Measurement and compensation of error motions of a diamond turning machine

This paper describes the measurement and compensation of error motions of a diamond turning machine for nanofabrication of large sinusoidal metrology grids. The diamond turning machine has a T-base design, which consists of a spindle with its rotation axis along the Z-direction and a cross-slide with its movement direction along the X-direction. A fast-tool-servo (FTS) unit is mounted on the X-slide to generate sinusoidal microstructures on a flat workpiece surface mounted on the spindle. The error motions of the X-slide and the spindle, which introduce Z-directional profile errors (out-of-flatness) on the grid surface, are measured and compensated. The out-of-straightness of the X-slide is measured to be approximately 60 nm over a travel of 80 mm by using the reversal method. It is also confirmed that the out-of-straightness of the X-slide has a 10-nm periodic component with a period of 11 mm corresponding to the diameter of the needles used in the roller bearing of the X-slide. The angular motion of the spindle is measured to be approximately 0.3″ by using an autocollimator, which can cause a 73-nm out-of-flatness over a workpiece 100 mm in diameter. The axial motion of the spindle is measured to be approximately 5 nm, which is the smallest error motion. The out-of-flatness of the workpiece is reduced from 0.27 to 0.12 μm through compensating for the error motions by utilizing the FTS unit based on the measurement results of error motions.     

Machining accuracy improvement for a dual-spindle ultra-precision drum roll lathe based on geometric error analysis and calibration

This paper performs a comprehensive analysis and calibration on the geometric error of the ultra-precision drum roll lathe with dual-spindle symmetrical structure and cross slider layout. Firstly, the volumetric error model which contains all geometric errors of the dual-spindle ultra-precision drum roll lathe (DSUPDRL) is developed based on the combination of the homogenous transfer matrix (HTM) and multi-body system (MBS) theory. Secondly, sensitivity analysis for the volumetric error model is conducted to identify the sensitive geometric error components of the DSUPDRL using an improved Sobol method based on the quasi-Monte Carlo algorithm. The result of sensitivity analysis laid the foundation for the subsequent geometric error calibration. Then, some sensitive error components along the X and Z directions are calibrated using a laser interferometer and a pair of inductance displacement probes. Besides the volumetric error model, the concentricity error caused by dual-spindle symmetrical structure is proposed and calibrated by the on-machine measurement using a classic reversal method. Finally, a large-scale roller mold with a diameter of 250 mm and a length of 600 mm is machined using the DSUPDRL after calibration. The experimental result shows that 1.4 μm/600 mm generatrix accuracy is obtained, which validate the effectiveness of the geometric error analysis and calibration.     

Self-calibration and compensation of setting errors for surface profile measurement of a microstructured roll workpiece

Microstructured roll workpieces have been widely used as functional components in the precision industries. Current researches on quality control have focused on surface profile measurement of microstructured roll workpieces, and types of measurement systems and measurement methods have been developed. However, low measurement efficiency and low measurement accuracy caused by setting errors are the common disadvantages for surface profile measurement of microstructured roll workpieces. In order to shorten the measurement time and enhance the measurement accuracy, a method for self-calibration and compensation of setting errors is proposed for surface profile measurement of microstructured roll workpieces. A measurement system is constructed for the measurement, in which a precision spindle is employed to rotate the roll workpiece and an air-bearing displacement sensor with a micro-stylus probe is employed to scan the microstructured surface of the roll workpiece. The resolution of the displacement sensor is 0.14 nm and that of the rotary encoder of the spindle was 0.15r~. Geometrical and mathematical models are established for analyzing the influences of the setting errors of the roll workpiece and the displacement sensor with respect to the axis of the spindle, including the eccentric error of the roll workpiece, the offset error of the sensor axis and the zero point error of the sensor output. Measurement experiments are carded out on a roll workpiece on which periodic microstructures are a period of 133 i~m along the circumferential direction. Experimental results demonstrate the feasibility of the self-compensation method. The proposed method can be used to detect and compensate the setting errors without using any additional accurate artifact.     

