scholarly journals Frequency Domain Analysis and Precision Realization in Deterministic Figuring of Ultra-Precision Shaft Parts

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4561
Author(s):  
Zizhou Sun ◽  
Hao Hu ◽  
Yifan Dai ◽  
Chaoliang Guan ◽  
Guipeng Tie ◽  
...  
Keyword(s):  
High Efficiency ◽  
Characteristic Curve ◽  
Frequency Domain Analysis ◽  
Contour Error ◽  
Power Spectral ◽  
Ultra Precision ◽  
Frequency Components ◽  
Limited Frequency ◽  
Precision Machine Tools ◽  
Aerostatic Spindle

An aerostatic spindle is a core component in ultra-precision machine tools. The rotor of the spindle has extremely high manufacturing accuracy, which cannot be directly achieved via traditional machining, but always via manual grinding. The deterministic figuring theory is introduced into the machining of shaft parts, which overcomes many shortcomings of manual grinding. The manufacturing error of the shaft’s surface contains different frequency components, which have different effects on its working performance and the figuring process. Because the deterministic figuring method can only correct the error within a limited frequency range, in order to ensure high efficiency and high precision of the figuring process, we need to use reasonable filtering parameters to filter out the error with unnecessary frequencies. In this paper, the influence of contour error with different frequencies and amplitudes on the air film are analyzed using computational fluid dynamics (CFD) software, and the amplitude–frequency analysis as a function of the power spectral density (PSD) characteristic curve is used to study the filtering parameters of the measured data. After the figuring experiment using the filtering parameters obtained from the analysis, the average roundness of the shaft converged from 0.419 μm to 0.101 μm, and the cylindricity converged from 0.76 μm to 0.35 μm. The precision reached the level of manual grinding, which proves the rationality of the analysis using filtering parameters in a shaft’s deterministic figuring.

scholarly journals Measurement and Compensation of Tool Contour Error Using White Light Interferometry for Ultra-Precision Diamond Turning of Freeform Surfaces

2020 ◽  
Vol 14 (4) ◽  
pp. 654-664 ◽  
Author(s):  
Kodai Nagayama ◽  
◽  
Jiwang Yan
Keyword(s):  
White Light ◽  
High Efficiency ◽  
Diamond Tool ◽  
Microlens Array ◽  
Diamond Turning ◽  
Contour Error ◽  
Form Accuracy ◽  
Freeform Optics ◽  
Ultra Precision ◽  
Quick Measurement

In ultra-precision diamond turning of freeform optics, it is necessary to obtain submicron-level form accuracy with high efficiency. In this study, we proposed a new method for the quick measurement and compensation of tool contour errors to improve the form accuracy of the workpiece. In this method, the nanometer-scale contour error of a diamond tool is quickly and precisely measured using a white light interferometer and then compensated for, before machining. Results showed that the contour of a diamond tool was measured with an error less than 0.05 μm peak-to-valley (P-V) and the feasibility of error compensation was verified through cutting experiments to create a paraboloid mirror and a microlens array. The form error decreased to 0.2 μm P-V regardless of the contour error of the diamond tools when cutting the paraboloid mirror, and that of the microlens array was reduced to 0.15 μm P-V during a single machining step.

Designing the Partially Porous Journal Bearings of an Aerostatic Spindle

2017 ◽  
Vol 868 ◽  
pp. 110-117
Author(s):  
Te Yen Huang ◽  
Song Chiang Shen ◽  
Shao Yu Hsu
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Low Cost ◽  
Journal Bearings ◽  
Porous Insert ◽  
Load Carrying ◽  
High Speed Rotation ◽  
Ultra Precision ◽  
Precision Machine Tools ◽  
Aerostatic Spindle

The aerostatic journal bearings are widely used in ultra-precision machine tools. Due to remarkable ability of the porous medium in flow restriction, the porous aerostatic journal bearings are better than other types of aerostatic bearings in load carrying capacity, stiffness, damping and dynamic stability. The partially porous aerostatic journal bearing has the advantages of easy production and low cost. Moreover, the gap between the porous insert and the spindle can be adjusted to reduce the eccentricity due to high speed rotation. In this study, the effects of the size of the porous insert and the thickness of the air gap between the spindle and the housing on the gap pressure, the stiffness and the load carrying capability of the partially porous aerostatic journal bearing were figured out for performance evaluation.

