scholarly journals Comparison of the internal fit of metal crowns fabricated by traditional casting, computer numerical control milling, and three-dimensional printing

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257158
Author(s):  
Wei-Ting Chou ◽  
Chuan-Chung Chuang ◽  
Yi-Bing Wang ◽  
Hsien-Chung Chiu
Keyword(s):  
3D Printing ◽  
Minimum Distance ◽  
Statistical Significance ◽  
Three Dimensional ◽  
Reference Points ◽  
Numerical Control ◽  
Maximum Distance ◽  
Cnc Milling ◽  
Low Viscosity ◽  
Internal Fit

This experimental study aimed to compare the internal fit (marginal fit and internal discrepancy) of metal crowns fabricated by traditional casting and digital methods (computer numerically controlled (CNC) milling and three-dimensional [3D] printing). Thirty standard master abutment models were fabricated using a 3D printing technique with digital software. Metal crowns were fabricated by traditional casting, CNC milling, and 3D printing. The silicon replica method was used to measure the marginal and internal fit. A thin layer of low-viscosity polyvinyl siloxane material was placed inside each crown and on the die (like a seat) until the material was set. Replicas were examined at four reference points under a microscope: the central pit (M1), cusp tip (M2), axial wall (M3), and margin (M4). The measured data were analyzed using a one-way analysis of variance (ANOVA) to verify statistical significance, which was set at p < 0.05. In the traditional casting group, the minimum distance measured was at M3 (90.68 ± 14.4 μm) and the maximum distance measured was at M1 (145.12 ± 22 μm). In the milling group, the minimum distance measured was at M3 (71.85 ± 23.69 μm) and the maximum distance measured was at M1 (108.68 ± 10.52 μm). In the 3D printing group, the minimum distance measured was at M3 (100.59 ± 9.26 μm) and the maximum distance measured was at M1 (122.33 ± 7.66 μm). The mean discrepancy for the traditional casting, CNC milling, and 3D printing groups was 120.20, 92.15, and 111.85 μm, respectively, showing significant differences (P < 0.05). All three methods of metal crown fabrication, that is, traditional casting, CNC milling, and 3D printing, had values within the clinically acceptable range. The marginal and internal fit of the crown was far superior in the CNC milling method.

Study on Simulation of Virtual Numerical Control Machining Process

2014 ◽  
Vol 701-702 ◽  
pp. 223-226
Author(s):  
Shuang Wu
Keyword(s):  
Three Dimensional ◽  
The Body ◽  
Numerical Control ◽  
Machining Process ◽  
Two Dimensional ◽  
Cnc Milling ◽  
Numerical Control Machining ◽  
Intersection Algorithm ◽  
Dimensional Simulation ◽  
Tool Cutting

This paper is study on the two-dimensional simulation of the machining process, and three-dimensional simulation. Analog three-axis CNC milling machining entity, it will be processed rough triangular facets discrete and discrete vector geometry and tool scans the body to do intersection algorithm to simulate the tool cutting process by continually updating the blank data to achieve material simulation removal process.

scholarly journals A Graphics Processor Unit-Accelerated Freeform Surface Offsetting Method for High-Resolution Subtractive Three-Dimensional Printing (Machining)

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Mohammad M. Hossain ◽  
Chandra Nath ◽  
Thomas M. Tucker ◽  
Richard W. Vuduc ◽  
Thomas R. Kurfess
Keyword(s):  
3D Printing ◽  
Three Dimensional ◽  
Boundary Representation ◽  
Numerical Control ◽  
Freeform Surface ◽  
Generation Process ◽  
Graphics Processor ◽  
Computer Aided ◽  
Processor Unit ◽  
Graphics Processor Unit

Machining is one of the major manufacturing methods having very wide applications in industries. Unlike layer-by-layer additive three-dimensional (3D) printing technology, the lack of an easy and intuitive programmability in conventional toolpath planning approach in machining leads to significantly higher manufacturing cost for direct computer numerical control (CNC)-based prototyping (i.e., subtractive 3D printing). In standard computer-aided manufacturing (CAM) packages, general use of B-rep (boundary representation) and non-uniform rational basis spline (NURBS)-based representations of the computer-aided design (CAD) interfaces make core computations of tool trajectories generation process, such as surface offsetting, difficult. In this work, the problem of efficient generation of freeform surface offsets is addressed with a novel volumetric (voxel) representation. It presents an image filter-based offsetting algorithm, which leverages the parallel computing engines on modern graphics processor unit (GPU). The compact voxel data representation and the proposed computational acceleration on GPU together are capable to process voxel offsetting at four-fold higher resolution in interactive CAM application. Additionally, in order to further accelerate the offset computation, the problem of offsetting with a large distance is decomposed into successive offsetting using smaller distances. The performance trade-offs between accuracy and computation time of the offset algorithms are thoroughly analyzed. The developed GPU implementation of the offsetting algorithm is found to be robust in computation, and demonstrates a 50-fold speedup on single graphics card (NVIDIA GTX780Ti) relative to prior best-performing algorithms developed for multicores central processing units (CPU). The proposed offsetting approach has been validated for a variety of complex parts produced on different multi-axis CNC machine tools including turning, milling, and compound turning-milling.

