Precision Of Workpiece Research Articles

Optimizing machining allowance for thin-walled aerospace parts with multi-milling features

Clamping complex and irregular preformed blanks can be challenging and time-consuming, especially when it comes to precise workpiece locating and allocating machining allowance to curved surfaces. The proposed method aims to improve the efficiency and accuracy of the clamping process. This paper presents a method for complex workpiece locating and machining allowance allocation based on scanned 3D point cloud. An edge detection method is introduced for the workpiece point cloud to preserve its essential features, enabling precise global alignment between the scanned point cloud and CAD models. Additionally, a method is proposed for extracting multiple machining areas from the point cloud, calculating allowances, and optimizing the process coordination to allocate machining allowance effectively. The experimental results show that the machining allowance range is reduced by 77.71 % after compensation, and the average machining allowance of the worst machining area increases by up to 29.69 % compared to the iterative closest point method.

Data preprocessing for flatness measurements of large precision workpieces

Abstract Measuring the flatness error of large precision workpieces quickly and accurately is a difficult problem. A new method for preprocessing flatness measurement data based on MSE (mean squared error) is proposed. A mathematical model of a new data preprocessing method was established, and the mathematical formula for model solving was derived in detail. The data were measured by digital level on the plane of the granite base with dimensions of 2340 m×1540 mm. The new method and SmartLevel (basic measurement system of the level computer) were used to calculate and process the data. The flatness errors after diagonal evaluation were 4.07 μm and 3.90 μm, respectively. The relative error of the two was 4.36%, which confirmed the reliability and accuracy of the new method. The data results show that this method can be effectively used for the engineering measurement of the flatness of large precision workpieces.

Machinability and Surface Properties of Cryogenic Poly(methyl methacrylate) Machined via Single-Point Diamond Turning.

Poly(methyl methacrylate) (PMMA), with a glass transition temperature (Tg) over 100 °C, shows good mechanical and optical properties and has broad applications after being machined with single-point diamond turning (SPDT) at room temperature. Because of the high Tg, current efforts mostly focus on optimizing machining parameters to improve workpiece precision without considering the modification of material properties. Cryogenic cooling has been proven to be an effective method in assisting ultra-precision machining for certain types of metals, alloys, and polymers, but has never been used for PMMA before. In this work, cryogenic cooling was attempted during the SPDT of PMMA workpieces to improve surface quality. The machinability and surface properties of cryogenically cooled PMMA were investigated based on the mechanical properties at corresponding temperatures. Nanoindentation tests show that, when temperature is changed from 25 °C to 0 °C, the hardness and Young's modulus are increased by 37% and 22%, respectively. At these two temperature points, optimal parameters including spindle speed, feed rate and cut depth were obtained using Taguchi methods to obtain workpieces with high surface quality. The surface quality was evaluated based on the total height of the profile (Pt) and the arithmetic mean deviation (Ra). The measurement results show that the values of Pt and Ra of the workpiece machined at 0 °C are 124 nm and 6 nm, respectively, while the corresponding values of that machined at 25 °C are 291 nm and 11 nm. The test data show that cryogenic machining is useful for improving the form accuracy and reducing the surface roughness of PMMA. Moreover, the relationship between temperature, material properties and machinability weas established with dynamic mechanical analysis (DMA) data and a theoretical model. This can explain the origin of the better surface quality of the cryogenic material. The basis of this is that temperature affects the viscoelasticity of the polymer and the corresponding mechanical properties due to relaxation. Then, the material property changes will affect surface profile formation during machining. The experimental results and theoretical analysis show that cryogenically cooled PMMA has good machinability and improved surface quality when using SPDT compared to that at ambient temperature.

