Uneven wall thickness in injection-molded products is a common challenge in mass production, often leading to defects such as sink marks, warpage, short shots, and stress cracking. These issues primarily stem from uneven melt filling, significant cooling disparities, and improper parameter settings. Coordinated adjustments to the process, mold, and equipment can effectively mitigate defects caused by thickness variations and stabilize product quality.
Prioritize the use of a multi-stage injection process: fill thin-walled areas at low speeds to prevent burning and gas marks, while moderately increasing the speed in thick-walled areas to ensure complete melt filling.
Appropriately reduce the holding pressure and shorten the holding time to prevent over-compaction in thick sections and deformation caused by pressure in thin sections.
Appropriately increase the barrel and mold temperatures to enhance melt fluidity and mitigate the resistance differential in material flow caused by variations in wall thickness.
Extending the overall cooling time compensates for temperature disparities-where thick-walled areas cool slowly while thin-walled areas are prone to overcooling-thereby balancing the molding and setting results.
Adjust the gate location to position it as centrally as possible, ensuring the melt flows evenly toward both thick and thin sections.
Moderately increase the gate dimensions to avoid unbalanced filling between thick and thin sections caused by an undersized gate.
Optimize the mold cooling channel layout: add channels in thick-walled areas to accelerate heat dissipation, appropriately regulate water flow in thin-walled areas, and minimize the overall mold temperature differential.
Control melt back-pressure and rotational speed to ensure uniform plasticization and prevent molding inconsistencies caused by fluctuations in melt density.
High-pressure, high-speed single-stage filling is strictly prohibited to minimize structural stress and molding deviations.
During mass production, periodic "first-article" comparisons are conducted to dynamically fine-tune parameters, adapting to fluctuations in ambient temperature and raw materials.
For products with uneven thickness, the core strategy involves zone-based speed control, balanced temperature regulation, and pressure-stabilized shaping; this approach can significantly reduce defect rates and enhance dimensional stability.
