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The control bandwidth of a flexure mechanism is typically limited by parasitic resonance frequencies with low structural damping. Such resonances can be suppressed by including active material in the mechanism, which is used to dissipate energy at specified frequencies. The active material is typically placed in areas with high strain, in order to obtain the highest possible coupling and therefore dissipation. However, due to the low ultimate strain of some common active materials, the included active material will limit the deflection of the mechanism. In this work we introduce a design method that improves the closed-loop performance of a low pivot shift cross hinge mechanism by including active material in the leaf springs, without sacrificing the achievable deflection of the mechanism. The coupling between the active material and a selected undesired parasitic frequency is maximised by placing the material in locations with high modal strain. At the same time, the piezoelectric patches are only included in regions where the strain due to the nominal deflection is limited, such that the maximum deflection of ± 15 degrees is maintained. Using the patches as sensors and actuators, positive position feedback control is applied. Using simulations, it is shown that a selected resonance peak can be decreased by 16.3 dB for the considered mechanism, enabling 88% higher bandwidth.

Many precision machines, such as wafer scanners, have an internal motion stage. These stages generate reaction forces that act directly on the machine frame. A common method to minimize the effect of these reaction forces is a balance mass. To eliminate the need for this balance mass, it is proposed to use an active vibration isolation system as a virtual balance mass. Such can be achieved by constructing a force that is based on the reference of the motion stage that cancels its correlated reaction force. This appends the primary objective of an active vibration isolation system, which is to reduce the sensitivity to direct and indirect disturbances. A self-tuning algorithm is implemented to deal with parameter uncertainty and variation. The performance of the proposed method is experimentally validated on a 6-DoF active vibration isolation system, which is appended with a flexure based, straight guided motion stage. A 300 Hz frame mode is introduced of which the displacement can be measured to assess the performance of the method. The proposed method improved the tracking accuracy of the motion stage by a factor of 3.8 and reduced the settling time of the frame mode by a factor of 91, compared to the system without a virtual balance mass.

Leafsprings are commonly used in flexure mechanisms to enable repeatable motion and provide support stiffness. In various applications, the torsional stiffness needs to be increased. This paper presents the concept of using warping constraints distributed along the leafspring to increase the torsional stiffness relative to the stiffness in other directions. A beam-based model of nonuniform torsion is used to estimate the relationship between the geometrical design parameters and the expected increase in torsional stiffness. The model predicts that an order of magnitude increase in stiffness is feasible. Compared to other solutions, the distributed warping constraints have a less obtrusive shape that offer more design freedom.

In the design process of high-precision motion stages, the dynamic behavior is of paramount importance. Manual design of such a stage is a time-consuming process, involving many iterations between engineers responsible for mechanics, dynamics and control. By using topology optimization in combination with additive manufacturing, post-processing using traditional machining and parts assembly, it is possible to arrive at an optimal design in an automated manner. The printing, machining, and assembly steps are incorporated in the optimization in order to directly arrive at a manufacturable design. With a motion stage demonstrator optimized for maximum eigenfrequencies, it is shown that combining additive manufacturing and topology optimization at industry-relevant design precision is within reach and can be applied to high-performance motion systems.

Six degree of freedom manipulation provides full control over position and orientation, essential for many applications. However, six degree of freedom closed kinematic (parallel) manipulators either have a limited range of motion combined with a good repeatability when comprising flexure joints, or they have limited repeatability with a large workspace when using traditional rolling- or sliding-element bearings. Employing recent developments in large stroke flexures and design optimization, a fully flexure-based large range of motion hexapod robot has been designed. The resulting system allows for ±100 mm of translational and more than ±10 degrees of rotational range of motion in each direction combined with a small mechanism volume below 0.25 m3. Furthermore, a dedicated flexure-based design for the actuators combines high actuation forces without impairing precision, allowing for accelerations exceeding 10g. Experiments on a preliminary prototype validate the large workspace and confirm a high repeatability below 0.1 µm can be achieved, which is currently limited by electronics.

