This PDF file contains the front matter associated with SPIE Proceedings Volume 10523, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Additive manufacturing enables the realization of complex shaped parts. This also provides a high potential for optical components. Thus elements with virtually any geometry can be realized, which is often difficult with conventional fabrication methods. Depending on the material and thus the manufacturing method used, either transparent optics or reflective optics can be developed with the aid of additive manufacturing. Ultimately, the application or the specification decides on the approach. For example, transmissive 3D printed parts exhibit the disadvantage of a significant reduced transmission. Conversely, reflective 3d printed optics often requires a greater amount of rework in order to achieve a sufficient optical quality of the surface. Here, we discuss 3D printed metal optics (manufactured using a selective laser melting machine) and 3D printed polymer optics (realized either by stereolithography or by multijet modling). In addition to the basic properties, the post-processing of the 3D printed optics is regarded. This includes, for example, cleaning and polishing of the surface using lasers, a robot based fluidjet process for metallic and polymer optics. In the case of the polymer optics a dip-coating process was developed in order to improve the surface quality, which is presented as well. Our aim is to integrate the additive manufactured optics into optical systems. Therefore we present different examples in order to point out new possibilities and new solutions enabled by 3D printing of the parts. In this context, the development of 3D printed reflective and transmissive adaptive optics will be discussed as well.

Lithography-based Additive Manufacturing Technologies (AMT) exploit the curing of photosensitive materials upon light exposure. We developed a hybrid exposure concept, which is able to overcome the dilemma of providing high surfaces qualities and an enhanced throughput by combining two light sources. Digital Light Processing (DLP) Light Engine (LE) -exposure allows a rapid curing of extended areas. However, round envelopes are approximated by single pixels, which leads subsequently to a spatial approximation and thus to lower surface qualities, whereas laser-based AMT systems enable smooth structures. However, with increasing layer crosssection and smaller laser-spot size the exposure time increases, since single laser lines are applied next to each other in order to provide a fully cured layer. In our system, a laser focused to 20 μm shapes the outline of the item whereas a DLP LE, with a pixel-size of 56 μm, cures the inner area. A dichroic mirror, which reflects the wavelength of the laser and transmits the light of the DLP LE, facilitates the beam-alignment. An online-monitoring camera array guaranties the control of both light sources. Our new technology enables the production of parts which previously could not be produced with traditional manufacturing methods. The layer-by-layer approach enables highly complex structures, leading to a design oriented engineering of items. A system with these specifications provides an alternative to many microinjection molding or injection molding processes for complex structures and small lot sizes.

This paper describes the additive manufacturing (AM) of glass using a fiber-fed laser-heated process. Stripped SMF-28 optical fiber with a diameter of 125 μm is fed into a laser generated melt pool. A CO₂ laser beam is focused onto the intersection of the fiber and the work piece, which is positioned on a four-axis computer controlled stage. The laser energy at λ=10.6 μm is directly absorbed by the quartz fiber, locally heating the glass above its working point. Through the careful control of process parameters such as laser power, feed rate and scan speed, bubble free parts such as walls and lenses may be printed. These parts are assessed on the grounds of their transmissivity and refractive index homogeneity, and issues unique to the process such as the thermal breakdown of the glass and refractive index mismatch present in SMF-28 are discussed.

Microfluidic chips known as μ-TAS or LoC have become versatile tools in cell research, since functional biochips are able to streamline dynamic observations of various cells. Glass or polymers are generally used as the substrate due to their high transparency, chemical stability and cost-effectiveness. However, these materials are not well suited to the microscopic observation at the fluid boundary due to the refractive index mismatch between the medium and the biochip material. For this reason, we have developed a method of fabricating three-dimensional (3D) microfluidic chips made of a low refractive index fluoric polymer CYTOP. CYTOP has a refractive index of 1.34, a value that is almost equivalent to that of water. This optical property is very important for clear 3D microscopic observations of cell motion near the solid boundary, due to the minimal mismatch between the refractive index values of the medium and the CYTOP substrate. Therefore, CYTOP microfluidics are expected to allow the generation of clear images of unique cell migratory processes near the microfluidic sidewall. Therefore, we established the fabrication procedure involving the use of femtosecond laser direct writing, followed by wet etching and annealing, to create high-quality 3D microfluidics inside a polymer substrate. A microfluidic chip made in this manner enables us to more clearly observe areas near the fluid surface, compared to the observations possible using conventional microfluidic chips.

