Reinforcement of micro injection molded weld line strength with ultrasonic oscillation

Abstract

Weld lines are the unfavorable defect not only in normal injection molding process but in micro injection molding process. In this study, polypropylene (PP) was chosen as the processing material and a micro dog-bone tensile test sample was selected as the objective part. The micro tensile part was prepared by the double gate injection mold. An ultrasonic generator was integrated in this mold in order to investigate the effect of ultrasonic oscillation on the micro injection molded weld line strength. The experiments were carried out for studying how the ultrasonic output power and the oscillation inducing time affect the weld line strength. Three output power levels (400, 600 and 800 W) and two inducing mode (Mode 1. the oscillation is induced from injecting moment to ejection moment; Mode 2. the oscillation is induced from injecting moment to packing procedure finishing) were set. The results show that ultrasonic oscillation has obvious influence on the weld line strength; Mode 2 always has better performance than Mode 1 for reinforcing the weld line strength; and when output power is 400 W the weld line strength is the highest. The mechanism of ultrasonic oscillation affecting the micro injection molded weld line was also analyzed by AFM (atomic force microscope) and polarized microscope.

Micro-Ultrasonic Viscosity Model Based on Ultrasonic-Assisted Vibration Micro-Injection for High-Flow Length Ratio Parts

“…Ultrasonic processing technology, as a novel molding processing technology, has been widely used in recent years for the injection molding, extrusion molding, and compression molding of polymers [9,10]. Despite different ways of applying ultrasonic energy, studies have found that ultrasounds can affect the microstructure filling performance [11], change the material properties [12], affect the extrusion swelling [13], improve the weld line strength of the plastic parts [14], and reduce the interface friction during ejection [15]. However, current studies are mainly based on experiments.…”

Tuning Power Ultrasound for Enhanced Performance of Thermoplastic Micro-Injection Molding: Principles, Methods, and Performances

“…Since the application of ultrasound technology in polymer micro-injection molding has not been systematically reviewed, the names of similar technologies have not yet been unified: ultrasonic injection molding (UIM) [ 18 ], ultrasonic vibration micro-injection mold (UVMIM) technology [ 38 ], ultrasonic-assisted injection molding (UAIM) [ 39 ], but the common point of this technology is that the ultrasonic action is aimed at the polymer melt, improving its fluidity and achieving high replication and quality requirement of parts. Polymer plasticization, metering, injection, and other processes rely on existing micro-injection-molding machines (ARBURG [ 31 , 40 ], FANUC [ 14 , 41 , 42 ], BOY [ 43 ], Wittmann-Battenfeld [ 44 ]). Considering the difference between micro-injection molding and injection molding and the auxiliary effect of ultrasound, this kind of technology can be classified as ultrasound-assisted micro-injection molding (UAMIM).…”

One- and two-component micro powder injection moulding derived from thermoplastic microreplication

“…Owing to the advantages of thermoplastic multicomponent injection moulding, such as reduced assembly expenditure and manufacture of multicomponent moulded parts, [22][23][24] efforts are undertaken to transfer this technology to PIM. However, this gives rise to additional process technology problems, in particular by shrinkage due to sintering.…”