Constructive-Technological Features of a Rotary Drawing of Geometrically Complex Hollow Shafts for Gas Turbine Engines

For manufacturing thin-walled shafts for gas turbine engines of heat-resistant steels and alloys, the labor-intensive multistage drawing of a sheet of the workpiece in dies is used. The following problem is posed in the work: to study the possibility of manufacturing such parts by a less labor-intensive method: the rotary drawing of a thick-walled workpiece (sheet) by a spinning lathe by rolling a roll under hot deformation conditions. For this purpose, the computer and physical modeling of the rolling process of hollow shafts of a thick-sheet steel workpiece was carried out. The important parameters of the technological process of manufacturing a geometrically complex shaft are determined: the initial workpiece shape and the changes in its shape when rolled on a mandrel mounted on the spindle of the spinning lathe of the PNC 600 type. The research results are used for rolling full-size shafts of chromium steel of the EI962-Sh grade.     

On-machine profile measurement of a micro cutting edge by using a contact-type compact probe unit

A new contact-type on-machine measurement system is designed and developed for the evaluation of a micro cutting edge profile. The measurement system is composed of a compact probe unit having a sharp stylus mounted on a flexible beam, an inner displacement sensor for the detection of the stylus displacement, and a two-axis precision positioning system. For the evaluation of tool faces having a steep slope, a new probing procedure with the enhancement of the inner displacement sensor integrated into the probe unit is newly proposed. After the design and development of the probe unit, the feasibilities of the developed measurement system and the proposed probing procedure are demonstrated through some basic experiments. Regarding the out-of-straightness and angular error motion of the two-axis positioning system employed in the developed measurement system, a pair of length gauges is newly employed to reduce the influences of error motions of the stage system. The topographic profile of the micro cutting edge obtained by the measurement system with the modified probe unit is then compared with those obtained by a commercial stylus profiler and a laser confocal microscope. The feasibility and effectiveness of the developed on-machine tool edge profile measurement system are also demonstrated through uncertainty analysis based on the GUM with the Monte-Carlo method.     

曲面类零件在线测量

利用数控车床和TP6C-T型触发式红外通讯测量头等软硬件建立了一套数控车床在线测量平台，分析异形测头的x、Y和z向误差、测量头原理误差等产生的原因，并提出了相应的解决方法，从而在数控车床上基本实现了曲面类零件轮廓在线测量。     

Measurement of lathe Z-slide straightness and parallelism using a flat land

A method is described to measure the straightness of travel of the carriage of a single-point diamond turning machine. The method also measures the slide parallelism to the workhead spindle. A cylindrical artifact was produced on the lathe and used as a straightedge. A flat land was cut in the artifact that was parallel to the workhead axis of rotation. The flat land was measured with a LVDT indicator. The method was demonstrated on a Moore Special Tool Co. M18 Aspheric Generator. The quality of measurements achieved were better than 0.1 μm.     

Effect of taper tension profile on the telescoping in a winding process of high speed roll to roll printing systems

Winding is an integral operation in almost every roll to roll system. A center-wound roll is one of the suitable and general schemes in a winding mechanism. In general, the quality of wound roll is known to be related to the lateral displacement error and starring defect of a wound roll. Especially, a telescoping within a center-wound roll can cause damages such as misalignment between layers, folding, wrinkle, etc. Taper tension is known to be one of the major factors which affect the shape of a wound roll. It is therefore necessary to analyze the relationship between taper tension profile and telescoping within the center-wound roll to prevent winding failure and to sustain high quality of the printed materials. It is hard to compensate for undesirable winding roll shapes such as telescoping, because a winding is commonly a final process in roll to roll systems and has no feedback control mechanism to correct winding roll shape directly during winding operation. Therefore, an optimal taper tension profile and the accurate control of it in a winding section could be one way to shape the fail-safe of a wound roll. Through the correlation between taper tension profile and telescoping in a winding process, a mathematical model for the telescoping due to tension distribution in cross machine direction was developed, and verified by experimental study. A new logic to determine the proper taper tension profile was designed by combining and analyzing the winding mechanism which includes nip induced tension model, relationship between taper tension profile and telescoping, relationship between taper value and telescoping. Numerical simulations and experimental results show that the proposed method is very useful for determining the desirable taper tension profile during the winding process and preventing defects of winding roll shape such as telescoping.     

