Accuracy of Ceramic Mould Filling with Liquid AlSi9 Aluminium Alloy in the Process Using Back-Pressure

Abstract The paper presents the effect of suction pressure exerted on the liquid AlSi alloy when it is introduced into a ceramic mould made in the investment process and the results compared with data obtained on gravity poured castings. The study used special pattern sets and ceramic moulds made with the alternately applied soluble silicate binder and ethyl silicate. Additionally, self-supported moulds based entirely on the Ekosil binder were used. In the analysis of castings, the following parameters were examined: a linear dimensional accuracy, the state of surface microgeometry and the possibility of metal penetration into a complex ceramic mould, allowing also for the presence of capillary phenomena. In the process of casting with back-pressure, the pressure values of 500 hPa, 600 hPa and 700 hPa were applied in the chamber where the ceramic mould was located, with the temperature of the said mould kept at a level of 150 ± 10°C.

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In Implementing a Metal 3D AM Machine

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.786.356 ◽

2018 ◽

Vol 786 ◽

pp. 356-363

Author(s):

Tero Jokelainen ◽

Kimmo Mäkelä ◽

Aappo Mustakangas ◽

Jari Mäkelä ◽

Kari Mäntyjärvi

Keyword(s):

Additive Manufacturing ◽

Selective Laser Melting ◽

Dimensional Accuracy ◽

Acceptance Test ◽

Aisi 316L ◽

Laser Melting ◽

Geometrical Accuracy ◽

Machine Performance ◽

Geometrical Features ◽

Made In

Additive Manufacturing (AM) does not yet have a standardized way to measure performance. Here a AM machines dimensional accuracy is measured trough acceptance test (AT) and AM machines capability is tested trough test parts. Test parts are created with specific geometrical features using a 3D AM machine. Performance of the machine is then evaluated trough accuracy of test parts geometry. AM machine here uses selective laser melting (SLM) process. This machine has done Factory acceptance test (FAT) to ascertain this machine ́s geometrical accuracy with material AISI 316L. Manufacturer promises accuracy of ±0.05 mm. These parts are used as comparison to AT parts made in this study. After installation two AT parts are manufactured with AM machine. One with AISI 316L and one AlSi10Mg. Dimensional accuracy of geometrical features on these parts are then compared to FAT part and to one another. Machines capability is measured trough two test parts done with material AlSi10Mg. Two of the test parts are done at the same time using same model as the FAT. Parts are printed without supports and with features facing same directions. Features of these parts were then evaluated. Another test to find out AM machines capability was to create part consisting of pipes doing 90˚ angle resulting in horizontal and vertical holes. Dimensional accuracy and circularity of holes was measured. Through these tests machines capability is benchmarked.

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An in-vitro study to evaluate the accuracy of dies obtained from dual arch impression trays using addition silicone impression material and tray combinations

Health Renaissance ◽

10.3126/hren.v12i2.14114 ◽

2015 ◽

Vol 12 (2) ◽

pp. 111-117

Author(s):

P K Parajuli ◽

S George ◽

V Shenoy

Keyword(s):

In Vitro Study ◽

Dimensional Accuracy ◽

Acrylic Resin ◽

Simultaneous Recording ◽

T Test ◽

Impression Material ◽

Tooth Preparation ◽

Made In ◽

Plastic Trays

Background: Dual-arch impression technique allows the simultaneous recording of tooth preparation, opposing anatomic tooth and maxillomandibular relationship. The accuracy of reproduction of this easy and quick technique, however, has not been studied in detail in past. Objective: To compare the accuracy of the impressions made by using the same impression material in dual arch plastic trays, dual-arch metal trays and acrylic resin custom trays. Methods: The dies obtained from the addition silicone impressions made in dual-arch plastic trays, dual-arch metal trays and full arch acrylic resin custom trays were compared for the dimensional accuracy with the prepared typodont tooth as a control. Student’s paired t-test and unpaired t-test were used for the data analyses using the Statistical Package for Social Studies (SPSS) version 11.5. Results: The dies obtained from all the impression combinations showed increased dimension (acrylic resin custom trays 9.4 mm±0.048, dual-arch plastic trays 9.5 mm±0.035, dual-arch metal trays 9.41 mm±0.017) as compared to the dimension of control (9.39 mm±0.007). Conclusion: All the tray-impression material combinations showed variable accuracies. Full arch acrylic resin trays resulted in greatest accuracy whereas dual-arch plastic trays the least accuracy.Health Renaissance 2014;12(2): pp: 111-117

