Research

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13 pages, 4326 KiB

Open AccessArticle

Surface Optimization of Micro-Integrated Reflective Optical Elements by Thermoset Injection Molding

by Thomas Guenther, Lars Diegel, Marcel Roeder, Marc Drexler, Mehmet Haybat, Peter Wappler, Mahdi Soltani and André Zimmermann

Appl. Sci. 2020, 10(12), 4197; https://doi.org/10.3390/app10124197 - 18 Jun 2020

Viewed by 2323

Abstract

Thermoset materials offer a multitude of advantageous properties in terms of shrinkage and warpage as well as mechanical, thermal and chemical stability compared to thermoplastic materials. Thanks to these properties, thermosets are commonly used to encapsulate electronic components on a 2nd-level packaging prior [...] Read more.

Thermoset materials offer a multitude of advantageous properties in terms of shrinkage and warpage as well as mechanical, thermal and chemical stability compared to thermoplastic materials. Thanks to these properties, thermosets are commonly used to encapsulate electronic components on a 2nd-level packaging prior to assembly by reflow soldering on printed circuits boards or other substrates. Based on the characteristics of thermosets to develop a distinct skin effect due to segregation during the molding process, the surface properties of injection molded thermoset components resemble optical characteristics. Within this study, molding parameters for thermoset components are analyzed in order to optimize the surface quality of injection molded thermoset components. Perspectively, in combination with a reflective coating by e.g., physical vapor deposition, such elements with micro-integrated reflective optical features can be used as optoelectronic components, which can be processed at medium-ranged temperatures up to 230 °C. The obtained results indicate the general feasibility since Ra values of 60 nm and below can be achieved. The main influencing parameters on surface quality were identified as the composition of filler materials and tool temperature. Full article

(This article belongs to the Special Issue Micro/Nano Manufacturing II)

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25 pages, 25785 KiB

Open AccessFeature PaperArticle

A Step by Step Methodology for Building Sustainable Cementitious Matrices

by Styliani Papatzani and Kevin Paine

Appl. Sci. 2020, 10(8), 2955; https://doi.org/10.3390/app10082955 - 24 Apr 2020

Cited by 10 | Viewed by 2065

Abstract

In an effort to produce cost-effective and environmentally friendly cementitious binders. mainly ternary (Portland cement + limestone + pozzolanas) formulations have been investigated so far. Various proportions of constituents have been suggested, all, however, employing typical Portland cement (PC) substitution rates, as prescribed [...] Read more.

In an effort to produce cost-effective and environmentally friendly cementitious binders. mainly ternary (Portland cement + limestone + pozzolanas) formulations have been investigated so far. Various proportions of constituents have been suggested, all, however, employing typical Portland cement (PC) substitution rates, as prescribed by the current codes. With the current paper a step by step methodology on developing low carbon footprint binary, ternary and quaternary cementitious binders is presented (PC replacement up to 57%). Best performing binary (60% PC and 40% LS (limestone)) and ternary formulations (60% PC, 20% LS, 20% FA (fly ash) or 43% PC, 20% LS 37% FA) were selected on the grounds of sustainability and strength development and were further optimized with the addition of silica fume. For the first time a protocol for successfully selecting and testing binders was discussed and the combined effect of highly pozzolanic constituents in low PC content formulations was assessed and a number of successful matrices were recommended. The present paper enriched the current state of the art in composite low carbon footprint cementitious binders and can serve as a basis for further enhancements by other researchers in the field. Full article

(This article belongs to the Special Issue Micro/Nano Manufacturing II)

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18 pages, 7700 KiB

Open AccessFeature PaperArticle

Experiment-Based Process Modeling and Optimization for High-Quality and Resource-Efficient FFF 3D Printing

by Ahmed Elkaseer, Stella Schneider and Steffen G. Scholz

Appl. Sci. 2020, 10(8), 2899; https://doi.org/10.3390/app10082899 - 22 Apr 2020

Cited by 62 | Viewed by 7992

Abstract

This article reports on the investigation of the effects of process parameters and their interactions on as-built part quality and resource-efficiency of the fused filament fabrication 3D printing process. In particular, the influence of five process parameters: infill percentage, layer thickness, printing speed, [...] Read more.

