Ultraprecision Machining of Hybrid Freeform Surfaces Using Multiple-Axis Diamond Turning

2017 ◽  
Author(s):  
Dennis Wee Keong Neo
Keyword(s):  
Diamond Turning ◽  
Ultraprecision Machining ◽  
Freeform Surfaces

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 Current State and Development Trends of Deterministic Ultraprecision Optical Surfaces Machining Technology

2007 ◽  
Vol 364-366 ◽  
pp. 351-357
Author(s):  
Song Bao Luo ◽  
Hui Yang ◽  
Jian Ming Zhang ◽  
Chang Tao Pang
Keyword(s):  
Single Point ◽  
Diamond Turning ◽  
Ultraprecision Machining ◽  
Development Trends ◽  
Current State ◽  
Quantum Leap ◽  
Computer Controlled ◽  
Magneto Rheological ◽  
Technical Features ◽  
Accuracy And Repeatability

The deterministic ultraprecision machining achieves accuracy and repeatability not possible using conventional optical machining techniques, greatly enhances product quality, providing a quantum leap in throughput, productivity, yield, and cost effectiveness. The deterministic ultraprecision machining technology, involving various ultraprecision process from turning, flycutting, grinding and polishing to finishing, is usually referred to the following technologies such as single point diamond turning (SPDT), deterministic microgrinding (DMG), magneto-rheological finishing (MRF),computer controlled polishing (CCP), and computer controlled optical surfacing(CCOS),etc. This paper discusses mainly the current state and development trends of the deterministic ultraprecision machining technologies at home and abroad. In addition, the paper also elaborates on the technical features of the various deterministic machining technologies mentioned.

Real-Time Identification of Incipient Surface Morphology Variations in Ultraprecision Machining Process

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Prahalad Rao ◽  
Satish Bukkapatnam ◽  
Omer Beyca ◽  
Zhenyu (James) Kong ◽  
Ranga Komanduri
Keyword(s):  
Surface Morphology ◽  
Real Time ◽  
Process Monitoring ◽  
Diamond Turning ◽  
Machining Process ◽  
Complex Signal ◽  
Ultraprecision Machining ◽  
Real Time Monitoring ◽  
Process Dynamics ◽  
Sensor Signals

Real-time monitoring and control of surface morphology variations in their incipient stages are vital for assuring nanometric range finish in the ultraprecision machining (UPM) process. A real-time monitoring approach, based on predicting and updating the process states from sensor signals (using advanced neural networks (NNs) and Bayesian analysis) is reported for detecting the incipient surface variations in UPM. An ultraprecision diamond turning machine is instrumented with three miniature accelerometers, a three-axis piezoelectric dynamometer, and an acoustic emission (AE) sensor for process monitoring. The machine tool is used for face-turning aluminum 6061 discs to a surface finish (Ra) in the range of 15–25 nm. While the sensor signals (especially the vibration signal in the feed direction) are sensitive to surface variations, the extraneous noise from the environment, machine elements, and sensing system prevents direct use of raw signal patterns for early detection of surface variations. Also, nonlinear and time-varying nature of the process dynamics does not lend conventional statistical process monitoring techniques suitable for characterizing UPM-machined surfaces. Consequently, instead of just monitoring the raw sensor signal patterns, the nonlinear process dynamics wherefrom the signal evolves are more effectively captured using a recurrent predictor neural network (RPNN). The parameters of the RPNN (weights and biases) serve as the surrogates of the process states, which are updated in real-time, based on measured sensor signals using a Bayesian particle filter (PF) technique. We show that the PF-updated RPNN can effectively capture the complex signal evolution patterns. We use a mean-shift statistic, estimated from the PF-estimated surrogate states, to detect surface variation-induced changes in the process dynamics. Experimental investigations show that variations in surface characteristics can be detected within 15 ms of their inception using the present approach, as opposed to 30 ms or higher with the conventional statistical change detection methods tested.

Analytical Topography Simulation of Micro/Nano Textures Generated on Freeform Surfaces in Double-Frequency Elliptical Vibration Cutting Based Diamond Turning

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Chengming Zuo ◽  
Xiaoqin Zhou ◽  
Qiang Liu ◽  
Rongqi Wang ◽  
Jieqiong Lin ◽  
...  
Keyword(s):  
Diamond Turning ◽  
Cutting Edge ◽  
Machined Surface ◽  
Freeform Surfaces ◽  
Vibration Cutting ◽  
Double Frequency ◽  
Elliptical Vibration ◽  
Tool Surface ◽  
Surface Profiles ◽  
The Ideal

The surfaces with textures have been widely used as functional surfaces, and the textures are usually generated on flat or cylindrical surfaces. Textured freeform surfaces will have more potential applications. The authors have proposed the double-frequency elliptical vibration cutting (DFEVC) method to machine freeform surfaces on steel materials. Based on this method, a new diamond turning method is developed, in which the variable-frequency modulations are utilized to control the tool marks left on the machined surface to generate the micro/nano dimple textures with high uniformity on the freeform surface. Different from the conventional surface topography model based on the ideal tool cutting edge with zero cutting edge radius, a new modeling approach based on the tool surface profiles is proposed, in which the rake face, the flank face, and the cutting edge surface with actual non-zero cutting edge radius instead of the ideal cutting edge are included for the tool model, the tool surfaces during the machining process are analytically described as a function of the tool geometry and the machining parameters, and the influences of the tool surface profiles on the topography generation of the machined surface are considered. A typical freeform surface is textured on die steel, and the measured results verify the feasibility of the proposed turning method. Compared with the topography prediction results based on the ideal cutting edge, the results considering the tool surfaces show improved simulation accuracy, and are consistent with the experimental results, which validates the proposed topography prediction approach.

A tool path generation method for quasi-intermittent vibration assisted swing cutting

2020 ◽  
Vol 234 (6) ◽  
pp. 624-633
Author(s):  
Zhimin Zhu ◽  
Mingming Lu ◽  
Jieqiong Lin ◽  
Jiakang Zhou ◽  
Allen Yi ◽  
...  
Keyword(s):  
Tool Path ◽  
Spline Interpolation ◽  
Interpolation Theorem ◽  
Tool Path Generation ◽  
Diamond Turning ◽  
Tool Geometry ◽  
Machining Accuracy ◽  
Path Generation ◽  
Freeform Surfaces ◽  
Tool Trajectory

During the machining of freeform surfaces, the tool path will directly affect the machining accuracy of the surface, the execution of each axis of the machine tool, and the machining efficiency. Therefore, tool path planning is a very critical link in all types of diamond turning processes. In this paper, a new tool path generation strategy is proposed for machining freeform surfaces by quasi-intermittent vibration assisted swing cutting (QVASC) method. Due to the unique tool swing motion law of QVASC, the effective central angle of tool nose arc participating in the cutting is a parameter that is ignored by traditional cutting and is considered. This makes the generation of tool trajectories, tool geometry selection and freeform surfaces very different from traditional diamond cutting. According to the principle of QVASC, the tool parameters are analysed, and the tool position is designed in the cylindrical coordinate system. Interpolation was then performed by the Hermite spline interpolation theorem. The application of this strategy is discussed, and the sinusoidal surface, sinusoidal mesh surface and toric surface are taken as examples to simulate. The simulation succeeded in obtaining the tool path corresponding to the three curved surfaces processed by the QVASC method. The results prove that the tool trajectory generation strategy proposed in this paper is feasible. The proposed tool path generation strategy can provide a new reference for future freeform surfaces processing.

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