Freeform 3D-Printing of Pure Ceramics

2020 ◽  
Author(s):  
Mohammadreza Mahmoudi ◽  
Scott R. Burlison ◽  
Salvador Moreno ◽  
Majid Minary
Keyword(s):  
3D Printing ◽  
Three Dimensional ◽  
Layer By Layer ◽  
Preceramic Polymer ◽  
Sem Images ◽  
Three Dimensional Printing ◽  
3D Print ◽  
Whole Process ◽  
Low Viscosity ◽  
Crosslinking Process

Abstract Polymer derived ceramics (PDC’s) offer a unique opportunity to 3D-print ceramics; however, 3D printing of such polymers require it to be combined with specialized light-sensitive agents and layer-by-layer crosslinking using an optical beam due to their low viscosity. Here, three-dimensional printing of ceramics enabled by dispensing the preceramic polymer from a nozzle inside a yield stress fluid is being demonstrated. The printed parts are crosslinked in the same gel. After crosslinking process, the printed parts are taken out of the gel and prepared for high temperature pyrolysis process that converts the cured parts to ceramic. The specially designed gel was three orders of magnitude more viscous than the preceramic polymer at no shear, which provided a stable medium during the whole process for maintaining the shape of the printed material and prevented possible instabilities. The SEM images of the cross section of the specimens showed that the printed material was dense and without any apparent porosity or cracks. Statistical analysis on the mechanical properties of the printed preceramic polymer specimens revealed that the printed specimens had characteristic strength (∼257 MPa).

An Accurate and Efficient Approach to Three-Dimensional Geometric Modeling of Undeformed Chips for the Geometric and the Physical Simulations of Three-Axis Milling of Complex Parts

2015 ◽  
Vol 138 (5) ◽  
Author(s):  
Zhiyong Chang ◽  
Zezhong C. Chen
Keyword(s):  
Geometric Modeling ◽  
High Performance ◽  
Physical Simulation ◽  
Three Dimensional ◽  
Numerical Control ◽  
Machining Process ◽  
Machining Parameters ◽  
Cnc Milling ◽  
Physical Simulations ◽  
Complex Parts

To pursue high-performance computer numerical control (CNC) milling of complex parts, it is crucial to simulate their machining process geometrically and physically with high fidelity beforehand. The geometric simulation is to construct three-dimensional (3D) models of the finished parts and to compute geometric deviation between the models and the part designs, in order to verify the planned tool paths. The physical simulation is to build undeformed chips geometric models and in-process workpiece models and to compute instantaneous cutting forces, in order to optimize the machining parameters. Therefore, it is essential to accurately and efficiently model undeformed chips geometry in machining complex geometric parts. Unfortunately, this work is quite challenging, and no well-established method for this work is available. To address this problem, our work proposes an accurate and effective approach to 3D geometric modeling of undeformed chips geometry in three-axis milling of complex parts. The outstanding feature of this approach is that undeformed chip models and in-process workpiece models can be effectively constructed. This approach lays a theoretical foundation for the geometric and the physical simulations of three-axis milling. It advances the technique of machining simulation and promotes high-performance machining of complex parts.

scholarly journals Accuracy and Internal Fit of 3D printed Occlusal Splint, according to the printing position

2018 ◽  
Author(s):  
Mayra Torres Vasques ◽  
Dalva Cruz Laganá
Keyword(s):  
3D Printing ◽  
Three Dimensional ◽  
Digital Technologies ◽  
3D Printer ◽  
Occlusal Splint ◽  
Three Dimensional Printing ◽  
Dimensional Measurement ◽  
3D Printed ◽  
Internal Fit ◽  
Dimensional Printing

Understanding the importance of 3D printing strategies is a key to obtain predictable, optimized and consistent dental appliances using digital technologies. This study aims to present the influence of printing orientation on the intraoral fit of full arch coverage splints. Splints were designed for two patients using the CAD software and printed in a SLA 3D printer with different orientations (0, 30, and 90 degrees), and the internal fit was checked on patients’ mouth. Differen­ces between the fit of the splints were verified, with the worst results for 90º oriented splints, although more detailed studies are recommended by the authors. DESCRIPTORS | Three-Dimensional Printing; Accuracy; Dimensional Measurement; Occlusal Splint; Print Orientation.

