In-process range-resolved interferometric (RRI) 3d layer height measurements for wire + arc additive manufacturing (WAAM)

In this work a range resolved interferometry (RRI) instrument for absolute distance measurements is integrated into a wire + arc additive manufacturing (WAAM) system to provide in-process monitoring of layer height, and prospects for volume and profile monitoring are discussed. Interferometry as a coherent optical technique offers a straightforward in-process measurement even in the harsh welding environment, as compared to non-coherent techniques based either on laser profiling or camera vision systems. RRI can be accomplished at significantly lower cost, and with higher depth of field (up to 10s of cm) than existing optical coherence tomography based weld monitoring. In this experiment titanium feedstock was used to create a 150mm long, 13.5mm high weld-wall comprised of 11 welded layers. The RRI in-process measurements are in very good agreement with both mid-process, on-machine micrometer measurements taken by hand after each weld, and post-process laser scanning measurements of the completed wall. The high depth of field allows direct referencing of the layer height measurements to the build plate making the measurement independent of the motion system and build plate bending, considerably lowering uncertainties. This, together with the capability for cost-effective in-process measurements in harsh environments, should make the proposed approach very interesting for routine use in WAAM systems.

A Sequential Inspection Procedure for Fault Detection in Multistage Manufacturing Processes

Fault diagnosis in multistage manufacturing processes (MMPs) is a challenging task where most of the research presented in the literature considers a predefined inspection scheme to identify the sources of variation and make the process diagnosable. In this paper, a sequential inspection procedure to detect the process fault based on a sequential testing algorithm and a minimum monitoring system is proposed. After the monitoring system detects that the process is out of statistical control, the features to be inspected (end of line or in process measurements) are defined sequentially according to the expected information gain of each potential inspection measurement. A case study is analyzed to prove the benefits of this approach with respect to a predefined inspection scheme and a randomized sequential inspection considering both the use and non-use of fault probabilities from historical maintenance data.

Optical In-Process Measurement: Concepts for Precise, Fast and Robust Optical Metrology for Complex Measurement Situations

Optical metrology is a key element for many areas of modern production. Preferably, measurements should take place within the production line (in-process) and keep pace with production speed, even if the parts have a complex geometry or are difficult to access. The challenge for modern optical in-process measurements is, therefore, how to simultaneously make optical metrology precise, fast, robust and capable of handling geometrical complexity. The potential of individual techniques to achieve these demands can be visualized by the tetrahedron of optical metrology. Depending on the application, techniques based on interferometry or geometrical optics may have to be preferred. The paper emphasizes complexity and robustness as prime areas of improvement. Concerning interferometric techniques, we report on fast acquisition as used in holography, tailoring of coherence properties and use of Multiple simultaneous Viewing direction holography (MultiView), self reference used in Computational Shear Interferometry (CoSI) and the simultaneous use of several light sources in Multiple Aperture Shear Interferometry (MArS) based on CoSI as these techniques have proven to be particularly effective. The use of advanced approaches based on CoSI requires a transition of the description of light from the use of the well-known wave field to the coherence function of light. Techniques based on geometric optics are generally comparatively robust against environmental disturbances, and Fringe Projection (FP) is shown to be especially useful in very demanding measurement conditions.

INVESTIGASI SUMBER AIR TANAH MENGGUNAKAN METODE GEOLISTRIK RESISTIVITAS KONFIGURASI SCHLUMBERGER DAN PENGEBORAN

Penelitian ini bertujuan untuk mencari keberadaan sumber air tanah. Metode yang digunakan adalah geolistrik resistivitas konfigurasi schlumberger dan proses pengeboran. Pengukuran dilakukan pada 4 titik dengan bentangan 400 meter dan jarak antar elektroda 10 meter. Hasil penelitian menunjukkan indikasi keberadaan air tanah ditemukan pada titik pengukuran 3 kedalaman 36-55 meter dibawah permukaan tanah dengan nilai resistivitas sebesar 0,97 Ωm. Proses pengeboran dilakukan pada titik 3 sesuai rekomendasi, adapun hasil dari pengeboran menunjukkan informasi keberadaan air tanah ditemukan pada kedalaman 46 m dibawah permukaan tanah, hasil ini sesuai dengan informasi yang diperoleh dari hasil penelitian. Identifikasi keberadaan air tanah menggunakan metode geolistrik resistivitas terbukti cukup ramah lingkungan, karena tidak ada kerusakan lingkungan yang ditimbulkan. Kata kunci: air tanah, geolistrik resistivitas, konfigurasi schlumberger, pengeboran. This study aims to determine the existence of groundwater. The method used in this research is the geoelectrical resistivity method with schlumberger configuration and drilling process. Measurements were made at 4 points with a span of 400 meters and a distance between electrodes of 10 meters. The results showed indications of the presence of groundwater were found at measurement point 3, a depth of 36-55 meters below the ground surface with a resistivity value of 0.97 Ωm. The drilling process was carried out at point 3 according to the recommendations, while the drilling results showed information on the presence of groundwater at a depth of 46 m below the ground surface, this result is the same as the information obtained from the research results. The identification of groundwater using geoelectrical resistivity method is proven to be quite environmentally friendly because there is no environmental damage caused. Keywords: drilling, geoelectrical resistivity, groundwater, schlumberger configuration.

