On-Machine Measurement of the Straightness and Tilt Errors of a Linear Slideway Using a New Four-Sensor Method

Although there are some multi-sensor methods for measuring the straightness and tilt errors of a linear slideway, they need to be further improved in some aspects, such as suppressing measurement noise and reducing precondition.In this paper, a new four-sensor method with an improved measurement system is proposed to on-machine separate the straightness and tilt errors of a linear slideway from the sensor outputs, considering the influences of the reference surface profile and the zero-adjustment values. The improved system is achieved by adjusting a single sensor to di erent positions. Based on the system, a system of linear equations is built by fusing the sensor outputs to cancel out the e ects of the straightness and tilt errors. Three constraints are then derived and supplemented into the linear system to make the coe cient matrix full rank. To restrain the sensitivity of the solution of the linear system to the measurement noise in the sensor outputs, the Tikhonov regularization method is utilized. After the surface profile is obtained from the solution, the straightness and tilt errors are identified from the sensor outputs. To analyze the e ects of the measurement noise and the positioning errors of the sensor and the linear slideway, a series of computer simulations are carried out. An experiment is conducted for validation, showing good consistency. The new four-sensor method with the improved measurement system provides a new way to measure the straightness and tilt errors of a linear slideway, which can guarantee favorable propagations of the residuals induced by the noise and the positioning errors.

Integration of Machining and Measuring Processes Using On-Machine Measurement Technology

This paper presents an integration methodology for ma chining and measuring processes using OMM (On-Machine Measurement) technology b ased on CAD/CAM/CAI integration concept. OMM uses a CNC machining center as a me asuring station by changing the tools into measuring probes such as touch-type, laser and vision. Although the measurement accuracy is not good compared to tha t of the CMM (Coordinate Measuring Machine), there are distinctive advantages us ing OMM in real situation. In this paper, two topics are handled to show the eff ectiveness of the machining and measuring process integration: (1) inspection pl anning strategy for sculptured surface machining and (2) tool path compensation for profile milling process. For the first topic, as a first step, effective mea suring point locations are determined to obtain optimum results for given sampli ng numbers. Two measuring point selection methods are suggested based on the CAD /CAM/CAI integration concept: (1) by the prediction of cutting errors and (2) by considering cutter contact points to avoid the measurement errors caused by cus ps. As a next step, the TSP (Traveling Salesman Problem) algorithm is applied to minimize the probe moving distance. Appropriate simulations and experiments are performed to verify the proposed inspection planning strategy, and the results are analyzed. For the second topic, a methodology for profile milling error comp ensation is presented by using an ANN (Artificial Neural Network) model trained by the inspection database of OMM system. First, geometric and thermal errors of the machining center are compensated using a closed-loop configuration for the improvement of machining and inspection accuracy. The probing errors are also t aken into account. Then, a specimen workpiece is machined and then the machi ning surface error distribution is measured on the machine using touch-type pro be. In order to efficiently analyze the machining errors, two characteristic err or parameters (W err and D err) are defined. Subsequently, these param eters are modeled by applying the RFB (Radial Basis Function) network approach a s an ANN model. Based on the RBF network model, the tool paths are compensated i n order to effectively reduce the errors by employing an iterative algorithm. In order to validate the approaches proposed in this paper, a concrete case of the machining process is taken into account and about 90% of machining error reduction is successfully accomplished through the proposed approaches.

Surface form inspection with contact coordinate measurement:a review

Parts with high-quality freeform surfaces have been widely used in industries,which require strict quality control during the manufacturing process.Among all the industrial inspection methods,contact measurement with coordinate measuring machines or computer numerical control machine tool is a fundamental technique due to its high accuracy,robustness,and universality.In this paper,the existing research in the contact measurement field is systematically reviewed.First,different configurations of the measuring machines are introduced in detail,which may have influence on the corresponding sampling and inspection path generation criteria.Then,the entire inspection pipeline is divided into two stages,namely the pre-inspection and post-inspection stages.The typical methods of each sub-stage are systematically overviewed and classified,including sampling,accessibility analysis,inspection path generation,probe tip radius compensation,surface reconstruction,and uncertainty analysis.Apart from those classical research,the applications of the emerging deep learning technique in some specific tasks of measurement are introduced.Furthermore,some potential and promising trends are provided for future investigation.

Two-sided ultrasonic surface rolling process of aeroengine blades based on on-machine noncontact measurement

As crucial parts of an aeroengine,blades are vulnerable to damage from long-term operation in harsh environments.The ultrasonic surface rolling process(USRP)is a novel surface treatment technique that can highly improve the mechanical behavior of blades.During secondary machining,the nominal blade model cannot be used for secondary machining path generation due to the deviation between the actual and nominal blades.The clamping error of the blade also affects the precision of secondary machining.This study presents a two-sided USRP(TS-USRP)machining for aeroengine blades on the basis of on-machine noncontact measurement.First,a TS-USRP machining system for blade is developed.Second,a 3D scanning system is used to obtain the point cloud of the blade,and a series of point cloud processing steps is performed.A local point cloud automatic extraction algorithm is introduced to extract the point cloud of the strengthened region of the blade.Then,the tool path is designed on the basis of the extracted point cloud.Finally,an experiment is conducted on an actual blade,with results showing that the proposed method is effective and efficient.