数控曲轴连杆轴颈车床平衡装置的典型设计

CK43140/6m数控曲轴连杆轴颈车床在对曲轴连杆轴颈进行车削偏心件加工时,存在车床左、右主轴箱中的主轴与工件不平衡的问题。通过对数控曲轴连杆轴颈车床衡装置的典型设计,克服了由于曲轴连杆轴径车床的主轴与工件不平衡,而导致的在加工工件过程中主轴轴承由于受偏载而磨损大,机床精度保持性差,影响机床的使用寿命等问题。     

Two-dimensional matrix-based non-complex axis-of-rotation error modeling

This work applies to the evaluation of a spindle as an integral part of a machine whose task is the measurement or modifying the shape or other parameter of a workpiece. This includes the co-influences of the spindle, its drive units and structural loop of the machine. First, the matrix-based two-dimensional simplified solution free of complex numbers is described. Second, bounds that encompass all possible radial error motions are determined from the matrix-based model. Third, it is shown that excited unidirectional resonances are improperly perceived as retrograde errors during evaluation due to the calculation and removal of reference ball eccentricity effects. Fourth, using a Fourier multi-dimensional spatial spectrum model, the stator referenced spindle error can result in a particular mth spectral component producing an effect at both the m + 1 and m − 1 spatial frequencies on the workpiece if the tool is mounted on the rotor. Fifth, it is shown how to directly calculate the (+ and −) mth characteristic rotating vectors. Sixth, a quick consideration will be given to estimating 3D part errors on radially varying surfaces such as but not limited to cones and spheres.     

机床主轴系统支承动态参数识别方法的研究

本文对传递矩阵法识别机床主轴系统支承动态参数的原理和应用进行了研究,并在此方法中引入了“拟合圆法”,以提高识别精度.用在此基础上编制的计算机程序,在主轴系统实际安装条件下,根据各测点的位移导纳试验数据,对机床主轴系统支承动态参数进行了识别计算.     

Radial deviation gauge

Preferred commercial methods of measuring the out-of-roundness of a workpiece are based upon radial methods. These incorporate a very accurate spindle either to carry the transducer or via a table to the workpiece. Consequently they are best operated in a controlled environment such as in an inspection room. However, there is a requirement for measuring the workpiece near to the machine. This paper describes one possibility both in theory and practice.     

ARX Modelling and Compensation of Roundness Errors in Taper Turning

The forecasting compensatory control (FCC) strategy is successfully applied to the taper turning process to improve the roundness accuracy of the workpiece during cutting. This strategy, which is based on active error sensing, stochastic modelling and forecasting control, is capable of compensating both repeatable and non-repeatable errors. In the stochastic modelling, the effect of cutting force is considered, thus yielding an autoregressive model with exogeneous input (ARX). The resultant force is obtained from the outputs of the piezoelectric force sensor while the relative motion error between the tool and the workpiece is determined by means of a master taper and a capacitive sensor. The forecast error is sent to a piezoelectric actuator that moves the cutter to compensate for the error motion. Practical tests were performed on an experimental lathe with the FCC system using models with different orders and forgetting factors. A maximum improvement of 33% can be achieved by this FCC strategy using ARX (3,3) and forgetting factor of 0.997.     