High accelerations of fast moving robots induce high fluctuating reaction forces and moments, resulting in undesirable vibrations and loss of accuracy. These fluctuations can be reduced or even eliminated by dynamic balancing techniques, e.g. by addition of counter-masses. However, these techniques typically disregard the flexibility of the mechanism. This flexibility potentially leads to undesirable eigenfrequencies and unbalance of an otherwise perfectly balanced mechanism. In this paper, the effect of link flexibility on the force balance quality is investigated in the frequency domain. This is done for a 2-DOF parallel manipulator with realistic stiffnesses. With the use of flexible multi-body software, the frequency transfer functions for the shaking forces are obtained for an unbalanced, a force balanced and a partially balanced case. The results show that, firstly, force balance results in a strong attenuation of the shaking forces’ frequency content up to the first eigenfrequency. Secondly, the addition of balance mass results in a reduction of the first parasitic eigenfrequency of the system leading to a worsened performance around the first eigenfrequency and a reduction in controller bandwidth. Identification of these effects leads to an optimal, intermediate solution, which mitigates the negative effects of dynamic balance, resulting in low-frequency shaking force attenuation of 30 dB without loss of controller bandwidth.

Flexure mechanisms are commonly designed to be exactly constrained to favour determinism, though at the expense of limitations on parasitic eigenfrequencies and support stiffness. This paper presents the use of viscoelastic material for providing additional stiffness without the indeterminism commonly associated with overconstraining. It is demonstrated experimentally that a custom synthesised elastomer compound can compensate for unintended misalignments without internal stress buildup, while improving the dynamic performance in terms of the first parasitic eigenfrequency. The measurements are corroborated by a nonlinear flexible multibody analysis.

Iron core torque motors provide a high power density, but require high off-axis stiffness, which is normally too demanding for flexure mechanisms especially when considering large range of motion applications. In this paper, a flexure-based suspension for a high torque iron core direct drive torque motor with a large range of motion of 60 degrees is presented. This flexure-based suspension provides the required high radial stiffness (>1000N/mm) combined with a high radial load capacity (500N) over the full range of motion. Furthermore, the suspension maintains a constant position of the pivot axis within 0.1mm, which is required to limit pull-in forces and to stay within alignment tolerances of the actuator. A prototype has been designed and constructed and experimental validations confirm the high radial stiffness and load capacity of the rotor suspension.

Interventional X-ray systems are used to acquire 2D and 3D images of complex anatomical structures (e.g. the cardiovascular system). These images provide a clinician with feedback in a medical procedure, which enables advanced minimally invasive treatments. A typical interventional X-ray system contains an X-ray source and detector, connected by a C-shaped arm. Several stacked motion systems enable the C-arm and imaging equipment to move spherically around an isocentre. This allows for 2D X-ray images to be taken at various projection angles. Other imaging techniques such as 3D computed tomography are enabled by this core functionality. Developments in interventional X-ray systems are often a compromise between performance, clinical usability, and cost. This paper presents three novel mechatronic architectures, which are designed to break through this trade-off. The proposed designs aim to improve the interventional X-ray system on multiple, application-specific levels. The first system focusses on improved image quality and clinical usability of 3D scans (high-end applications). A dual stage design allows for significantly extended and faster scanning motions, with a 55% smaller footprint in the operating room. It is based on a quasi-kinematic roll guide design, resulting in less nonlinear behaviour, and improved alignment of the imaging equipment. The second system decreases cost and installation requirements, while maintaining and adding to the current imaging capability (low-end applications). By reconsidering the degrees of freedom needed, a lightweight design is created (>50% mass reduction), with an improved stiffness to mass ratio. Both system 1 and 2 present an evolutionary improvement on existing architectures. As a revolutionary alternative, the third system pursues high-end performance and optimised workflow, at reduced overall cost. It features a compact and lightweight (~500 kg) mechatronic design which makes optimal use of the space available in the operating room. A full scale mock-up of this system has been built. Currently, a detailed design, including hardware realisation is being made for experimental performance validation at subsystem level.

