Sculptured Surfaces Research Articles

Optimized Tool Motion Symmetry for Strip-Width-Max Mfg of Sculptured Surfaces with Non-Ball Tools Based on Envelope Approximation

Optimized Tool Motion Symmetry for Strip-Width-Max Mfg of Sculptured Surfaces with Non-Ball Tools Based on Envelope Approximation

On-machine inspection and compensation for thin-walled parts with sculptured surface considering cutting vibration and probe posture

Abstract On-machine inspection has a significant impact on improving high-precision and efficient machining of sculptured surfaces. Due to the lack of machining information and the inability to adapt the parameters to the dynamic cutting conditions, theoretical modeling of profile inspection usually leads to insufficient adaptation, which causes inaccuracy problems. To address the above issues, a novel coupled model for profile inspection is proposed by combining the theoretical model and the data-driven model. The key process is to first realize local feature extraction based on the acquired vibration signals. The hybrid sampling model, which fuses geometric feature terms and vibration feature terms, is modeled by the lever principle. Then, the weight of each feature term is adaptively assigned by a multi-objective multi-verse optimizer. Finally, an inspection error compensation model based on the attention mechanism considering different probe postures is proposed to reduce the impact of pre-travel and radius errors on inspection accuracy. The anisotropy of the probe system error and its influence mechanism on the inspection accuracy are analyzed quantitatively and qualitatively. Compared with the previous models, the proposed hybrid profile inspection model can significantly improve the accuracy and efficiency of on-machine sampling. The proposed compensation model is able to correct the inspection errors with better accuracy. Simulations and experiments demonstrate the feasibility and validity of the proposed methods. The proposed model and corresponding new findings contribute to high-precision and efficient on-machine inspection, and help to understand the coupling mechanism of inspection errors.

A new Trachyaspis-like pan-cheloniid turtle from the Bartonian of Kazakhstan

The article describes a fossil pan-cheloniid Protrachyaspis shorymensis gen. et sp. nov. from the Karakeshi, Kert, Kuyulus, and Monata localities of the Shorym Formation (Bartonian, middle Eocene), as well as unknown localities of the Mangyshlak Peninsula, Kazakhstan. In addition, the shell bones of small pan-cheloniids from the Kuyulus and Tuzbair localities of the Shorym Formation with some traits of P. shorymensis are described, which probably represent remains of juvenile specimens of this species. The new taxon is characterized by a number of features rarely found in pan-cheloniids, including serrated dentaries, distally displaced lateral process of the humerus, and deeply sculptured external carapace surface. These features indicate a likely herbivorous diet and pelagic lifestyle of the new pan-cheloniid. According to the results of the cladistic analysis, P. shorymensis is sister to the Neogene species Trachyaspis lardyi Meyer, 1843, from which it differs in the absence of ridges on the carapace in adult individuals, the configuration of the scutes on the parietal bone, and the structure of the plastron. The stratigraphic gap between the appearance of P. shorymensis and its sister T. lardyi suggests a long ghost lineage of members of this clade throughout the Bartonian – Aquitanian (ca. 20.7 million years) preceding the appearance of T. lardyi. In most trees, the P. shorymensis + T. lardyi clade is located within the Chelonini clade, which, taking into account the middle Eocene age of P. shorymensis, indicates the early divergence of crown cheloniids, previously established based on molecular data. The new taxon is similar to the fragmentary remains of pan-cheloniids with a sculptured external surface of the shell, previously described from four localities of the upper part of the Buchak and lower part of Kiev formations in the south of European Russia and Ukraine, which makes it possible to determine these materials as cf. Protrachyaspis sp., and probably extends the appearance of the P. shorymensis + T. lardyi clade back to the middle Lutetian.

Micromorphological study of some Salsola species (Amaranthaceae) in Iran and its systematic significance using scanning electron microscopy.

