Mirror Mapping of Laser Interferometer Measurement System on Ultra-precise Movement Stage

The accuracy and repeatability of the laser interferometer measurement system （LIMS） are often limited by the mirror surface error that comes from the mirror surface shape and distortion. This paper describes a new method to calibrate mirror map on ultraprecise movement stage （UPMS） with nanopositioning and to make a real-time compensation for the mirror surface error by using mirror map data tables with the software algorithm. Based on the mirror map test model, the factors affecting mirror map are analyzed through geometric method on the UPMS with six digrees of freedom. Dam processing methods including spline interpolation and spline offsets are used to process the raw sampling data to build mirror map tables. The linear interpolation as compensation method to make a real-time correction on the stage mirror unflatness is adopted and the correction formulas are illuminated. In this way, the measurement accuracy of the system is obviously improved from 40 nm to 5 nm.

Ultra-precision positioning control technique based on neural network

Due to the non-linearity behavior of the precision positioning system, an accurate mathematical control model is difficult to set up, a novel control method for ultra-precision alignment is presented. This method relies on neural network and alignment marks that are in the form of 100μm pitch gratings. The 0-th order Moire signals＇ intensity and its intensity rate are chosen as input variables of the neural network. The characteristics of the neural network make it possible to perform self-training and self-adjusting so as to achieve automatic precision alignment. A neural network model for precision positioning is set up. The model is composed of three neural layers, i.e. input layer, hidden layer and output layer. Driving signal is obtained by mapping Moire signals＇ intensity and its intensity rate. The experimental results show that neural network control for precision positioning can effectively improve positioning speed with high accuracy. It has the advantages of fast, stable response and good robustness. The device based on neural network can achieve the positioning accuracy of ± 0. 5μm.

Ultra-precision alignment technique based on modified Moiré signals

A novel method for automatic ultra-precision alignment is presented.This method relies on the modified Moiré technique,and alignment marks are used in the form of gratings.The modified Moiré technique can effectively improve detecting sensitivity of signals and simplify the control system by using only one pair of laser-Moiré sensors.We present the mathematical model and simulation results of diffracting two gratings.The effect of various parameters on Moiré signals is studied theoretically and experimentally,and the results are found to be consistent.A computer controlled alignment device using one pair of Moiré sensors is designed.The device can achieve a fully automatic precision alignment by the modified Moiré signal.The experimental result shows that the alignment device can obtain the resolution of 5 nm and the positioning accuracy of ±0 5 μm.

Novel Batch Polishing Method of Ceramic Cutting Inserts for Reducing Tool Wear

Ceramic cutting inserts are a type of cutting tool commonly used in high-speed metal cutting applications.However,the wear of these inserts caused by friction between the workpiece and cutting inserts limits their overall effectiveness.In order to improve the tool life and reduce wear,this study introduces an emerging method called magnetic field-assisted batch polishing(MABP)for simultaneously polishing multiple ceramic cutting inserts.Several polishing experiments were conducted under different conditions,and the wear characteristics were clarified by cutting S136H steel.The results showed that after 15 min of polishing,the surface roughness at the flank face,edge,and nose of the inserts was reduced to below 2.5 nm,6.25 nm,and 45.8 nm,respectively.Furthermore,the nose radii of the inserts did not change significantly,and there were no significant changes in the weight percentage of elements before and after polishing.Additionally,the tool life of the batch polished inserts was found to be up to 1.75 times longer than that of unpolished inserts.These findings suggest that the MABP method is an effective way to mass polish ceramic cutting inserts,resulting in significantly reduced tool wear.Furthermore,this novel method offers new possibilities for polishing other tools.

Research status and challenges in the manufacturing of IR conformal optics

The infrared conformal window is one of the most critical components in aircraft.Conformal windows with high performance bring low aberrations,high aerodynamic performance,reliability in extreme working environments,and added value for aircraft.Through the past decades,remarkable advances have been achieved in manufacturing technologies for conformal windows,where the machining accuracy approaches the nanometer level,and the surface form becomes more complex.These advances are critical to aircraft development,and these manufacturing technologies also have significant reference values for other directions of the ultra-precision machining field.In this review,the infrared materials suitable for manufacturing conformal windows are introduced and compared with insights into their performances.The remarkable advances and concrete work accomplished by researchers are reviewed.The challenges in manufacturing conformal windows that should be faced in the future are discussed.

