Study of application of ultrasonic wave to injection molding

Abstract

We have developed an ultrasonic injection molding (UIM) system, which applies ultrasonic waves to injection molding, as a precision injection molding technology. Molding of optical lenses showed that the lens weight increased when the ultrasonic wave was applied immediately after the resin was filled into a cavity. Results showed that, by applying ultrasonic waves, oscillatory flow was generated inside the cavity and consequently the weight of the lens was increased. The surface finish of the molded lens was also significantly improved in UIM when compared with that in conventional molding. The part of shrinkage during the packing and holding stages was suppressed by the oscillatory flow provided by the ultrasonic vibration. Because of ultrasonic energy absorption, local heating was generated inside the resin, resulting in the formation of oscillatory flow during packing and holding stages. Local heating, occurring especially between molten and skin layers, reduces the skin layer's deformation resistance. Consequently, replication during the packing and holding stages is facilitated by the UIM. Moreover, evaluation of the residual optical strain of concave lens revealed that the strain was much lower in UIM than in conventional molding. The decreased strain was attributed to the local heat generation by the ultrasonic waves. POLYM. ENG. SCI., 49:768-773, 2009. ª

Investigation of micro-injection molding based on longitudinal ultrasonic vibration core

“…Compared with an audible sound, the ultrasonic wave is of very high frequency, and the direction of propagation can be ensured very well within a small space. Since the acceleration of medium particles in ultrasonic transmission is very large, the ultrasonic wave can exert a significant effect on the energy of the medium material [15,16]. Thereby, in this investigation, the ultrasonic wave is employed on the polymer melt to improve the flow property by the energy exchange between the ultrasonic wave and the melt polymer.…”

Evaluation of replication properties on moulded surface by ultrasonic injection moulding system

“…In the authors' previous studies, [26][27][28][29] a mechanism of improvement of replication ratio was caused by oscillatory flow. The replication properties during packing and holding stages were improved by the oscillatory flow provided by the ultrasonic vibration from the oscillation part.…”

“…Many studies have investigated polymer processing using ultrasonic waves. In the authors previous studies, [23][24][25][26][27][28][29] the apparent fluidity of resin was improved by the action of sound pressure and by the reduction in apparent friction between the wall surface in the cavity and the resin using the UIM system. Furthermore, the reaction force (inertia force) of vibration and local heating improved the replication of microstructure of the moulded surface.…”

Effects of Supersonic Vibration Field on Flow Characteristics and Filling Behavior of Glass-fiber-enhanced Polybutylene Terephthalate Microstructural Injection Molding Melt

“…This causes the molecular chain in the melt to wriggle, which decreases the number of chain entanglement points, thereby decreasing the melt viscosity and increasing the slip velocity of the melt along the wall. (15)(16)(17) Moreover, the thermal effect of supersonic vibration increased the temperature of the melt, enabling the melt to continue to fill the cavity. Consequently, the filling quality is improved.…”