Design of Particle Dampers for Laser Powder Bed Fusion

Additively manufactured particle dampers can significantly improve component damping. However, if designed incorrectly, the damping can be worsened. For the design of additively manufactured particle dampers, there are not yet sufficient design rules and models to describe the effect due to numerous design parameters. The research question answered in this paper describes how the effect of particle damping can be characterised as a function of excitation force and excitation frequency for different cavity sizes. To characterise the effect of particle damping, a 33 full factorial test plan is constructed, and the damping is determined experimentally. It is shown that the damping can be reliably evaluated with the circle‐fit method. The effect of particle damping is investigated for beams made of AlSi10Mg, 1.2709 and Ti6Al4V. As a result, a positive effect of the particle damping in a frequency range from 500 to 30,000 Hz and partly up to the 9th bending mode can be proven. It is shown that, for the first bending mode, there is an optimum at approx. 2000 Hz. For the optimum, the increase of the damping for the tool steel 1.2709 to 28 and for the aluminium alloy AlSi10Mg to 18 can be proven. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Concepts for integrating laser polishing into an additive manufacturing system

With the introduction of Additive Manufacturing, many industrial sectors benefit from the freedom of design and capabilities of this technology. Components can be individually designed and extended with different functions. However, high effort in the post-processing is necessary, since surfaces have to be processed and support structures have to be removed. This post-processing usually takes place outside the Additive Manufacturing machine. Therefore an additional effort is necessary for the machining process, but also for pre- and post-processing of the components. For example, positioning in a CNC milling machine has to be done. It is not feasible to fabricate complete systems consisting of multiple components in a single manufacturing operation. Especially optical systems require high surface qualities. The surfaces usually have to be milled or polished. In order to install the optical system afterwards, an enormous adjustment and assembly effort is needed. This can be bypassed, when both optics and mechanics are manufactured during the same process. However, integrating subtractive post-processing should be avoided as it may cause contaminants that cannot be removed from the system. Transformative processes like laser polishing do barely cause contaminants and are more suited for parallel processing. In this work the integration of a laser polishing system is evaluated, which can be used to reduce surface roughness. The requirements for the light source, manufacturing accuracy, etc. are clarified and concepts, how the integration can be implemented are developed. In addition, possibilities for processing additional materials to manufacture optical systems in one machine are discussed. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only

Hybrid Ray Tracing

Nowadays optical systems are predominantly developed using conventional ray tracing methods such as sequential and non-sequential ray tracing. Sequential ray tracing is used in particular to design and optimize imaging systems. However, non-sequential ray tracing allows to take into account the resulting absorption losses and Fresnel reflections within an optical system and therefore enabling realistic predictions about the efficiency of optical systems. The increasing complexity of optical systems combined with the demand of high efficiency and high image quality leads to the fact that conventional methods reach their limits. This challenge can be met by implementing a hybrid ray tracing method. The objective here is to achieve an application-specific ratio between the imaging quality and the efficiency of the optical system. This contribution introduces a tool for the development of highly efficient optical systems considering imaging quality using a hybrid ray tracing method. We will show how the efficiency determined in non-sequential ray tracing can be used in sequential ray tracing to optimize the optical system

Imaging and non-imaging illumination of a DLP for high resolution headlamps

Matrix-LED systems offer different functionalities to increase road safety, e.g. glare-free high beam and marking light. Shortly after their introduction, efforts have been made to increase the amount of pixels. One of the results is the EVIYOS LED consisting of 1024 individually controllable pixels, which practically set the stage for pixel light systems. Current efforts to implement high-resolution pixel light systems are focused towards the exploration of an efficient light source in combination with the use of spatial light modulators. One approach to implement high-resolution pixel light systems is the use of LED arrays as a light source to illuminate a DLP. Unlike video projectors which require a homogeneous illumination of the DLP in order to obtain a homogeneous projection, headlamps require an inhomogeneous light distribution with high illuminance in the center. In order to receive a high system efficiency preforming the desired illuminance onto the active area of the modulator is advantageous. To further increase the systems efficiency an imaging illumination of the DLP, where the images of the emission surfaces of the LEDs are superposed onto the active area of the DLP, is worthwhile. In this paper, concepts for imaging and non-imaging illumination strategies of a DLP for high resolution headlamps will be introduced. For both illumination strategies the most promising concept will be selected to set up an optical system to illuminate a DLP. The paper concludes with a comparative analysis of the imaging and non-imaging optical system with regards to the system architecture and system efficiency

Product-Service-Systems : What and why Developers can learn from Mass Customization

Despite their very similar objectives, delimitations or associations between the two business types of mass customization and providers of product-service-systems (PSS) cannot be found in literature. In the following article, both business types are compared with each other and mapped into a common businesstypological framework, the product-process-baseline-change matrix. Following that, the development of PSS is characterized especially with regard to the (re-)configurability of PSS over the life-cycle. Since product configuration is one of the key tools in the development and the customer co-design process in mass customization, its application to PSS is evaluated and present PSS-configuration approaches are discussed

Temperature issues with white laser diodes, calculation and approach for new packages

