Two-shot Injection Molding Service

Two-shot injection molding is not merely a process; it is a design liberation for the home appliance industry. This advanced technology enables the creation of a single, flawless component from two distinct materials or colors within one seamless cycle. It transforms traditional design constraints into opportunities — eliminating costly secondary assembly, unreliable adhesives, and inconsistent finishing steps that plague conventional manufacturing.

At its technical core, two-shot molding is an integrated manufacturing solution. It produces complex, multi-material parts in one operation by injecting a second material onto a pre-formed substrate. The result is a monolithic bond at the molecular level, creating a union stronger than any post-process glue or mechanical fastener. For appliance brands, this translates to unparalleled part integrity, where soft-touch grips won’t peel, and integrated seals won’t leak — directly enhancing product lifespan and user safety.

The true value for appliance manufacturers lies in tangible outcomes. This process involves the seamless fusion of rigid frames with flexible seals, the combination of translucent indicators with opaque housings, and the integration of textured, non-slip surfaces without a single extra step. By consolidating multiple parts into one, it reduces assembly labor, supply chain, and accelerates time-to-market — delivering superior aesthetics, function, and reliability while driving down total system cost.

一. Overview of Two-shot Mold Parting Surface Design

a. Selection of Parting Lines

When selecting the parting line, considerations must include product ejection and simplification of the mold structure. Furthermore, the parting lines for both materials must be identical (the same parting line).

b. Typical Mold Structure Configuration

Generally, the moving halves (cores) of the two mold sets are identical in shape and size. The stationary halves (cavities) have different shaping surfaces, each forming one of the two materials.

c. Design of the Second-Shot Cavity & Clearance Analysis

When designing the cavity for the second shot, clearance must be provided to prevent it from scraping or damaging the already-formed first-shot part. However, the structural integrity of every sealing surface must be critically evaluated. The analysis must determine if, under high injection pressure, the plastic could deform, potentially leading to flash during the second shot.

d. Control of Flow-Induced Distortion

Attention must be paid to whether the plastic flow during the second shot could impact and displace the first-shot part, causing its geometry to deform. If this risk exists, the design must be modified to mitigate it.

e. Design of Core-Crossing Areas

For product features involving core crossing (shut-offs), the draft angle must be significantly increased.

二. Key Points for Parting Line Fitting in Two-Shot Molds

Two-Shot Mold Fitting Procedure

a. The hard-shot and soft-shot mold sets are to be fitted simultaneously on a mold clamping/try-out press.

b. After the parting lines of both mold sets are fitted, install them on the injection molding machine and first mold the hard-shot parts independently.

c. Once molded, the hard-shot parts are to be placed into the soft-shot cavity to fit and verify the sealing surfaces.

d. Caution must be taken to avoid crushing the hard-shot parts during this fitting process. This requires a "Zero-to-Zero" design intent, where the fitted sealing surfaces achieve precise, flush contact without interference.

三. Mold Base Design Specifications for a two-shot mold

a. Uniform Plate Thickness: The two mold sets must have identical plate stack heights (i.e., the combined thicknesses of the moving halves must be equal, and the combined thicknesses of the stationary halves must be equal). If the heights differ, after one set is mounted and the mold rotates, the other set will fail to close properly on the injection machine.

b. Secured Mounting & Clearance: The entire mold must be securely mounted to the injection machine using bolts only for safety. Adequate clearance must be provided on all corresponding plates to allow for bolt access and prevent binding. (Refer to the diagram below.)

c. Center Alignment for Single-Base Designs: For two-shot molds designed on a single mold base, alignment dowel pins must be incorporated into the fixed plate on the rotating side. Their position must match the dowel pin holes on the injection machine's rotary platen. This prevents misalignment between the mold center and the machine's rotation center, ensuring successful installation

Two-shot injection molding is emerging as a core driver in premium home appliance manufacturing, fueling three key trends: integration, sensory experience, and reliability. The technology seamlessly combines structural rigid components with soft-touch or sealing elements in a single cycle, eliminating traditional assembly, bonding, and painting processes. This directly meets the growing demand for seamless aesthetics, integrated waterproof sealing, and personalized tactile surfaces.

Technically, two-shot molding creates a molecular-level bond, offering far superior reliability and longevity compared to secondary processes. It empowers appliance brands to launch more compact, durable, and aesthetically refined products at an accelerated pace. Beyond aesthetics, its value lies in simplifying supply chains, boosting production yield, and lowering total system costs—building a solid competitive barrier. As smart home ecosystems and personalization evolve, two-shot technology will be fundamental for integrating functional modules, enabling interactive surfaces, and facilitating sustainable, recyclable designs.