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Patterns of cell division, cell death and chondrogenesis in cultured aggregates of normal and talpid3 mutant chick limb mesenchyme cells

Development ◽

10.1242/dev.27.1.245 ◽

1972 ◽

Vol 27 (1) ◽

pp. 245-260

Author(s):

D. A. Ede ◽

O. P. Flint

Keyword(s):

Cell Death ◽

Cell Division ◽

Limb Bud ◽

Intercellular Matrix ◽

Blue Stain ◽

Special Pattern ◽

Mesenchyme Cells ◽

Division Cell ◽

Made In

Aggregates were prepared from dissociated mesenchyme cells obtained from normal and talpid mutant chick limb buds at stage 26 and were maintained for 4 days in culture. They were shown by autoradiographic techniques to consist initially of populations of unifoimly dedifferentiated cells within which chondrogenesis was initiated between 1 and 2 days, leading to the formation of areas of precartilage in the interior of the aggregates. Measurements of cell population density, cell death and cell division were made in precartilage and non-cartilage regions on sections prepared from normal and mutant aggregates fixed at 1-day intervals and were related to the pattern of chondrogenesis. Non-cartilage areas consisted of cells surrounding the precartilage areas and extended to the surface of the aggregate; these cells showed no special pattern or histochemical reaction. Precartilage areas consisted of one or more “;condensations”, comprising cells arranged in concentric rings around a central cell or group of cells, characterized by uptake of [35S]sulphate and taking up alcian blue stain in the intercellular matrix. Chondrogenesis was initiated al the condensation foci and spread centrifugally. Condensations were arranged in a simple pattern, roughly equidistantly from each other and never at the surface of the aggregate. The shape and arrangement of the cells comprising them suggested that they were formed by a process of aggregation towards the condensation foci. The relation of these observations to events in the intact limb bud developing in vivo is discussed.

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Studies in the physical properties of soils: IV. A further contribution to the theory of capillary phenomena in soil

The Journal of Agricultural Science ◽

10.1017/s0021859600018499 ◽

1927 ◽

Vol 17 (2) ◽

pp. 264-290 ◽

Cited By ~ 128

Author(s):

William B. Haines

Keyword(s):

Physical Properties ◽

Water Distribution ◽

Capillary Rise ◽

Moisture Distribution ◽

Suction Pressure ◽

Moist Soil ◽

Ideal Case ◽

Capillary Phenomena ◽

Differences Of Opinion ◽

The Ideal

The theory of the capillary behaviour of moist soil has been further amplified for the ideal case and its relationship to various soil properties considered. Over part of the moisture range which has been dealt with by other authors it is found that there are alternative forms for the water distribution. This appears to explain why some differences of opinion have been expressed regarding some of the main points presented in a previous paper.The theory is considered in relation to capillary rise in soils as well as to the problem of cohesion previously dealt with. It is shown that the moisture distribution attained by capillary rise can be inferred from simple direct measurement of the suction pressure. Various other experimental illustrations of the theoretical conclusions are introduced.

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Study of the quality of the marginal gap of artificial crown frames made with the use of traditional and digital technologies

Aspirantskiy Vestnik Povolzhiya ◽

10.17816/2072-2354.2020.20.1.85-90 ◽

2020 ◽

Vol 20 (1-2) ◽

pp. 85-90

Author(s):

Evgenii N. Zhulev ◽

Yuliya A. Vokulova

Keyword(s):

Laser Scanner ◽

Dimensional Accuracy ◽

Marginal Gap ◽

Casting Method ◽

Significance Level ◽

Average Value ◽

Cad Cam ◽

Grinding Machine ◽

Made In

The aim of the study is to evaluate the quality of the marginal gap of the frames of artificial crowns made with the use of CAD/CAM system and by casting method. Materials and methods. The article presents an assessment of the quality of the edge fitting of artificial crown frames made by means of CAD/CAM system KaVo ARCTICA on digital images of dentition created by intraoral laser scanner iTero Cadent and frames made of Co-Cr by the method of casting. The Image J computer program was used to study the quality of the marginal gap of artificial crown frames. For statistical analysis of the obtained data nonparametric Wilcoxon-Mann-Whitney test was used for the evaluation of the related samples. Results. We found that the average value of the marginal gap between the tooth stump of the experimental model and the frames of artificial crowns made in the KaVo ARCTICA Engine milling and grinding machine from the titanium blank Titan-Blank is 21.79 microns. The average value of the cement gap of the frames of artificial crowns made by the traditional casting method is 77.18 microns. The value of the marginal gap of artificial crown frames made by using the CAD/CAM system KaVo ARCTICA was 2.8 times less than the value of the marginal gap of frames made by the traditional casting method with a significance level of р 0.05 (V-Wilcoxon criterion for related samples = 0, р = 0.001). Conclusion. The results of our study indicate that the frames of artificial crowns made with the use of CAD/CAM system KaVo ARCTICA have a greater dimensional accuracy of the marginal gap compared to the frames of artificial crowns made by the traditional casting method.

