Microinjection Molding of Out-of-Plane Bistable Mechanisms

Abstract

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.

Rapid Development of an Injection Mold with High Cooling Performance Using Molding Simulation and Rapid Tooling Technology

“…The alternative coolants such as cool air [ 63 ] or oil [ 64 ] can also be used in the experiment for investigating the difference in the cooling performance of an injection mold with optimum CCCs. Lastly, the molds or dies with CCCs fabricated by the proposed method can also be employed in metal injection molding [ 65 ], rotational molding [ 66 ], centrifugal molding, thermoforming [ 67 ], transfer molding [ 68 ], hot stamping [ 69 ], plastic injection molding [ 70 , 71 ], microinjection molding [ 72 , 73 ], or blow molding [ 74 ]. These issues are currently being investigated and the results will be presented in a later study.…”

Micro-scale Realization of Compliant Mechanisms: Manufacturing Processes and Constituent Materials—A Review

“…Other widely used structural materials include polymers, such as polydimethylsiloxane (PDMS) and polyformaldehyde (POM), which are normally cast into a predefined mold (Figure 7). Molds are usually defined by silicon processing or electrical discharge micromachining (EDM) [4,25,79]. PDMS or POM is then poured into the mold, cured at a specific temperature, and finally ejected out of the mold.…”

Rapid Numerical Estimation of Pressure Drop in Hot Runner System

“…The pressure drop is especially important in microsystem. Injection molding of a micro-device requires a high pressure at the gate to drive the filling flow in the micro-cavity [ 2 , 3 , 4 , 5 ]. To maintain the required pressure at the gate, the pressure drop through the runner should be suppressed.…”