This article reports on the investigation of the effects of process parameters and their interactions on as-built part quality and resource-efficiency of the fused filament fabrication 3D printing process. In particular, the influence of five process parameters: infill percentage, layer thickness, printing speed, printing temperature, and surface inclination angle on dimensional accuracy, surface roughness of the built part, energy consumption, and productivity of the process was examined using Taguchi orthogonal array (L50) design of experiment. The experimental results were analyzed using ANOVA and statistical analysis, and the parameters for optimal responses were identified. Regression models were developed to predict different process responses in terms of the five process parameters experimentally examined in this study. It was found that dimensional accuracy is negatively influenced by high values of layer thickness and printing speed, since thick layers of printed material tend to spread out and high printing speeds hinder accurate deposition of the printed material. In addition, the printing temperature, which regulates the viscosity of the used material, plays a significant role and helps to minimize the dimensional error caused by thick layers and high printing speeds, whereas the surface roughness depends very much on surface inclination angle and layer thickness, which together determine the influence of the staircase effect. Energy consumption and productivity are primarily affected by printing speed and layer thickness, due to their high correlation with build time. Full article

(This article belongs to the Special Issue Micro/Nano Manufacturing II)

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19 pages, 4503 KiB

Open AccessFeature PaperArticle

Conceptual Planning of Micro-Assembly for a Better Utilization of Reconfigurable Manufacturing Systems

by Christoph Gielisch, Karl-Peter Fritz, Benedikt Wigger and André Zimmermann

Appl. Sci. 2020, 10(8), 2806; https://doi.org/10.3390/app10082806 - 18 Apr 2020

Cited by 1 | Viewed by 1984

Abstract

Reconfigurable manufacturing systems (RMS) can be used to produce micro-assembled products that are too complex for assembly on flat substrates like printed circuit boards. The greatest advantage of RMS is their capability to reuse machine parts for different products, which enhances the economical [...] Read more.

Reconfigurable manufacturing systems (RMS) can be used to produce micro-assembled products that are too complex for assembly on flat substrates like printed circuit boards. The greatest advantage of RMS is their capability to reuse machine parts for different products, which enhances the economical efficiency of quickly changing or highly individualized products. However, often, process engineers struggle to achieve the full potential of RMS due to product designs not being suited for their given system. Guaranteeing a better fit cannot be done by static guidelines because the higher degree of freedom would make them too complex. Therefore, a new method for generating dynamic guidelines is proposed. The method consists of a model, with which designers can create a simplified assembly sequence of their product idea, and another model, with which process engineers can describe the RMS and the procedures and operations that it can offer. By combining both, a list of possible machine configurations for an RMS can be generated as an automated response for a modeled assembly sequence. With the planning tool for micro-assembly, an implementation of this method as a modern web application is shown, which uses a real existent RMS for micro-assembly. Full article

(This article belongs to the Special Issue Micro/Nano Manufacturing II)

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12 pages, 16750 KiB

Open AccessArticle

Simultaneous Nano-Texturing onto a CVD-Diamond Coated Piercing Punch with Femtosecond Laser Trimming

by Tatsuhiko Aizawa, Tomomi Shiratori, Yoshihiro Kira and Tadahiko Inohara

Appl. Sci. 2020, 10(8), 2674; https://doi.org/10.3390/app10082674 - 13 Apr 2020

Cited by 13 | Viewed by 2892

Abstract

In this study, a CVD (Chemical Vapor Deposition)-diamond coated tungsten carbide cobalt (WC (Co)) punch was trimmed to adjust its surface roughness and to significantly reduce its edge curvature for fine piercing by femtosecond laser processing. Through this laser trimming, the surface quality [...] Read more.

In this study, a CVD (Chemical Vapor Deposition)-diamond coated tungsten carbide cobalt (WC (Co)) punch was trimmed to adjust its surface roughness and to significantly reduce its edge curvature for fine piercing by femtosecond laser processing. Through this laser trimming, the surface quality of the diamond coating and the punch edge profile were improved to less than 0.5 μm at the maximum roughness and 2 μm in the edge width, respectively. In parallel with this improvement of surface quality, the side surface of the diamond coating was modified to include nano-textures via the LIPSS (Laser Induced Periodic Surface Structuring) process. Through the fine piercing process, this nanotexture was transcribed onto the pierced hole surface together with fine shearing of the hole by piercing. WLI (White-Light Interferometry) and SEM (Scanning Electron Microscopy) were utilized to describe this transcription of nanotextures during the piercing process. These semiregular nanotextures with an LIPSS period of 300 nm on the pierced hole surface induced a blue colored surface plasmon. Full article

(This article belongs to the Special Issue Micro/Nano Manufacturing II)

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14 pages, 3598 KiB

Open AccessFeature PaperArticle

Dimensional Errors Due to Overhanging Features in Laser Powder Bed Fusion Parts Made of Ti-6Al-4V

by Amal Charles, Ahmed Elkaseer, Lore Thijs and Steffen G. Scholz

Appl. Sci. 2020, 10(7), 2416; https://doi.org/10.3390/app10072416 - 01 Apr 2020

Cited by 26 | Viewed by 2966

Abstract

The rise in popularity of Additive Manufacturing technologies and their increased adoption for manufacturing have created a requirement for their fast development and maturity. However, there is still room for improvement when compared with conventional manufacturing in terms of the predictability, quality, and [...] Read more.

