Manufacturing Accuracy Research Articles

Accuracy of thick and thin intraocular lens power formulas using paraxial vergence calculation.

To compare the prediction errors of several thick IOL formulas to a thin lens approach using variations of the same paraxial vergence calculation formula. Department of Ophthalmology, Randers Regional Hospital, Denmark. Prospective, non-interventional study. We prospectively and consecutively performed optical low coherence reflectometry biometry in 132 eyes with subsequent phacoemulcification and insertion of the same aspherical IOL model. Clinical refraction was performed two months postoperatively. We retrospectively used the same paraxial vergence formula and varied only the methods for calculating the postoperative IOL position, thickness, and curvatures to construct four formulas: Næser I formula based on thick lens calculation using the manufacturer´s cutting card information; Næser II formula based on thick lens calculation using calculated IOL data from open sources; Næser III formula based on thick lens calculation and a fixed IOL thickness of 0.62 mm; Næser IV formula based on thin lens calculation with fixed IOL position 0.31 mm anterior to the postoperative capsule. Each formula was optimized separately, hereby assuring a mean error of zero. The prediction error (PE) was defined as the difference between the measured and predicted spherical equivalent refraction. Mean absolute error amounted to 0.30 (±0.26) D for all four formulas with no statistically significant difference. PE averaged zero for short, normal, and long eyes. The additional optical information provided by thick IOL calculations appears insignificant compared to other sources of error, related to the accuracy of IOL manufacturing, natural lens refractive index, and postoperative refraction.

Effect of an AC-DC composite longitudinal magnetic field on the microstructure and mechanical properties of WAAM Al-5 %Mg alloy

To address issues of poor forming accuracy, high porosity, and inadequate mechanical properties in wire arc additive manufacturing of aluminum alloys, this study applied external direct current (DC) and alternating current (AC) composite magnetic fields (ECMF) (AC+DC) in cold metal transition wire arc additive manufacturing (CMT-WAAM) of Al-5 % Mg alloys. The aim was to enhance the quality of forming and overall mechanical properties of the deposited specimens. Optimal ECMF (AC+DC) parameters-DC 3 A, AC 1 A, and alternating frequency 100 Hz-were determined through orthogonal experiments. Results showed that ECMF (AC+DC) facilitated arc expansion and stirred the molten pool via Lorentz force generation, thereby accelerating molten flow and improving forming precision. Compared to specimens without ECMF (AC+DC), those with ECMF (AC+DC) exhibited reduced porosity (1.07 % to 0.31 %, a decrease of 71.03 %) and finer grain size in the deposited layer (84.80 ±30.5μm to 69.10±25.1μm, an 18.51 % decrease). Additionally, average microhardness increased (83.83 HV to 96.70 HV, a 15.35 % increase), transverse tensile strength improved (239.66±1.6 MPa to 263.00± 1 MPa, a 9.86 % increase), and elongation at break enhanced from 25.50±3.8 % to 27.17±0.33 %. Longitudinal tensile strength also rose (232.33±14.33 MPa to 248.33±8.33 MPa, a 6.88 % increase), with elongation at break increasing from 19.00±7.5 % to 19.40±4.2 %. Moreover, the mechanical properties' anisotropy decreased. Consequently, ECMF (AC+DC) significantly enhanced the overall properties of CMT-WAAM Al-5 % Mg alloy deposition, providing valuable insights for extending engineering applications of Al-5 % Mg alloy WAAM.

Additively manufactured conductive and dielectric 3D metasurfaces for independent manipulation of broadband orbital angular momentum