Marginal and internal fit of provisional crowns fabricated using 3D printing technology

2020 ◽  
Vol 28 (6) ◽  
pp. 635-642 ◽  
Author(s):  
Saurabh Chaturvedi ◽  
Nasser M. Alqahtani ◽  
Mohamed Khaled Addas ◽  
Mohammed A. Alfarsi
Keyword(s):  
3D Printing ◽  
Periodontal Diseases ◽  
Three Dimensional ◽  
Compression Molding ◽  
Finish Line ◽  
Printing Technology ◽  
Significance Level ◽  
3D Printing Technology ◽  
Dunnett's Test ◽  
Internal Fit

BACKGROUND: Clinicians routinely provide provisional crowns following teeth preparation. Three-dimensional (3D) printing technology could be used over conventional methods for better fit as lack of adequate fit would result in plaque accumulation, micro-leakage, teeth sensitivity, caries and periodontal diseases. OBJECTIVE: The aim of the study was to evaluate the marginal and internal fit of provisional crowns fabricated using 3D printing technology and to compare it with that of compression molding and milling methods. METHODS: Ninety study models were fabricated by duplicating metal master models of the maxillary first premolar molar with three different finish line chamfer, rounded shoulder and rounded shoulder with bevel. On each study model, provisional crowns were fabricated using compression molding (Mo. group, n= 30 – by over impression technique), milling (Mi. group, n= 30 – by 5-axis dental milling machine), and 3D printing method (3D-P. group, n= 30 – by 3D printer). Marginal and internal fit of the samples were evaluated by measuring gap using a scanning electron microscope with a magnification of 27 ×, at 7 zones A–G on different finish line models. The data were statistically analysed using one-way analysis of variance (ANOVA) at the 0.05 significance level. The p-values were calculated using Dunnett’s test. RESULTS: The marginal gap was minimal for the 3D-P. group for each finish line with lowest for rounded shoulder with bevel at zone A 30.6 ± 5.3 and at zone G 32.8 ± 5.4. In axial area, i.e. zones B and F, the minimum gap was noticed for the Mo. group and in Occlusal area (cusp and fossa), for zones C–E maximum gap was determined in Mi. group followed by Mo. and 3D-P. groups. CONCLUSIONS: 3D printed provisional crowns have better marginal and internal fit compared to milled and molded provisional crowns.

Application of Reverse Engineering for Redesigning and Manufacturing of a Printer Spare Part

2013 ◽  
Vol 690-693 ◽  
pp. 2708-2712 ◽  
Author(s):  
Ivan Buranský ◽  
Ladislav Morovič ◽  
Jozef Peterka
Keyword(s):  
Reverse Engineering ◽  
Three Dimensional ◽  
Spare Part ◽  
Numerical Control ◽  
Cnc Machine Tools ◽  
Cnc Milling ◽  
Cnc Machine ◽  
Computer Aided ◽  
3D Digitization ◽  
Cam Software

The paper deals with the application of Reverse Engineering (RE) in the process of redesigning and manufacturing of a printer spare part. The paper presents the devices for transfer of a damaged printer part into a digital model by non-contact three-dimensional (3D) digitization. The paper discusses the 3D computer-aided designing (CAD) of a model with CAD software based on a digitized real part. The paper presents two proposals for spare part manufacturing: a) manufacturing by computer numerical control (CNC) milling, which is projected and programmed in computer-aided manufacturing (CAM) software with regard to production potential of selected CNC machine tools; b) manufacturing by Rapid Prototyping (RP) technology. The article concludes with a comparison of the proposed methods of manufacturing of printer spare part in term of production time.

scholarly journals Step Ring-Based Three-Dimensional Path Planning Via Graphics Processing Unit Simulation for Subtractive Three-Dimensional Printing

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Zhengkai Wu ◽  
Thomas M. Tucker ◽  
Chandra Nath ◽  
Thomas R. Kurfess ◽  
Richard W. Vuduc
Keyword(s):  
3D Printing ◽  
Path Planning ◽  
Material Removal ◽  
Graphics Processing Unit ◽  
Three Dimensional ◽  
Numerical Control ◽  
Scale Model ◽  
Processing Unit ◽  
Cad Model ◽  
Graphics Processing