System integration for on-machine measurement using a capacitive LVDT-Iike contact sensor

In this study, an air-bearing capacitive linear variable differential transformer （LVDT）-like contact sensor with a rounded diamond tip was mounted to a desktop machine tool to construct an on-machine （OM） measuring system. The measuring system was capable of decoding the digital signals of linear encoders mounted on the machine tool and acquiring the analog signal of the contact sensor. To verify the measuring system, experimental examinations were performed on an oxygen-free copper （OFC） convex aspheric mold with a diameter of 5 mm and a curve height of 0.46 mm. The acquired signals were processed by the implemented Gaussian regression filter （GRF）, removing the tilt of measured profile, and compensating for the radius of probe tip. The profile obtained was compared to that measured using a commercially available device, and a maximum deviation of 14.6μm was found for the rough cutting. The compensation cutting was then performed according to the form error of OM measurement. As a result, the PV form error compared with the designed profile was reduced from 19.2μm over a measured diameter of 4 mm to 9.7 μm over a measured diameter of 3.1 mm, or a percentage improvement of 35.4% in form accuracy. Through the examination for aspheric machining, the effectiveness of the implemented OM measuring system was demonstrated, and the technical details of system implementation were presented. Further improvement was suggested to reduce the diameter of probe tip and measuring force.

On-machine measurement of tool nose radius and wear during precision/ultra-precision machining

The tool state exerts a strong influence on surface quality and profile accuracy during precision/ultraprecision machining.However,current on-machine measurement methods cannot precisely obtain the tool nose radius and wear.This study therefore investigated the onmachine measurement of tool nose radius on the order of hundreds of microns and wear on the order of a few microns to tens of microns during precision/ultra-precision machining using the edge reversal method.To provide the necessary replication,pure aluminum and pure copper soft metal substrates were evaluated,with pure copper exhibiting superior performance.The feasibility of the measurement method was then demonstrated by evaluating the replication accuracy using a 3D surface topography instrument;the measurement error was only 0.1%.The wear of the cutting tool was measured using the proposed method to obtain the maximum values for tool arc wear,flank wear,and wear depth of 3.4 lm,73.5 lm and 3.7 lm,respectively.

Precision Milling of Integrated Turbine Based on a Non-Contact On-Machine Measurement System

The machining accuracy of the curved surfaces of integrated turbine blades directly determines the performance and service life of the turbojet engine system.In this paper,a non-contact on-machine measurement system is developed for precision milling of integrated turbines to reduce the impact of workpiece deformation,overcutting,tool chatter,and material work hardening.Milling with the on-machine measurement system obtained high-quality integrated turbine surfaces.The geometric accuracy error(PV)is below 3μm,and the surface roughness(Ra)is less than 2μm.The processed integrated turbine blade can achieve the accuracy requirements in the design and manufacturing and can be practically applied to the entire turbojet engine.

Multi-parameter optimization of machining impeller surface based on the on-machine measuring technique

Selecting the optimal machining parameters for impeller surface is a challenging task in the automatic manufacturing industry, due to its free-form surface and deep-crooked flow channel.Existing experimental methods require lots of machining experiments and off-line tests, which may lead to high machining cost and low efficiency. This paper proposes a novel method of machining parameters optimization for an impeller based on the on-machine measuring technique. The absolute average error and standard deviation of the measured points are used to define the grey relational grade for reconstructing the objective function, and the complex problem of multi-objective optimization is simplified into a problem of single-objective optimization. Then, by comparing the values of the defined grey relational grade in a designed orthogonal experiment, the optimal combination of the machining parameters is obtained. The experiment-solving process of the objective function corresponds to the minimization of the used errors, which is advantageous to reducing the machining error. The proposed method is efficient and low-cost, since it does not require re-clamping the workpiece for off-line tests. Its effectiveness is verified by an on-machine inspection experiment of the impeller blade.