亚微米数控车床误差补偿技术研究

在分析亚微米超精密数控车床样机误差源的基础上,采用在线测量和离线测量相结合的方法辨识误差补偿量,建立了误差补偿控制系统,实验结果表明所用的误差补偿策略是相当有效的。     

High Resolution Clinometers for Measurement of Roll Error Motion of a Precision Linear Slide

This paper proposes a new method for measurement of the roll error motion of a slide table in a precision linear slide. The proposed method utilizes a pair of clinometers in the production process of a precision linear slide, where the roll error motion measurement will be carried out repeatedly to confirm whether the surface form errors of slide guideways in the linear slide are su ciently corrected by hand scraping process. In the proposed method, one of the clinometers is mounted on the slide table, while the other is placed on a vibration isolation table, on which the precision linear slide is mounted, so that influences of external disturbances can be cancelled. An experimental setup is built on a vibration isolation table, and some experiments are carried out to verify the feasibility of the proposed method.     

High Resolution Clinometers for Measurement of Roll Error Motion of a Precision Linear Slide

This paper proposes a new method for measurement of the roll error motion of a slide table in a precision linear slide. The proposed method utilizes a pair of clinometers in the production process of a precision linear slide, where the roll error motion measurement will be carried out repeatedly to confirm whether the surface form errors of slide guideways in the linear slide are sufficiently corrected by hand scraping process. In the proposed method, one of the clinometers is mounted on the slide table, while the other is placed on a vibration isolation table, on which the precision linear slide is mounted, so that influences of external disturbances can be cancelled. An experimental setup is built on a vibration isolation table, and some experiments are carried out to verify the feasibility of the proposed method.     

机床主轴系统支承动态参数识别方法的研究

对传递矩阵法识别机床主轴系统支承动态参数的原理和应用进行了研究，并在此方法中引入了“拟合圆法”，以提高识别精度，用在此基础编制的计算机程序，在主轴系统实际安装条件下，根据各测点的位移异纳试验数据，对机床主轴系统支承动态参数进行了识别计算。     

Sensor design and evaluation for on-machine probing of extruded tool joints

This paper describes the design and evaluation of two contact probes used to measure the length and bore concentricity of cylindrical, extruded tool joints while clamped in a production lathe spindle. The probes consisted of an LVDT, a spring-preloaded shaft supported by linear bearings used to isolate the LVDT from side loads, and a hardened steel sphere to contact the rough surface. For bore concentricity measurements, a parallelogram leaf-type flexure and 45° surface was used to transfer radial deviations to the spindle/part/LVDT axis. The LVDT output was used in conjunction with the lathe turret position to determine the extruded part dimensions prior to machining. Experimental results are provided for measurements of multiple parts; variations in length, internal diameter, and bore concentricity are compared to the nominal dimensions. Additionally, a calibration artifact is described which enabled evaluation of the measurement accuracies for the two probes. Given the pre-machining part dimensions, it is shown how this information can be used to select from a pre-defined matrix of part programs to reduce cycle time and machining cost.     

Predicting Machining Errors in Turning Using Hybrid Learning

A recent model-based approach for predicting the compensation required on the next part to be turned on a CNC machine solely on the basis of three independent measurements conducted at selected locations on a limited set of previously machined parts under a similar cutting set-up is reviewed. A new method of achieving the same objective through the use of the learning capability of an adaptive neuro-fuzzy network is developed and tested against experimental data for cylindrical turning. This method requires only one on-machine measurement per sample. It is conducted by a novel contact sensor that probes with the tool and facilitates automation by providing proximity information as the tool approaches the workpiece.     

Effect of roll gap change of oval pass on interfacial slip of workpiece and roll pressure in round-oval-round pass rolling sequence

This paper presents a study of the effect of varying the roll gap of oval pass in round-oval-round pass sequence on the interfacial slip of workpiece, entrance and exit velocities, stresses and roll load that the workpiece experiences during rolling, by applying analytical method, finite element simulation and verification through hot bar rolling tests. The results have shown that the roll gap variation of oval pass affects the interfacial slip of workpiece along the groove contact and the specific roll pressure. The optimum conditions in terms of minimum interfacial slip and minimum specific roll pressure, which might influence the maximum groove life, is obtained when the subsequent round pass is completely filled.