In this paper, both software model visualization with path simulation and associated machining product are produced based on the step ring-based three-axis path planning to demo model-driven graphics processing unit (GPU) feature in tool path planning and 3D image model classification by GPU simulation. Subtractive 3D printing (i.e., 3D machining) is represented as integration between 3D printing modeling and computer numerical control (CNC) machining via GPU simulated software. Path planning is applied through visualization of surface material removal in high-resolution and 3D path simulation via ring selective path planning based on accessibility of path through pattern selection. First, the step ring selects critical features to reconstruct computer-aided design (CAD) design model as stereolithography (STL) voxel, and then, local optimization is attained within interested ring area for time and energy saving of GPU volume generation as compared to global automatic path planning with longer latency. The reconstructed CAD model comes from an original sample (GATech buzz) with 2D image information. CAD model for optimization and validation is adopted to sustain manufacturing reproduction based on system simulation feedback. To avoid collision with the produced path from retraction path, we pick adaptive ring path generation and prediction in each planning iteration, which may also minimize material removal. Moreover, we did partition analysis and G-code optimization for large-scale model and high density volume data. Image classification and grid analysis based on adaptive 3D tree depth are proposed for multilevel set partition of the model to define no cutting zones. After that, accessibility map is computed based on accessibility space for rotational angular space of path orientation to compare step ring-based pass planning verses global path planning of all geometries. Feature analysis via central processing unit (CPU) or GPU processor for GPU map computation contributes to high-performance computing and cloud computing potential through parallel computing application of subtractive 3D printing in the future.

scholarly journals Development of Client-Server Application by Using UDP Socket Programming for Remotely Monitoring CNC Machine Environment in Fixture Process

2016 ◽  
Vol 12 (2) ◽  
pp. 48
Author(s):  
Darmawan Darmawan ◽  
Pharmayeni Pharmayeni
Keyword(s):  
Three Dimensional ◽  
Integrated System ◽  
Numerical Control ◽  
Cnc Milling ◽  
Cnc Machine ◽  
Machining Performance ◽  
Server Side ◽  
Client Side ◽  
Server Application ◽  
Cnc Controller

The use of computer technology in manufacturing industries can improve manufacturing flexibility significantly, especially in manufacturing processes; many software applications have been utilized to improve machining performance. However, none of them has discussed the abilities to perform direct machining. In this paper, an integrated system for remote operation and monitoring of Computer Numerical Control (CNC) machines is put into consideration. The integrated system includes computerization, network technology, and improved holding mechanism. The work proposed by this research is mainly on the software development for such integrated system. It uses Java three-dimensional (3D) programming and Virtual Reality Modeling Language (VRML) at the client side for visualization of machining environment. This research is aimed at developing a control system to remotely operate and monitor a self-reconfiguration fixture mechanism of a CNC milling machine through internet connection and integration of Personal Computer (PC)-based CNC controller, a server side, a client side and CNC milling. The performance of the developed system was evaluated by testing with one type of common protocols particularly User Datagram Protocol (UDP).  Using UDP, the developed system requires 3.9 seconds to complete the close clamping, less than 1 second to release the clamping and it can deliver 463 KiloByte.

Some quantitative applications of vascular corrosion casting

1992 ◽  
Vol 50 (1) ◽  
pp. 738-739
Author(s):  
Fred E. Hossler
Keyword(s):  
Blood Vessels ◽  
Nuclear Orientation ◽  
Three Dimensional ◽  
Surrounding Tissue ◽  
Confocal Laser ◽  
Corrosion Casting ◽  
Venous Valve ◽  
Casting Technique ◽  
Low Viscosity ◽  
Quantitative Measurements

Preparation of replicas of the complex arrangement of blood vessels in various organs and tissues has been accomplished by infusing low viscosity resins into the vasculature. Subsequent removal of the surrounding tissue by maceration leaves a model of the intricate three-dimensional anatomy of the blood vessels of the tissue not obtainable by any other procedure. When applied with care, the vascular corrosion casting technique can reveal fine details of the microvasculature including endothelial nuclear orientation and distribution (Fig. 1), locations of arteriolar sphincters (Fig. 2), venous valve anatomy (Fig. 3), and vessel size, density, and branching patterns. Because casts faithfully replicate tissue vasculature, they can be used for quantitative measurements of that vasculature. The purpose of this report is to summarize and highlight some quantitative applications of vascular corrosion casting. In each example, casts were prepared by infusing Mercox, a methyl-methacrylate resin, and macerating the tissue with 20% KOH. Casts were either mounted for conventional scanning electron microscopy, or sliced for viewing with a confocal laser microscope.

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