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Two-Color Rotational Molds: How Dual-Color Products Achieve One-Step Integrated Molding

Views: 0 Author: Site Editor Publish Time: 2025-12-11 Origin: Site

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I. Opening: Why Are Dual-Color Products Gaining Popularity?

Pick up your phone case—you’ll notice it has a wear-resistant hard outer layer and a non-slip soft inner layer. Touch the control panel buttons in your car: the surface is a skin-friendly elastic material, while the base is a sturdy hard plastic. Even the handle of your daily toothbrush features a "hard core + soft rubber" dual-color integrated design. These products that balance appearance, feel, and functionality all rely on a key technology: two-color rotational molds.

Unlike traditional dual-color products made by single-color injection molding plus post-assembly, two-color rotational molds achieve "one-step molding" through mold core rotation. This not only ensures seamless bonding between two materials/colors but also significantly boosts production efficiency, making it a "blockbuster tool" in industries like consumer electronics, automotive, and daily necessities. Today, we’ll break down this black technology—exploring how it works and the amazing products it creates.

II. Two-Color Rotational Molds: What’s the Core Principle?

In simple terms, the core logic of two-color rotational molds is "two injections + mold core rotation":

The mold consists of two independent injection systems (for two materials/colors) and a rotatable male mold (core);

The first injection forms the product’s "substrate" (e.g., a hard plastic shell);

The core rotates 180° (or a specific angle) to accurately transfer the semi-finished product to the second injection station;

The second injection injects a second material (e.g., a non-slip soft rubber layer) onto the semi-finished product. The two materials fuse at high temperature inside the mold to form an integrated dual-color product.

The key advantage: No post-adhesion or assembly is needed. The product bonds tightly without peeling, has no visible seams, and its production efficiency is 2-3 times that of traditional processes.

III. 3 Mainstream Production Processes: Adapting to Different Product Needs

The process of two-color rotational molds varies by equipment type. Below are the three most common models in industrial production, covering scenarios from small parts to mass-produced items:

1. Horizontal Two-Color Machine (Split Mold Design): Preferred for Consumer Electronics

This is the most mainstream process, suitable for medium-sized products like phone cases, smartwatch straps, and electronic buttons. Its core feature is "synchronous dual-station operation":

First-color injection: The fixed mold and non-operator-side male mold close, and hard plastic (e.g., ABS, PC) is injected to form the product substrate;

Core rotation: After mold opening, the male mold rotates 180° with the machine’s large turntable, transferring the semi-finished product to the operator-side station. Meanwhile, an empty male mold moves to the non-operator side to prepare for the next round of first-color injection;

Second-color injection: The operator-side fixed mold closes with the male mold holding the semi-finished product, and soft plastic (e.g., TPR, TPE) is injected to bond seamlessly with the hard substrate;

Demolding cycle: After secondary cooling, the mold opens, and ejector pins push out the dual-color finished product. The machine immediately starts the next cycle for continuous production.

2. Vertical Turret Machine (Specialized for Small Parts)

Ideal for small products like toothbrush handles and small hardware accessories, this mold is equipped with a "turret-type slider holder" for a more compact process:

Mold opening and runner removal: The mold opens, ejector pins push out runner waste, and robots remove it simultaneously;

Slider rotation: Three slider holders (arranged at 120°) rise and rotate with the turret. The holder with the semi-finished product moves to the second-color station, the holder with the finished product to the demolding station, and the empty holder to the first-color station;

Synchronous injection: The slider holders lower and lock. Both injection stations work simultaneously—one for the first color, the other for the second;

Product transfer: Finished products are ejected at the demolding station and transferred to the conveyor belt by robots. The entire process is automated, suitable for mass production.

3. Four-Sided Rotational Mold (High-Efficiency Mass Production)

Designed exclusively for standardized products like bottle caps and containers, its core is "four-station cycle operation" for maximum efficiency:

The mold’s core is a cubic rotating body with 4 sets of tooling, corresponding to 4 stations: First-color injection → Cooling → Second-color injection → Demolding;

Each 90° rotation triggers synchronous operations at all stations: A new tooling completes the first-color injection, the semi-finished product enters the cooling station, the cooled semi-finished product undergoes the second-color injection, and the finished product is ejected;

It’s equivalent to "producing a batch of finished products every 90 seconds," suitable for large-scale production with a daily output of over 100,000 units.

IV. These Blockbuster Products Are Made Possible by It!

The application scenarios of two-color rotational molds have long penetrated all aspects of life. Here are the most typical categories:

Consumer Electronics: Dual-color phone cases (hard plastic for drop protection + soft rubber for non-slip grip), smartwatch straps, laptop bezels, keyboard keycaps (hard frame + soft key surface);

Automotive Industry: Control panel buttons, door handles (soft coating + hard substrate), car lamp covers (transparent + opaque areas), steering wheels (non-slip soft rubber + hard core);

Daily Necessities: Toothbrush handles, razor handles, spatula handles (shockproof and non-slip), dual-color plastic basins, stationery pen barrels;

Medical/Packaging: Surgical instrument handles (stable hard core + comfortable soft rubber), medicine bottle caps (child-resistant dual-color design), dual-color cosmetic bottle caps;

Industrial Tools: Drill and pliers handles (non-slip soft rubber + high-strength hard plastic), instrument panels (dual-color distinction between key areas and display areas).

V. Technical Advantages: Why Are Enterprises Switching to Two-Color Rotational Molds?

Compared to the traditional "single-color injection + post-assembly" process, its core advantages lie in three aspects:

Higher Product Quality: The two materials are integrated at high temperature, with a bonding strength 3-5 times that of adhesion processes—no peeling or cracking. The appearance has no seams, enhancing aesthetics;

Doubled Production Efficiency: One-step molding eliminates secondary processing, reducing assembly and adhesion steps. Labor costs are cut by over 50%, and production cycles are shortened by 30%-60%;

Greater Design Freedom: It supports arbitrary combinations of "hard + soft," "transparent + opaque," and "different colors," enabling complex structures that traditional processes can’t achieve, and facilitating product differentiation and innovation.

VI. Closing: Technological Iteration, the Future of Dual-Color Products Is Promising

As consumers’ demands for product appearance, feel, and functionality continue to rise, the technology of two-color rotational molds is constantly advancing—such as more precise core positioning (error ≤ 0.001mm), better compatibility with eco-friendly materials (biodegradable plastic dual-color molding), and smarter automated integration (AI monitoring of injection parameters).

Whether enterprises want to create blockbuster products or designers aim to break through process limitations, two-color rotational molds are undoubtedly one of the most noteworthy injection molding technologies today. If you’ve found any interesting dual-color products in daily life, feel free to share them in the comments!

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