Using scanning electron microscopy (SEM), six Salsola species from Iran were examined for their epidermis, seed, and fruit micromorphology. Among them were S. brachiata from section Heterotricha, S dendroides, S. incanescens, and S. orientalis from section Caroxylon, S. kali from section Kali, and S. turcomanica from section Physurus. Epidermal cells are divided into three types. There were diamond, irregular, and polygonal cells, as well as straight and undulated walls. Studied species of Salsola have smooth or sculptured fruit surfaces, and there are three main types of fruit surface ornamentation. There is a significant difference between these species based on the type of hair and density of the fruit. Seed shape and color have little systematic significance. The seed epidermis is composed of polygonal, elongated polygonal, irregular, and diamond cells. Although polygonal and irregular testa cells are most common, their size and shape can provide additional information and useful diagnostic characteristics at both specific and infraspecific levels. For taxonomic separation, the current study provides novel insights at micromorphological levels. RESEARCH HIGHLIGHTS: This article reports halophyte are shown as models for adaptation to extreme habitats. These plants are placed among the ecological communities of xerophytes. Here, for the first time, the microstructural analysis of Salsola has been investigated. Additionally, it provides new insights into plant species' response to extreme conditions, as well as possible adaptation strategies at the micromorphological level.

Multi-stage error compensation with closed-loop quality control in five-axis flank milling of sculptured surface

Multi-stage error compensation with closed-loop quality control in five-axis flank milling of sculptured surface

Machining behaviour analysis of PBF-LB warped components with internal lattice microstructures

Metal additive Powder Bed Fusion, Laser Based (PBF-LB) manufacturing offers significant improvements in the design of complex parts of inner components areas for several sectors, from dies and moulds, to blades and aerofoils. Generating internal structures helps to move fluids, work as heat exchanges, or achieve dramatic weight relief, only possible by additive manufacturing, concretely PBF-LB. Along with these designs, sculptured surfaces and warped surfaces are also common in blades and other aerodynamic pieces. However, it is mandatory that these designs accomplish the final required mechanical properties without surface damage and non-admissible dimensional deviations. In this study, the five-axis milling of a part containing internal structures has been investigated. Two types of PBF-LB Inconel® 718 blades were manufactured, one solid and one with internal microstructures. They were finished using two types of ball-ended mills, ball and barrel-lens tooltip. The analysis of the blade with internal structures shows better machining behaviour, dynamic behaviour, and surface quality.

Skin Imaging: A Digital Twin for Geometric Deviations on Manufactured Surfaces

Closed-loop manufacturing is crucial in Industry 4.0, since it provides an online detection–correction cycle to optimize the production line by using the live data provided from the product being manufactured. By integrating the inspection system and manufacturing processes, the production line achieves a new level of accuracy and savings on costs. This is far more crucial than only inspecting the finished product as an accepted or rejected part. Modeling the actual surface of the workpiece in production, including the manufacturing errors, enables the potential to process the provided live data and give feedback to production planning. Recently introduced “skin imaging” methodology can generate 2D images as a comprehensive digital twin for geometric deviations on any scanned 3D surface including analytical geometries and sculptured surfaces. Skin-Image has been addressed as a novel methodology for continuous representation of unorganized discrete 3D points, by which the geometric deviation on the surface is shown using image intensity. Skin-Image can be readily used in online surface inspection for automatic and precise 3D defect segmentation and characterization. It also facilitates search-guided sampling strategies. This paper presents the implementation of skin imaging for primary engineering surfaces. The results, supported by several industrial case studies, show high efficiency of skin imaging in providing models of the real manufactured surfaces.

Artist profiling using micro-CT scanning of a Rijksmuseum terracotta sculpture.

In the fine arts, impressions found on terracotta sculptures in museum collections are scarcely reported and not in a systematic manner. Here, we present a procedure for scanning fingermarks and toolmarks found on the visible surface and inner walls of a terracotta sculpture using 3D micro-computed tomography, as well as methods for quantitatively characterizing these impressions. We apply our pipeline on the terracotta sculpture Study for a Hovering Putto, attributed to Laurent Delvaux and housed in the Rijksmuseum collection. On the basis of combined archaeology and forensics research that assigns age groups to makers of European ancestry from ridge breadth values, we estimate that the fingermarks belong to an adult male. Given that each fingerprint is unique and the carving tools were exclusively made in the artist's workshop, we give incentive to aim for artist profiling using innovative computational approaches on preserved impressions from terracotta sculptures.

