Plastic insert molding is a specialized injection molding process used to encapsulate a pre-formed component made from metal or other solid material within thermoplastic. This integrated approach enhances part structural integrity, functionality, and flexibility.

The insert can be an individual item or an assembly of multiple components, precisely placed in a custom-built tool. As a result, secondary operations are eliminated, which shortens cycle times and often reduces costs.

Insert Molding vs. Overmolding

While both insert molding and overmolding involve combining materials during the molding process, there are key differences:

Insert molding: A metal or other solid component is placed in a custom-built tool, then resin is injected into the tool cavity, coating the insert in a smooth layer of plastic
Overmolding: A thin layer of plastic is applied over a compatible plastic or a metal base to create a durable, rubber-like exterior

Types of Insert Molding

The versatility of insert molding solutions make them ideal for meeting specific design, performance, and production needs:

SINGLE-PART INSERT MOLDING

The most common method of insert molding, a single solid component is placed into the tool cavity and encapsulated by molten thermoplastic injected into the tool cavity.

Single-part injection molding is ideal for applications that require enhanced structural support or wear resistance, such as threaded inserts or reinforcing pins.

MULTI-COMPONENT INSERT MOLDING

For more complex insert assemblies, multiple components are arranged within the tool prior to injection molding. The pre-configurations enable integrated part multi-functionality in single parts.

Multi-component insert molding is common in industrial, medical, or other applications where precision and durability are essential.

VERTICAL INSERT MOLDING

In this approach, the tool closes vertically to use gravity in accurately holding inserts in place during resin injection, ensuring precision alignment and placement within finished parts. Vertical presses often have rotary tables or shuttles to make production more efficient and compatible with line automation.

HORIZONTAL INSERT MOLDING

Horizontal molding machines optimize high-volume runs or larger part geometries. Due to multiple tool cavities and automated insert placement, horizontal insert molding is consistent and repeatable, cutting cycle times while increasing part production.

Benefits of Insert Molding

Insert molding brings measurable value throughout all phases of an injection molding program, including:

The ability to combine materials, features, and functionality into a single part gives engineers design options that may not otherwise be available through traditional injection molding methods. This is particularly beneficial for achieving tight tolerances and sophisticated geometries in complex applications.

Insert Molding Expertise

At Kaysun, we leverage advanced insert molding technology to deliver high-quality, precision-molded components tailored to your project's needs.

Our capabilities include:

Automated Insert Placement: Using both horizontal and vertical molding machines maximizes automation and ensures consistent, accurate insert positioning
In-House Engineering Support: Our team provides comprehensive services, including Design for Manufacturability (DfM) analysis, material selection, and tooling design, to optimize your program from concept to production
Quality Assurance: As with all of our programs, rigorous quality control measures and scientific molding principles are in place during insert molding to ensure each part meets exact specifications

Insert Molding Services

What is Insert Molding?