In Additive Layer Manufacturing, the layer-based nature of the process results in error in the final object, termed staircase error. This error can be reduced by using a smaller layer thickness, and hence more layers, to print the object. However, in 3D printing with stereolithography, the print time is mostly determined by the number of layers, since the movement of the laser in the X-Y plane is much faster than the movement of the build platform. Therefore, using finer layer thicknesses can significantly increase the print time.

In this work, we propose a novel adaptive slicing algorithm that balances accuracy and print time. The proposed, near-optimal, dynamic programming (DP) based algorithm for adaptive slicing minimizes the number of layers subject to a global volumetric error constraint. Our approach reduces slice count by up to 36% (52%) compared to a state of the art adaptive slicing (uniform slicing) method under the same volumetric error. The results were tested on Formlabsunder the same volumetric error. The results were tested on Formlabs Form1+ SLA-based printers. The print time was improved by up to 32% (53%) for a selection of objects.

Within the field of laser assisted additive manufacturing, the application of ultrashort pulse lasers for selective laser melting came into focus recently. In contrast to conventional lasers, these systems provide extremely high peak power at ultrashort interaction times and offer both the opportunity of nonlinear absorption and the potential to control the thermal impact at the vicinity of the processed region by tailoring the pulse repetition rate. Consequently, transparent materials like borosilicate glass or opaque materials with extremely high melting points like copper, tungsten or even special composites like AlSi40 can be processed. In this publication, we present the selective laser melting of glass by using 500 fs laser pulses at MHz repetition rates emitted at a center wavelength of 515 nm. In order to identify an appropriate processing window, a detailed parameter study was performed. We demonstrate the fabrication of porous bulk glass parts as well as the realization of structures featuring thicknesses below 30 μm, which is below typical achieved structural sizes using pulsed or CO₂ laser [1]. In contrast to alternative approaches [2], due to the nonlinear absorption and therefore complete melting of the material, there was no need for binding materials. This work demonstrates the potential for 3D printing of glass using the powder bed approach.

In this paper, the use of Vertical-Cavity Surface-Emitting Lasers (VCSEL) for thermoplastic tape placement is presented. Thanks to their individually addressable emitters, high-power VCSEL modules enable a customized irradiation, whereby a (speed-adaptive) control of the materials' thermal state becomes viable. Especially of interest for us was the temperature gradient in through-thickness direction within the tape. The irradiation approach promises a new level of thermal controllability through not only controlling the surface temperature (state of the art), but also the thermal penetration and thereby the melt pool depth, melt dwell time and bond interface cooling rate. The novel control approach could improve the placement rate of (in-situ) thermoplastic tape placement beyond 1 m/s, without losses of the weld strength. To achieve a purposeful control of the materials’ thermal state with the VCSEL, a prior inverse computation was required to predict the appropriate irradiation setting. The methods and results of inverse computations will be presented – numerical and analytical. A comparison of the computations with experiments was done by thermal imaging equipment. The experimental setup will be shown as well as the realization of the “tailored” irradiation by the VCSEL (the approximated ideal irradiation distribution). Finally, the advantages for the thermoplastic tape placement process will be discussed. These include an influence on the degree of intimate surface contact, autohesion and state of crystallization in the bond interface. The research work focuses on the thin tape, but is transferable to the generally thicker substrate.