Numerical investigation on design parameters of orifice plate for positioning of workpiece in cavitation zone for cavitation machining

ABSTRACT The recent development of non-traditional machining techniques, such as cavitation machining (CM), has been gaining traction amongst researchers due to its sustainable nature. The present research focuses on the use of computational fluid dynamics (CFD) model to predict the location of workpiece in the fluid domain and bubble distribution during CM process. For efficient CM, the correct positioning of a workpiece in cavitation zone is essential, as the implosion of the cavity bubble leads to formation of micro-jet and shock waves for a few milli-to-microseconds generating high temperature and pressure on workpiece. The aim is to harness cavitation phenomena in material processing, particularly by using orifice plates as a common tool to induce hydrodynamic cavitation. To generalise the investigation, the flow simulation through orifice plate with different aspect ratios (l/d) are carried out. For the bubble distribution and their diameters, the Lagrangian discrete phase model (DPM) is used in the downstream side of the flow domain. Using this information, bubble dynamics have also been investigated using the Keller–Miksis (KM) model to compute the implosion time and intensity in the zone. The presented exploration determines the orifice dimensions to optimize implosion intensity, ensuring precise workpiece placement in real-time CM.

Simplifying the monoscopic deflectometric measurement by extra-facility-free workpiece positioning

Monoscopic deflectometry is a powerful and flexible measuring method for optical surfaces. Precise workpiece positioning is of significance because it directly determines the reliability of the measurement results. But unfortunately, the need for additional facilities severely limits the application of the monoscopic deflectometry. In this paper, a self-positioning method is proposed by combining the ray-tracing and Gaussian process regression. The phases retrieved from the captured images are parameterized using the Zernike polynomials. Then a training model is established for describing the relationship between the Zernike coefficients and the workpiece positions. Workpiece positioning is implemented by computing the associated joint Gaussian distribution. Experimental results show that the positioning accuracy of optical surfaces is comparable with that of a coordinate measuring machine, with a deviation less than 8 × 10−4° in tilt and 4 μm in translation. This greatly simplifies the sophisticated operation and improves the practicability and efficiency of deflectometric measurements.

Pengaruh Variasi Kecepatan Putaran Spindle dan Kedalaman Pemakanan Terhadap Kekasaran Permukaan Alumunium ADC12 pada Mesin Bubut CNC Okuma L150T

In the rapidly growing manufacturing industry, especially in the field of machining, the use of computer systems has become increasingly prevalent. Consumer demands for precise workpieces with consistent quality, quick completion, and large quantities can be more easily achieved using CNC (Computer Numerical Control) machine tools compared to conventional machine tools. To determine the influence of spindle rotational speed and feed depth variation on the surface roughness of ADC12 aluminum in the Okuma L150T CNC lathe, an experimental study was conducted. Aluminum ADC12 specimens were used, and variations in spindle rotational speed and feed depth were tested for surface roughness using a Mitutoyo SJ-210 surface roughness tester. The obtained data were then analyzed and discussed based on statistical correlation and hypothesis testing. From the results of this study, the following conclusions can be drawn: (1) There is an influence of spindle rotational speed variation. At speeds of 900 rpm, 1500 rpm, and 2100 rpm, the average surface roughness levels of the workpiece were 7.45 μm, 6.35 μm, and 5.23 μm, respectively. Therefore, higher spindle rotational speeds result in lower surface roughness of the workpiece. (2) There is an influence of feed depth variation. At depths of 0.25 mm, 0.50 mm, and 0.75 mm, the average surface roughness levels of the workpiece were 5.23 μm, 6.32 μm, and 7.42 μm, respectively. Thus, deeper feed depths lead to higher surface roughness of the workpiece. (3) The combination of feed depth variation and spindle rotational speed that resulted in the workpiece with the lowest average surface roughness was achieved at a feed depth of 0.25 mm and spindle rotational speed of 2100, which amounted to 5.23 μm.