INFLUENCE OF WHEEL STRUCTURAL PARAMETERS ON MACHINING ACCURACY OF ULTRA-PRECISION PLANE HONING

A new idea for designing wheel patterns is presented so as to solve theproblems about machining accuracy of workpiece and wear of honing wheel in ultra-precision planehoning. The influence factors on motion principle and pattern structures are analyzed andoptimization machining parameters are obtained. By calculating effective cutting length on thesurface of workpiece cut by wheel's abrasive and the orbit of one point on the surface of workpiececontacting with wheel, the wear coefficient of different kinds of wheels and accuracy coefficient ofworkpiece machined by corresponding wheels are obtained. Furthermore, the simulation results showthat the optimal pattern structure of wheel turns out to have lower wheel wear and higher machiningaccuracy.

Dynamic Accuracy Design Method of Ultra-precision Machine Tool

Ultra-precision machine tool is the most important physical tool to machining the workpiece with the frequency domain error requirement, in the design process of which the dynamic accuracy design(DAD) is indispensable and the related research is rarely available. In light of above reasons, a DAD method of ultra-precision machine tool is proposed in this paper, which is based on the frequency domain error allocation.The basic procedure and enabling knowledge of the DAD method is introduced. The application case of DAD method in the ultra-precision flycutting machine tool for KDP crystal machining is described to show the procedure detailedly. In this case, the KDP workpiece surface has the requirements in four different spatial frequency bands, and the emphasis for this study is put on the middle-frequency band with the PSD specifications. The results of the application case basically show the feasibility of the proposed DAD method. The DAD method of ultra-precision machine tool can effectively minimize the technical risk and improve the machining reliability of the designed machine tool. This paper will play an important role in the design and manufacture of new ultra-precision machine tool.

Systematic analysis of error sources during ultra-precision machining

During ultra-precision machining, machining accuracy is determined by many factors and interaction of these factors. Error sources are systematically analyzed for ultra-precision machine tools, and the influencing degree of each factor is presented to provide orientation for error reduction and error compensation.

Study of material removal behavior on R-plane of sapphire during ultra-precision machining based on modified slip-fracture model

In this paper, the modified slip/fracture activation model has been used in order to understand the mechanism of ductile-brittle transition on the R-plane of sapphire during ultra-precision machining by reflecting direction of resultant force. Anisotropic characteristics of crack morphology and ductility of machining depending on cutting direction were explained in detail with modified fracture cleavage and plastic deformation parameters. Through the analysis, it was concluded that crack morphologies were mainly determined by the interaction of multiple fracture systems activated while, critical depth of cut was determined by the dominant plastic deformation parameter. In addition to this, by using proportionality relationship between magnitude of resultant force and depth of cut in the ductile region, an empirical model for critical depth of cut was developed.

TWO-COORDINATE DUAL-SERVO CONTOURERROR COMPENSATION TECHNOLOGY FOR ULTRA-PRECISION MANUFACTURING

A technology of two-coordinate dual-servo(TCDS) is proposed. Using this technology which is based on error compensation, workpieces of higher contour accuracy could he turned on ultra-precision machine tool with Poor dynamic performances. The principle, constitute and operation of a TCDS system are described. Mathematical proof and experiments are achieved in addition.

Mesoplasticity Approach to Studies of the Cutting Mechanism in Ultra-precision Machining

There have been various theoretical attempts by researchers worldwide to link up different scales of plasticity studies from the nano-, micro- and macro-scale of observation, based on molecular dynamics, crystal plasticity and continuum mechanics. Very few attempts, however, have been reported in ultra-precision machining studies. A mesoplasticity approach advocated by Lee and Yang is adopted by the authors and is successfully applied to studies of the micro-cutting mechanisms in ultra-precision machining. Traditionally, the shear angle in metal cutting, as well as the cutting force variation, can only be determined from cutting tests. In the pioneering work of the authors, the use of mesoplasticity theory enables prediction of the fluctuation of the shear angle and micro-cutting force, shear band formation, chip morphology in diamond turning and size effect in nano-indentation. These findings are verified by experiments. The mesoplasticity formulation opens up a new direction of studies to enable how the plastic behaviour of materials and their constitutive representations in deformation processing, such as machining can be predicted, assessed and deduced from the basic properties of the materials measurable at the microscale.