Handling Measurement Delay in Iterative Real-Time Optimization Methods

This paper is concerned with the real-time optimization (RTO) of chemical plants, i.e., the optimization of the steady-state operating points during operation, based on inaccurate models. Specifically, modifier adaptation is employed to cope with the plant-model mismatch, which corrects the plant model and the constraint functions by bias and gradient correction terms that are computed from measured variables at the steady-states of the plant. This implies that the sampling time of the iterative RTO scheme is lower-bounded by the time to reach a new steady-state after the previously computed inputs were applied. If analytical process measurements (PAT technology) are used to obtain the steady-state responses, time delays occur due to the measurement delay of the PAT device and due to the transportation delay if the samples are transported to the instrument via pipes. This situation is quite common because the PAT devices can often only be installed at a certain distance from the measurement location. The presence of these time delays slows down the iterative real-time optimization, as the time from the application of a new set of inputs to receiving the steady-state information increases further. In this paper, a proactive perturbation scheme is proposed to efficiently utilize the idle time by intelligently scheduling the process inputs taking into account the time delays to obtain the steady-state process measurements. The performance of the proposed proactive perturbation scheme is demonstrated for two examples, the Williams–Otto reactor benchmark and a lithiation process. The simulation results show that the proposed proactive perturbation scheme can speed up the convergence to the true plant optimum significantly.

Differences in hip fracture care in Europe: a systematic review of recent annual reports of hip fracture registries

Purpose Hip fractures are of growing interest due to their increasing number, subsequent functional decline and high institutionalization rate of patients, mortality, and costs. Several process measurements are essential for hip fracture care. To compare and improve these, hip fracture registries in Europe became popular. This systematic review aims to describe the differences between hip fracture registries in Europe as well as the differences in hip fracture treatment between countries. Methods A systematic search using the keywords “hip fracture” AND “national” AND “database OR audit OR registry OR register” was performed in PubMed, Embase and Cochrane Library according to PRISMA guidelines till 3rd December 2020. Recent annual reports of identified hip fracture registries in Europe were additionally identified in June 2021. Comparisons of most common case-mix, process and outcome measurements were performed. Results 11 registries in Europe were identified. Differences were observed regarding inclusion criteria of the different registries. Comparison of the different registries was difficult due to differences in the way to report measurements. While mortality rates differed substantially between countries, most of the process measurements met recommendations according to recent guidelines. Conclusion Hip fracture registries were a valid tool to compare hospitals within one country. However, a comparison between registries of different countries should have also been easily possible. For this, the registries need to make their data easily accessible and further unify their way of measuring and reporting.

Adaptive First Principles Model for the CAS-OB Process for Real-Time Applications

A model-based system for real-time monitoring and operational support has been developed for the Composition Adjustment by Sealed argon-bubbling with Oxygen Blowing (CAS-OB) process. The model of the system is based on a previously developed dynamic model using first principles, i.e., mass and energy balances, reaction kinetics, and thermodynamics. Adaptive estimation of state variables has been implemented using a Kalman filter to ensure that the model is able to correct for deviations between measured and calculated temperatures in real-time operation. The estimation technique reduces the standard deviation of the predicted end temperature from 19.5 °C to 5.5 °C in a data series with more than 1000 heats. The system also includes an endpoint optimisation, which calculates the amount of scrap or oxygen to be added to achieve the target temperature at the end of the heat. The model has been implemented in the Cybernetica® CENIT™ framework. The overall model can be regarded as a hybrid digital twin, where a first principles model is adapted in real time using process measurements. The system also includes user interfaces for operators where process predictions can be followed, and suggested optimised inputs are presented. The system has been deployed at two refining stations at SSAB Europe OY in Raahe, Finland. The optimized suggestions for oxygen and scrap are presented to the operators in the graphical user interface. A projected temperature profile is calculated into the near future using the planned operational procedure as well as the projected temperature profile using optimised inputs. Both profiles are displayed in the user interface. Based on these trajectories, the operator can decide on whether to follow the nominal trajectory, or the recommendation from the optimisation This will help the operators make better decisions, which in turn reduces the number of rejected heats in the CAS-OB process.

A New Prototype for Automatic Identification of Stone Block Internal Structure

Nowadays, the inner shape and economic viability of a stone block is dependent on the skill and experience of the “expert” that makes predictions based on external observations. This actual procedure is an extremely high empirical method, and when it fails, substantial work, time, and money is wasted. At present, researchers are committed to developing models to predict the stone block internal structure based on non-destructive tests. Ultrasonic tomography and electrical resistivity tomography are the tests that best fit these objectives. Trying to improve the existing procedures for collecting stone information and data exporting, a novel approach to perform both tomographies is proposed in this paper. This novel approach presents sound advantages regarding the current manual procedure: namely, (i) high accuracy due to a new automatic positioning system; (ii) no need for highly skilled operators to process measurements; (iii) measurements are much easier to derive, and results are quickly delivered. A comparison between the new automatic process and the current manual procedure shows that the manual procedure has a very low accuracy when compared to the new developed automatic system. The automatic measurements show extremely significant time savings, which is a relevant issue for the future competitiveness of the stone sector.

A novel device for in-situ force measurements during laser powder bed fusion (L-PBF)

Purpose The purpose of this paper is to detail the design and first use of a force transducer device to study the development of forces during the laser-powder bed fusion (L-PBF) process from which residual stresses can be inferred. Design/methodology/approach The proposed novel device consists of an array of load cells for in-situ measurement of forces over time during the L-PBF additive manufacturing process. Measurements of the developed forces layer by layer were recorded in a first build using a 67-degree rotating scan strategy using Inconel 625 build material. Findings Preliminary experimental results from in-situ measurements using a 67-degree rotating scan strategy showed that the forces induced in the first five layers represented approximately 80% of the maximum on completion of the build and were distributed such as to induce concave deformation of the part, i.e. tension in the centre and compression at the edges of the part. Originality/value This paper describes a novel device for in-process measurement of the spatial distribution and time-varying nature of the forces induced during the L-PBF process as well as an evaluation of the residual forces following the completion of the build.