Recent developments in conductive and dielectric multi-material additive manufacturing have generated significant interest for their potential to enhance the performance of electronic devices. Lights-out digital manufacturing, a sophisticated multi-material printing technique, facilitates the seamless sintering of silver nanoparticles and acrylate inks, enabling the creation of functional electronic devices. In this study, the LDM process is utilized to prototype intricate 3D metasurface designs. A comprehensive analysis of the properties of the printed materials confirms the practicality of this multi-material printing approach. The research examines various element distributions within multi-metal layer structures, including carbon, phosphorus, oxygen, sulfur, and fluorine, to investigate the interfaces between conductive and dielectric structures. In addition, the conductivities of silver nanoparticle inks at different curing temperatures are studied to identify optimal printing conditions. Both the conductive and dielectric inks exhibit precisely controlled particle sizes and exceptional stability, which are critical for accurate additive manufacturing. Using this sophisticated printing solution, the paper presents a broadband 3D metasurface engineered to independently manipulate two distinct orbital angular momentum states in the V-band (60–70 GHz) and W-band (79–90 GHz), suitable for high-speed wireless communications. The integration of deep neural networks helps reduce the phase coupling between the frequency bands, enabling independent control of the OAM states. The structure of the dual-band metasurface features four distinct silver layers yet is fabricated on a single ultra-thin planar substrate, demonstrating its potential for applications in future wireless communication systems.

LUT-based phase error compensation method for large-step phase-shifting algorithm in DLP4500-based FPP system.

As a low-cost professional digital light projection device, the DLP4500 have been widely applied in fringe projection profilometry (FPP), for both laboratory and practical application. However, our recent experiments revealed a new hardware-induced projection instability when the projection pattern data exceeds its buffer capacity (48 bits). This phenomenon undermines the measurement accuracy advantage of the phase-shifting (PS) algorithms with large number of shifting steps, and eventually leads unwanted and complicated error to 3D reconstruction. In this paper, we experimentally investigate the new hardware-induced phase error and proposed a LUT-based phase error compensation method. In this method, a standard plate with a precision manufactured plate is used as the standard reference for the phase error evaluation, where an ideal plane fitting and the projector pixel reprojection process are introduced to generate the ideal reference phase. Comprehensive experiments are conduct to verify the stability of the proposed method in LUT creation. Comprehensive experiments are conduct, and the results show that (i) the method works creates LUTs stably at different plate positions, (ii) the plate with regular manufacturing accuracy (not exceeding 0.01 mm) can meet the application requirements of the proposed method. Both quantitative and qualitative experimental results successfully verify the effectiveness of proposed method in LUT creation and phase error reduction.

Innovations in Additive Manufacturing for Socket Fabrication: An Overview

Additive Manufacturing (AM) has transformed the prosthetics industry, particularly in socket production, which plays a critical role in the comfort, fit, and functionality of prosthetic limbs. This article examines the latest advancements in AM technologies and their applications in socket fabrication. Key techniques like stereolithography (SLA), selective laser sintering (SLS), and fused deposition modeling (FDM) have facilitated the production of highly personalized, lightweight, and durable prosthetic sockets. These methods not only improve design precision but also allow for the use of biocompatible, flexible materials, enhancing both comfort and functionality. Digital design tools have streamlined the production process, reducing lead times and costs, while improving accuracy and repeatability in socket manufacturing. This review explores the current state of AM in prosthetic socket development, emphasizing the benefits, challenges, and future directions of this fast-evolving field. By analyzing recent research and case studies, the article provides insights into how AM is reshaping prosthetics, offering more accessible solutions for individuals needing prosthetic limbs. It also discusses the challenges of material selection, regulatory considerations, and the potential for scaling production for broader use.

Фотонные кристаллы: оптимизация характеристик и перспективы оптических приложений

Background: Photonic crystals (PCs) have emerged as a new material for light manipulation, providing unprecedented control over light-matter interaction. This unique capacity is due to their periodic dielectric structure, which may produce photonic band gaps that impact photon transmission. Objective: The article summarizes current advances in photonic crystal design and use, focusing on their significance in creating next-generation optical systems. Methods: The article performed a complete literature analysis, concentrating on the most recent PC production and characterization approaches. Innovative techniques like 3D printing, nanoimprint lithography, self-assembly, and advanced computational modelling were studied in depth to optimize their optical characteristics. Results: Recent studies show that PC manufacturing accuracy has increased significantly, allowing for more effective light manipulation and enhanced optical device functioning. Applications such as ultrasensitive sensors, improved optical fibers, and innovative laser designs demonstrate PCs' rising value. Conclusion: The ongoing advancement of photonic crystal technology is laying a solid basis for the next generation of optical devices. These developments improve existing applications and provide opportunities to investigate new functionality in optical and other electromagnetic systems. Incorporating PCs into numerous technical sectors holds the prospect of significant advances in both commercial and scientific fields.

