The impact of mold cavity polishing accuracy on demolding resistance in the plastic mold for an electric toothbrush handle shell persists throughout the entire injection molding process. Its mechanisms of action involve multiple aspects, including surface friction characteristics, material flow behavior, and product quality, directly determining production efficiency and product yield.
Mold cavity polishing accuracy primarily affects demolding resistance by changing surface roughness. When microscopic irregularities or machining marks are present on the cavity surface, the plastic melt mechanically engages the mold surface during cooling, resulting in additional frictional forces to overcome during demolding. This friction is not only related to the contact area but also depends on the geometric characteristics of the surface microtopography. High-precision polishing can achieve a mirror-like finish on the cavity surface, reducing the coefficient of friction and significantly reducing the external force required for demolding.
Polishing accuracy has a dual impact on the molding quality of the electric toothbrush handle shell. On the one hand, a rough cavity surface can cause defects such as scratches and ripples on the part surface, further increasing localized stress concentrations during demolding. On the other hand, insufficient surface finish can cause adhesion between the part and the mold, especially in thin-walled structures or areas with complex curves. This adhesion can significantly increase demolding resistance. By optimizing the polishing process, the surface quality of the part can be achieved while reducing energy loss during demolding.
At the material flow level, cavity polishing accuracy directly affects the filling behavior of the plastic melt. A highly precision-polished cavity surface provides a more uniform flow path for the melt, reducing flow hysteresis caused by surface friction differences. When the melt fills the cavity uniformly, shrinkage rates across the part are consistent, preventing mold jamming caused by localized shrinkage differences. Conversely, if the cavity has blind spots in the polishing process, stress concentrations can occur in areas where melt flow is blocked, leading to part deformation or fracture during demolding.
The mold temperature distribution is coupled with cavity polishing accuracy. A well-polished cavity surface offers improved heat transfer efficiency, maintaining a more uniform temperature gradient during the cooling process. This uniform temperature distribution reduces residual stress within the product, thereby reducing the risk of deformation caused by stress release during demolding. Furthermore, a uniform temperature field prevents material degradation caused by localized overheating, ensuring product dimensional stability.
From a mold lifespan perspective, high-precision polishing significantly reduces the wear rate of the cavity surface. Over long-term production, a rough cavity surface will accelerate wear due to repeated friction, resulting in reduced dimensional accuracy and increased demolding resistance. Precision-polished cavity surfaces, however, form a stable oxide layer that effectively resists chemical attack and mechanical wear from the plastic melt, thereby extending mold life and reducing production costs.
In the actual production of electric toothbrush handle shells, cavity polishing accuracy must be optimized in conjunction with mold design parameters. For example, in molds with side-pulling core structures, insufficient polishing accuracy can hinder slide movement, leading to demolding failures. In multi-cavity molds, the consistency of polishing accuracy across cavities directly impacts product dimensional repeatability. Therefore, the polishing process must form a closed-loop control loop with mold structure design, material selection, and injection molding process parameters.
The cavity polishing accuracy of the electric toothbrush handle shell plastic mold has a multi-dimensional impact on demolding resistance, affecting key aspects such as material flow, heat conduction, surface friction, and mold wear. Improving polishing accuracy not only reduces demolding resistance and improves production efficiency, but also ensures product dimensional accuracy and surface quality, providing reliable support for the manufacturing of precision consumer electronics products such as electric toothbrushes.
