Application of ultrasonic-assisted injection molding for improving melt flowing and floating fibers

2016 ◽  
Vol 36 (2) ◽  
pp. 119-128 ◽  
Author(s):  
Yi-Jen Yang ◽  
Chung-Ching Huang ◽  
Jie Tao
Keyword(s):  
Injection Molding ◽  
Glass Fiber ◽  
Flow Behavior ◽  
Line Strength ◽  
Pressure Sensors ◽  
Weld Line ◽  
Flow Characteristics ◽  
Local Heat ◽  
Melt Flow ◽  
Ultrasonic Assisted

Abstract In this study, we investigated the use of ultrasonic technology in assisted injection molding and mold designs. We used an ultrasonic device installed in a mold to vibrate a melt directly, thereby converting kinetic energy into thermal energy. In addition, we developed three flat specimens of different thicknesses (3, 1, and 3-1-3 mm) produced by ultrasonic-assisted injection molds. An ultrasonic oscillation device 45 mm in diameter was placed in the cavity and used to vibrate a polycarbonate or a polycarbonate with 30% glass fiber melt at a frequency of 20 kHz. Furthermore, cavity pressure sensors were positioned at the front and rear of the vibration region for analyzing the melt flow behavior under ultrasonic-assisted injection molding conditions. Because of the absorption of ultrasonic energy, local heat was generated inside the resin, thus forming an oscillatory flow during the packing and holding stages, improving the flow characteristics of the melt, and changing the melt flow behavior around the skin layer to reduce the molecular orientation and high shear effect. The freezing rate of the melt was also reduced to eliminate the glass fiber streaks, floating fibers, and fiber orientation, particularly for thinner parts; the hesitation phenomena were then improved to increase the weld line strength.

Effects of ultrasonic injection molding conditions on the plate processing characteristics of PMMA

2018 ◽  
Vol 38 (9) ◽  
pp. 905-914
Author(s):  
Yi-Jen Yang ◽  
Chung-Ching Huang
Keyword(s):  
Injection Molding ◽  
Manufacturing Industry ◽  
Flow Behavior ◽  
Pressure Sensors ◽  
Flow Characteristics ◽  
Local Heat ◽  
Skin Layer ◽  
Polymer Processing ◽  
Melt Flow ◽  
Diverse Field

AbstractPolymer processing is a crucial and diverse field in the manufacturing industry. We investigated the process characteristics and effects of injection molding using ultrasonic vibration. An ultrasonic device was installed in an injection mold; polymer was directly vibrated during injection. An ultrasonic oscillation device 45 mm in diameter was placed in the cavity and used to vibrate a poly(methyl methacrylate) melt at 19 kHz. The amplitude of the acoustic unit was set at 15 μm for the measurements. Moreover, cavity pressure sensors were positioned at the front and rear sides of the vibration region to determine the melt flow behavior under ultrasonic-assisted injection molding conditions. Because of the absorption of ultrasonic energy, local heat was generated inside the resin, thus improving the flow characteristics of the melt. Moreover, the melt flow behavior around the skin layer was changed; the molecular orientation and high shear effect were reduced. Furthermore, the freezing rate of the melt was reduced; thus, the amount of melt pressure lost through the cavity was decreased and the residual stress inside the injection-molded component generated during the photoelastic stress analysis was lower.

Weld-Line Strength of Rubber in Injection Molding: Effect of Injection Factors and Compound Characteristics

2002 ◽  
Vol 75 (1) ◽  
pp. 83-92 ◽  
Author(s):  
M. Seadan ◽  
P. Pongbhai ◽  
P. Thairaj ◽  
T. Watana Kamtornkul
Keyword(s):  
Injection Molding ◽  
Cross Section ◽  
Line Strength ◽  
Weld Line ◽  
Circular Cross Section ◽  
High Viscosity ◽  
Mold Cavity ◽  
Cavity Pressure ◽  
Mooney Viscosity ◽  
Weld Area