Improving the photon collection efficiency in light-sensitive devices is key for the development of next generation optical detectors and solar cells. In this talk, I will present two paradigmatic examples that illustrate how laser additive manufacturing (AM) can be used to fulfill this goal. The first one consists in the fabrication of micro-optical elements by laser printing of polymeric materials. Thus, light concentrators such as microlenses or microlens arrays can be directly obtained with controlled geometry and size at targeted positions in optoelectronic devices. The second one is based on the laser-induced localized growth of stable perovskite crystals with diverse forms, ranging from microcrystals to nanocuboids. By simply scanning the laser beam in a precursor solution spread on top of a substrate, luminescent and photoconductive wires and microplates can be arbitrarily generated. The so-fabricated optoelectronic systems show excellent performance, while maintaining the core advantages of AM in terms of customization, single-step processing and in-situ synthesis. These results pave the way for low cost printed electronic devices that exhibit an enhanced optical response.

Recently, 3D printing has gone beyond being an industrial prototyping process and has gradually evolved as the tool to manufacture production-quality parts that are otherwise challenging by using traditional methods. Especially, translating 3D printing technique into the optical realm would dramatically improve the time- and cost-efficiency of customized optical elements, while conventional methods such as multiaxial lathes polishing, magnetorheological finishing, molding techniques are relatively expensive and time consuming. However, 3D printing also suffers from the inherent drawback: the reduced surface quality associated with the stair-stepping effect as a direct result of the layered deposition of the material. In this paper, we have demonstrated a time- and cost-effective single photon micro-stereolithography based 3D printing method to eliminate the layer stair-stepping effect. This method supports not only sub-voxel accuracy (~ 2 μm) of the surface in the range of 2 mm diameter, but also features deep sub-wavelength roughness (< 10 nm) of the surfaces and extremely good reproducibility. Furthermore, we designed and rapidly prototyped the aspherical lenses which not only feature low distortion, but also show remarkable optical quality in a broadband wavelength range from 400 nm to 800 nm.

In the recent years, Laser Additive Manufacturing (LAM) has become a rather well-established manufacturing process to produce metallic parts. However, the very special consolidation conditions during AM with multiple heating and cooling at high rates may lead to complex out-of-equilibrium microstructures, pronounced element segregation and crack formation in the bulk alloy. However, there have been only a limited number of reliably processable alloys used in LAM so far, and the processing parameters are usually obtained in a trial-and-error approach. In order to exploit the advantages of LAM, novel alloys and composites adapted to the special processing conditions during LAM need to be developed. This requires a deep understanding of the materials consolidation process during LAM, which is currently still lacking. This talk will give an overview of the challenges and opportunities in LAM from a materials scientist’s perspective. Results of the LAM related research at Empa with a special emphasize on the optimization of Ti, Al and Cu based alloys will be presented.

Recent development of a station dedicated to Laser Shock Peening around newly developed BIVOJ laser system is reported. We also describe further plans related to upgrade of the laser system itself as well as plans for establishment of a dedicated sample preparation and characterization lab.

The direct injection type laser cladding system using combined multi lasers, which supplies a clad powder from a center nozzle, was developed for realize of low dilution area and micro cladding. A fiber coupled diode laser was employed. The six-diode lasers were guided to focusing head with every optical fiber, which core diameter is 100 μm. Beam profile at focal point of the combined six lasers was set a spot diameter of 300 μm by CCD camera. Here, A cobalt-chromium alloy (CoCr-alloy) called by Stellite, which has excellent properties such as wear resistance, corrosion resistance and resistance to environment, was used as a cladding material. The focusing head has a function to supply a CoCr-alloy powder at a focal point from a center nozzle. When the laser irradiation and powder supply are simultaneously performed toward to a stainless steel 304 substrate, the CoCr-alloy powder was melted and solidified on the substrate to form a cladding layer. The melting and solidification process for CoCr-alloy was observed in real time using synchrotron radiation imaging technique at BL22XU in SPring-8. From results, it was clarified that the CoCralloy melt-solidification phenomenon greatly differs for laser output power. At the output power of 60W, it was found that a minimum amount of molten pool was formed and then solidified to form the cladding layer.