原位检测系统中触发式测头的误差分析与补偿

在分析了原位检测系统中触发式测头误差来源的基础上,提出了自动调整测头偏心的方法,并用标定球对测头的实际作用半径进行了校准。同时,面向实际测量任务,提出了基于在线标定和双线性插值技术的逐点测头半径补偿方法,实验验证,所提出的半径补偿方法比商用软件提供的方法更准确,提高了测量结果的准确性。

渐开线齿形磨削精度的在机测量方法研究

在机测量是实现制造过程闭环控制的重要技术。由于数控机床伺服轴数量往往存在冗余,即一个测量任务存在多个满足要求的伺服运动控制方案。因此,如何科学合理地确定测量方案以实现高性能在机测量,是亟待解决的问题。为此,提出了一种测量方案创成方法。首先,应用多体系统理论及齐次坐标变换方法分别建立数控机床运动功能模型及渐开线螺旋面综合测量模型;随后,以渐开线齿形成形运动为约束,建立了以被测渐开线构型与数控机床各轴的伺服运动量之间的函数方程。通过解析该方程的解,获得所有的在机测量方案;为确定最优在机测量方案,依据方案创成结果,简化了机床构型,推导了对应于各测量方案的数控机床空间精度模型,建立了机床空间误差与测量误差之间的映射关系;最后,以测量精度为判据,综合评价各方案的优劣,确定了最优的测量方案。在五轴数控成形砂轮磨齿机上进行了齿形偏差在机测量实验,实验结果验证了方法的可行性及可靠性。

数控加工精度在机检测技术研究现状

通过为数控机床配备零件精度检测用测头以及相应的检测代码,即构成在机检测系统。该技术将加工和检测集成在同一台机床上完成,避免了多次装夹、重复定位误差,可以较好地解决零件精度超差难以修正和辅助时间长等现实问题。主要介绍数控加工精度在机检测技术的国内外研究现状与进展,包括在机检测系统开发应用、测头预行程误差补偿技术和带修正功能的在机检测系统开发等。并指出目前在该领域存在的一些关键问题,急需进一步解决和提升。

Design and Construction of a Low-Force Stylus Probe for On-machlne Tool Cutting Edge Measurement

A new on-machine profiler employing a cantilever beam was proposed and developed to measure the sharp micro-cutting edges of precision cutting tools with low measuring force of 0.1 mN.The proposed profiler consists of a probe unit and a positioning unit.The probe unit employs a stylus mounted on the free end of a hollow triangular cantilever beam and a laser displacement sensor to detect the detlection of the cantilever beam.The positioning unit consists of two single-axis DC servo motor stages for precise positioning of the probe unit.The cantilever is designed with the assistance of the finite element method.In order to demonstrate the feasibility of the proposed measurement system,experiments are conducted and the measurement result for a micro-cutting edge is compared with that by a commercial profiler.Furthermore,a method to com-pensate for the measurement error caused by the lateral displacement of the cantilever beam is proposed.The compensated measurement results show good agreement within±2μm with those obtained by the commercial profler.

笔记本电脑组装厂与外壳供应商尺寸测量一致性提高研究

文章首先分析了课题的内容和意义,然后,介绍了A公司笔记本电脑组装厂与零部件供应商的尺寸测量现状,从而引出笔记本组装厂和外壳供应商F公司和R公司做光学测量仪之间的尺寸测量一致性提高研究内容,文章详细论述了影响光学测量仪测量一致性的关键影响因素,并提出了改善建议。

IABC: An iteratively automatic machine learning boosted hand-eye calibration method for laser displacement sensor

An on-machine measuring(OMM)system with a laser displacement sensor(LDS)is designed for measuring free-form surfaces of hypersonic aircraft’s radomes.To improve the measurement accuracy of the OMM system,a novel Iteratively Automatic machine learning Boosted hand-eye Calibration(IABC)method is proposed.Both the hand-eye relationship and LDS measurement errors can be calibrated in one calibration process without any hardware changes via IABC.Firstly,a new objective function is derived,containing analytical parameters of the handeye relationship and LDS errors.Then,a hybrid calibration model composed of two kernels is proposed to solve the objective function.One kernel is the analytical kernel designed for solving analytical parameters.Another kernel is the automatic machine learning(AutoML)kernel designed to model LDS errors.The two kernels are connected with stepwise iterations to find the best calibration results.Compared with traditional methods,hand-eye experiments show that IABC reduces the calibration RMSE by about 50%.Verification experiments show that IABC reduces the measurement deviations by about 25%-50%and RMSEs within 40%.Even when the training data are obviously less than the test data,IABC performs well.Experiments demonstrate that IABC is more accurate than traditional hand-eye methods.

Profile Compensation for Single-Point Diamond Turning of Microlens Array

To improve the efficiency and consistency of machined microlens array using single-point diamond turning technology,a theoretical model of surface form error is proposed in this paper.Then,a compensation method for this model is studied.In the proposed tool equivalent tilt angle model,the microlens array is regarded as a freeform surface.The corresponding curvature radius of the surface at each cutting point along the cutting direction is calculated by establishing a slow slide servo cutting model.In the spatial form error model,the assumption is that surface form error has a linear relationship with z-axis maximum speed vz.An empirical linear equation is obtained and verified,with a maximum deviation of 0.4μm.Then,after machining,the surface form error is measured and processed using on-machine measurement.The theoretical and measured surface form errors are consistent.The surface form error is compensated in the machining program.The peak-to-valley value is reduced from 5.4 to 0.6μm after compensation.Findings show that the single-point diamond turning and compensation method for the microlens array presented in this paper can predict the surface form error and significantly improve machining accuracy and consistency.