Summary Background Maternal vitamin D status has been associated with bone mass of offspring in many, but not all, observational studies. However, maternal vitamin D repletion during pregnancy has not yet been proven to improve offspring bone mass in a randomised controlled trial. We aimed to assess whether neonates born to mothers supplemented with vitamin D during pregnancy have greater whole-body bone mineral content (BMC) at birth than those of mothers who had not received supplementation. Methods The Maternal Vitamin D Osteoporosis Study (MAVIDOS) was a multicentre, double-blind, randomised, placebo-controlled trial that recruited pregnant women from three study sites in the UK (Southampton, Oxford, and Sheffield). Eligible participants were older than 18 years, with a singleton pregnancy, gestation of less than 17 weeks, and a serum 25-hydroxyvitamin D (25[OH]D) concentration of 25–100 nmol/L at 10–17 weeks' gestation. P'articipants were randomly assigned (1:1), in randomly permuted blocks of ten, to either cholecalciferol 1000 IU/day or matched placebo, taken orally, from 14 weeks' gestation (or as soon as possible before 17 weeks' gestation if recruited later) until delivery. Participants and the research team were masked to treatment allocation. The primary outcome was neonatal whole-body BMC, assessed within 2 weeks of birth by dual-energy x-ray absorptiometry (DXA), analysed in all randomly assigned neonates who had a usable DXA scan. Safety outcomes were assessed in all randomly assigned participants. This trial is registered with the International Standard Randomised Controlled Trial registry, ISRCTN 82927713, and the European Clinical Trials Database, EudraCT 2007–001716–23. Findings Between Oct 10, 2008, and Feb 11, 2014, we randomly assigned 569 pregnant women to placebo and 565 to cholecalciferol 1000 IU/day. 370 (65%) neonates in the placebo group and 367 (65%) neonates in the cholecalciferol group had a usable DXA scan and were analysed for the primary endpoint. Neonatal whole-body BMC of infants born to mothers assigned to cholecalciferol 1000 IU/day did not significantly differ from that of infants born to mothers assigned to placebo (61·6 g [95% CI 60·3–62·8] vs 60·5 g [59·3–61·7], respectively; p=0·21). We noted no significant differences in safety outcomes, apart from a greater proportion of women in the placebo group with severe post-partum haemorrhage than those in the cholecalciferol group (96 [17%] of 569 mothers in the placebo group vs 65 [12%] of 565 mothers in the cholecalciferol group; p=0·01). No adverse events were deemed to be treatment related. Interpretation Supplementation of women with cholecalciferol 1000 IU/day during pregnancy did not lead to increased offspring whole-body BMC compared with placebo, but did show that 1000 IU of cholecalciferol daily is sufficient to ensure that most pregnant women are vitamin D replete, and it is safe. These findings support current approaches to vitamin D supplementation in pregnancy. Results of the ongoing MAVIDOS childhood follow-up study are awaited. Funding Arthritis Research UK, Medical Research Council, Bupa Foundation, and National Institute for Health Research.

Objective To compare the effectiveness of insulin pumps with multiple daily injections for adults with type 1 diabetes, with both groups receiving equivalent training in flexible insulin treatment.Design Pragmatic, multicentre, open label, parallel group, cluster randomised controlled trial (Relative Effectiveness of Pumps Over MDI and Structured Education (REPOSE) trial).Setting Eight secondary care centres in England and Scotland.Participants Adults with type 1 diabetes who were willing to undertake intensive insulin treatment, with no preference for pumps or multiple daily injections. Participants were allocated a place on established group training courses that taught flexible intensive insulin treatment (“dose adjustment for normal eating,” DAFNE). The course groups (the clusters) were then randomly allocated in pairs to either pump or multiple daily injections.Interventions Participants attended training in flexible insulin treatment (using insulin analogues) structured around the use of pump or injections, followed for two years.Main outcome measures The primary outcomes were a change in glycated haemoglobin (HbA1c) values (%) at two years in participants with baseline HbA1c value of ≥7.5% (58 mmol/mol), and the proportion of participants achieving an HbA1c value of Results 317 participants (46 courses) were randomised (156 pump and 161 injections). 267 attended courses and 260 were included in the intention to treat analysis, of which 235 (119 pump and 116 injection) had baseline HbA1c values of ≥7.5%. Glycaemic control and rates of severe hypoglycaemia improved in both groups. The mean change in HbA1c at two years was −0.85% with pump treatment and −0.42% with multiple daily injections. Adjusting for course, centre, age, sex, and accounting for missing values, the difference was −0.24% (−2.7 mmol/mol) in favour of pump users (95% confidence interval −0.53 to 0.05, P=0.10). Most psychosocial measures showed no difference, but pump users showed greater improvement in treatment satisfaction and some quality of life domains (dietary freedom and daily hassle) at 12 and 24 months.Conclusions Both groups showed clinically relevant and long lasting decreases in HbA1c, rates of severe hypoglycaemia, and improved psychological measures, although few participants achieved glucose levels currently recommended by national and international guidelines. Adding pump treatment to structured training in flexible intensive insulin treatment did not substantially enhance educational benefits on glycaemic control, hypoglycaemia, or psychosocial outcomes in adults with type 1 diabetes. These results do not support a policy of providing insulin pumps to adults with poor glycaemic control until the effects of training on participants’ level of engagement in intensive self management have been determined.Trial Registration Current Controlled Trials ISRCTN61215213.

