Mandrel

A mandrel is a precision-engineered cylindrical component that forms the internal surface of hollow profiles during extrusion through an annular die. It maintains dimensional accuracy, controls wall thickness uniformity, and provides structural support to prevent collapse of the material being extruded. In annular die systems, the mandrel is typically mounted concentrically within the die body, creating the annular gap through which material flows to form pipes, tubes, or other hollow cross-sections.

The mandrel works by creating a fixed internal boundary within the annular die gap. As molten material (plastic, rubber, or metal) is forced through the die under pressure, it flows around the mandrel, taking the shape of the annular space between the mandrel's outer surface and the die's inner surface. The mandrel's precise geometry determines the internal dimensions and surface finish of the extruded product while providing thermal management and preventing material sagging or deformation.