Individually shaped light distributions become more and more important in lighting technologies and thus the importance of additively manufactured reflectors increases significantly. The vast field of applications ranges from automotive lighting to medical imaging and bolsters the statement. However, the surfaces of additively manufactured reflectors suffer from insufficient optical properties even when manufactured using optimized process parameters for the Selective Laser Melting (SLM) process. Therefore post-process treatments of reflectors are necessary in order to further enhance their optical quality. This work concentrates on the effectiveness of post-process procedures for reflective optics. Based on already optimized aluminum reflectors, which are manufactured with a SLM machine, the parts are differently machined after the SLM process. Selected finishing methods like laser polishing, sputtering or sand blasting are applied and their effects quantified and compared. The post-process procedures are investigated on their impact on surface roughness and reflectance as well as geometrical precision. For each finishing method a demonstrator will be created and compared to a fully milled sample and among themselves. Ultimately, guidelines are developed in order to figure out the optimal treatment of additively manufactured reflectors regarding their optical and geometrical properties. Simulations of the light distributions will be validated with the developed demonstrators.

The large interest on using femtosecond pulses to accomplish laser-materials processing is associated to the reduction of thermal effects and the ability to change material’s properties at nano/micro scale, supporting the development of all-optical devices. Variations of methods based on direct laser writing have enabled the fabrication of waveguides, couplers and splitters in glasses, as well as photonic crystals, resonators and microenvironments in polymers. Although considerable advances have been obtained on material processing with fs-laser pulses, each class of material usually requires specific experimental conditions, impairing the application of a unique methodology to explore a wide range specimen. Thus, in this study, we investigated the usage of Laser induced forward transfer (LIFT) as a general tool to process polymers, glasses and metals. The method consists on the backside irradiation of a donor substrate containing the target material to be transfer for a second substrate, called receptor, located in close proximity or in contact with the first one enabling the printing functional materials over a variety of surfaces. In order to achieve the printing of high-resolution patterns, we have applied LIFT with femtosecond laser pulses, which is advantageous for minimizing thermal effects and due to multiphoton absorption effects. As representative of each materials class, thin films of noble metals, chalcogenide glasses and conducting polymers were chosen as target materials, all being important for photonics applications. Our results showed that when applying pulses energy close to the damage threshold, the original material properties and structure are preserved on the micropatterning produced by fs-LIFT, enabling the deposition of 2D-complex geometries with thickness around 50 nm and width close to 2 μm. In addition, the deposition of nanoparticles has been observed for the fs-LIFT of metal and glass, where the former shown the surface plasmon resonance and the later displays a self-assemble pattern, explained based on the effect of laser induced periodic surface structure (LIPSS).

Laser bioprinting is a powerful tool in many biological fields due to its versatility in placing and construct different geometries of biological materials. The high accuracy and non-destructive nature of this method can be applied to the study of complex biological systems. In particular, single cell laser bioprinting helps to understand the relationships between cells and their local environment. Immunology is a transversal field that is governed by a complex network of genetic and signalling pathways subtending a network of interacting cells. In this context, mobility of the cells in a network along with their situation and the gene products they interact with, plays an important roll in the behaviour of the immune system. In this work we use a laser induced forward transfer blister assisted (BALIFT) approach to assess these cell-cell interaction and mobility in vitro. This method helps to understand properly the role of a cell in such networks to increase our knowledge of the immune system response. This work presents BALIFT bioprinting of single hematopoietic cells and chemoattractant proteins with high spatial resolution. In particular NK cells (natural killer), T-lymphocyte and chemokines and cytokine molecules are printed in specific patterns to study cell-cell and cell-environment interaction and cell migration. Whereby placing cellular components on a matrix previously designed on demand allow us to test the molecular interactions between lymphocytes and pathogens; as well as the generation of two-dimensional structures printed ad hoc in order to study the mechanisms of mobilization of immune system cells.