Fabrication of Circular Defects in 2-Dimensional Photonic Crystal Lasers with Convex Edge Structure

We have developed circular defects in 2-dimensional photonic crystal lasers that allow current injection for interconnected optical communications. However, when cleaving the sample to measure the output light, the output light intensity changes due to the cleaving position. In a previous study, we proposed a new end face structure called a convex edge structure. In this paper, we design the electron beam lithography patterns to fabricate this structure. With this design, it is possible to eliminate the effect of different cleaving positions and ensure that the cleavage tolerance is larger than the cleavage position error. We also develop the fabrication technology for this structure, fabricate samples, and measure the output light experimentally. The optical properties of the fabricated sample are similar to well-fabricated samples with normal cleavage edge faces. We are assured that these results contribute to future work such as accurate manufacturing and improving the end face configuration to obtain higher outputs.

In vitro comparison of guide planes for removable partial dentures prepared with CAD-CAM-assisted templates, guiding rod templates, and freehand

ObjectivesThis study aimed to evaluate the accuracy of computer-aided design and computer-aided manufacturing (CAD-CAM)-assisted templates (CCAT), guiding rod templates (GRT), and freehand (FH) preparation of guide planes. MethodsForty-five identical maxillary resin casts were divided into three groups, in which the guide planes of the two abutment teeth were prepared using a CCAT (n=15), GRT (n=15), and FH (n=15). The CCAT and GRT were digitally designed on a digital cast of virtually prepared guide planes and fabricated using three-dimensional printing (3DP) technology. To assess the 3D trueness, the prepared guide planes were digitally scanned and compared to the virtually designed guide planes. The angle deviation was measured to assess the trueness of the direction of the guide plane preparation. Shapiro–Wilk and Levene's tests were used to check the normality and equivalence of the variance of the data. The data were compared by using the Kruskal‒Wallis H test (α=0.05). ResultsThe CCAT group exhibited significantly better 3D trueness (78.5±19.8 μm) than the GRT group (211.3±42.4 μm, p<0.05) and the FH group (198.9±44.3 μm, p<0.05). Additionally, the CCAT group (1.31±0.50°) showed significantly smaller direction trueness compared to the GRT (4.65±0.72°, p<0.05) and FH (5.64±0.70°, p<0.05) groups. ConclusionsThe novel CAD-CAM-assisted template significantly improved the quality of the guide planes compared with the GRT and FH procedures. This enhancement suggests that removable partial dentures can be predictably inserted immediately after guide plane preparation. Clinical SignificanceCAD-CAM-assisted templates improve the quality of guide plane preparation.

Analysis and Verification on Buckling Mechanism of Spatial Tow Steering in Automated Fiber Placement

Automated fiber placement (AFP) enables the efficient and precise fabrication of complex-shaped aerospace composite structures with lightweight and high-performance properties. However, due to the excessive compression on the inner edge of the tow placed along the curved trajectory, the resulting defects represented by buckling and wrinkles in spatial tow steering can induce poor manufacturing accuracy and quality degradation of products. In this paper, a theoretical model of tow buckling based on the first-order shear deformation laminate theory, linear elastic adhesion interface and Hertz compaction contact theory is proposed to analyze the formation mechanism of the wrinkles and predict the formation of defects by solving the critical radius of the trajectory, and finite element analysis involving the cohesive zone modeling (CZM) is innovated to simulate the local buckling state of the steered tow in AFP. Additionally, numerical parametric studies and experimental results indicate that mechanical properties and geometric parameters of the prepreg, the curvature of the placement trajectory and critical process parameters have a significant impact on buckling formation, and optimization of process parameters can achieve effective suppression of placement defects. This research proposes a theoretical modeling method for tow buckling, and conducts in-depth research on defect formation and suppression methods based on finite element simulation and placement experiments.

