Kim Wook-Bae, Han Sol-Yi
Department of Mechanical Design Engineering, Korea Polytechnic University, Siheung 15073, Korea.
R&D Devision, Eosystem, Incheon 22829, Korea.
Micromachines (Basel). 2020 Jan 30;11(2):155. doi: 10.3390/mi11020155.
We present a novel fabrication technique of a miniaturized out-of-plane compliant bistable mechanism (OBM) by microinjection molding (MM) and assembling. OBMs are mostly in-plane monolithic devices containing delicate elastic elements fabricated in metal, plastic, or by a microelectromechanical system (MEMS) process. The proposed technique is based on stacking two out-of-plane V-beam structures obtained by mold fabrication and MM of thermoplastic polyacetal resin (POM) and joining their centers and outer frames to construct a double V-beam structure. A copper alloy mold insert was machined with the sectional dimensions of the V-beam cavities. Next, the insert was re-machined to reduce dimensional errors caused by part shrinkage. The V-beam structure was injection-molded at a high temperature. Gradually elongated short-shots were obtained by increasing pressure, showing the symmetrical melt filling through the V-beam cavities. The as-molded structure was buckled elastically by an external-force load but showed a monostable behavior because of a higher unconstrained buckling mode. The double V-beam device assembled with two single-molded structures shows clear bistability. The experimental force-displacement curve of the molded structure is presented for examination. This work can potentially contribute to the fabrication of architected materials with periodic assembly of the plastic bistable mechanism for diverse functionalities, such as energy absorption and shape morphing.
我们提出了一种通过微注塑成型（MM）和组装来制造小型化平面外柔顺双稳态机构（OBM）的新颖技术。OBM大多是平面内的整体式器件，包含用金属、塑料或通过微机电系统（MEMS）工艺制造的精密弹性元件。所提出的技术基于堆叠两个通过热塑性聚甲醛树脂（POM）的模具制造和MM获得的平面外V形梁结构，并连接它们的中心和外框架以构建双V形梁结构。用V形梁型腔的截面尺寸加工一个铜合金模具镶件。接下来，对镶件进行再加工以减少由零件收缩引起的尺寸误差。V形梁结构在高温下注塑成型。通过增加压力获得逐渐拉长的短射料，显示出通过V形梁型腔的对称熔体填充。成型后的结构在外力载荷作用下发生弹性屈曲，但由于较高的无约束屈曲模式而表现出单稳态行为。由两个单模结构组装而成的双V形梁器件显示出明显的双稳态。给出了成型结构的实验力-位移曲线以供检验。这项工作可能有助于制造具有周期性组装塑料双稳态机构的多功能建筑材料，如能量吸收和形状变形。