Conservation Processing of Modern and Contemporary Outdoor Bronze Sculptures

‘Pieta’(1980) by Se Choong Kim required scientific analysis and conservation treatment due to long outdoor exhibitions and paint on surface of bronze sculpture. However, there was a concern that the originality of artwork and ‘moral rights of the artist(the right of integrity)’ could be violated by including conservation treatment methods that were inevitably irreversible, such as removing the old layer and re-patination. Accordingly, the brown color that was mainly used during the artist’s lifetime, was selected as the patination color through collaboration with various stakeholders. As a result of analyzing the making technique of ‘Pieta’, it was found that it was cast in Cu-Zn-Sn-Pb quaternary art bronze. The material, methods, and environment at the time of making artwork were confirmed by comparing the result of scientific analysis of welding, repair, and defects with inerviews with casting engineers. The paint painted on the surface of the bronze sculpture was confirmed as painted twice with metalic paint mixed with polystyrene and copper powder and graphite-based paint. Laser cleaning was applied after a preliminary experiments to stably remove paint, and 95% of the paint layer area was uniformly removed as a result of comparing and analyzing the volume before and after removal through 3D scanning. Brown patina was applied through patination then wax coating to finish.

Corrosion Behaviors of Artificial Chloride Patina for Studying Bronze Sculpture Corrosion in Marine Environments

Copper trihydroxychlorides, which are known as “bronze disease”, are dangerous corrosion products that compromise the stability and conservation of bronze sculptures. Here, we performed artificial patina corrosion experiments on quaternary bronze (Cu-Zn-Sn-Pb) to examine the corrosion behavior of the chloride patina commonly found in bronze objects in marine environments. The chromaticity and reflectance of the patina in the context of the corrosion products indicate that copper trihydroxychloride, which is commonly found in a single color in marine environments, was produced early in the corrosion experiment. Furthermore, the corrosion of bronze had different effects on the alloying elements, contrary to pure copper corrosion. The chloride patina formed a single patina layer of copper trihydroxychlorides. This patina layer was divided into the outer porous powder and inner uniform layers. Furthermore, the interaction of oxygen in the atmosphere with the corrosion layer and internal oxidation of tin in the alloy promoted powdering. These results provide important basic data for research on sculpture conservation and corrosion characteristics, such as changes in color, chemical composition, and corrosion products on the patina surfaces of outdoor bronze sculptures.

Seasonal Variations in Fungal Communities on the Surfaces of Lan Na Sandstone Sculptures and Their Biodeterioration Capacities.

Environmental factors and climate are the primary factors influencing the microbial colonization and deterioration of cultural heritage in outdoor environments. Hence, it is imperative to investigate seasonal variations in microbial communities and the biodeterioration they cause. This study investigated the surfaces of sandstone sculptures at Wat Umong Suan Phutthatham, Chiang Mai, Thailand, during wet and dry seasons using culture-dependent and culture-independent approaches. The fungi isolated from the sandstone sculptures were assessed for biodeterioration attributes including drought tolerance, acid production, calcium crystal formation, and calcium precipitation. The results show that most of the fungal isolates exhibited significant potential for biodeterioration activities. Furthermore, a culture-independent approach was employed to investigate the fungal communities and assess their diversity, interrelationship, and predicted function. The fungal diversity and the communities varied seasonally. The functional prediction indicated that pathotroph-saprotroph fungi comprised the main fungal guild in the dry season, and pathotroph-saprotroph-symbiotroph fungi comprised the dominant guild in the wet season. Remarkably, a network analysis revealed numerous positive correlations among fungal taxa within each season, suggesting a potential synergy that promotes the biodeterioration of sandstone. These findings offer valuable insights into seasonal variations in fungal communities and their impacts on the biodeterioration of sandstone sculptures. This information can be utilized for monitoring, management, and maintenance strategies aimed at preserving this valuable cultural heritage.

Retracted: Dimensional Defect Detection Research on the Sculpture Surface Combining the Convolutional Neural Network and Gabor

Retracted: Dimensional Defect Detection Research on the Sculpture Surface Combining the Convolutional Neural Network and Gabor

Predicting cutting forces in 5-axis milling of sculptured surfaces directly from a CAM tool path

The present work is motivated by the fact that for predicting the cutting forces which arise under various cutting conditions, workpiece-tool pairs, machining depths and tool orientation, numerical methods are slower and less efficient than analytical methods. In addition, recent developments in Computer Assisted Machining (CAM) techniques have enabled analytical methods to be applied even with complex workpiece geometry. The method developed in this paper is both practical and inexpensive. It is based on an analytical method using only few approximations and uses the toolpath file as the main information source for the machined surface. This method takes into account both tool position and orientation in a 5-axis finishing milling process with ball-end cutter, independent of the machining parameters and the couple of tool-workpiece materials. However, this calculation must be supplemented by a mechanistic approach in order to obtain results equivalent to those of the experiment. The result is a model which is implemented in a program allowing the visualization of the cutting forces along a given path. The program is easy to apply in practical cases with the possibility of implementing it in a machining software.

