scholarly journals Investigation of a dynamics-oriented engineering approach to ultraprecision machining of freeform surfaces and its implementation perspectives

2021 ◽  
Vol 4 (4) ◽  
pp. 043002
Author(s):  
Ali Khaghani ◽  
Kai Cheng
Keyword(s):  
Ultraprecision Machining ◽  
Freeform Surfaces ◽  
Engineering Approach

Investigation on multi-body dynamics based approach to the toolpath generation for ultraprecision machining of freeform surfaces

2019 ◽  
Vol 234 (3) ◽  
pp. 571-583 ◽  
Author(s):  
Ali Khaghani ◽  
Kai Cheng
Keyword(s):  
Rotational Symmetry ◽  
Single Point ◽  
Equations Of Motion ◽  
Critical Role ◽  
Diamond Turning ◽  
Ultraprecision Machining ◽  
Time Step ◽  
Freeform Surfaces ◽  
Time Step Size ◽  
Toolpath Generation

This article presents an innovative approach to toolpath generation for ultraprecision machining of freeform optic surfaces based on the principle of Automatic Dynamics Analysis of Mechanical Systems. As components with freeform surfaces often have non-rotational symmetry, there are potential challenges facing their ultraprecision machining through single-point diamond turning, such as the projected points in complex large sag surfaces, which likely find it difficult to communicate with the control system and, thus, do not perform successfully. In ultraprecision machining, to achieve the highest performance in freeform surface resolution, the factors of dynamics, material and mechanical stiffness, frictions, tooling and accuracy of the servo component should be considered. The investigation is focused on an integrated approach and the associated scientific understanding of precision engineering design, ultraprecision machining and metrology of freeform surfaces as well as their application perspective. In this approach, the toolpath for very complex freeform surfaces can be generated using the Newton–Raphson method to solve the kinematics and dynamics equations of motion. The effect of friction and contact force are also investigated for accurate toolpath curve generation. Moreover, the Gear stiff (GSTIFF)/ Wielenga stiff (WSTIFF) integrator for solving the non-linear equations of motion is employed, and the result shows the time step size, playing a critical role in generating toolpath curves with a higher accuracy and resolution.

The Control Algorithm of Ultrasonic-Magnetorheological Combined Finishing for Rotary Symmetrical Aspheric Surface

2010 ◽  
Vol 97-101 ◽  
pp. 2099-2102
Author(s):  
Fei Hu Zhang ◽  
Xing Bin Yu ◽  
Yong Zhang ◽  
Yong Yong Lin ◽  
Dian Rong Luan
Keyword(s):  
Computer Simulation ◽  
Dwell Time ◽  
Control Algorithm ◽  
Curvature Radius ◽  
Aspheric Surface ◽  
Ultraprecision Machining ◽  
Freeform Surfaces ◽  
Aspheric Surfaces ◽  
A New Technique ◽  
Derivation Process

Concave aspheric surface with small curvature radius is difficult to fabricate by most of existing technologies. Ultrasonic- magnetorheological combined finishing (UMC) is a new technique for the ultraprecision machining of aspheric surfaces, especially for the ultrasmooth surfaces machining of small-radiuses concave surfaces and freeform surfaces. According to the characteristics of rotary symmetrical aspheric surface, path algorithms for UMC finishing have been developed. Propose and compare two kinds of polishing dwell time algorithms, and the derivation process and computer simulation result of the algorithms was also presented. The experiments using the control algorithm have been conducted, and the efficiency of algorithm is proved by experimental results.

On the nominal transverse shear strain to characterize the severity of creasing

TAPPI Journal ◽  
2018 ◽  
Vol 17 (04) ◽  
pp. 231-240
Author(s):  
Douglas Coffin ◽  
Joel Panek
Keyword(s):  
Shear Strain ◽  
Transverse Shear ◽  
Elastic Limit ◽  
Experimental Results ◽  
Transverse Shear Strain ◽  
Maximum Strain ◽  
Machine Direction ◽  
Engineering Approach ◽  
Wide Range ◽  
Analytic Expression

A transverse shear strain was utilized to characterize the severity of creasing for a wide range of tooling configurations. An analytic expression of transverse shear strain, which accounts for tooling geometry, correlated well with relative crease strength and springback as determined from 90° fold tests. The experimental results show a minimum strain (elastic limit) that needs to be exceeded for the relative crease strength to be reduced. The theory predicts a maximum achievable transverse shear strain, which is further limited if the tooling clearance is negative. The elastic limit and maximum strain thus describe the range of interest for effective creasing. In this range, cross direction (CD)-creased samples were more sensitive to creasing than machine direction (MD)-creased samples, but the differences were reduced as the shear strain approached the maximum. The presented development provides the foundation for a quantitative engineering approach to creasing and folding operations.

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