A unilateral injection sheath mold is a specialized tooling system used for producing protective sheaths or sleeves by injecting molten material from one side only. It is commonly applied in the manufacture of medical catheters, electrical wiring protection, fiber-optic components, and other elongated products requiring a precise, consistent outer layer. The term “unilateral injection” refers to the fact that the melt enters the cavity from a single injection side, which simplifies the structure of the runner system and can improve stability and repeatability in mass production.The mold typically consists of a core and cavity structure designed to form a thin, tubular or semi-tubular sheath around an internal component, such as a wire, tube, or rod. The internal component is usually positioned along the mold’s longitudinal axis and fixed by centering fixtures or positioning pins to ensure uniform wall thickness of the sheath. The mold may feature multiple cavities arranged in parallel to increase output. Cooling channels are integrated around the cavity to control the temperature gradient, improve cycle times, and maintain dimensional accuracy.Gate and runner design is a critical aspect of a unilateral injection sheath mold. The gate is located on one side of the mold, and flow balance must be carefully engineered to avoid weld lines, voids, or uneven wall thickness. The molten polymer, typically thermoplastic materials such as PVC, PE, PP, or specialized medical-grade resins, is injected under controlled pressure and speed. The unilateral injection approach often simplifies the hot runner design and can make maintenance and part changeover more convenient.To prevent deformation or eccentricity of the sheath, the mold usually incorporates precise alignment systems and rigid clamping structures. Venting grooves at the end of flow paths allow trapped air to escape, reducing the risk of burn marks and short shots. Surface finishes inside the cavity can be polished or textured depending on whether the final sheath requires a smooth, low-friction surface or enhanced grip.Another important feature is the demolding mechanism. Because sheath products are typically long and slender, the mold must allow for smooth ejection without stretching, scratching, or collapsing the product. This can be achieved by stripper plates, air ejection, or specially contoured ejector pins positioned to avoid visible marks on functional surfaces. In cases where the sheath is formed around an internal component that remains inside the product, the mold design must allow the assembly to be withdrawn in a straight and controlled motion.Process control also plays a key role in the performance of a unilateral injection sheath mold. Parameters such as injection speed, packing pressure, mold temperature, and cooling time are carefully optimized to ensure consistent wall thickness, concentricity, and surface quality. When properly designed and maintained, this type of mold offers high efficiency, reliable repeatability, and stable product quality in high-volume production of sheath-type components.