Sippy cup straws require molds with extremely long, thin cores to form their internal passages. Designing these cores to be durable and cool effectively is a major mold engineering challenge. This article explores the solutions.
The defining feature of a sippy cup straw is its long, narrow internal lumen. Creating this feature in a mold requires an ultra-fine, long core pin. These pins, often less than 2mm in diameter but 30mm or more in length, are prone to deflection, buckling, and difficult cooling, making them one of the most challenging aspects of the mold design.
To combat deflection, TYM uses high-strength, wear-resistant tool steels for these cores and supports them with precision-ground shoulders and backing pins. The core assembly is designed to be as short and rigid as possible while still allowing ejection. Advanced mold flow analysis helps determine the optimal core diameter and support structure for a given straw design.
Cooling these slender cores is equally critical. Standard cooling channels in the mold block cannot effectively reach the core's interior. Therefore, we often employ specialized techniques such as drilled cross-holes at the base of the core or even conformal cooling lines created via direct metal deposition (DMD) or similar technologies. These methods ensure the core cools uniformly and rapidly, preventing overheating which can lead to part distortion or longer cycle times. This careful engineering ensures the cores last and the straws meet quality standards.