The development of rapid prototyping techniques for the fabrication of microelectronic structures has seen rapid growth over the past decade. In particular, laser-induced forward transfer (LIFT) is a non-lithographic direct-write technique that offers the advantages of high speed / throughput, high resolution, materials versatility, and substrate compatibility. Because of the high degree of control over size and shape of printed material, the development of a wide range of microelectronic components, including interconnects, antennas, and sensors, has become possible using LIFT. In this paper, we explore the use of LIFT to print various 3D microstructures including high aspect ratio micro pillars using high viscosity Ag nanopastes. In addition, we demonstrate the fabrication of interconnects via LIFT on RF switches that, after printing and subsequent curing, perform similarly to an analogous wire-bonded device.

Additive manufacturing (commonly called “3D printing”) fabricates the desired final part directly from the input CAD (Computer Aided Design) file by depositing and fusing layer upon layer of the source material. New engineering designs are possible in which a single optimized part with novel topology can replace several traditional parts. The complex physics of metal deposition leads to variations in quality and to new flaws and residual stresses not seen in traditional manufacturing. Additive manufacturing currently has gaps in knowledge. Mission assurance will require: qualification and certification standards; sharing of data in handbooks; predictive models relating processing, microstructure and properties; and development of closed loop process control and non-destructive evaluation to reduce variability.

A complete inkjet printed 3D structure containing broadband antennas in a phased array configuration along with a fixed time delay phase shifter is demonstrated via simulation to allow for a Frequency Scanning Array. Continuous steering as a function of frequency and the necessary broadband antenna structures are explored, which allows for free space wireless communications and remote sensing applications. Finally, the capability of a single antenna to receive from multiple angles simultaneously is described.

3D meso-scale structures, that can reach up to cm in overall size but retain micro- or nano-features, proved to be promising in various science fields from micro-mechanical metamaterials to photonics. In this work we present an approach of synchronizing linear positioning and galvo-scanning for efficient femtosecond 3D optical printing of objects at meso-scale. In such configuration linear stages provide stitchless structuring at nearly limitless (up to tens of cm) working area, while galvo-scanners allow to achieve translation velocities in the range of mm/scm/ s without sacrificing nano-scale positioning accuracy. The capabilities of this approach are demonstrated by fabricating mm sized but μm features retaining structures with free movable parts, scaffolds for cell growth, microlenses and photonic crystals. Provided results show that synchronization of this kind is crucial for an end goal of industrial-scale implementation of this technology.

Research on the selective laser melting (SLM) method of laser powder bed fusion additive manufacturing (AM) has shown that surface and internal quality of AM parts is directly related to machine settings such as laser energy density, scanning strategies, and atmosphere. To optimize laser parameters for improved component quality, the energy density is typically controlled via laser power, scanning rate, and scanning strategy, but can also be controlled by changing the spot size via laser focal plane shift. Present work being conducted by The Aerospace Corporation was initiated after observing inconsistent build quality of parts printed using OEM-installed settings. Initial builds of Inconel 718 witness geometries using OEM laser parameters were evaluated for surface roughness, density, and porosity while varying energy density via laser focus shift. Based on these results, hardware and laser parameter adjustments were conducted in order to improve build quality and consistency. Tensile testing was also conducted to investigate the effect of build plate location and laser settings on SLM 718. This work has provided insight into the limitations of OEM parameters compared with optimized parameters towards the goal of manufacturing aerospace-grade parts, and has led to the development of a methodology for laser parameter tuning that can be applied to other alloy systems. Additionally, evidence was found that for 718, which derives its strength from post-manufacturing heat treatment, there is a possibility that tensile testing may not be perceptive to defects which would reduce component performance. Ongoing research is being conducted towards identifying appropriate testing and analysis methods for screening and quality assurance.

Laser cladding, which is one of laser metal deposition (LMD) technologies, is an effective metal surface coating technique capable of increasing component lifetimes, in which an additive material such as a powder or a wire is melted by a laser beam and deposited on the substrate surface. We developed a multi-beam processing head with six high intensity infrared (IR) diode lasers, which was based on multi laser combining method, in order to realize a high quality cladding layer having a dense, fine and purity. An IR diode laser light with the power of 50 W was output from an optical fiber. Total laser power on the base plate was 300 W since six laser beams were overlapped. A nozzle to supply the powder was in the center of the processing head. The processing head was installed in a machine tool (simultaneous 5-axis machining). Hardness and abrasion resistances of blade edge and shaft made from stainless steel were improved by cladding of cobalt-base alloy powder, which was one of the applications with the machine. We also designed a multi-beam processing head with high intensity blue diode lasers for cladding of copper powder. We have developed a high intensity blue diode laser with the power of 100 W. The blue laser light was output from an optical fiber whose core diameter and NA were 100 m and 0.22, respectively. The three blue diode lasers would be installed to the processing head to obtain the power of 300 W on the base plate