Maschinelles Lernen als modernes Werkzeug für Additive Fertigung

Abstract In modern manufacturing systems, quality monitoring is crucial for efficient and cost-effective production. Conventional systems rely on thresholds and process windows, but machine learning (ML) techniques promise greater accuracy and efficiency. However, pre-processing the data is still timeconsuming. This paper presents an approach to visually verify two Variational Autoencoders (VAEs) using contextual information such as print job numbers and timestamps, with the aim of predicting time series data from image data to optimize additive manufacturing processes in time. The approach focuses on the Digital Light Processing (DLP) printing process and emphasizes the importance of accurate data pre-processing and contextual visualization. The approach utilizes VAE-generated latent spaces to improve prediction accuracy in additive manufacturing and implement quality monitoring without thresholds and process windows.

FreeArcs Knife: a Novel Stereotactic Radiosurgery System

This paper describes the design of an innovative linear accelerator image-guided radiosurgery (IGRS) device, which is based on a composite twofold rotary gantry structure. The paper discusses five aspects of the innovative device: its overall composition, the safety net space created by the accelerator radiation head as it rotates around the patient's longitudinal axis, the non-coplanar spherical coverage in the direction of the incidence angle for quasi-4π delivery, the structural features of the composite twofold rotary gantry, and the processes of treatment planning and implementation. It elaborates on the device's manufacturing feasibility, safety, effectiveness, accuracy, and efficiency. The conclusion is that this innovative device design holds significant development value and market promotion potential.

Trueness and precision of digital light processing fabricated 3D printed monolithic zirconia crowns

ObjectivesThe present study aimed to evaluate the trueness and precision of monolithic zirconia crowns (MZCs) fabricated by 3D printing and milling techniques. MethodsA premolar crown was designed after scanning a prepared typodont. Twenty MZCs were fabricated using milling and 3D-printing techniques (n = 10). All the specimens were scanned with an industrial scanner, and the scanned data were analyzed using 3D measurement software to evaluate the trueness and precision of each group. Root mean square (RMS) deviations were measured and statistically analyzed (One-way ANOVA, Tukey's, p ≤ 0.05). ResultsThe trueness of the printed MZC group (140 ± 14 μm) showed a significantly higher RMS value compared to the milled MZCs (96 ± 27 μm,p < 0.001). At the same time, the precision of the milled MZCs (61 ± 17 μm) showed a significantly higher RMS value compared to that of the printed MZCs (31 ± 5 μm,p < 0.001). ConclusionsThe Fabrication techniques had a significant impact on the accuracy of the MZCs. Milled MZCs showed the highest trueness, while printed MZCs showed the highest precision. All the results were within the clinically acceptable error values. Clinical SignificanceAlthough the trueness of the milled MZCs is higher, the manufacturing accuracy of the 3D-printed MZCs showed clinically acceptable results in terms of trueness and precision. However, additional clinical studies are recommended. Furthermore, the volumetric changes of the material should be considered.

Testing of spherical mirrors with extremely large R numbers using a quasi-autocollimation method.

Spherical mirrors with large R numbers have extreme advantages in optical systems with large apertures and long focus lengths for improving imaging resolution and field of view. Their manufacturing and testing accuracy directly affects the final wavefront aberration of the systems. However, due to the influence of airflow disturbance in the long optical path, testing large R number spherical mirrors with high precision is difficult for the direct testing method. In this paper, a quasi-autocollimation test (QACT) method is proposed based on the consistency and reverse compensation between sphere and paraboloid with large R numbers. In QACT, the length of the testing path is reduced to half, and the test sensitivity of the surface figure error is doubled. According to the Kolmogorov turbulence theory, the suppressed degree of QACT to airflow disturbance is quantitatively evaluated, and QACT can suppress the random error in test to 35%. A comparative experiment between direct test and QACT method is carried out on a ∅100 spherical mirror with 8-meter radius of curvature. Airflow disturbance in the testing environment is calculated by mathematical fitting and the repeated accuracy is improved from 4 nm to 1.4 nm in a single test using the QACT method, which is consistent with theoretical analysis. The research results will provide a new strategy for ultra-precision and efficiency tests of large R number spherical mirrors.