The rise in popularity of Additive Manufacturing technologies and their increased adoption for manufacturing have created a requirement for their fast development and maturity. However, there is still room for improvement when compared with conventional manufacturing in terms of the predictability, quality, and robustness. Statistical analysis has proven to be an excellent tool for developing process knowledge and optimizing different processes efficiently and effectively. This paper uses a novel method for printing overhanging features in Ti-6Al-4V metal parts, by varying process parameters only within the down-facing area, and establishes a methodology for predicting dimensional errors in flat 45° down-facing surfaces. Using the process parameters laser power, scan speed, scan spacing, scan pattern, and layer thickness, a quadratic regression equation is developed and tested. An Analysis of variance (ANOVA) analysis concluded that, within the down-facing area, the laser power is the most significant process parameter, followed by the layer thickness and scan speed. Comparatively, the scanning pattern is determined to be insignificant, which is explained by the small down-facing area where the various scanning patterns play no role. This paper also discusses the interaction effects between parameters. Some thoughts on the next steps to be taken for further validation are discussed. Full article

(This article belongs to the Special Issue Micro/Nano Manufacturing II)

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13 pages, 3781 KiB

Open AccessArticle

Analysis of a Sound Signal for Quality Monitoring in Laser Microlap Welding

by Bo-Si Kuo and Ming-Chyuan Lu

Appl. Sci. 2020, 10(6), 1934; https://doi.org/10.3390/app10061934 - 12 Mar 2020

Cited by 7 | Viewed by 2434

Abstract

This study focused on correlation analysis between welding quality and sound-signal features collected during microlaser welding. The study provides promising features for developing a monitoring system that detects low joint strength caused by a gap between metal sheets after welding. To obtain sound [...] Read more.

This study focused on correlation analysis between welding quality and sound-signal features collected during microlaser welding. The study provides promising features for developing a monitoring system that detects low joint strength caused by a gap between metal sheets after welding. To obtain sound signals for signal analysis and develop the monitoring system, experiments for laser microlap welding were conducted on a laser microwelding platform by installing a microelectromechanical system (MEMS) microphone away from the welding point, and an acoustic emission (AE) sensor on the fixture. The gap between two metal sheet layers was controlled using clamp force, a pressing bar, and the appropriate installation of a thin piece of paper between the metal sheets. After sound signals from the microphone were collected, the correlation between features of time-domain sound signals and of welding quality was analyzed by categorizing the referred signals into eight sections during welding. After appropriately generating the features after signal analysis and selecting the most promising features for low-joint-strength monitoring on the basis of scatter index J, a hidden Markov model (HMM)-based classifier was applied to evaluate the performance of the selected sound-signal features. Results revealed that three sound-signal features were closely related to joint-strength variation caused by the gap between two metal-sheet layers: (1) the root-mean-square (RMS) value of the first section of sound signals, (2) the standard deviation of the first section of sound signals, and (3) the standard deviation to the RMS ratio of the second section of sound signals. In system evaluation, a 100% classification rate was obtained for normal and low-bonding-strength monitoring when the HMM-based classifier was developed on the basis of the three selected features. Full article

(This article belongs to the Special Issue Micro/Nano Manufacturing II)

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Review

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16 pages, 3098 KiB

Open AccessReview

Micromachining in Powder-Mixed Micro Electrical Discharge Machining

by Gunawan Setia Prihandana, Muslim Mahardika and Tutik Sriani

Appl. Sci. 2020, 10(11), 3795; https://doi.org/10.3390/app10113795 - 29 May 2020

Cited by 19 | Viewed by 3949

Abstract

Micromachining in the micro-electric discharge machining (μ-EDM) process requires high material-removal rate with good surface quality. Power-mixed μ-EDM, a modified machining process by introducing specific powder into the dielectric fluid, is among the key inventions to achieving these requirements. This article presents a [...] Read more.

Micromachining in the micro-electric discharge machining (μ-EDM) process requires high material-removal rate with good surface quality. Power-mixed μ-EDM, a modified machining process by introducing specific powder into the dielectric fluid, is among the key inventions to achieving these requirements. This article presents a review of the implementation of powder-mixed micro-EDM processes for microfabrication. Special attention was given to the influence of the powder characteristics, such as the concentration, electrical conductivity, shape and size of the powder. Subsequently, when describing the use of powder for obtaining a high material-removal rate and surface quality, other major applications in μ-EDM for surface modification and geometrical accuracy were also discussed. Finally, some of the varied methods that are used in powder-mixed μ-EDM and industrialization challenges are extensively elaborated. Full article

(This article belongs to the Special Issue Micro/Nano Manufacturing II)

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