Double color injection moulds, also known as two-shot or 2K moulds, represent one of the most advanced innovations in the field of plastic injection moulding. These moulds enable the production of complex parts made from two different materials or colors within a single cycle. The technology has transformed manufacturing in industries such as automotive, consumer electronics, medical devices, and home appliances by enhancing design flexibility, surface aesthetics, and functional integration.
With the increasing demand for products that combine both aesthetics and performance, double color injection moulding (also referred to as K2 moulding) has become essential for modern manufacturers. By eliminating secondary processes such as assembly or painting, this method improves production efficiency, reduces waste, and enhances product quality. This comprehensive guide explores the principles, structure, materials, applications, and market trends of double color moulds — offering engineers, designers, and buyers an in-depth understanding of how to optimize their moulding projects.
Double color injection moulds are specialized tools designed for two-component injection moulding. In this process, two different materials — often thermoplastics with distinct colors or properties — are injected sequentially or simultaneously into the same mould to form an integrated part. The first shot forms the base component, while the second shot adds an over-moulded layer, often for aesthetic enhancement or functional improvement.
The term “K2 moulds” is sometimes used interchangeably with “2K moulds” to denote dual-material moulding. This technology can combine rigid and soft materials (e.g., PC + TPE) or create multi-colored designs (e.g., ABS in two shades). It is widely adopted in applications such as automotive knobs, toothbrush handles, medical instruments, mobile phone shells, and home appliances.
The double color injection moulding process involves two injection units working in coordination. The sequence typically includes:
The mould’s core design must ensure precise alignment and sealing between the two injection stages. Rotating platen or core transfer systems are commonly used to switch the part between cavities. The success of 2K moulding depends heavily on accurate synchronization between machine parameters, mould temperature, and material compatibility.
While single-color moulds are relatively simple and designed for one-shot injection, double color moulds are significantly more complex. Key differences include:
Designing a high-quality double color mould requires deep understanding of material behavior, flow dynamics, and mechanical structure. The mould typically consists of two sets of cavities and cores, precision alignment systems, runners, cooling circuits, and ejection mechanisms. Major design considerations include:
There are two main configurations:
Materials must bond physically or chemically during the second shot. Compatibility testing is essential to avoid delamination or separation. For instance, PC pairs well with ABS, and PP bonds well with TPE.
The gating system must ensure even filling, pressure balance, and temperature stability between two shots. Hot runner systems are preferred to maintain consistency and reduce waste.
Efficient cooling channels are critical for minimizing warpage and ensuring dimensional accuracy. Each shot may require separate temperature zones, as the two materials can have different thermal characteristics.
High-precision guiding pins and locking mechanisms ensure perfect registration between the first and second cavities, preventing flash and misalignment.
The production of a 2K mould involves multiple stages, each requiring precision and expertise. A typical workflow includes:
The selection of mould material affects lifespan, precision, and corrosion resistance. For double color moulds, commonly used steels include:
In addition, coating technologies such as TiN or DLC can improve wear resistance and extend mould life. The choice depends on production volume, plastic material properties, and desired surface quality.
2K moulding requires specialized injection machines equipped with dual barrels and independent control systems. Key parameters include injection pressure, temperature control, and synchronization. There are two main configurations:
Advanced control systems integrate servo motors, closed-loop temperature regulation, and precise injection timing. This ensures consistent bonding and part quality even for challenging geometries or thin-wall structures.
Proper cooling and venting play a critical role in the performance of double color moulds. Since different materials can have distinct cooling rates, balanced temperature management is essential. Optimized cooling channels are designed to prevent hotspots and deformation.
Venting channels allow trapped gases to escape during injection, preventing burn marks or short shots. The ejection system — including ejector pins, plates, and air-assist mechanisms — must operate smoothly to avoid damaging delicate features of the finished part.