In this study, malondialdehyde (MDA), ceruloplasmine (CER) and adenozine deaminase (ADA) concentrations were investigated in cattle with cystic echinococcosis. Group I consisted of 15 cattle with cystic echinococcosis whereas Group II consisted of 10 clinically healthy cattle aged 2-3 years. Venous blood samples were taken from the animals before being slaughtered in the Samsun province. At necropsy, suspiciousstructurs in lesions were examined parazitologically concerning cystic echinococcosis in various organs and animals with protoscolex formed the experimental group and the control group consisted of animals which were found clinically healthy and without any lesions in their examinations. Serum MDA, CER and ADA levels were measured in positive animals and compared with the levels of healthy animals. Serum concentrations of MDA, CER and ADA (mean ± standard deviation) of Group I were determined as 1.9 ± 0.6 nmol/ml, 10.2 ± 1.8 mg/dl and 43.2 ± 3.9 U/L whereas in the control group, they were 1.4 ± 0.7 nmol/ml, 5.6 ± 1.4 mg/dl and 19.5 ± 4.1 U/L respectively. There was a statistically significant difference in MDA (p < 0.05) and ADA (p < 0.001) values between Group I and II while the difference in CER value (p > 0.05) was not significant., Bu çalışmada, kistik ekinokokkozisli sığırlarda serum malondialdehit (MDA), seruloplazmin (CER) ve adenozin deaminaz (ADA) konsantrasyonlarının araştırılması amaçlanmıştır. Çalışmada 2-3 yaşlarında 15 adet kist hidatik (E.granulosus) ile enfekte hayvan Grup I’i ve 10 adet sağlıklı ve kist hidatik negative hayvan da Grup II’yi oluşturdu. Samsun yöresinde mezbahaneye gelen sığırlar venöz kan alındıktan sonra kesime sevk edildi. Nekropsi sonucu değişik organlarda kistik ekinokokkozis açısından şüpheli lezyonlardaki kistik yapılar parazitolojik olarak incelendi ve protoskoleks yönünden pozitif olan sığırlar çalışmanın deneme grubunu, klinik olarak sağlıklı ve organ muayenelerinde herhangi bir lezyon bulunmayan sığırlar ise kontrol grubunu oluşturdu. Pozitifliği saptanan hayvanların serum MDA, CER ve ADA düzeyleri ölçülerek sağlıklı hayvanlar ile kıyaslandı. Kistik ekinokokozis ile enfekte sığırlarda serum MDA, CER ve ADA düzeyleri sırası ile, 1,9 ± 0,6 nmol/ml, 10,2 ± 1,8 mg/dl ve 43,2 ± 3,9 U/L, kontrol grubu sığırlarda ise, 1,4 ± 0,7 nmol/ml, 5,6 ± 1,4 mg/dl ve 19,5 ± 4,1 U/L bulundu. Enfekte ve sağlıklı gruplar arasında serum MDA (p < 0,05) ve ADA (p < 0,001) düzeyleri yönünden fark önemli bulunurken, CER değerleri yönünden fark önemsiz bulundu