Process development and validation of next generation 3D calibration standards for application in optical microscopy

Abstract A scalable wafer-based fabrication process for a new generation of 3D standards enabling the 3D calibration of optical microscopes is presented and validated. The 3D standards are based on step pyramids with several layers in the µm range and a system of cylindrical knops distributed across the layers as marks for coordinate based calibration. This enables calibration for the three coordinate axes and the orthogonality error between them in a single measurement step. The requirements necessary for such a calibration, as optical non-transparency, reproducible flatness of the pyramid step heights and the lowest possible deviations of the lateral marks coordinates, are met by optimizing the manufacturing process: The deviation of the height steps distributed over the wafer is ±3.6 nm and is primarily caused by the layer deposition processes. The lateral manufacturing accuracy was determined using calibrated scanning electron microscope (SEM) and show a mean deviation of 20 or 60 nm, depending on the lateral size of the structures. The electron beam lithography process and the level of inaccuracy of the SEM standard have an influence on the lateral scaling accuracy. Based on the tactilely generated height values and the coordinates of the mark determined by a calibrated SEM, an example calibration of a confocal laser scanning microscope was successfully performed and showed good conformity to conventional calibration techniques.

Remote sensing monitoring of changes in forest cover in the Volyn region: a cross section for the first two decades of the 21st century

The aim of the article. This article highlights the significance of forest cover as an important indicator of the state of the environment. It discusses the findings of the Food and Agriculture Organization of the United Nations (FAO) Forest Resources Assessment (FRA) 2020 report, which states that the world's forest area has decreased by 178 million hectares since 1990. The case study of Volyn region shows how cloud processing and vegetation classification can help quantify forest dynamics from 2000 to 2020, allowing local authorities and decision makers to monitor and analyze trends in near real time. Overall, this work provides insights into the importance of monitoring forest dynamics and the potential for remote sensing technology to facilitate this process. Data &amp; Methods. Remote sensing is an effective tool for monitoring forest ecology and management, and Google Earth Engine (GEE) is an online platform that combines data from various agencies to analyze environmental data. The article presents a case study of the Volyn region and how cloud processing and vegetation classification were used to assess forest dynamics from 2000 to 2020. The study used data from Landsat 7 Collection 1 Tier 1 composites and the CART algorithm for binary decision tree building. The study was based on information provided by the Main Department of Statistics in the Volyn region on the area of forests and areas where logging was carried out during the specified period. Research results. It is interesting to note that despite the decrease in logging activities, there is an increase in forest cover loss within forest ranges. This could be due to various reasons, such as illegal logging or natural disturbances like fires or disease outbreaks. The use of machine learning methods like CART classification can help to identify and monitor these changes, which can then be used to inform policy decisions and management practices to reduce forest cover loss. In general, in the Volyn region, there is a gradual decrease in the areas where various kinds of logging are carried out from 524 km2 in 2003 to 239 km2 in 2020. In contrast, forest cover loss within forest ranges increased rapidly from 37.85 km2 in 2015 to 84.01 km2 in 2017 and beyond from 5.53 km2 to 10.80 km2 in 2015 and 2017 respectively. In this study, the accuracy assessment was performed using 30% of the control points obtained initially, based on data on the reliability of the land cover. The manufacturer's accuracy and user accuracy were calculated to evaluate error omissions and possibilities of a pixel being categorized in a certain category. The spatial resolution of Landsat 7 data used in this study was 30 m, with a minimum calculation area of 0.337 hectares. The overall accuracy and the coefficient κ are the most representative measures of accuracy, with an average accuracy of classification of OAav=98.82% and κav=0.9764.

