Plastic Plate Overmolded Silicone Keypad Injection Mold

Mold Information

Mold Design and Key Technology

Two-Stage Overmolding Design

The mold is engineered for a sequential or rotary overmolding process. The first cavity forms the rigid plastic substrate. This substrate is then transferred within the mold to the second cavity, where liquid silicone rubber (LSR) is injected over designated areas to form the soft buttons, ensuring perfect adhesion and registration.

Precision Cooling for LSR

Special attention is given to the cooling layout around the silicone button areas. Uniform and controlled temperature is critical for proper curing of the silicone, achieving optimal elastomeric properties, and preventing defects.

High-Polish & Textured Surfaces

Core and cavity inserts are made from S316 stainless steel and polished to a high-gloss finish (e.g., SPI-A1) for excellent plastic part appearance. Specific areas may have targeted texture to aid in demolding or for aesthetic effect on the final part.

Robust Ejection System

Designed to handle the dual-material part without distortion. Ejector pins are strategically placed under the rigid plastic plate. The design ensures the flexible silicone buttons do not stick or tear during ejection.​

Integrated Lifter/Slider Mechanism

The small square opening with the central pin on the product (Image 2) likely requires an internal lifter or a side-core action to form the undercut, which is seamlessly integrated into the mold design.

FAQs

Q1: Why are different steels (P20 and S316) used for the mold base and core?

A:​ This optimizes cost and performance. P20 steel offers an excellent balance of strength, machinability, and cost for the large mold base which provides structural support. S316 stainless steel is used for the core/cavity inserts that directly form the part because of its superior corrosion resistance (important for processing some plastics and for mold maintenance) and its ability to achieve a very high, durable polish for a flawless part surface finish.

Q2: What is the advantage of a cold runner system for this part?

A:​ A cold runner system is often preferred for overmolding applications, especially when using materials like Liquid Silicone Rubber (LSR) or for certain engineering plastics. It is simpler, more robust, and lower cost than a hot runner. It avoids the risk of thermal degradation of the first-shot material during the transfer phase and allows for easier color/material changes.

Q3: How does the 2-cavity design benefit production?

A:​ A 2-cavity design doubles the output per machine cycle compared to a single-cavity mold, significantly improving production efficiency and reducing the per-part cost for high-volume orders. It represents an optimal balance between mold cost, required clamping force, and production throughput for this part size.