Direct metal laser sintering (DMLS) is an emerging additive manufacturing technology that has great potential to change the way parts are manufactured. Some benefits of DMLS, such as reduction of components, can lead to reduction of weight and quicker assembly times. Complex features and internal channels that are impossible to machine can also be created. In order to leverage this, it will be necessary to put aside some of the conventional manufacturing design rules, and look for ways to take advantage of DMLS.

In the present report, we demonstrate how Selective laser melting (SLM) process can contribute to a 4D manufacturing of functional and structural properties of shape memory alloys (SMAs) in-situ synthesized into Ni-Ti and Cu-Al-Ni powdered systems. Correlations of specific resistance and phase structure in Ni-Ti and Cu-Al-Ni intermetallic phases after the SLM were experimentally observed. It was shown that electrical resistivity of the phases studied (austenite, rhombohedral and martensite phases) increases with temperature but the slopes are quite different. Intermediate R-phase in nitinol (NiTi – intermetallide) shows generally higher electrical resistivity than the austenite phase, but its value grows with the decrease of temperature for laser melted samples. We explained this fact by an accumulation of dislocation with the continuous increase of the R-phase with the decrease of temperature. Hysteresis loop of the electrical resistivity and phase-structural properties of SL-Melted samples are correlated with conditions of SLM process, additional heating during the layerwise process, 3D part's porosity. It will be important for perspective 4D printed biomedical applications (bio-MEMS - sensors, drug delivery systems, implants, etc.) of fabricated self- self-initiating and self-fixing SMAs.

Additive manufacturing gained increasing interest during the last decade due to the potential of creating 3D devices featuring nearly any desired geometry. One of the most widely used methods is the so-called powder bed method. In general, conventional cw and pulsed laser sources operating around 1030 nm and CO₂ lasers at 10.6 μm are usually applied. Among other materials like polymers, these systems are feasible for several metals, alloys and even ceramics, but easily reach their limitation at a wide range of other materials, regarding required absorption and intensity. In order to overcome these limits, ultrashort pulse laser systems are one approach. Due to the increased peak power and ultrashort interaction times within the femtosecond and picosecond time range, materials with extraordinary high melting points, increased heat conductivity or new composites with tailored specifications are coming into reach. Moreover, based on the nonlinear absorption effect, also transparent materials can be processed.

Here, we present the selective laser melting of pure copper using ultrashort laser pulses. This work involves a comparative study using 500 fs pulses at processing wavelengths of 515 nm and 1030 nm. The repetition rate of the applied laser system was varied within the MHz range in order to exploit heat accumulation. By using the ultrashort interaction times and tailoring the repetition rate, the induced melt pool can be significantly optimized yielding robust copper parts revealing thin-wall structures in the range below 100 μm.

A method is presented that combines pulsed laser ultrasonics with laser heterodyne interferometry for possible application as an in-situ process control for additive manufacturing. The method implements two lasers that are focused near the build area (i.e. heat affected zone : 1) a pulsed laser that excites a surface acoustic wave (the probe signal) at or near the build area and 2) a CW laser heterodyne interferometer operating as a sensor that measures the time resolved features of the propagated waves. We have conducted investigations on the utility of this type of in situ probe-sensor system for real time measurement of the local temperature, surface defects, surface roughness, and grain boundary (grain size) determination. The all-optical method allows for remote in-situ process control that can be tailored for different build situations and materials. The current setup utilizes a UV (355 nm) or visible (532 nm) pulse laser and a narrow band 488 nm CW laser. By measuring the surface displacements with sub nm accuracy and by conducting analyses on the arrival time of the signal and frequency, the interferometric technique can characterize materials akin to non-destructive evaluation (NDE). Prior, we have presented evidence on the utility of the technique to measure local temperature, we now present evidence for surface defects/roughness and grain boundary identification. In addition, we are now exploring the utility of laser ultrasound to monitor changes in residual stress.