Computer model for detecting tsunami wave hazard on built-up land using machine learning and sentinel 2A satellite imagery

&lt;p&gt;The aim of this research is to compile a tsunami wave hazard scale based on built-up land density extracted and classified by machine learning from Sentinel 2A satellite and digital elevation model (DEM) imageries. This research was carried out in 5 stages, namely: (i) pre-processing of Sentinel 2A and DEM images, (ii) Classification of VI data using the machine learning algorithms, (iii) Spatial prediction using the ordinary kriging method, (iv) Field testing using the confusion matrix method, (v) Preparation of decision matrix for tsunami wave hazard. The results of the study show that the most accurate classification algorithm for classifying built-up indices data is the k-nearest neighbor (k-NN) algorithm. The results of the statistical accuracy test show that the most accurate is normalized difference built-up index (NDBI) with a mean of square error (MSE) value of 0.073 and a mean of absolute error (MAE) of 0.003. DEM analysis shows that the research area is at an altitude of 0–15 meters above sea level so it is in the high vulnerability to medium vulnerability category. Field testing showed user accuracy of 91.11%, manufacturer accuracy of 92.16%, and overall average accuracy of 91%.&lt;/p&gt;

A Flexible and Accurate Additive Manufacturing Data Retrieval Method Based on Probabilistic Modeling and Transformation-Invariant Feature Learning

A Flexible and Accurate Additive Manufacturing Data Retrieval Method Based on Probabilistic Modeling and Transformation-Invariant Feature Learning

Secondary ion mass spectrometry helps semiconductor manufacturing

Adapting SIMS to monitor rapid thermal anneal enables more accurate and reliable semiconductor device manufacturing.

Influence of Machine Tool Operating Conditions on the Resulting Circularity and Positioning Accuracy

The operating conditions of the production process significantly influence the resulting dimensional and form accuracy of the workpiece. The operating conditions include the position of the workpiece location, with internal and external heat sources influenced not only by the machine location but also by its operation. In addition, there are the cutting conditions and the feed rate requirements of CNC machine tools. These changes, such as workpiece position, feed rates, and machine heat load, are further reflected in the ability of the machine to run at the position required and interpolate within the given tolerances of circularity. For the accuracy and repeatability of positioning, the machine was set up according to ISO 230-2 and for the circular interpolation tests according to ISO 230-4. The obtained results show the importance of attention to the appropriate setting of the operating conditions of the production process, where the knowledge of the geometric accuracy of the CNC machine tool in its working space can systematically increase the manufacturing accuracy itself or be another tool suitable for predicting the dimensional and form accuracy of workpieces.

The rotation stability of the tapered rollers in a novel ring-type lapping process

This work introduces a novel ring-type lapping method for precision machining of tapered rollers. In contrast to the conventional centerless grinding, this method allows for the simultaneous machining of a group of tapered rollers. The stable rotation of the tapered rollers during the lapping process is a prerequisite for achieving a high manufacturing accuracy. Therefore, an investigation is conducted to examine the criteria for achieving a stable rotation of the tapered rollers. First, the equilibrium equation for the tapered rollers in the lapping process was established. The stable rotation region for the tapered rollers was determined according to the stable rotation criteria. The impacts of the included angle of straight groove and the contact force of lapping sleeve on the stable rotation region were examined. The results demonstrated that the tapered roller's stable rotation can only be realized when a specific parameter combination was satisfied. Subsequently, to expand the stable rotation region, the electromagnetic driving force was introduced to enhance the lapping process. An electromagnetic lapping sleeve structure was designed according to the critical electromagnetic force required for the tapered roller's lapping process. Furthermore, the structure of the electromagnetic lapping sleeve was optimized by electromagnetic simulation in order to improve the uniformity of the electromagnetic driving force exerted on each tapered roller. Finally, the rotation movement of the tapered rollers and the critical electromagnetic forces exerted on the tapered rollers were validated on a ring-type tapered roller lapping platform. The results demonstrated that the stable rotation of the bearing rollers in the lapping process can be achieved throughout a wide range of processing parameters. The roundness of the tapered rollers was significantly improved from 0.83 μm to 0.47 μm on the stable rotation condition. This study established a solid foundation for the precision machining of tapered rollers.