Measurement and analysis for frequency domain error of ultra-precision spindle in a flycutting machine tool

2016 ◽  
Vol 232 (9) ◽  
pp. 1501-1507 ◽  
Author(s):  
Guoda Chen ◽  
Yazhou Sun ◽  
Chenhui An ◽  
Feihu Zhang ◽  
Zhiji Sun ◽  
...  
Keyword(s):  
Machine Tool ◽  
Frequency Domain ◽  
Frequency Domain Analysis ◽  
Frequency Characteristics ◽  
Machining Process ◽  
Machining Accuracy ◽  
Machined Surface ◽  
Ultra Precision ◽  
Machining Process Planning ◽  
Aerostatic Spindle

The ultra-precision spindle is the key component of ultra-precision machine tool, which largely influences the machining accuracy. Its frequency characteristics mainly affect the frequency domain error of the machined surface. In this article, the error measurement setup for the ultra-precision aerostatic spindle in a flycutting machine tool is established. The dynamic and multi-direction errors of the spindle are real-time measured under different rotation speeds. Then, frequency domain analysis is carried out to obtain its regularity characteristics based on the measurement result. Through the analysis, the main synchronous and asynchronous errors with relatively large amplitude of the spindle errors are found, and the amplitude change law of these main spindle errors is obtained. Besides, the cause of the main synchronous and asynchronous errors is also analyzed and indicated. This study deepens the understanding of ultra-precision spindle dynamic characteristics and plays the important role in the spindle frequency domain errors’ control, machining process planning, frequency characteristics analysis and oriented control of the machined surface errors.

A Compact Aerostatic Spindle Integrated with an Axial Positioning Actuator for Micro and Ultra-Precision Machine Tools

2008 ◽  
Vol 2 (1) ◽  
pp. 56-63 ◽  
Author(s):  
Tadahiko Shinshi ◽  
◽  
Kaiji Sato ◽  
Akira Shimokohbe ◽  
Keyword(s):  
Machine Tools ◽  
Laser Interferometer ◽  
Voice Coil Motor ◽  
Milling Machine ◽  
Main Shaft ◽  
Air Motor ◽  
Ultra Precision ◽  
Precision Machine Tools ◽  
Aerostatic Spindle ◽  
The Voice

An aerostatic spindle integrated with an axial positioning actuator and an air motor has been proposed and fabricated for use in a compact high-precision milling machine. The main shaft of the spindle itself can be axially positioned using a built-in voice coil motor and rotated using an air motor so that the compact spindle system can realize both functions of a one-DOF positioning table and the spindle. The prototype main shaft, which is 20 mm in diameter, 147.5 mm in length and 0.26 kg in weight, could rotate at over 15,000 rpm. The main shaft can also be positioned using a laser interferometer system with an axial positioning range of..5 mm, and axial resolutions of 1.24 nm at rest and 24.7 nm at a speed of 15,000 rpm. Furthermore, the disturbance observer using the axial displacement and the current in the voice coil motor could react to an axial step force of 2 mN.

Study on the Compound Fuzzy Motion Control for the Ultra Precision Machine Tools

2006 ◽  
Vol 315-316 ◽  
pp. 813-816
Author(s):  
Bo Wang ◽  
Ying Chun Liang ◽  
Shen Dong
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Main Idea ◽  
Contour Error ◽  
Tracking Accuracy ◽  
Compound Control ◽  
Precision Machine ◽  
Contour Control ◽  
Ultra Precision ◽  
Precision Machine Tools

This paper presents a sophisticated trajectory tracking algorithm based on the utilization of the compound control and fuzzy contour control for the ultra precision machine tools. The main idea is to use the compound control to broaden the bandwidth of the servo system and, therefore, improve the tracking accuracy of the single axis. Then, FUZZY cross coupled contour control is introduced to compensate for the contour error caused by imperfect dynamics of the tracking axis and the mismatch of the control parameters of the servo systems. Experiments carried out on the HCM-1 ultra precision machine tool with a T-type layout show that the integration of the compound control with the fuzzy cross coupled contour control can effectively improve the contour tracking accuracy of the ultra precision machine tool.

scholarly journals Modal analysis of an aerostatic spindle system for ultra-precision machine tools at different spin speeds

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401879852 ◽  
Author(s):  
Peng Chen ◽  
Hui Zhuang ◽  
Yu Chang ◽  
Jianguo Ding ◽  
Qidi Zhong ◽  
...  
Keyword(s):  
Flow Field ◽  
Rotational Speed ◽  
Machine Tools ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Spindle System ◽  
Precision Machine ◽  
Ultra Precision ◽  
Precision Machine Tools ◽  
Aerostatic Spindle