In this study, we developed an innovative approach to achieving a higher sustainability in the experimentally guided combinatorial design of metal-matrix gradient structural composites. The titanium carbide of nano sizes or titanium diboride of submicron sizes were incorporated into the titanium matrix during the selective laser melting (SLM) process of Ti+(10, 15, 20 wt.%) TiC/TiB₂ powder mixtures. Optimal regimes of 3D laser powder bed process were determined. We compared how the interfacial properties would change due to the composition differences in case of TiC and TiB₂ reinforcing titanium matrix composites (TMC). Phase analysis of the fabricated TMC showed that the initial TiC and TiB₂ particles dissolved with different velocities after remelting. Special attention was paid to carbon and boron dilution and secondary carbides and borides phase formation mechanisms when TiC/TiB₂ were mixed with titanium. Microstructure, phase constitution and mechanical properties of the TMCs were investigated by the OM, SEM, XRD and microhardness measurement in order to validate the rapid alloy prototyping (RAP) concept in single technological approach.

With the rapid development of additive manufacturing to an established industrial manufacturing process, arises an increasing demand for process control. Especially industrial sectors with stringent safety regulations like aerospace, automotive or medicine, require a high level of quality monitoring. The limited space and the variety of possible beam incidence angle and position configurations inherent to laser scanning systems, constitute special framework conditions, only inadequately provided by state of the art beam diagnostic devices. To meet these requirements we developed a novel and compact measuring instrument capable of addressing scanner specific measurement tasks, including quantities so far inaccessible to conventional beam diagnostics. These involve for example the examination of the field flatness, pincushion distortion, position dependent focal shift, or accuracy of position and marking speed. Even more sophisticated issues like the accurate stitching of two overlapping exposure schemes are feasible. The working principle is based on a pattern of scattering structures within a glass plate. When scanned across the pattern, a small fraction of the laser beam is scattered and the light is collected with a photo-diode, allowing the reconstruction of the light path and derivation of the beam width. All above mentioned quantities are measured with high resolution and reproducibility. The current state of the experiments is presented, and the prospects of this novel measuring technology for scanner system diagnostics discussed.

According to the current great interest concerning Large-Scale Metrology applications in many different fields of manufacturing industry, technologies and techniques for dimensional measurement have recently shown a substantial improvement. Ease-of-use, logistic and economic issues, as well as metrological performance, are assuming a more and more important role among system requirements. The project is planned to conduct experimental studies aimed at identifying the impact of the application of the basic laws of chip and microlasers as radiators on the linear-angular characteristics of existing measurement systems. The project is planned to conduct experimental studies aimed at identifying the impact of the application of the basic laws of microlasers as radiators on the linear-angular characteristics of existing measurement systems. The system consists of a distributed network-based layout, whose modularity allows to fit differently sized and shaped working volumes by adequately increasing the number of sensing units. Differently from existing spatially distributed metrological instruments, the remote sensor devices are intended to provide embedded data elaboration capabilities, in order to share the overall computational load.

We have developed a technique which can accurately read engraved letters for controlling physical distribution on a bloom of temperature of 800 and installed it in producing line of our steelworks. In our target producing line, physical distribution is controlled by visually confirming tracking information about a computer system for uniformly controlling the works physical distribution and engraved letters on manufactured and conveyed blooms (Depth 0.3 mm, Letter width: 10mm, Height: 20mm, and so on). However, there is a problem that different materials could possibly flow out because of human errors caused by the work depending on human eyes. For solving the problem, we have developed the measuring system in which a two- dimensional laser distance meter with an optical filter and an athermanous filter moves in the direction of rows of engraved letters over the edge of stopped bloom and measures the surface of the bloom. Engraved letters can be recognized and read by means of our developed processes including distinction between the surface and the engraved letters part by characteristics that the distance of the part of engraved letters from the laser distance meter is longer than that of the surface of the bloom, extraction of just engraved letters by binarization process, and pattern matching process of learned letters. Additionally, we have improved reading rate of letters to 95 % and prevented different materials from flowing out by reciprocating laser distance meter over the surface of the bloom.