Publisher Copyright: © 2021 Proceedings of the 21st International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2021. All rights reserved. Aerostatic bearings are externally pressurized gas lubricated bearings. Aerostatic bearings are used in high speed and precision motion applications due to low friction and high accuracy. They use a restrictor to limit the flow of the gas into the bearing gap. The presence of the restrictor increases the stability of the bearing against self-excited vibrations. This study focuses on porous graphite restrictors and the effect of permeability on the behaviour of the bearing. The bearings were studied both experimentally and with a simulation model. Flat bearing pads with 37 mm diameter and different restrictor bulk permeability were manufactured and tested. Experimental measurements were conducted on a test setup allowing loading of the bearing against a ground steel plate. The load was supplied with a series of weights. The air gap was measured with a linear length gauge, measuring the displacement of the air bearing. The pressure was controlled with a regulator and the flow rate into the bearing was measured.In order to build an accurate simulation model, the permeability of the used material was calculated from the measured short circuit flow through each 4.5 mm thick sample. The flow in the porous material and in the restrictive layer follows Darcy’s law, the flow in the air gap is described by the Navier-Stokes-equation. The simulation model was validated with experimental results. Measurement and simulation results include the air gap height, load and flow rate at a supply pressure of 0.4 MPa. According to previous research and preliminary results the surface restrictor layer has increased the resistance of the bearing to self-excited air-hammer vibration, leading to a higher load capacity.

High aspect ratio manufacturing in the micro dimensional range by the micro milling process represents some difficulties for diverse applications such as micro moulds, micro channels, micro gears, miniaturized surgical instruments, etc. This study investigates the thin wall machining with different machining approaches and applies 3D finite element modelling (FEM) for the minimum machinable wall thickness to improve the experimental machining and enhance the quality of the machined features. The high stress distribution during machining the thin features are presented and the smallest machined wall is investigated. Finally, the FEM prediction resultsare compared against the experimental tests.

Portable machine tools are developed to address specific applications needs, such as machining of large components. However, they lack in performance such as stiffness. For such a low-stiffness portable machine tool, in this work, it is analysed the possibility and feasibility of employing the motors absorbed current measurements during actual machining operations as a means to monitor the cutting process and eventually compensate the tool deformations due to the cutting forces. In-process tool-path compensation achieved through a sensorized machine is of extreme interest from the costs point of view, especially for portable or dedicated task machine tool. In this paper, measurements of cutting forces, feed axes and spindle motors absorbed currents were carried out simultaneously for different cutting conditions. It is found that good correlations can be established between specific feature of the cutting force and axis motors absorbed current, the result demonstrates that the absorbed current measurements are reliable indirect measurements of the cutting forces and can therefore be employed in an in-process tool-path compensation.

Micro polishing is an important process when fine surface quality and low form error are required in the micro scale domain. This process has several differences from conventional polishing and some of the factors can not be neglected any longer. In this work, a study on the thermal behaviour of a micro hexapod-based machine is conducted. The main causes of thermal deformations are addressed and analysed. The contributions are then evaluated and compensation path strategies are discussed. The main criticalities when dealing with micro polishing are due to the small tools used. Micro tools require higher speeds than conventional polishing. High spindle speeds generate heat and therefore thermal deformations. This adds up to the movement of the Hexapod while performing polishing. The observed total deformation in the polishing tool axial direction reached 8.2 μm. Such a large deformation can introduce a potential error in the final material removal up to 50% if not adequately compensated.

The present work focuses on the influence of the composition of the protective gas (argon or nitrogen) used in laser‐based powder bed fusion (L‐PBF) on the nitrogen content, microstructure and hardness of AISI 316L austenitic stainless steel. L‐PBF of AISI 316L powder using Ar gas resulted in loss of nitrogen in the final part. On the other hand, L‐PBF using N2 gas resulted inan increase in nitrogen content in the final part, showing that nitrogen is absorbed during L‐PBF manufacturing in N2 gas. The nitrogen absorption implies that the build part is actually AISI 316LN rather than AISI 316L.The microstructures of 316L specimens manufactured in both atmospheres exhibited highly elongated γ‐austenite grains, with acellular structure. The hardness of the part manufactured in N2 gas was systematically higher than the part manufactured in Ar. For the part manufactured in Ar, a clear gradual decrease in hardness was observed with increasing distance from the build plate, whilefor the N2 manufactured part this hardness decrease is first observed at some distance from the build plate.For the part manufactured in Ar, a larger variation in the measured nitrogen content was observed. Moreover, a systematically lower and position dependent micro‐hardness and inhomogeneous etching response of this specimen indicate an inhomogeneous microstructure in the build.The results demonstrate that the nitrogen content of L‐PBF manufactured AISI 316L depends on the composition of the gas atmosphere used in the chamber. It is discussed qualitatively how desorption and absorption of nitrogen from the applied atmosphere play a role on the resulting composition and microstructure of the build part.

