精确的模具对于微注射成型(μ-IM)或热压花产品的无缺陷生产至关重要。由于摩擦,这种成型和成型过程的脱模阶段对薄微型特征的完整性提出了严重挑战,附着力,和热应力。通常,微型模具涉及几何纹理图案或特征,如线性脊,柱子,频道,和洞,其特征尺寸范围为10至300μm。实际上复杂的模具设计,包含精密的微观特征(增强的圆角半径和正拔模角)和高表面质量,在这项工作中提出。基于正向脉冲电流(PC)的电抛光已用于成型和抛光Ni微模具,该模具包含多组微米尺度的线性脊和星形图案,以便在脱模和脱模过程中易于将模制的聚合物零件从金属模具中分离。正向脉冲电流的使用通过增加圆角半径和拔模角度同时保持低的表面粗糙度和保持良好的表面光泽来改进模具设计。在2.8V的工艺条件下,使用氨基磺酸镍的绿色溶液对正向PC进行优化研究,改变EP时间(0-70分钟)和占空比(40、50、60和70%),50°C,和250转/分钟。对于典型的微流体通道(w×h,100×110μm),EP时间为70分钟,占空比为50%:圆角半径增加3.8μm,拔模角为3.3°,通道宽度减少了11.4%,表面粗糙度变化了8.6%,表面光泽提高了48.9%。使用热压印进行实验验证,其中电抛光的Ni模具复制了PMMA芯片中的微通道和星形图案,并且毛刺明显较少,材料堆积,并且没有特征失真。此外,在电抛光Ni模具的PDMS铸造中,微通道的侧壁粗糙度降低了16%。因此,这项工作提出了一个显著的科学贡献,以提高微模具工具的效率,并减少了缺陷引起的摩擦和粘附在复制的聚合物部件。
Precise tooling is vital for defect-free production of micro injection moulded (μ-IM) or hot-embossed products. The demoulding stage of such moulding and forming processes poses a serious challenge to the integrity of thin miniature features because of friction, adhesion, and thermal stresses. Typically, micro moulds involve geometrically textured patterns or features such as linear ridges, pillars, channels, and holes, the characteristic dimensions of which range from 10 to 300 μm. Realistically complex mould designs, containing precision micro features (enhanced fillet radius and positive draft angle) and high surface quality, are presented in this work. Electropolishing based on forward pulse currents (PC) has been used to shape and polish Ni micro moulds that contain sets of micron-scaled linear ridges and star patterns in order to ease the separation of moulded polymeric parts from the metallic mould during ejection and demoulding. The use of forward pulsed currents improved the mould design by increasing the fillet radii and draft angle while keeping the surface roughness low and maintaining a good surface shine. An optimization study of forward PC using a green solution of nickel sulfamate varied EP times (0-70 min) and duty cycles (40, 50, 60, and 70%) at a process conditions of 2.8 V, 50 °C, and 250 rpm. The best topographical and morphological changes were observed for a typical microfluidic channel (w × h, 100 × 110 μm) with an EP time of 70 min and 50% duty cycle: fillet radius increased by 3.8 μm, draft angle by 3.3°, and the channel width reduced by 11.4% while surface roughness changed by 8.6% and surface shine improved by 48.9%. Experimental validation was performed using hot embossing wherein the electropolished Ni mould replicated the micro channels and star patterns in PMMA chips with notably fewer burrs, material pile up, and no feature distortion. Moreover, there was a reduction in the side wall roughness of micro channels in PDMS casting with electropolished Ni mould by 16%. Hence, this work presents a significant scientific contribution to improving the efficiency of micro mould tools and reduces the defects caused by friction and adhesion in replicated polymeric parts.