Selective Laser Melting technology (SLM) is a thermal process, and control of thermal effects is of great importance since enhanced productivity of modern SLM equipment can be achieved by increased laser power. To provide acceptable physical resolution of image recording, the TEM₀₀ lasers are applied, for example fiber lasers which power reaches today several kW. However, the Gaussian intensity distribution of single-mode powerful lasers brings some problems in SLM: inhomogeneous intensity in focused spot results in non-uniform temperature profile and subsequent irregularities of melting process, unwished evaporation or sparking; another issue relates to optics – dynamic gradient heating of optical components and subsequent induce of waist shift and wave aberrations resulting in variation of size and intensity distribution of focused spot in working plane. The thermally induced effects are especially important for protective windows which are inevitably contaminated by fine powder inducing higher heating. Solution suggested to provide uniform temperature in working spot is beam shaping optics made from high purity fused silica and creating optimum for uniform melting flat-top or doughnut profiles. To stabilize the size and intensity of working spot it is suggested to apply athermalized protective windows from optical material self-compensating geometrical and refractive thermal effects. Detailed measurements of beam properties and measurements of real manufactured parts confirmed correctness of suggested approach, its possibility to stabilize drastically the SLM process. The paper presents description of optics applied; measurements of process parameters and analysis of properties of manufactured parts are presented as well.

A blue direct diode laser cladding system, which uses multi laser combining method, was developed in order to realize a high quality cladding layer having a dense, fine and purity. In order to clarify the mechanism of copper layer formation, the layer formation process when forming a copper layer using a blue direct diode laser was observed using in situ X ray observation. The six-blue diode lasers were guided to focusing head with every optical fiber, which core diameter is 100 μm. Beam profile at focal point of the combined six lasers was set a spot diameter of 400 μm. The focusing head has a function to supply a pure copper powder at a focal point from a center nozzle. As the results, it was found that the stainless steel 304 substrate was melted and generate some bubble in molten pool at laser fluence of 1221 kJ/cm², and output power of 92W. At laser fluence of 407 kJ/cm², the bubble was not appeared because only a slight molten pool was formed on the surface of the substrate. It was found that amount of bubble and penetration depth was depended on the laser fluence with blue direct diode laser. By controlling the amount of input energy, the copper coating was produced minutely with no weld penetration.

Direct Laser Metal Deposition (DLMD) has been successfully applied for the coating or the repair of several kind of components, such as molds and dies. Recently, the aeronautical sector is also showing a high interest in this process for the repair of turbines and transmissions. However, technical requirements to be met for the repair of aeronautical components are much more stringent than standards of other industrial fields. Some of the deposited material defects that need to be carefully controlled are cracks and porosity, which largely depend on the temperature peaks and the cooling rates generated during the process. The aim of this work is to monitor the temperature field that was generated during the DLMD process, analyze its variation with some process parameters and study its effects on clad geometry and on dilution with the substrate. In this research, a number of experimental tests were designed for the deposition of single clads of a Nickel superalloy powder on an AISI 304 stainless steel substrate, using an Ytterbium fiber laser source. Temperature fields monitoring was carried out using a thermal camera capable of detecting temperatures up to 2500 °C.

Laser additive manufacturing (LAM) is layer by layer built up a 3-D part using either a bed or stream of powdered material. In this paper, the heat transfer and melt solidification of iron powder in the direct metal laser sintering (DMLS) process with low laser powers have been experimental investigated. The experimental results of various properties of each layer and properties among the multiple layers due to the laser power, the scanner rate, of the frequency of the laser pulse, have been shown and discussed. The process will be improved by numerical modeling in the future.