, and minimize reliance on additional equipment.

 

 

The Process of In Mold Assembly

 

Overmolding is an advanced injection molding technique that uses two or more materials into a single, unified component—often embedding functional features such as terminals or busbars to boost structural strength and reliability. In mold assembly builds on this concept by placing prefabricated inserts—typically metal parts are directly inserted in the mold, eliminating all downstream pick‑and‑place and fastening steps. IMA proceeds in two stages, commonly called “first shot and second shot” or “pre-mold and overmolding,” each in its mold cavity:

1. First shot (pre mold): Molten plastic is injected into the mold to form the base substrate. During this shot, you can place metal inserts such as terminals into the cavity. As the plastic cures, it locks these inserts firmly into position, creating a sophisticated, ready‑to‑augment framework.
2. Second shot (overmolding): The pre-molded substrate is transferred into a second mold. A secondary material is injected around or over the existing structure. This shot can merge multiple pre-molded pieces into a single form and introduce new inserts (bushings, fasteners) for mechanical or sealing functions.

Depending on material choices and mold design, the two polymers bond through mechanical interlock or chemical adhesion. Once cooled, the result is a fully integrated part—complete with embedded metal elements—delivered from the mold, with no manual assembly steps required in traditional processes.

 

 

The Applications of In Mold Assembly

 

Automotive & EV In Mold Assembly: Modern vehicles demand components that are both lightweight and robust, with integrated electronics and power‑management functions. By embedding metal inserts—such as lead frames directly into structural parts (e.g., housings of EV charge ports, battery modules, power‑distribution units, and sensor assemblies), manufacturers create seamless electrical pathways without bulky wiring harnesses. This in‑mold integration simplifies assembly, cuts error rates, and delivers superior safety, reliability, and overall vehicle performance. Moreover, these components are engineered to pass stringent IPX environmental‑protection tests—such as IPX9—ensuring fully waterproof and dustproof performance for dependable operation in the harshest conditions. The products and the list below use automotive of an example how in mold assembly is applied in different functions.

 Automotive Premomold + Overmolding Parts

 

 

 

 

Consumer & Electronics In mold Assembly: IoT modules, industrial sensor housings, LED‑lighting assemblies, medical‑monitoring devices, and power‑tool enclosures—the demand for compact, multifunctional designs is relentless. Embedding conductive elements such as busbars, lead frames, and terminals, directly into molded housings via in‑mold assembly lets engineers optimize PCB layouts, enhance thermal dissipation, and curb electromagnetic interference. This deep integration not only accelerates production and reduces material waste but also yields tougher, more reliable products perfectly suited to rugged industrial and advanced consumer‑tech applications.

 Consumer & Electronics Premomold + Overmolding Parts

 

 

  

The Benefits of In Mold Assembly

1. Integrated electrical pathways: In mold assembly creates low resistance circuits with perfect alignment, eliminating secondary wiring and loose connectors.
2. Built-in isolation: You can design molded insulation barriers around embedded inserts—busbars, connectors, and contact pins—to prevent short circuits and minimize electromagnetic interference in mixed‑signal environments.
3. Save material: Integrating metal parts or micro‑connectors directly into the plastic frees up board space and sheds extra wiring bulk—critical for automotive, aerospace, and compact industrial electronics.
4. Optimize thermal management: Embedded metal elements can be positioned to form heat‑dissipation pathways, channeling heat away from sensitive components and improving cooling in power modules and LED‑lighting assemblies.
5. Lowered cost: In mold assembly has fewer discrete parts (no separate wiring harnesses or housings) combined with fewer assembly stages to drive down material and processing expenses—making your design more competitive.
6. Enhanced durability: In mold assembly encases busbars, lead frames, terminals, and connectors in a protective polymer skin, shielding them from vibration, moisture, and environmental stress for longer service life. 

 

 

Layana’s In Mold Assembly Capabilities

We refined our manufacturing expertise by combining overmolding with insert molding with precision progressive die stamping, all performed in-house. We create robust, high-performance assemblies tailored for variable applications.

 

The Bi-material Integration at Layana brings several key advantages Design Flexibility and Miniaturization: The integrated process and the ability to provide Total Engineering Assistance during DFM offers designers the freedom to develop compact, multifunctional components that meet strict performance standards. Streamlined Production and Supply Chain Efficiency: With both metal stamping and plastic molding performed in-house, Layana reduces logistical complexities and minimizes exposure to external supply chain disruptions. Full Automation Scalability: Layana’s in‑house industrial automation engineering team enables each project to transition seamlessly from manual lines through progressive levels of semi‑automation to fully automated systems, adjusting precisely to the real‑time demand of every product.

Conclusion

In today’s fiercely competitive manufacturing landscape, companies are constantly seeking ways to boost efficiency and enhance product quality. In mold assembly has emerged as a game‑changing technique, replacing traditional step‑by‑step processes with a single, integrated operation inside the mold. Layana Company stands out as one of the industry’s leading specialists in in‑mold assembly, the integration of plastic injection and metal stamping and its full suite of in‑house capabilities—from industrial automation to mold design and fabrication—all under one roof. This end‑to‑end approach enables Layana to respond with remarkable speed and precision, delivering cutting‑edge in‑mold solutions—especially for complex lead frame pre‑mold and overmolding designs in power electronics and next‑gen EV applications.