Accurate prediction of machining cycle times and feedrates with deep neural networks using BiLSTM

This paper presents a deep neural network-based approach to predict machining cycle (run) times along complex 3-axis machining part programs. CAD/CAM systems are utilized to generate part programs to machine parts with complex geometries and sculptured surfaces. The part program is processed by the numerical control (NC) unit of the machine tool to plan a feed profile. For such complex part programs, the actual (observed) feed profile and commanded (desired) one are significantly different. This paper uses bi-directional long short-term memory deep networks (bi-LSTM) to model the interpolation behavior of the NC systems to accurately predict how the feedrate profile is planned for any given part program. The G-line length, commanded feed, change in the feed direction through consecutive G-lines are used as a primary set of inputs to the network. The neural network is then trained by running series of toolpaths on the NC system and recording the resultant feedrate profile. Simulation and experimental studies are conducted on NC kernels to validate effectiveness of the proposed strategy. It is shown that machining cycle times on complex toolpaths can be predicted with > 94 % accuracy.

Prediction of Surface Location Error Considering the Varying Dynamics of Thin-Walled Parts during Five-Axis Flank Milling

Surface location error (SLE) caused by forced vibration is a key factor to determine the quality of the finished part. When machining thin-walled structures with sculptured surfaces, the complicated milling process is significantly influenced by the vibration due to the flexibility of the part. The dynamics of the part are dominant and vary with the material removal during machining. This paper presents a prediction method of SLE considering the varying dynamics of thin-walled parts in five-axis flank milling. The in-process part is decomposed into unmachined and machined portions, which are both modelled based on the thin-plate theory. The dynamics models of the two portions are coupled using the substructure method. Coordinate transformation based on the screw theory and the general cutting dynamics model for five-axis flank milling is employed to transform the cutting force vectors and frequency response function (FRF) to the same coordinate system for the prediction of SLE. The proposed method is validated with five-axis flank milling tests and SLE measurements on a thin-walled twisted part. It is shown that the average error of the proposed method for SLE prediction is less than 5 μm, and the calculation is almost 8 times faster than the typical finite element method.

Will to the Original: Platonism in Henry James’ Roderick Hudson

Will to the Original: Platonism in Henry James’ <i>Roderick Hudson</i>

Plant Products as Biocides for Conservation of Cultural Asset Sustainable for Human and Environmental Health

In the last decades plants products are increasingly used also in defining innovative procedures for sustainable conservation of cultural heritage. Particularly, essential oils or hydro-alcoholic extracts have been fruitful applied to contrast microbial colonization on organic and inorganic artworks or insect infestation (Anobidae) having regard to the repellent action.&#x0D; In this paper, extracts from Asteraceae and Lamiaceae plant families are utilized to counteract widespread microbial colonization (bacteria, cyanobacteria, fungi) due to their antimicrobial activity. In order to define the adequate concentration correlating it to microbial species detected, the antimicrobial activity of natural products is preliminary in vitro assayed by Agar Disc and Well Plate Diffusion methods. Moreover, an integrated approach based on morphological analysis (optical, scanning and confocal electron microscopy), in vitro cultures (Nutrient or Sabouraud agar) and molecular investigation (genomic microbial DNA extraction, sequencing and sequence analysis) are routinely performed for the identification of largest number of microbial taxa.&#x0D; Besides, to enhance the antimicrobial activity different protocols have been performed, such as for Thymus vulgaris products directly applied on wooden sculpture surface as hydro-alcoholic extract, followed by exposure, in a dedicated chamber, to the volatile compound of the corresponding Essential Oil. In other case studies, the exposure to volatile compounds of Crithmum maritmum, Inula critmoides, Thymus vulgaris and Origanum vulgare essential oils was performed under controlled vacuum conditions, comparing the effects to environmental condition exposure. These studies confirm the possible use of plant extracts in replacing synthetic chemical biocides, in full respect of human health and environment sustainability.