High dimensional accuracy is vital in K2 moulds. The combined two-shot process requires exact alignment between cavities, typically controlled within ±0.01mm. Manufacturers use high-end measuring equipment such as Coordinate Measuring Machines (CMM), optical profilers, and laser scanners to verify mould geometry.
Thermal expansion, shrinkage, and pressure variation must be compensated through accurate simulation and tooling adjustments. Continuous monitoring and calibration during production help maintain tight tolerances over thousands of cycles.
Despite the advantages of 2K moulding, engineers face several challenges during production. The most frequent problems include material separation, warpage, and flash. Common solutions are as follows:
Systematic design review and process optimization are crucial to minimize these defects and ensure high yield rates in mass production.
Surface finishing plays a crucial role in the performance and appearance of double color injection moulded parts. The finish not only determines the tactile feel and gloss of the product but also affects its resistance to wear, friction, and environmental stress. In 2K moulding, achieving consistent surface quality is more challenging because two different materials with varying shrinkage and flow behaviors must integrate seamlessly.
Double color injection moulds are used in a wide range of industries that require multi-material components for aesthetic or functional purposes. Below are some major application sectors:
Compared to traditional single-shot moulding, double color injection moulding offers a range of functional and economic advantages:
The global two-color (2K) injection moulding market has been expanding rapidly, driven by the demand for multi-functional, visually appealing products in automotive, electronics, and healthcare sectors. According to recent industry analysis, the market is expected to grow steadily over the next decade, with Asia-Pacific leading the innovation in 2K moulding technology.
Quality assurance is a critical phase in the production of double color moulded parts. Each mould and product must undergo rigorous testing to ensure dimensional stability, adhesion between materials, and long-term performance.
Choosing the right manufacturer determines the success of your 2K moulding project. When evaluating suppliers, consider the following factors:
As a professional manufacturer with years of experience in injection mould development and production, our company provides a full range of moulding solutions, including:
We have exported moulds and injection moulded parts to markets worldwide, including Europe, the Middle East, and North America. Our engineering team offers complete project support, from concept design and mould flow analysis to mould testing and mass production. With advanced manufacturing facilities, strict quality management, and a commitment to technological innovation, we are your trusted partner for high-quality moulding solutions.
Our company has completed multiple successful projects involving double color injection moulds:
The future of double color injection moulding is shaped by digital manufacturing, sustainability, and smart production technologies. The trend is moving toward fully automated lines with integrated sensors, predictive maintenance, and data-driven quality control. Meanwhile, bio-based and recyclable materials will play a greater role as manufacturers aim for eco-friendly production. Companies that combine precision engineering with green technology will lead the next generation of mould innovation.
2K moulding involves injecting two materials in one mould using two injection units, while overmoulding typically refers to moulding a second material over a pre-formed substrate in a separate mould or stage.
Common materials include ABS, PC, PMMA, PP, and TPE. Material compatibility and bonding characteristics are key design considerations.
Yes. Transparent and translucent combinations, such as PC + PMMA or PC + TPE, are widely used in lighting and decorative applications.
The lead time depends on mould complexity and size, typically ranging from 6 to 12 weeks including design, machining, assembly, and testing.
Automotive, medical, electronics, and consumer goods industries all gain advantages from 2K moulding due to improved functionality and design aesthetics.
Double Color Injection Moulds, also known as K2 or 2K moulds, represent the pinnacle of innovation in plastic injection technology. They allow manufacturers to produce parts that combine aesthetics, ergonomics, and durability in a single process. With growing market demand and technological advancements, investing in high-quality 2K moulding solutions is a strategic move for companies seeking superior product performance and brand differentiation.
Our company continues to lead the industry through precision engineering, continuous R&D, and customer-oriented service. Whether you need a complex two-shot mould, precision mechanical part, or a complete injection moulding solution, we deliver excellence from design to delivery.
RM1223, 12F, No.1, Fuji Bldg, No. 6018 Longgang RD. , Longgang Dist., Shenzhen,China.
Tel: 0086-755-89618186
Contact: Paul Hu 0086-18675501028
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