The dynamic properties of aerostatic spindle systems vary with the spindle speed and have a significant impact on the processing quality of ultra-precision machine tools. In this article, using the ICEM CFD, the structured grid model of a large-span scale gas film is built under the condition in which the ratio of the spindle gas film length to the gas film thickness is 13,100. Integral calculation model of spindle and thrust is established and CEL expressions are compiled based on dynamic meshing technique to acquire trajectory of aerostatic spindle system. The degree of freedom method is used to obtain flow field of spindle system. Considering the spindle system as an elastomer, the influence of rotational speed on natural frequencies is studied under the flow field boundary. The results indicate that the former four-order natural frequencies of the aerostatic spindle system will clearly increase as the rotational speed increases. The increase in the fifth- to seventh-order natural frequencies is small, and the eighth-order natural frequency is almost invariable. The flow field has little influence on the mode shapes of the aerostatic spindle system. The former four-order natural frequencies of spindle system decrease considering rotation effects. Rotational speed and rotation effects mainly impact the tilting motion natural frequencies of spindle and thrust.

scholarly journals Automatic detection of 39 fundus diseases and conditions in retinal photographs using deep neural networks

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ling-Ping Cen ◽  
Jie Ji ◽  
Jian-Wei Lin ◽  
Si-Tong Ju ◽  
Hong-Jie Lin ◽  
...  
Keyword(s):  
Deep Learning ◽  
High Efficiency ◽  
Characteristic Curve ◽  
Weighted Average ◽  
Age Related Macular Degeneration ◽  
Learning Platform ◽  
Age Related ◽  
Public Data ◽  
Primary Test ◽  
Retinal Fundus

AbstractRetinal fundus diseases can lead to irreversible visual impairment without timely diagnoses and appropriate treatments. Single disease-based deep learning algorithms had been developed for the detection of diabetic retinopathy, age-related macular degeneration, and glaucoma. Here, we developed a deep learning platform (DLP) capable of detecting multiple common referable fundus diseases and conditions (39 classes) by using 249,620 fundus images marked with 275,543 labels from heterogenous sources. Our DLP achieved a frequency-weighted average F1 score of 0.923, sensitivity of 0.978, specificity of 0.996 and area under the receiver operating characteristic curve (AUC) of 0.9984 for multi-label classification in the primary test dataset and reached the average level of retina specialists. External multihospital test, public data test and tele-reading application also showed high efficiency for multiple retinal diseases and conditions detection. These results indicate that our DLP can be applied for retinal fundus disease triage, especially in remote areas around the world.

scholarly journals Ultra-precision: enabling our future

2012 ◽  
Vol 370 (1973) ◽  
pp. 3993-4014 ◽  
Author(s):  
Paul Shore ◽  
Paul Morantz
Keyword(s):  
Mass Production ◽  
Machine Tools ◽  
Well Being ◽  
First Century ◽  
Precision Engineering ◽  
Precision Machine ◽  
Ultra Precision ◽  
Manufacturing Accuracy ◽  
Precision Machine Tools ◽  
Wealth Generation

This paper provides a perspective on the development of ultra-precision technologies: What drove their evolution and what do they now promise for the future as we face the consequences of consumption of the Earth’s finite resources? Improved application of measurement is introduced as a major enabler of mass production, and its resultant impact on wealth generation is considered. This paper identifies the ambitions of the defence, automotive and microelectronics sectors as important drivers of improved manufacturing accuracy capability and ever smaller feature creation. It then describes how science fields such as astronomy have presented significant precision engineering challenges, illustrating how these fields of science have achieved unprecedented levels of accuracy, sensitivity and sheer scale. Notwithstanding their importance to science understanding, many science-driven ultra-precision technologies became key enablers for wealth generation and other well-being issues. Specific ultra-precision machine tools important to major astronomy programmes are discussed, as well as the way in which subsequently evolved machine tools made at the beginning of the twenty-first century, now provide much wider benefits.

Indentation Crack Initiation and Ductile to Brittle Transition Behavior of Fused Silica

2013 ◽  
Vol 797 ◽  
pp. 667-672 ◽  
Author(s):  
Peng Yao ◽  
Wei Wang ◽  
Chuan Zhen Huang ◽  
Jun Wang ◽  
Hong Tao Zhu ◽  
...  
Keyword(s):  
Penetration Depth ◽  
High Efficiency ◽  
Fused Silica ◽  
Load Range ◽  
Brittle Transition ◽  
Ductile Mode ◽  
Indentation Crack ◽  
Ultra Precision ◽  
Ductile To Brittle Transition ◽  
Brittle Mode

To provide a fundamental knowledge for the high efficiency grinding and ultra-precision grinding of fused silica, ductile mode and brittle mode material removal mechanisms were investigated by conducting micro/nanoindentation experiments in the range of 4.9 mN - 1960 mN. Before observing cracks and determining the ductile to brittle transition penetration depth, the samples were etched with hydrofluoric acid to expose cracks. The typical damage morphology of fused silica was discussed by observing the surface and cross-section of indentations, and the depth of SSD was found to be determined by the cone cracks or borderline cracks in the different load range. The ductile to brittle transition penetration depth of fused silica under Vickers indentation was 180 nm.

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