What is a core pin in molding?

From our perspective as a leading provider of precision mold solutions here in Dongguan, Guangdong Province, China, Dongguan Hie Hardware Co., Ltd. understands the intricate details that go into creating functional plastic parts. One such crucial detail is often formed by a seemingly simple component: the core pin.

So, what exactly is a core pin in the context of plastic molding, specifically injection molding?

A core pin is a precision-machined, typically cylindrical or shaped component inserted into a mold cavity to create internal features within the molded plastic part. These internal features can include holes, slots, undercuts, or other specific geometries that cannot be directly formed by the main cavity surfaces.

Think of the mold as a negative space that the molten plastic fills. The core pin acts as a positive insert within that negative space, effectively displacing the plastic and creating a void or a specific internal contour in the final part.

Key Functions of Core Pins:

• Creating Internal Geometries: The primary function of a core pin is to form internal shapes and features within the plastic part. Without core pins, many complex designs with internal cavities or holes would be impossible to achieve in a single molding step.
• Forming Undercuts: Strategically placed core pins, sometimes in conjunction with slides or lifters, can be used to create undercuts – features that prevent the part from being directly ejected from a simple two-part mold.
• Ensuring Dimensional Accuracy: Precision-machined core pins are essential for achieving the required dimensional accuracy and tolerances for internal features. Their precise placement and stability within the mold are critical.
• Facilitating Cooling: Core pins, being metallic, can also aid in the cooling process of the plastic, especially in areas where the plastic might otherwise remain thicker and take longer to solidify. Some core pins are even designed with internal cooling channels for enhanced heat transfer.
• Simplifying Mold Design: In some cases, using core pins to create internal features can simplify the overall mold design compared to trying to integrate these features directly into the main cavity and core halves.

Key Characteristics of Core Pins:

• High Precision: Core pins are manufactured to very tight tolerances to ensure the accuracy of the internal features they create.
• Durable Materials: They are typically made from hardened tool steels (like H13 or M2) or other wear-resistant materials like tungsten carbide to withstand the high temperatures and pressures of the injection molding process.
• Variety of Shapes and Sizes: Core pins come in a wide range of diameters, lengths, and tip geometries (e.g., straight, tapered, stepped, shaped) to create diverse internal features.
• Secure Mounting: They are securely held within the mold plates (usually the B-plate or core side) to prevent movement during the injection process.

Examples of Features Created by Core Pins:

• Through holes for fasteners or assembly.
• Blind holes for locating pins or mating parts.
• Internal threads (often requiring unscrewing mechanisms with the core pin).
• Slots or grooves for sliding components.
• Internal cavities or voids to reduce weight or create specific functions.
• Undercuts for snap fits or complex assemblies.

In Conclusion:

Core pins are indispensable components in plastic injection molding, acting as the key elements in shaping the internal architecture of countless plastic parts. Their precision and durability are crucial for achieving the desired functionality and dimensional accuracy of the final product. At Dongguan Hie Hardware Co., Ltd., we understand the critical role of well-designed and manufactured core pins in delivering high-quality and complex molded plastic parts to our clients.