Custom Rotary Two Shot Injection Mold - Core Back Mechanism Multi Material Plastic Parts

This two-shot injection mold (also known as two-color mold, 2K mold, overmolding tooling, bi-injection mold, or double-color mold) is engineered for producing multi-material, multi-color plastic parts in a single molding cycle. Designed with a precision rotary platen interface and independent cooling circuits for both first and second shots, it delivers strong interlayer bonding, sharp color boundaries, and consistent dimensional accuracy — ideal for automotive interior components, consumer electronics, power tools, and cosmetic packaging.

Material & Construction

The mold is precision-machined from premium P20 / H13 / S136 / 2316 / NAK80 tool steel (customer-selectable based on production volume and resin type), with cavity and core inserts hardened to 48–56 HRC for exceptional wear resistance and polished surface quality. The mold base features a natural steel finish, guided by large-diameter guide pillars and self-lubricating bronze bushings. Critical sealing surfaces and shut-offs are precision-ground to ensure flash-free overmolding.

Key Performance

· Two-shot / overmolding capability — integrates hard substrate and soft elastomer (or two colors) in one cycle

· Rotary platen / core-back compatible — works with standard two-shot injection machines

· Independent dual cooling circuits — optimized cooling for both first and second shot materials

· Cavity number: 1+1 or 2 cavities (customizable)

· Cycle time: 30–60 seconds (depending on part size, wall thickness & resin combination)

· Tolerance: ±0.02 mm on critical fitting and bonding surfaces

· Mold life: 500,000 – 1,000,000+ shots with proper maintenance

· Surface finish: SPI A-2 / A-3 / texture / VDI grain (customer-specified)

Working Principle

In the first shot, a rigid substrate material (PC / ABS / PC+ABS / PP / PA) is injected into cavity A. The mold then opens and the rotary platen rotates 180° (or the core-back mechanism shifts), transferring the first-shot part to cavity B. In the second shot, a softer elastomer (TPE / TPU / silicone) or a differently colored resin is overmolded onto the substrate, creating a permanent chemical and mechanical bond. The finished two-material part is then ejected — eliminating secondary assembly and improving part integrity.

Applications

Specifications

Why Choose This Mold?

The two-shot overmolding design eliminates secondary assembly and adhesive bonding, reducing production cost and improving part durability. Precision-machined shut-offs and balanced dual cooling ensure clean color boundaries and strong interlayer adhesion, while hardened tool steel guarantees long-term stability for high-volume automotive and consumer product manufacturing — a reliable solution for multi-material part producers seeking integrated molding and consistent quality.