Bright white light sources are of significant importance for automotive front lighting systems. Today's upper class systems mainly use HID or LED light sources. As a further step laser diode based systems offer a high luminance, efficiency and allow the realization of new dynamic and adaptive light functions and styling concepts. The use of white laser diode systems in automotive applications is still limited to laboratories and prototypes even though announcements of laser based front lighting systems have been made. But the environment conditions for vehicles and other industry sectors differ from laboratory conditions. There for a model of the system's thermal behavior is set up. The power loss of a laser diode is transported as thermal flux from the junction layer to the diode's case and on to the environment. There for its optical power is limited by the maximum junction temperature (for blue diodes typically 125 - 150°C), the environment temperature and the diode's packaging with its thermal resistances. In a car's headlamp the environment temperature can reach up to 80°C. While the difference between allowed case temperature and environment temperature is getting small or negative the relevant heat flux also becomes small or negative. In early stages of LED development similar challenges had to be solved. Adapting LED packages to the conditions in a vehicle environment lead to today's efficient and bright headlights. In this paper the need to transfer these results to laser diodes is shown by calculating the diodes lifetimes based on the presented model. © 2015 SPIE

Potential of additively manufactured particle damped compressor blades: A literature review

The high-cycle fatigue of compressors significantly impacts the lifetime of aircraft engines. Excitations in resonance lead to early blade fractures; therefore, vibration reduction measures for blades must be taken. Additively manufactured particle dampers are a suitable measure to suppress vibrations. The focus of this paper is to analyze the applications of additively manufactured particle dampers in compressor blades through a literature review. The design requirements, previous vibration reduction measures for compressor blades and properties of additively manufactured particle dampers are investigated in three studies. In order to evaluate the application of additively manufactured particle dampers in compressor blades, the findings are compared and research demand is derived. The main requirements on compressor blades are stiffness, vibration reduction and wear-resistance. Recent vibration reduction measures are focused on friction dampers. To optimize damping multiple vibration suppression measures shall be used. Few studies exist for additively manufactured particle dampers and some prove their damping improvement in compressor blades. Due to the complicated operation conditions, further studies are needed, which are listed to give researchers an approach for further steps

Beam pre-shaping methods using lenslet arrays for area-based high-resolution vehicle headlamp systems

High-resolution light distributions are lately in demand for vehicle headlamp systems as an innovative lighting approach. This lighting approach can realize functionalities, such as precise glare avoidance and on-road projection, which are useful for improving traffic comfort and safety. For achieving the required high-resolution light distribution, area-based projection technologies, such as DMD, LCD, and LCoS, are considered to be integrated into such headlamps. These projection devices demand rectangular illumination areas with specific light distributions to fulfill the requirements for illumination efficiency and performance in headlamp systems. Lenslet arrays, based on the principle of Kohler illumination, can effectively homogenize the light and shape it into rectangular shapes simultaneously. Such components are widely used in projection applications. However, they also show functional potentialities to be applied in high-resolution headlamps. This paper explains the design principles and methods of lenslet arrays for beam pre-shaping in headlamp systems. It validates the homogenization using a self-designed and manufactured lenslet array in a demonstrator in the first place. Afterward, this paper introduces two new methods for the centralized beam shaping required by some headlamps. These methods are validated by optical simulations

High-resolution headlamps: Innovative functionalities and the potential of using laser diodes as light sources

High-resolution headlamp systems are increasingly attracting attentions from OEMs and researchers, while plenty of innovative lighting functionalities such as precisely glare avoidance of high beam, fully adaptive driving beam and on-road projection bring a huge potential for improving the driving safety and comfort. Besides, as a respond to the trend of intelligent transportation and autonomous driving in the future, lighting based communication between drivers and other road participants is also a possible supplementary functionality of such headlamp systems. The growth of such headlamps raises specific illumination demands regarding to the functionalities consequently. To achieve these high resolution dynamic light functions and to fulfill the relevant requirements, several additive or subtractive projection technologies are considered by OEMs and researchers. Due to the different applied circumstances and intentions, the uses of these technologies in headlamp systems are different from those in video projectors. Headlamp systems demand a high optical efficiency with highly compact constructions, which raises requirements to the design and arrangement on both mechatronic and optical systems. As a result, particular schemes for different projection technologies have been developing and brought up in recent years. Moreover, the pursuit of efficiency and compaction suggests the appliance of laser diodes as light sources. Laser diodes have intense optical output power with relatively small emission areas and narrow divergent angles, leading to the use of small optical components for realizing compact modules. Besides, other peculiar properties of laser diodes such as linear polarizations and likely fiber-coupled can be utilized for specific designs as well. In this article, the development of headlamp systems in Germany with correspondent innovative functionalities and requirements are discussed, prototypes composed of different technologies are illustrated, and furthermore, the advantages of using laser diodes for these technologies are also presented

Concepts of inhomogeneous illumination of area-based light modulators for high-resolution headlamps

Adaptive headlamps with innovative lighting functionalities can increase traffic safety. Subtractive light modulators such as Digital-Micromirror-Devices (DMD), liquid crystal displays (LCD) or liquid crystal on silicon devices (LCoS) are considered to be used as an implementation with a high resolution. In order to realize the regulated light distribution as well as to improve the optical efficiency and on-road projection quality of such headlamp systems, an inhomogeneous illumination on the modulator and whereafter low distortion projection optics are considered. In this paper we present simulation results of an optical concept of inhomogeneous illumination for headlamps