Different fabrication methods can be applied for micro fabrication, all characterized by their specific processing time and cost. However, by using the additive manufacturing (AM) technologies for direct micro manufacturing of complex micro geometries the average production time and cost can be drastically reduced. This study investigates an AM-based fabrication method for the production of microstructure surfaces with different feature sizes (50-150 μm). The experiments presented in this work have been carried out in a specifically designed vat photopolymerization AM machine suitable for precision printing developed, built and validated at the Technical University of Denmark (DTU). The AM method was evaluated in terms the capability of the system to produce micro pillars and holes array in different sizes and with increasing geometrical complexity.

Images semantic segmentation on moulds is presented to achieve automatic and continuous defect detection during injection moulding (IM) processing. Generally, a vital prerequisite of training a robust segmentation neural network is to build a suitable dataset, which requires a large amount of image data with plentiful mould colours, different illumination conditions and specific defect labels. The approach requires long data preparation to collect a sufficient dataset, which could meet the needs of online defect detection during injection moulding. To address robust dataset development, the present work uses 3D CAD modelling software to fabricate defects and colours on moulds, creating an augmented dataset mixed with virtual data and real-process data. In this investigation, moulds printed by vat photopolymerization is used as object for which both mould pictures during injection moulding process and virtual mould pictures from 3D modelling software are collected. Mixed datasets with different proportion of virtual images are labelled and fed into the segmentation neural network. The experimental work shows that the proposed method provides a reliable augmentation on the dataset for subsequent IM semantic segmentation framework.

Highly miniaturized systems find applications in key technological fields such as health-care, mobility, communications and optics. Required innovations for precision manufacturing of micro components can be achieved through post-process and in-process measurement of process input and output parameters. Hence, it is of critical importance to reduce the measurement and optimization effort, since process and product quality control can take a significant part of the production time in micro manufacturing. To solve this challenge, research is undertaken in order to define, investigate, implement and validate the “Product/Process Micro Manufacturing Fingerprint” concept. In particular, in the Horizon2020 Innovative Training Network “Process Fingerprint for Zero-defect Net-shape MICROMANufacturing”, 9 beneficiaries and 14 industrial partners are collaborating to establish this concept for several manufacturing technologies, such as micro injection and micro ultrasonic moulding, micro mechanical and micro plasma polishing, micro electrical discharge machining, micro electrochecmical machining, micro grinding, micro laser machining, micro extrusion, micro metrology, micro sintering. The project has reached its goals of developing novel methods in micro scale manufacturing process monitoring and control, as well as micro and sub-micro product quality assurance. The overall result has been the establishment of effective micro product and process fingerprints for the considered manufacturing technologies.

Although micro-milling has been regarded as the most promising method to repair the micro-defects on KH2PO4 (KDP) optics surfaces, residual tool marks are inevitably generated on the repaired surfaces and would pose a direct impact on the laser-induced damage (LID) threshold of repaired KDP optics. In this work, a residual tool marks model was developed to characterize the repaired surface morphologies processed by different milling strategies (e.g. layer-milling and spiral-milling strategies). Then the predicted tool marks were utilized to built a light-filed intensity modulation model to reveal the relationship between the residual tool marks and its related optical performance. The practical of LID tests well verified the simulation results. It was revealed that the milling strategies indeed have a significant influence on the ultimate LID resistance of KDP optics after repair through impacting the generation of residual tool marks. The spiral-milling method with a smaller path interval can produce a laser-friendly repaired surfaces, which have a equivalent laser-induced resistance with the original fly cutitng surface, while the layer-milling method has a higher machining efficiency. Therefore, an optimized repair procedure, adopting layer-milling path as rough milling and spiral-milling as fine milling, was proposed for pratical engineering application in ICF facilities in the future.

With the increase in use of L-PBF for functional components, an increase in productivity demands higher laser power and continuous operation. However, both these factors can affect the optics involved. The principal components of a Laser Powder Bed Fusion system are the galvanometer mirrors and the focusing lens.In the present work a method for identification and quantification of thermal lensing is proposed. Laser powder bed fusion experiments of stainless steel 316L powder was carried out at varying scan speeds and scan strategies in order to study the effects, of long exposure times, on the quality of single layer scans.It was observed that the heating of silver-coated mirrors under continuous exposure led to a significant decrease in the beam quality as evidenced by weld track widening and loss in depth of melt pool penetration. Power measurements conducted at various locations along the beam path indicated that the mirrors were absorbing up to 42 % of the total power coming from the laser while also defocusing the beam.Thus demonstrating the importance of including identification and quantification of thermal influence and possible instability of the optical elements as cause for irregular weld tracks.