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The accuracy of holes drilled in the side surface of plywood

BioResources ◽

10.15376/biores.15.1.117-129 ◽

2019 ◽

Vol 15 (1) ◽

pp. 117-129

Author(s):

Maciej Sydor ◽

Tomasz Rogoziński ◽

Kinga Stuper-Szablewska ◽

Karol Starczewski

Keyword(s):

Phenol Formaldehyde ◽

Adhesive Layer ◽

Dimensional Accuracy ◽

Side Surface ◽

Drilling Machine ◽

Geometric Accuracy ◽

Hole Axis ◽

Birch Veneer ◽

Made In ◽

Nominal Position

Dimensional accuracy of machining translates into susceptibility to defects in assembly of furniture elements. In the initial drilling phase, the tip of the drill may slip due to the properties of the workpiece, which may result in inaccurate machining. Taking this into account, it was decided to investigate this phenomenon for drilling in the side of the plywood board. Samples for testing were made of 18 mm thick, 13 layer birch-alder plywood, covered with melamine film, glued with phenol-formaldehyde glue. With the use of an industrial dowel drilling machine, 30 holes in each of three examined layer were made. All holes were made parallel to the layers – on the side of the plywood board, and their axes were located in three adjacent layers: the birch veneer layer, the adhesive layer, and the alder veneer layer. Two types of geometric accuracy of holes were analyzed: the distance between the real center of the hole and the nominal position and also the inclination of the hole axis from the nominal axis. The holes made in the adhesive layer showed approximately twice larger deviations compared with the holes made in two adjacent layers of veneer. There was no significant relationship between the deviations of the angle of holes axis and the inaccuracies in the position of their centers. Main conclusion: When drilling in the side surface of the plywood board, less accurate holes are obtained if the hole axis is located in the adhesive layer, and there is more accuracy if the hole axis is located in the veneer layer.

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Dimensional Accuracy of Stone Casts Obtained with Multiple Pours into the Same Mold

ISRN Dentistry ◽

10.5402/2012/730674 ◽

2012 ◽

Vol 2012 ◽

pp. 1-5 ◽

Cited By ~ 2

Author(s):

Valdimar da Silva Valente ◽

Artêmio Luiz Zanetti ◽

Pedro Paulo Feltrin ◽

Ricardo Tatsuo Inoue ◽

Carmem Dolores Vilarinho Soares de Moura ◽

...

Keyword(s):

Stainless Steel ◽

Coordinate Measuring Machine ◽

Dimensional Accuracy ◽

Wait Time ◽

Type Iv ◽

Impression Technique ◽

Fixed Prosthesis ◽

Measuring Machine ◽

Master Model ◽

Made In

Aim. The aim of the present study was to compare the dimensional accuracy of stone casts obtained with vinyl polysiloxane molds through the double-impression technique with three pours into the same mold. Methods. A stainless steel master model was constructed simulating a three-unit fixed prosthesis. Twelve impressions were taken of this master model with addition silicone, using the double-impression technique. Three pours of type IV gypsum were then made into each mold, thus producing 36 casts. The pours were made 1 hour, 6 hours and 24 hours after the impression procedure. Next, intra- and interabutment measurements were made in a coordinate measuring machine. Results. Comparative analysis of the dimensional accuracy of stone casts resulting from multiple pours was not statistically significant in pours first and second (P>0.05). These values, however, were statistically significant at third pour in the height in abutment 1 and upper distance interabutment. Conclusion. The wait time (1 hour, and 6 hours) observed before pouring the stone into the same molds did not cause significant dimensional accuracy of the casts.