Research of Digital Manufacturing Technology Application on Ultra-precision Optical Workpiece Machining

Digital manufacturing technology can be used in optical field to solve many problems caused by traditional machining. According to the characters of digital manufacturing and the practical applications of ultra-precision machining,the process of digital ultra-precision machining and its technical contents were presented in this paper. In the conclusions,it was stated that the digitalization of ultra-precision machining will be an economical and efficient way for the production of new sorts of optical workpieces.

Dynamic modeling of ultra-precision fly cutting machine tool and the effect of ambient vibration on its tool tip response

The dynamic performances of an ultra-precision fly cutting machine tool(UFCMT)has a dramatic impact on the quality of ultra-precision machining.In this study,the dynamic model of an UFCMT was established based on the transfer matrix method for multibody systems.In particular,the large-span scale flow field mesh model was created;and the variation in linear and angular stiffness of journal and thrust bearings with respect to film thickness was investigated by adopting the dynamic mesh technique.The dynamic model was proven to be valid by comparing the dynamic characteristics of the machine tool obtained by numerical simulation with the experimental results.In addition,the power spectrum density estimation method was adopted to simulate the statistical ambient vibration excitation by processing the ambient vibration signal measured over a long period of time.Applying it to the dynamic model,the dynamic response of the tool tip under ambient vibration was investigated.The results elucidated that the tool tip response was significantly affected by ambient vibration,and the isolation foundation had a good effect on vibration isolation.

Active vibration control of spindle in ultra-precision turning machine

In order to minimize vibration and improve rotary precision of spindle, we apply active vibration control technique to ultra-precision turning machine based on the analysis of vibration characteristic of aerostatic bearing spindle. Using aerostatic bearing itself as actuator, the vibration of spindle is controlled by adjusting admission pressure respectively and by changing pressure distribution in the bearing. The experiments and simulations prove that this method can minimize the vibration of spindle effectively.

Optimization of Honing Wheel Structure Parameters in Ultra-precision Plane Honing

Free abrasive particle machining in simple machine such as: honing, polishing can get higher surface finish mirror, but surface error, and working procedure is hard to control. Therefore, the vertical disposed ultra-precision plane honing method by ultra-particle diamond honing wheel is put forward to. The results of experiments indicate: plane-honing wheel has higher machining accuracy and machining efficiency. But at the same time the structure parameters of honing wheel effects on machining accuracy. By analyzing the relation of honing wheel structure parameters and workpiece machining accuracy, the relation of honing wheel and wear coefficient, then this paper gets honing wheel structure parameters in the condition of best accuracy coefficient and wear coefficient, and resolve the problem of choosing honing wheel structure parameters in ultra-precision plane honing at last. This paper analyses the relation of honing wheel structure parameters and workpiece machining accuracy coefficient and wear coefficient, by building relative movement math model of honing wheel and workpiece in plane honing. Through theory calculating, the result indicate: about honing machine tools for large volume manufacture, honing wheel wear is main effect factor, so honing wheel should adopt obverse triangle radial structure. About honing machining for high accuracy and low-batch quantities, machining accuracy coefficient is main factors; so honing wheel should adopt reverse triangle radial structure. Neglected the manufacturing factors of honing wheel, then we can design honing wheel with high power curve structure to meet the need of machining accuracy coefficient and honing wheel wear coefficient in higher accuracy honing.

Tool path generation of ultra-precision diamond turning: A state-of-the-art review

With the increasing market demand for optical complex surface parts,the application of multi-axis ultraprecision single-point diamond turning is increasing.A tool path generation method is very important to decrease manufacturing time,enhance surface quality,and reduce cost.Compared with the tool path generation of the traditional multi-axis milling,that of the ultra-precision single-point diamond turning requires higher calculation accuracy and efficiency.This paper reviews the tool path generation of ultra-precision diamond turning,considering several key issues:cutter location(CL)points calculation,the topological form of tool path,interpolation mode,and G code optimization.

