Study on the Propagation of Dimensional Deviation in the Hull Block Building Process

2020 ◽  
Vol 36 (02) ◽  
pp. 143-151
Author(s):  
Changhui Liu ◽  
Jianfeng Liu ◽  
Yansong Zhang ◽  
Sun Jin ◽  
Can Wang ◽  
...  
Keyword(s):  
Critical Role ◽  
Dimensional Accuracy ◽  
Butt Joint ◽  
Measured Data ◽  
Accuracy Control ◽  
Bottom Block ◽  
Whole Process ◽  
Building Process ◽  
Dimensional Deviation ◽  
Industry Practice

Dimensional accuracy of hull block plays a critical role in guaranteeing the whole ship accuracy and reducing the hull butt-joint cost. The current industry practice of dimensional control in shipbuilding mainly focuses on the prediction of cutting and welding deformation based on engineering experience. Its main limitation is that the propagation and accumulation of deviations in the whole building process are neglected. In this article, cutting errors, assembly deviations, welding shrinkages, turnover distortions, and thermal expansions generated at different stages are analyzed. The propagation and accumulation of deviations and variations in the double-bottom block building process are studied based on the measured data in the whole process. Finally, the correlations of deviations between the adjacent stage are concluded. The conclusions can be used to guide the accuracy control in the hull block building process and reduce dimension trimming.

Systematic Process Chain Creation for CFRP Structures in Early Product Development Stages

2016 ◽  
Vol 1140 ◽  
pp. 328-334
Author(s):  
Matthias Behr ◽  
Carsten Schmidt
Keyword(s):  
Composite Structures ◽  
Production Costs ◽  
Preliminary Design ◽  
Process Chain ◽  
Whole Process ◽  
Reinforced Plastic ◽  
Building Process ◽  
Process Chains ◽  
Carbon Fibre Reinforced Plastic ◽  
Specific Sequences

A planning method is presented which allows to systematically building process chains based on a preliminary design of composite structures. The method utilises the specific sequences of procedural steps that occur in the production of carbon fibre reinforced plastic (CFRP) structures, to build sub process chains for each component of the structure. Process restrictions are considered to evaluate the suitability of different production processes. To obtain the whole process chain of the structure, different joining methods are applied in addition to combine the components and its sub process chains. The results of the presented method are used in an overarching development procedure to investigate resulting impacts on the solution. Possible impacts could be the production costs or the material characteristics.

Miniaturized Embossed Low Resistance Fine Line Coils in LTCC

2009 ◽  
Vol 6 (1) ◽  
pp. 42-48 ◽  
Author(s):  
R. Perrone ◽  
H. Bartsch de Torres ◽  
M. Hoffmann ◽  
M. Mach ◽  
J. Müller
Keyword(s):  
Thick Film ◽  
Cross Section ◽  
Screen Printing ◽  
Dimensional Accuracy ◽  
High Dimensional ◽  
Stencil Printing ◽  
Fine Line ◽  
Low Resistance ◽  
Whole Process ◽  
Line Widths

Embedded ceramic coils stand out because of their excellent dielectric, thermal, and RF properties. However the relatively high sheet resistance (low thickness) of printed thick-film conductors restricts their functionality for applications where current values of several amps are needed. Using embossed structures it is possible to manufacture conductors with increased thickness and low resistance on LTCC tapes. The manufacturing process for wide conductors with high dimensional accuracy was shown in previous publications. In this work fine line embossed structures with line widths and spaces of 50 and 75 μm respectively were realized. The cross section of the embossed channels was about 50 μm. The fine line screen printing, stencil printing, and the photo definable Fodel® processes were used to fill the small structures with thick-film ink. The whole process was used to manufacture several types of low resistance coils in LTCC that can be used for current values up to approximately 3 A. They were realized as embedded as well as SMD components. Thus, the functionality of LTCC modules and LTCC SMD coils was increased. In this paper, the filling and patterning characteristics of all structuring methods are compared and the results discussed. Furthermore, the advantages of this process are shown by electrical, thermal, and RF measurements.

Process Design and Thermal Performance in Deep Drawing of SiCp/2024Al Composite Sheet Using Pulse Current Heating

2013 ◽  
Vol 712-715 ◽  
pp. 678-682
Author(s):  
Xiao Ming Lai ◽  
Zhe Wang ◽  
Yu Liang Zhang ◽  
Bo Wang ◽  
Kai Feng Zhang ◽  
...  
Keyword(s):  
Deep Drawing ◽  
Pulse Current ◽  
Dimensional Accuracy ◽  
Heating System ◽  
Temperature Control System ◽  
Free Products ◽  
Whole Process ◽  
Good Surface ◽  
Process System ◽  
System Temperature

The deep drawing of SiC/2024Al composites using pulse current heating were designed and established in this works. The whole process system mainly include pulse current heating system, electrode lifting system, temperature control system and deep drawing forming system. In addition, the feasibility of thermal deep drawing using pulse current heating was experimentally investigated and the optimal process parameters were explored to ensure defect-free products. The temperature of specimen is up to around 673K at a rate of 13.5K/s under the current density of 21.7A/mm2. The stainless steel inserts make temperature difference reducing by 73.3%. Moreover, the workpiece was successfully deep drawn and exhibited good surface quality. The dimensional accuracy achieved within ±0.2mm.