Abstract The effect of injection molding system to weld-line strength in rubber O-rings was studied using a V-shape two-stage REP injection machine. Two types of injection molds were designed and built, a standard dumbbell mold with double gates and a circular cross-section O-ring mold. Several formulations of carbon black filled NR and SBR compounds were used and vulcanization temperature was either 180 or 200 °C throughout. The results show that mold cavity pressure, compound viscosity and compound scorch time are important variables for the weld-line strength of the products. The shot volume change had no direct effect on strength, but mold cavity pressure was an important factor; unfilled shot volume gave low cavity pressure thus lowering the weld-line strength of the O-rings. The compounds having 45 or lower Mooney viscosity, ML(1 + 4)120 °C, had the same weld area strength as that of the other regions of the O-ring, but the high viscosity compounds produced low weld-line strength. Only the compounds with Mooney scorch time shorter than 10 minutes gave low weld-line strength.

Pressure Effects on Rheological Behavior of Melt Polymers – A Discussion in Relation to Polymer Processing

1986 ◽  
Vol 7 (1) ◽  
pp. 47-76 ◽  
Author(s):  
Yasushi Oyanagi ◽  
Kazuhisa Kubota
Keyword(s):  
Shear Stress ◽  
Injection Molding ◽  
Rheological Properties ◽  
Flow Behavior ◽  
Experimental Studies ◽  
Polymer Processing ◽  
Pressure Effects ◽  
Deformation Pattern ◽  
Melt Flow ◽  
Bulk Compressibility

Abstract Polymers have large bulk compressibility in the molten state /1/ and their rheological properties are largely affected by pressure applied in polymer processing. The volumetric strain induced by pressure consists of instantaneous and retarded elastic strains, both of which are proportional to pressure, and recover reversibly when pressure is removed. In many crystalline polymers, as observed by B. Maxwell for polyethylene, retarded elastic strain is large, and due mostly to pressure crystallization. This paper describes results of experimental studies relating pressure effects on rheological properties of melt polymers with polymer processing and bulk properties of products. The following items are discussed: pressure induced shear stress, analysis of local deformation pattern, critical shear stress for melt flow fracture, relationship between power law index and bulk compressibility, effects of hydrostatic pressure on melt flow behavior, pressure efficiency of injection molding, jetting phenomena, shrinkage in injection moldings, residual strain, and super-high-pressure injection molding process.

scholarly journals The Low Breaking Fiber Mechanism and Its Effect on the Behavior of the Melt Flow of Injection Molded Ultra-Long Glass Fiber Reinforced Polypropylene Composites

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2492
Author(s):  
Po-Wei Huang ◽  
Hsin-Shu Peng ◽  
Sheng-Jye Hwang ◽  
Chao-Tsai Huang
Keyword(s):  
Injection Molding ◽  
Glass Fiber ◽  
Fiber Length ◽  
Mold Cavity ◽  
Fiber Breakage ◽  
Melt Flow ◽  
Molding Machine ◽  
Glass Fiber Reinforced ◽  
Long Glass Fiber ◽  
Long Fibers

In this study, fiber breaking behavior, fiber orientation, length variation, and changes in melt flow ability of long glass fiber reinforced polypropylene (L-FRP) composites under different mold cavity geometry, melt fill path, and plasticization parameters were investigated. The matrix material used was polypropylene and the reinforcement fibers were 25 mm long. An ultra-long-fiber composite injection molding machine (with a three-stage plunger and injection mechanism design) was used with different mold cavity geometry and plasticization parameters. Different screw speeds were used to explore the changes in fiber length and to provide a reference for setting fiber length and parameter combinations. Flow-length specimen molds with different specimen thickness, melt fill path, and gate design were used to observe the effect of plasticizing properties on the flow ability of the L-FRP composite materials. The experimental results showed that the use of an injection molding machine with a mechanism that reduced the amount of fiber breakage was advantageous. It was also found that an increase in screw speed increased fiber breakage, and 25 mm long fibers were shortened by an average of 50% (to 10 mm). Long fibers were more resistant to melt filling than short fibers. In addition, the thickness of the specimen and the gate design were also found to affect the filling process. The rounded angle gate and thick wall product decreased the flow resistance and assisted the flow ability and fiber distribution of the L-FRP injection molding.

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