Digital Twin Modelling Method of Five-Axis Machine Tool for Predicting Continuous Trajectory Contour Error

The CNC machine tool is the passive executor of machining code. It cannot predict the machining accuracy during machining. If the error is found to be out of tolerance after processing, it will not only scrap the parts, but also greatly affect the processing efficiency. This phenomenon is very prominent when machining sculptured surface parts with five-axis machine tools. Therefore, this paper proposes a Digital Twin (DT) modeling method of five-axis machine tools for predicting Continuous Trajectory Contour Error (CTCE) caused by tracking errors and geometric errors. The DT consists of three parts: the Setpoints Trajectory (ST) model, the Actual Trajectory (AT) model considering tracking errors and geometric errors and the CTCE model. For a specific machine tool, according to the basic geometric information of the machine tool (tool length, kinematic chain information, etc.) and 41 geometric errors, the DT can be established. Inputting the Setpoints Positions (SPs) and the Linear Encoder Detection Positions (LEDPs), the DT can be used to predict the Tool-Tip Position Trajectory (TTPT) contour error and the Tool Orientation Trajectory (TOT) contour error. In order to verify the proposed method experimentally, the KMC400S U five-axis machine tool is selected to establish its DT by which the contour error of the S-shaped trajectory are predicted offline. Then, the DMU50 five-axis machine tool is selected to establish its DT to predict the contour error of the circular trajectory in real time. Combined with the deep motion mechanism, this paper proposes a DT modeling method for the vertical application scene of parts machining accuracy prediction, which is of great significance to developing the DT application theory and ensuring the machining accuracy of parts.

CWE identification and cutting force prediction in ball-end milling process

Ball-end milling of sculptured surfaces is an efficient and cost effective manufacturing technique when compared with other methods. However, an accurate cutting force prediction is still challenging when the Cutter Workpiece Engagement (CWE) and Instantaneous Undeformed Chip Thickness (IUCT) vary simultaneously. In order to predict the milling force accurately, an algorithm is designed to obtain the CWE boundaries with the variable tool orientations. Inspired by the main idea of analytical CWE model, an improved Z-map method is developed, which is based on the classic Z-map method. The point cloud of tool envelope surface method is generated based on the classic Z-map and the points of the CWE are screened according to the chosen criteria. Afterwards, the IUCT is calculated numerically by the accurate cutting thickness model. In order to overcome the drawbacks of the IUCT method, a simplified IUCT model is proposed to eliminate the iterative calculation. Related milling experiments were carried out on Al7075 workpiece to validate the proposed models showing a good agreement with errors smaller than 12.5%. It can be concluded from simulation results that tool postures have a significant effect on the machining process. This contributes to in-depth understanding the material removal process and optimizing the process parameters of multi-axis machining processes.

Collision-free and smooth path generation method of five-axis ball-end milling considering effective tool diameter change

Ball-end cutters are widely used in five-axis sculptured surface machining. It is desired to avoid drastic changes of rotary axis movements for improving the kinematics performance of machine tools while ensuring collision-free during five-axis machining. It cannot acquire the optimum solution when cutter orientations are first generated and then adjusted to avoid collisions. The cutter orientations should be generated and optimized in their feasible regions wholly while the computation load is usually large. Different relative postures between a ball-end cutter and workpiece during the machining process will produce different effective tool diameters of the ball-end cutter, resulting in different cutting speeds. Using a variable cutting speed along a tool path can unfavorably affect the process' technological effects (e. g. surface quality, tool life). It is desired to keep the effective tool diameter constant or at a very slightly varying value during five-axis ball-end machining. Moreover, it is also desired to make the cutting point in a high position of the ball-end cutter tool edge, increasing the effective tool diameter. A smooth and collision-free tool path generation method of five-axis ball-end machining while minimizing the effective tool diameter variation and increasing the effective tool diameter of the ball-end cutter along a tool path is proposed. Tool orientations along a tool path are generated and optimized within their feasible regions and the proposed method solves the smoothness tool path generation problem by applying sequentially for the rough and fine search spaces to reduce the computing time. The numerical examples and the machining experiment illustrate the effectiveness of the proposed method.