Stochastic Assessment and Applications for Welding Shrinkage Impact on Production Cost

2012 ◽  
Author(s):  
H. Y. Heo ◽  
D. H. Youn ◽  
H. Chung
Keyword(s):  
Production Cost ◽  
Value Added ◽  
Dimensional Accuracy ◽  
Control Procedure ◽  
Total Production ◽  
Accuracy Control ◽  
Element Analysis ◽  
Intermediate Products ◽  
Welding Sequence

Since ship hull blocks are constructed by assembling numerous intermediate parts, negligible dimensional variations in the parts can easily accumulate to cause serious misalignment in block erection stage. Considering the welding – the primary joining process in ship production which inherently causes distortions, the quality of block’s dimensional variations during the assembly would deteriorate even faster. Thinking that the intermediate products with low dimensional quality in the ship production are not scrapped but reworked, the productivity of each workstation greatly depends on the dimensional quality of these dimensionally critical intermediate products. Reworks such as recutting, mechanical and/or thermal correction against misalignment, excessive welding for wide gap and thermal straightening are commonly subsequently increases the total production cost. One of the major dimensional accuracy control activities is the shrinkage margin design. The optimal length of excess edge is assigned to plates in order to compensate welding shrinkage. In the past, the welding shrinkage is predicted based mostly on the empirical formula or just designer's experience, so the accuracy of the assigned was relatively poor and could not effectively help reducing non-value-added rework activities. The simplified margin calculation procedure could not consider the welding sequence as well as process variations such as welding heat input. This work aims to develop the optimal shrinkage margin calculation system for dimensional quality improvement. The proposed system calculates the optimal shrinkage margin using computer-aided engineering toolsets based on finite element analysis as well as design point searching procedure adopting the quality loss function and statistical values considering shrinkage variation values during welding. The developed scheme improves the accuracy control procedure in the ship production process thus enhance competitiveness of shipbuilders in dimensional accuracy technology by minimizing the accuracy impact on productivity.

Decentralization—The Management Key to Effective Accuracy Control

1987 ◽  
Vol 3 (02) ◽  
pp. 75-86
Author(s):  
Tamara S. Upham ◽  
W. Mark Crawford
Keyword(s):  
Organizational Structure ◽  
Statistical Methods ◽  
Dimensional Accuracy ◽  
Accuracy Control ◽  
Statistical Accuracy ◽  
Three Phase ◽  
Control Department

This paper presents the organizational structure, methods, and results of National Steel and Shipbuilding Company's (NASSCO) efforts to decentralize the responsibility of statistical accuracy control from a central Accuracy Control Department to the hourly production workforce. It includes an accounting of the problems and successes encountered during implementation. The results are both quantitative and qualitative in form, including methods for measuring reductions in rework. During this study, workteams were established in the Hull Fabrication Shop. A three phase methodology was used to introduce the workteams to statistical methods for improving the dimensional accuracy of their products.

An assessment of the dimensional accuracy and geometry-resolution limit of desktop stereolithography using response surface methodology

2019 ◽  
Vol 25 (7) ◽  
pp. 1169-1186 ◽  
Author(s):  
Ivana Cotabarren ◽  
Camila Andrea Palla ◽  
Caroline Taylor McCue ◽  
Anastasios John Hart
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Layer Thickness ◽  
Orientation Angle ◽  
Dimensional Accuracy ◽  
Process Performance ◽  
Feature Location ◽  
Resolution Limit ◽  
Content Type ◽  
Dimensional Deviation

Purpose This paper aims to apply a robust methodology to establish relationships between user-configurable process parameters of commercial desktop stereolithography (SLA) printers and dimensional accuracy of a custom-designed test artifact. Design/methodology/approach A detailed response surface methodology study, Box–Behnken incomplete factorial design of four factors with three levels, was carried out to evaluate process performance of desktop SLA printers. The selected factors were as follows: printing orientation angle in x-direction, printing orientation angle in y-direction, position on build platform in spatial x-coordinate, position on build tray in spatial y-coordinate and layer thickness. The proposed artifact was designed to include 12 feature groups including thin walls, holes, bosses, bridges and overhangs. Two responses were associated with the features: the dimensional deviation according to the designed value and the minimum feature size. Findings Layer thickness was the most significant factor in 70% of the analyzed responses. For example, measurement deviation was reduced about 90% when cylindrical holes were printed with the lowest layer thickness. Further, in many cases, dimensional deviation was minimized for features at the center of the platform, where the beam cures the resin in a straight line. However, at distant positions, accuracy could be improved by compensating for beam deviation by changing the object orientation angle. Originality/value The findings of this study can serve, both generally and specifically, for SLA designers and engineers who wish to optimize printing process variables and feature location to achieve high-dimensional accuracy and further understand the many coupled considerations among part design, build configuration and process performance.

scholarly journals Dimensional Accuracy and Clinical Value of 3D Printed Models in Congenital Heart Disease: A Systematic Review and Meta-Analysis

