Injection moulding of optical functional micro structures using laser structured, PVD-coated mould inserts

Hopmann, Christian; Weber, M.; Schöngart, Maximilian; Schäfer, Christian; Bobzin, Kirsten; Bagcivan, Nazlim; Brögelmann, Tobias; Theiß, Sebastian; Münstermann, Tobias; Steger, Michael F.

doi:10.1063/1.4918478

Cited by 7 publications

(5 citation statements)

References 8 publications

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“…On the contrary, this restriction of heating reduced a lot of trouble in the heating process, especially for the mold structure of micro part. This is also a benefit of Ex-GMTC against other heating methods for injection mold [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ].…”

Section: Resultsmentioning

confidence: 99%

“…With flame heating [ 15 ], the heating speed at the cavity surface is very fast; however, the mold structure, part geometry, and heat control remain issues when applied in injection molding, which is the reason for its rare use. In microinjection molding, laser heating is the choice for temperature control at the cavity surface [ 16 , 17 ] due to the extremely fast heating rate; however, heating by laser is only appropriate for small-sized products and requires additional equipment and coating of cavity surface. Induction heating, which applies the principle of electromagnetic induction, has been known over the last 10 years for its ability to quickly raise the cavity temperature of molds [ 18 , 19 ].…”

Section: Introductionmentioning

confidence: 99%

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External Gas-Assisted Mold Temperature Control Improves Weld Line Quality in the Injection Molding Process

et al. 2020

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Simulations and experiments were conducted with gas temperatures of 200–400 °C to investigate the impact of external gas-assisted mold temperature control (Ex-GMTC) on the quality of weld line of molding products. In the heating step, the heating rate was 19.6 °C/s from 30 to 128.5 °C in the first 5 s in a 400 °C gas environment. When applied to heating the weld line area of an injection mold, Ex-GMTC improved the appearance of the weld line when the cavity temperature was preheated to 150 °C. For the tensile strength test, a melt flow simulation comparing the packing pressure of different mesh thicknesses revealed that Ex-GMTC helped maintain a high pressure in the weld line area in different packing periods. This was verified by an experiment where Ex-GMTC was applied with 400 °C gas to change the mesh area temperature. The result indicated that an increase in the weld line area temperature from 60 to 180 °C improves the tensile strength of all mesh thicknesses, which was more pronounced with thinner parts, especially at 0.4 mm. The simulations revealed that high temperature is concentrated in the weld line area of the cavity surface, thus reducing the energy wasted during heating.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

External Gas-Assisted Mold Temperature Control Improves Weld Line Quality in the Injection Molding Process

et al. 2020

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“…As mentioned, conventional tooling, which is standardly applied for manufacturing tool inserts, is limited in accuracy and by the tool geometries [6]. Laser ablation is a technique that can be applied directly on the metal inserts [7] and fs-lasers can generate very small structures, but obtaining smooth surfaces is a challenge because worn off material is likely to redeposit on the surface. Chemical or physical etching might be directly used on metals, but due to the principle of the etching process, few structures are accessible because they are limited by the material's etching properties.…”

Section: State Of the Artmentioning

confidence: 99%

Concave Diffraction Gratings by High-Precision Injection Moulding

Walch¹,

Wörle²

2019

Eurosensors 2018

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As an example of the applicable process chain, a concave grating (1175 grooves/mm) with an active area of approx. 24 mm to 24 mm has been replicated by means of electroplating and further by injection moulding with polycarbonate, resulting in a surface accuracy even below 4 µm peak-to-valley (PV). The obtained moulds were further metallised with bare aluminium to obtain components for optical applications. To our knowledge, this is the first time that such a large nanostructured nonplanar surface has been manufactured by injection moulding in such an accuracy.

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“…In this way, the center of the mold surface could reach over 180 °C after the heating process [ 9 , 10 , 11 ]. For microinjection molding, laser heating was considered for mold temperature control [ 12 , 13 ] because it is advantageous for small products with a high heating rate; however, this method required coating of the cavity surface and additional equipment. In addition, induction heating was suggested as a method that had a rapid heating rate with a proper coil design [ 14 ].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

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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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Injection moulding of optical functional micro structures using laser structured, PVD-coated mould inserts

Cited by 7 publications

References 8 publications

External Gas-Assisted Mold Temperature Control Improves Weld Line Quality in the Injection Molding Process

External Gas-Assisted Mold Temperature Control Improves Weld Line Quality in the Injection Molding Process

Concave Diffraction Gratings by High-Precision Injection Moulding

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

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