Design of Ultra-Precision CNC Grinding Machine and Its Application in Machining Large Aspheric Mirrors

Large aspheric mirrors are needed for the remote sensing and ground based telescope optical systems,these mirrors are made of hard and brittle materials which require ultra-precision grinding process to guarantee the high profile accuracy and machining efficiency. The ultra-precision aspheric CNC grinding machine( UAG900) is presented by this paper,as well as its grinding capability. The hydrostatic bearings of high accuracy and stiffness are adopted by the linear and rotary motions to guarantee the mirror accuracy,material removal rate and subsurface damage. Disk type grinding wheel with arc edge is used. The material removal rate can be up to 360 mm3/ min to guarantee the machining efficiency during rough grinding using D180 diamond grinding wheel while the fine grinding is performed using D15 grinding wheel. It indicates that the grinding wheel radius measuring error is proportional to the profile error induced by the grinding path. The grinding step size is better to be 0. 01 mm for the reduction of the grinding movement accelerations and program length. The grinding path is planned and expressed based on the grinding mode according to the mirror shape. One540 mm×450 mm× 100 mm zerodur mirror is ground and re-ground using the measuring data acquired by the Leitz CMM. The final surface accuracy of P-V value is less than 5 μm after compensation grinding.

3D surface topography formation in ultra-precision turning

The generation process of 3D surface topography in ultra-precision turning is analyzed, as the result of superimposing between actual roughness surface,waviness surface and geometrical form texture surface. From the viewpoints of machine technical system and manufacturing process,factors influencing on roughness surface, waviness surface and geometrical form texture surface in ultra-precision turning are discussed further.The 3D topography of ideal roughness surface and actual surface affected by cutting vibration are simulated respectively.

Research on Large Depth Diameter Ratio Ultra-precision Aspheric Grinding System

In this paper, the factors of affecting surface roughness and profiles accuracy of the machined larege depth diamter ratio aspheric surfaces in ultra-precision grinding process are analyzed theoretically. An ultra-precision aspheric grinding system is then designed and manufactured. Aerostatic form is adopted to build the spindle of the workpiece, transverse guideway, longitudinal guideway and the spindle of the grinder in this system. The following specification is achieved, such as the turning accuracy of the spindle of the workpiece is 0.05 μm, radial rigidity of the spindle is GE 220N/μm, axial rigidity is GE 160 N/μm, radial rigidity of the guideway is GE 200N/μm, the highest rotational speed of the grinder is 80 000 rev/min and its turning accuracy is 0.1 μm, the resolution of linear displacement of the transverse and longitudinal guideway is 4.9 nm. Adjusting range of this adjusting mechanism is 2 mm in the Y direction, the adjusting accuracy of the precise adjusting mechanism is 0.1 μm. Micro displacement measuring system of this ultra-precision aspheric grinding adopts two-backfeed strategy, and angle displacement back-feed is realized by photoelectric encoder, it’s resolution is 655 360 pulse/rev. after 4 frequency multiplication, it’s angle displacement resolution is achieved 2 621 440 pulse/rev. Straight-line displacement is monitored by single frequency laser interferometer (DLSTAX LTM-20B, made in Japan). This CNC system adopts inimitable bi-arc step length flex CN interpolation algorithm, it’s CN system resolution is 5 nm.So this aspheric grinding system ensures profile accuracy of the machined part. The resolution of this interferometer is 5 nm. Finally, lots of ultra-precision grinding experiments are carried out on this grinding system. Some optical aspheric parts, with profiles accuracy of 0.3 μm, surface roughness less than 0.01 μm, are obtained.

Prediction of cutting force in ultra-precision machining of nonferrous metals based on strain energy

The effects of the nonuniform cutting force and elastic recovery of processed materials in ultra-precision machining are too complex to be treated using traditional cutting theories,and it is necessary to take account of factors such as size effects,the undeformed cutting thickness,the tool blunt radius,and the tool rake angle.Therefore,this paper proposes a new theoretical calculation model for accurately predicting the cutting force in ultra-precision machining,taking account of such factors.The model is first used to analyze the material deformation of the workpiece and the cutting force distribution along the cutting edge of a diamond tool.The size of the strain zone in different cutting deformation zones is then determined by using the distribution of strain work per unit volume and considering the characteristics of the stress distribution in these different deformation zones.Finally,the cutting force during ultra-precision machining is predicted precisely by calculating the material strain energy in different zones.A finite element analysis and experimental data on ultra-precision cutting of copper and aluminum are used to verify the predictions of the theoretical model.The results show that the error in the cutting force between the calculation results and predictions of the model is less than 14%.The effects of the rake face stress distribution of the diamond tool,the close contact zone,and material elastic recovery can be fully taken into account by the theoretical model.Thus,the proposed theoretical calculation method can effectively predict the cutting force in ultra-precision machining.