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ANALYSIS OF SURFACE MICROGEOMETRY AND STRUCTURE OF LAYERED BIOMATERIALS USED FOR PROSTHETIC CONSTRUCTIONS IN DIGITAL TECHNOLOGIES

Tribologia ◽

10.5604/01.3001.0013.6567 ◽

2019 ◽

Vol 287 (5) ◽

pp. 101-113

Author(s):

Wojciech RYNIEWICZ ◽

Anna M. RYNIEWICZ ◽

Łukasz BOJKO ◽

Beata LESZCZYŃSKA-MADEJ ◽

Andrzej RYNIEWICZ

Keyword(s):

Surface Roughness ◽

Surface Layer ◽

Digital Technologies ◽

Metal Powders ◽

Roughness Parameters ◽

Complex Load ◽

Stomatognathic System ◽

Surface Microgeometry ◽

Load Conditions ◽

Made In

Veneering layers of prosthetic substructures are responsible for tribological cooperation with opposite teeth in the stomatognathic system (SS). Investigations of microgeometry and structure of veneering layers are aimed at checking to what extent these layers replicate enamel parameters, which, under complex load conditions, are characterized by the phenomenon of resistance to tribological wear. Ceramic veneering layers are dedicated for substructures made in digital technologies from factory fittings by milling and laser sintering of metal powders. Using a confocal microscope, contactless tests of the surface layer stereometry were performed and surface roughness parameters were determined on samples of ceramics veneering of prosthetic substructures. The analysis was performed in comparison to the natural enamel of premolars and molars. The shaping of the surface of materials veneering the substructures is similar to the regularity determined in the statistical analysis of the enamel roughness. Layers facing samples from milling technology are characterized by lower values of roughness parameters than layers created on substructures made of SLM technology.

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RISK MANAGEMENT IN COMMERCIAL BANKS

Scientific bulletin of the Southern Institute of Management ◽

10.31775/2305-3100-2018-3-68-73 ◽

2018 ◽

pp. 68-73 ◽

Cited By ~ 1

Author(s):

N. V. Magzumova ◽

V. D. Fedotov

Keyword(s):

Risk Management ◽

Organizational Structures ◽

Commercial Activity ◽

Banking Services ◽

Commercial Property ◽

Banking Activity ◽

Increased Risk ◽

Investment Process ◽

Market Relations ◽

Made In

The current stage in the development of the banking structure is characterized by serious changes in organizational structures, the introduction of innovations and the use of progressive management methods. In the conditions of market relations, the probability of risks in banking activity increases. Risk is an activity connected with overcoming uncertainty in a situation of unavoidable choice, in the process of which it is possible to quantitatively and qualitatively assess the probability of achieving the expected result, failure and deviation from the goal. Banking activity is characterized by an increased risk. The decisions that are made in the investment process are almost always accompanied by risks. In this regard, it is necessary to develop a decision-making mechanism that will manage various risk factors. Risk management plays an important role in the commercial activity of the bank and attaches great importance to the effective functioning of the risk management system. The policy of a commercial bank for the management of claims is aimed at monitoring, analyzing, coordinating and managing claims, in which case an assessment of the magnitude of the risk and establishing compliance with acceptable limits is necessary. In order to take into account the volatile situation in the banking services market, activities in the management of commercial property claims must be constantly reviewed and adjusted.

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Influence of Thermal Gravitational Convection on Solidi Fication Processes

MRS Proceedings ◽

10.1557/proc-87-85 ◽

1986 ◽

Vol 87 ◽

Cited By ~ 2

Author(s):

Hans M. Tensi ◽

Joachim J. Schmidt

Keyword(s):

Thermal Convection ◽

Solidification Front ◽

Dendritic Morphology ◽

Process Data ◽

Gravitational Convection ◽

Alsi Alloy ◽

Gradient Furnace ◽

The Stability ◽

The Moment ◽

Made In

AbstractThe aim of these experiments in the Gradient Furnace with Quenching device (GFQ) during the German D-1 Mission was to study the influence of thermal convection on– the diffusion in the melt ahead of the solidification front in an AlCu-alloy– the stability of a smooth solidification front in an Al-Cualloy and– the morphology of the solidification front in an AlSi-alloyduring the directional solidification of the binary alloys AlCu with 0.3 wght.-% Cu and AlSi with 7.0 wght.-% Si. Altogether five samples had been successfully processed during the D1-Mission. After getting the complete values from the process data (above all the velocity of the solidification front and the temperature gradient) reference experiments were made in the same GFQ under lg-conditions.Additional experiments under lg with a transparent fluid were done to obtain information about the thermal convection in a cylindrical cell while measuring temperature distribution at the same time.A first result having the same crystallization condition is the more than twice thicker diffusion boundary layer in AlCu 0,3-specimen than in the lg-reference specimen. The diffusion coefficient and the dendritic morphology are to be determined. The evaluation of all specimens (flight- and lg-samples) is not finished in the moment.

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