Multi-Layer Counter-Pressure Injection Molding for Thick-Walled Optical Lens

2021 ◽  
Vol 36 (2) ◽  
pp. 131-136
Author(s):  
Y. Liu ◽  
L. Cao ◽  
W.-K. Chi ◽  
L.-Y. Zhang ◽  
W.-M. Yang ◽  
...  
Keyword(s):  
Injection Molding ◽  
Injection Molding Process ◽  
Optical Performance ◽  
Molding Process ◽  
Optical Lens ◽  
Optical Prism ◽  
Counter Pressure ◽  
Pressure Injection ◽  
Critical Issues ◽  
Optical Applications

Abstract In precision optical applications, plastics thick-walled optical lenses are increasing. Dimensional stability and optical performance are the critical issues that should be addressed for plastic thick-walled lenses. A novel multi-layer counter-pressure injection molding process is proposed in this study. The experimental prism mold with moveable pistons was developed to investigate the effects of layering methods, counter-pressure and their combination on thick-walled optical lenses. The experimental results reveal that counter-pressure injection molding is effective in improving shrinkage, transmittance and refractive index of the thick-walled optical prism. Counter-pressure of the piston provided lower melt velocity and shorter flow path of melt to improve polymer molecules orientation, and also offered continuous holding pressure during the filling stage to eliminate defects such as shrinkage or short shots. The combination of counter-pressure and multi-layer injection molding technology further improved the dimension stability and optical performance of the thick-walled optical lens. Much thinner layers than the final wall thickness of prism ensures shrinkage reduction during the cooling stages. A thick-walled optical prism was fabricated successfully upon applying a multi-layer counter-pressure injection molding process.

The Status of Magnesium Injection Molding in China

2019 ◽  
Vol 285 ◽  
pp. 436-440 ◽  
Author(s):  
Yi Bing Zhu ◽  
Stephen P. Midson
Keyword(s):  
Injection Molding ◽  
New Technology ◽  
Casting Process ◽  
Injection Molding Process ◽  
Solid Alloy ◽  
Molding Process ◽  
The Status ◽  
Near Net Shape ◽  
Semi Solid ◽  
Plastic Injection

Thixomolding, or magnesium injection molding as it is more generally known, is an established semi-solid casting process for producing thin-walled near net shape components from magnesium alloys. Magnesium injection molding produces components using a machine similar to a plastic injection molder, where magnesium-alloy chips are feed into the back end, and a rotating screw feeds the chips forward as they are heated to the semi-solid temperature range. The semi-solid alloy collects in a nozzle at the front of the screw, where it is then injected into a re-usable steel die. This paper will initially describe the commercial status of magnesium injection molding in China, and will review several types of components being produced commercially. Comparisons to conventional hot chamber magnesium die casting will be made, and a new magnesium injection molding machine design that incorporates an intensifier will be introduced. In addition, new technology trends utilizing the magnesium injection molding process will be described. One such application involves the magnesium injection molding of Mg-Li alloys. Lithium has the lowest density of all metals, and so the addition of lithium further reduces the density of the magnesium.

Filling Behavior of Polymer Material into Sub-^|^mu;m Structure in Injection Molding Process

2013 ◽  
Vol 133 (4) ◽  
pp. 105-111
Author(s):  
Chisato Yoshimura ◽  
Hiroyuki Hosokawa ◽  
Koji Shimojima ◽  
Fumihiro Itoigawa
Keyword(s):  
Injection Molding ◽  
Polymer Material ◽  
Injection Molding Process ◽  
Molding Process

scholarly journals Study on External Gas-Assisted Mold Temperature Control with the Assistance of a Flow Focusing Device in the Injection Molding Process

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 965 ◽  
Author(s):  
Nguyen Truong Giang ◽  
Pham Son Minh ◽  
Tran Anh Son ◽  
Tran Minh The Uyen ◽  
Thanh-Hai Nguyen ◽  
...  
Keyword(s):  
Injection Molding ◽  
Temperature Control ◽  
Mold Temperature ◽  
Injection Molding Process ◽  
Melt Flow ◽  
Flow Focusing ◽  
Molding Process ◽  
Heating Efficiency ◽  
Flow Length ◽  
Insert Plate

In the injection molding field, the flow of plastic material is one of the most important issues, especially regarding the ability of melted plastic to fill the thin walls of products. To improve the melt flow length, a high mold temperature was applied with pre-heating of the cavity surface. In this paper, we present our research on the injection molding process with pre-heating by external gas-assisted mold temperature control. After this, we observed an improvement in the melt flow length into thin-walled products due to the high mold temperature during the filling step. In addition, to develop the heating efficiency, a flow focusing device (FFD) was applied and verified. The simulations and experiments were carried out within an air temperature of 400 °C and heating time of 20 s to investigate a flow focusing device to assist with external gas-assisted mold temperature control (Ex-GMTC), with the application of various FFD types for the temperature distribution of the insert plate. The heating process was applied for a simple insert model with dimensions of 50 mm × 50 mm × 2 mm, in order to verify the influence of the FFD geometry on the heating result. After that, Ex-GMTC with the assistance of FFD was carried out for a mold-reading process, and the FFD influence was estimated by the mold heating result and the improvement of the melt flow length using acrylonitrile butadiene styrene (ABS). The results show that the air sprue gap (h) significantly affects the temperature of the insert and an air sprue gap of 3 mm gives the best heating rate, with the highest temperature being 321.2 °C. Likewise, the actual results show that the height of the flow focusing device (V) also influences the temperature of the insert plate and that a 5 mm high FFD gives the best results with a maximum temperature of 332.3 °C. Moreover, the heating efficiency when using FFD is always higher than without FFD. After examining the effect of FFD, its application was considered, in order to improve the melt flow length in injection molding, which increased from 38.6 to 170 mm, while the balance of the melt filling was also clearly improved.

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