This paper presents the optimization of a state-of-the-art self-peeling vat for vat photopolymerization (VP) processes. One of the research goals of the Additive Manufacturing (AM) group from the Technical University of Denmark is to achieve the highest resolution, maximum precision and process optimization for the AM machines and the fabricated components. To achieve this goal, it is essential to have control over every single stage of the manufacturing process. One concern mayor concern in VP is the vat performance, which has to withstand with adhesion forces and wear. The previous setup designed by this research group already outperformed industrial vats by 814% [1], by lowering the normal forces induced by the adhesion between the vat and the part with the aid of a flexible membrane system. Although an improvement on the release-capability was achieved, failure was found in several materials with higher material bonding, which ultimately deformed the surface of the parts. In this work, optimization is achieved by increasing the surface area of the vat, diminishing the stress on the membrane. The building area is moved from the center which creates different peeling angles on each side of the part. The angle asymmetry combines easy peeling with low forces, together with an induced passive tilting mechanism that leads to higher quality of the manufactured samples when microfeatures are present.

Additive Manufacturing (AM) is a notable procedure for direct production of miniaturized polymer components, mainly due to the ability of the process to produce complex geometries with time and cost effective iteration cycles in the development of new plastic products. This study evaluate the capability of the vat photopolymerization in terms of geometry, when printing features of different sizes and shape. Continuous Liquid Interface Production (CLIP) technology was used for printing the features which is a new method to produce monolithic polymer parts at high speed. For this purpose, two test artifact specimens designed with micro features of different geometries and printed in different batches and evaluated the variability of the results in a single and in various prints.

Most commercially available laser powder bed fusion (L-PBF) systems are limited to process one material at a time. The ability to spatially apply multiple materials within the same component will strongly expand the available design space for engineers. A typical problem with multi-material components is stress concentration at discrete material interfaces. Functionally graded interfaces could be used to overcome this limitation. In this work, an open-architecture L-PBF system from Aurora Labs was used to mix and process stainless steel 316L and maraging steel MS1 powder. Thereby, continuous and discrete interfaces between both materials were generated and characterized regarding microstructure, micro-hardness, and elemental composition. An L-PBF process window was found to gradually change the composition of 316L to MS1 creating a continuous interface. The controlled mixing of the powders in each layer indicates the versatility of the powder dispensation setup for multi-material combinations. This contribution will further pave the way towards the development of functionally graded L-PBF components.

Continuous Liquid Interface Production (CLIP) is an additive manufacturing (AM) method developed as an evolution of the Digital Light Processing (DLP) principle. Utilizing an oxygen-permeable window below the ultraviolet image projection plane, the step-wise motion of the DLP printer can be avoided by maintaining a persistent liquid interface, thus allowing for a continuous growth of the printed specimen. To investigate the capabilities of this new process, a state-of-the-art CLIP AM machine was utilized to manufacture a series of reference specimens developed following the design of existing metrological transfer standards. The reference specimens were measured by a tactile coordinate measuring machine (CMM) to assess the manufacturing capability of the CLIP printer. Measurands included dimensions of 1D, 2D and 3D geometrical features as well as form errors (flatness, roundness, sphericity). Specifically, a flat hole-plate containing a grid of 25 evenly spaced holes (nominal diameter 5.5 mm, nominal pitch 25 mm) was used to assess the in-plane printing accuracy and precision of the holes’ centres. Additionally, a ball-plate specimen containing 4 spheres (nominal diameter 22 mm) was produced measured to characterise the sphericity, as well as the printing accuracy and precision of the spheres’ centres. The metrological characterization of the two reference specimens by CMM metrology allowed to determine the production capability of the used CLIP machine, and to highlight advantages and limitations of the CLIP method. The traceability of the CMM measurements was established by performing an uncertainty assessment using the calibrated artefacts corresponding to the two additively manufactured CLIP specimens. Eventually, the data collected will enable adjustments for improving the manufacturing accuracy of the CLIP machine and for paving the way towards the quality assurance of production based on the CLIP technique.