2019 ◽  
Vol 8 (9) ◽  
pp. 1483 ◽  
Author(s):  
Ivan Wen Wen Lau ◽  
Zhonghua Sun
Keyword(s):  
Systematic Review ◽  
Congenital Heart Disease ◽  
Heart Disease ◽  
Congenital Heart ◽  
Imaging Modality ◽  
Meta Analysis ◽  
Critical Role ◽  
Dimensional Accuracy ◽  
Mean Deviation ◽  
Clinical Value

The aim of this paper is to summarize and evaluate results from existing studies on accuracy and clinical value of three-dimensional printed heart models (3DPHM) for determining whether 3D printing can significantly improve on how the congenital heart disease (CHD) is managed in current clinical practice. Proquest, Google Scholar, Scopus, PubMed, and Medline were searched for relevant studies until April 2019. Two independent reviewers performed manual data extraction and assessed the risk of bias of the studies using the tools published on National Institutes of Health (NIH) website. The following data were extracted from the studies: author, year of publication, study design, imaging modality, segmentation software, utility of 3DPHM, CHD types, and dimensional accuracy. R software was used for the meta-analysis. Twenty-four articles met the inclusion criteria and were included in the systematic review. However, only 7 studies met the statistical requirements and were eligible for meta-analysis. Cochran’s Q test demonstrated significant variation among the studies for both of the meta-analyses of accuracy of 3DPHM and the utility of 3DPHM in medical education. Analysis of all included studies reported the mean deviation between the 3DPHM and the medical images is not significant, implying that 3DPHM are highly accurate. As for the utility of the 3DPHM, it is reported in all relevant studies that the 3DPHM improve the learning experience and satisfaction among the users, and play a critical role in facilitating surgical planning of complex CHD cases. 3DPHM have the potential to enhance communication in medical practice, however their clinical value remains debatable. More studies are required to yield a more meaningful meta-analysis.

Binder System for Coarse Powders Processed by Metal Injection Molding (MIM)

2008 ◽  
Vol 591-593 ◽  
pp. 169-173
Author(s):  
A.P.G. Nogueira ◽  
Ricardo Machado ◽  
Paulo A.P. Wendhausen ◽  
Diego Fernando Portaluppi
Keyword(s):  
Particle Size ◽  
Injection Molding ◽  
Dimensional Accuracy ◽  
Melt Flow Index ◽  
Metal Injection Molding ◽  
Flow Index ◽  
Binder System ◽  
Sintered Part ◽  
Dimensional Deviation ◽  
Modified Binder

Research on determined alloys produced by metal injection molding has been done for cost reduction purposes through the use of powders with bigger particle size. However, regarding feedstock homogeneity, certain limitations are presented when coarse particles are used. For instance, homogeneity strongly influences rheological behavior of the feedstock and dimensional control of the sintered part. Therefore, the purpose of this work was to evaluate effectiveness of a modified binder system with the addition of a surfactant polymer which makes the feedstock more homogeneous. This study was carried out on a FeNiP alloy currently processed by MIM, where 50%wt of the iron powder was replaced with course powder having a particle size distribution of D90 less than 47 ,m. Effectiveness of binder systems using a Melt Flow Index (MFI) and the behavior of dimensional accuracy at sintered part were analyzed. Results showed more feedstock homogeneity and less dimensional deviation when a surfactant agent was used.

scholarly journals Fast Updating National Geo-Spatial Databases with High Resolution Imagery: China's Methodology and Experience

2014 ◽  
Vol XL-4 ◽  
pp. 41-50 ◽  
Author(s):  
J. Chen ◽  
D. Wang ◽  
R. L. Zhao ◽  
H. Zhang ◽  
A. Liao ◽  
...  
Keyword(s):  
High Resolution ◽  
Image Matching ◽  
Large Scale ◽  
Spatial Databases ◽  
Technological Development ◽  
Critical Role ◽  
Semantic Integration ◽  
Process Data ◽  
Whole Process ◽  
High Resolution Imagery

Geospatial databases are irreplaceable national treasure of immense importance. Their up-to-dateness referring to its consistency with respect to the real world plays a critical role in its value and applications. The continuous updating of map databases at 1:50,000 scales is a massive and difficult task for larger countries of the size of more than several million's kilometer squares. This paper presents the research and technological development to support the national map updating at 1:50,000 scales in China, including the development of updating models and methods, production tools and systems for large-scale and rapid updating, as well as the design and implementation of the continuous updating workflow. <br><br> The use of many data sources and the integration of these data to form a high accuracy, quality checked product were required. It had in turn required up to date techniques of image matching, semantic integration, generalization, data base management and conflict resolution. Design and develop specific software tools and packages to support the large-scale updating production with high resolution imagery and large-scale data generalization, such as map generalization, GIS-supported change interpretation from imagery, DEM interpolation, image matching-based orthophoto generation, data control at different levels. <br><br> A national 1:50,000 databases updating strategy and its production workflow were designed, including a full coverage updating pattern characterized by all element topographic data modeling, change detection in all related areas, and whole process data quality controlling, a series of technical production specifications, and a network of updating production units in different geographic places in the country.

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