Frequency Domain Error Analysis in Ultra-Precision Flycutting

In some special fields such as precision optics, the part surface has strict requirements on the frequency domain errors, besides the conventional spatial domain errors such as surface roughness error. In light of the available works lacking of the frequency domain error analysis in ultra-precision flycutting, this paper therefore presents its frequency domain error analysis. A case study of KDP crystal flycutting is carried out to show its detailed processes, where the processing parameters, tool geometry, motion dynamic error of the machine guideway and tool-work vibration induced dynamic error are considered. A surface profile generation method is put forward. Two cases with different tool-work vibration frequencies are carried out. The spatial frequency spectrum is obtained based on the FFT analysis of the generated profile in the specified direction. After the in-depth analysis, the inherent correlation of the generated spatial frequency components with feed spatial frequency and machine dynamic errors induced spatial frequency under certain machining conditions are found, which is very meaningful for the frequency domain error prediction in the real application. The proposed analysis method can also be applied into other types of surface machining.

Download Full-text

An Investigation of the Cutting Strategy for the Machining of Polar Microstructures Used in Ultra-Precision Machining Optical Precision Measurement

Micromachines ◽

10.3390/mi12070755 ◽

2021 ◽

Vol 12 (7) ◽

pp. 755

Author(s):

Chen-Yang Zhao ◽

Chi-Fai Cheung ◽

Wen-Peng Fu

Keyword(s):

Precision Measurement ◽

Detection Algorithm ◽

Surface Generation ◽

Precision Machining ◽

Tool Geometry ◽

Depth Of Cut ◽

Machining Parameters ◽

Ultra Precision ◽

Transition Points ◽

Cutting Strategy

In this paper, an investigation of cutting strategy is presented for the optimization of machining parameters in the ultra-precision machining of polar microstructures, which are used for optical precision measurement. The critical machining parameters affecting the surface generation and surface quality in the machining of polar microstructures are studied. Hence, the critical ranges of machining parameters have been determined through a series of cutting simulations, as well as cutting experiments. First of all, the influence of field of view (FOV) is investigated. After that, theoretical modeling of polar microstructures is built to generate the simulated surface topography of polar microstructures. A feature point detection algorithm is built for image processing of polar microstructures. Hence, an experimental investigation of the influence of cutting tool geometry, depth of cut, and groove spacing of polar microstructures was conducted. There are transition points from which the patterns of surface generation of polar microstructures vary with the machining parameters. The optimization of machining parameters and determination of the optimized cutting strategy are undertaken in the ultra-precision machining of polar microstructures.

Download Full-text

Coconuts and curtain cakes: The production of wh-questions in ASD

Autism & Developmental Language Impairments ◽

10.1177/2396941520982953 ◽

2021 ◽

Vol 6 ◽

pp. 239694152098295

Author(s):

Nufar Sukenik ◽

Eléonore Morin ◽

Naama Friedmann ◽

Philippe Prevost ◽

Laurice Tuller

Keyword(s):

Error Analysis ◽

Language Disorder ◽

Syntactic Structure ◽

Autism Spectrum ◽

Production Rates ◽

Fine Grained ◽

Depth Analysis ◽

Wh Questions ◽

Analysis Of Error ◽

Error Types

Background and aims Children with autism spectrum disorders (ASD) have been found to exhibit difficulties in wh-question production. It is unclear whether these difficulties are pragmatic or syntactic in nature. The current study used a question elicitation task to assess the production of subject and object wh-questions of children with ASD in two different languages (Hebrew and French) wherein the syntactic structure of wh-questions is different, a fact that may contribute to better understanding of the underlying deficits affecting wh-question production. Crucially, beyond the general correct/error rate we also performed an in-depth analysis of error types, comparing syntactic to pragmatic errors and comparing the distribution of errors in the ASD group to that of children with typical development (TD) and children with Developmental Language Disorder (DLD). Results Correct production rates were found to be similar for the ASD and DLD groups, but error analysis revealed important differences between the ASD groups in the two languages and the DLD group. The Hebrew- and French ASD groups were found to produce pragmatic errors, which were not found in children with DLD. The pragmatic errors were similar in the two ASD groups. Syntactic errors were affected by the structure of each language. Conclusions Our results have shown that although the two ASD groups come from different countries and speak different languages, the correct production rates and more importantly, the error types were very similar in the two ASD groups, and very different compared to TD children and children with DLD. Implications: Our results highlight the importance of creating research tasks that test different linguistic functions independently and strengthen the need for conducting fine-grained error analysis to differentiate between groups and gain insights into the deficits underlying each of them.

Download Full-text

Study on Ultra-Precision Ball Surface Floating Polishing Kinematics Mechanism

Materials Science Forum ◽

10.4028/www.scientific.net/msf.532-533.109 ◽

2006 ◽

Vol 532-533 ◽

pp. 109-112

Author(s):

Xun Lv ◽

Ju Long Yuan ◽

Dong Hui Wen ◽

Qian Fa Deng ◽

Fei Yan Lou

Keyword(s):

Chemical Conversion ◽

Processing Parameters ◽

Precision Machining ◽

High Tech ◽

National Defense ◽

Ball Surface ◽

Angular Velocities ◽

Ultra Precision ◽

Relationship Of ◽

The Mathematical Model

The high precision balls are requested in national defense, astronautics and high-tech commercial domain urgently. Conventional precision machining methods are sensitive to uniformity of abrasives and machining environment. After precision machining, there are easily to produce thick damaged layer on the ball surface because of machining stress and chemical conversion. On the basis of the floating polishing mechanism, a new scatheless ultra-precision polishing method of ball surface can solve the problems of abrasives uniformity effectively and damaged layer. In order to ensure that the new polishing method polishes ball surface equally, the appropriate angular velocities of the ball should be selected. This paper sets up the mathematical model about the motion of ball. By analyzing and simulating the relationship of the angular velocities, the best processing parameters are acquired.

Download Full-text