A Novel Measurement Method for Determining Geometric Errors of Rotary Tables by Using LaserTRACER and Reflectors

In this paper, a novel and robust measurement method is proposed for obtaining the geometric errors of rotary tables by using LaserTRACER and the reflectors mounted on the reflector standard fixture. For the machining accuracy, the six-degree-of-freedom (6-DOF) geometric errors of the rotary axes interactively influence the manufacturing quality of the precise workpieces. Therefore, this paper mainly aims to develop a measurement method for identifying the 6-DOF geometric errors of rotary tables without using the external linear axis. Furthermore, the set-up errors of the reflector standard fixture are also considered and identified to reduce the influence of the 6-DOF geometric error measurements. For each rotary table geometric error measurement, the positions of the LaserTRACER as well as the relative distance between the reflectors and the LaserTRACER are measured and obtained for determining the 6-DOF geometric errors of the rotary tables. In addition, the homogeneous transformation matrix (HTM), multilateration method, and least squares method are used for building the mathematical measurement algorithm. Moreover, the experimental verifications are implemented to demonstrate the accuracy of the proposed measurement method. Conclusively, the experiment and simulation verification results clearly delineate that the maximal relative differences in the linear errors and the angular errors of the 6-DOF geometric errors are, at most, 3.25% and 2.30%, respectively.

Angular error measurement of workpiece repositioning using a full-scale rotation detection method.

Workpiece repositioning error has always been a key factor affecting manufacturing accuracy. The issues become more sensitive when machining microstructures with special morphologies, where the declination error caused by the repositioning may lead to microstructural defects. To solve this practical problem, in this paper, we report the design of a fixture that can detect the plane angular displacement error between the workpiece and the tool, namely the Rotation Correction Fixture (RCF). The fiducial marker referred to as polar microstructure is proposed and placed on the RCF edge. Angular displacement measurement is realized by observing the microstructural changes. Simultaneously, a Full-scale Rotation Detection (FRD) method is proposed to obtain the full-scale and high-precision angular displacement, including coarse extraction based on Fourier transform and fine extraction based on the Fast and Robust Feature-based Positioning method. Template matching is employed to eliminate the phase ambiguity in the Fourier transform. The results show that the proposed method can realize the calibration of the workpiece declination with a standard deviation error of 250.24 seconds, which meets the needs of workpiece precision positioning well.

Development of cubic freeform optical surface for wavefront coding application for extended depth of field Infrared camera

Freeform surfaces are being developed for number of applications like illumination systems, compact projection systems, head up display, ophthalmic and automotive industries. One of the important use of such surfaces in optical imaging application is wavefront coding for large depth of focus camera. The thermal induced defocus is the well-known problem in infrared (IR) imaging systems. The efficient technique to mitigate the effect of defocus is wavefront coding, The phase profile for wavefront coding application with IR camera is a cubic freeform profile, that enables the focus invariant across the region near the focal plane. This work presents the development of a high precision cubic freeform profile on Germanium (Ge) substrate and its application for extended depth of focus for IR imaging camera. The cubic freeform profile on the surface is generated using single point diamond turning (SPDT) in slow tool servo (STS) configuration. It is further polished by using bonnet polisher with polyurethane and uninap-13 pads in seven axis polishing machine. The precise work piece alignment during the generation and characterization of the surface is very important aspect which is taken care by introducing fiducials from the beginning of the process of realization of the component. Full field measurement of grinded surface is carried out by using long wavelength interferometer. Computer generated hologram (CGH) in Fizeau interferometer is used for corrective polishing metrology and final testing of the surface profile. Precise work piece alignment and full field measurement starting from the grinding stage helped to achieve surface with residual error of 0.2 µm PV and 1.4 nm RMS roughness (Rq). The developed cubic profile is used in infrared camera for wavefront coding in an experimental setup for the verification of the intended results.

Study on the application of a granite composite material in five-axis CNC-VMC machine Tool

A five-axis CNC-VMC machine tool generally has a high-speed spindle spinning at a maximum rotation of 50,000 rpm, under which the machine tool bed will violently vibrate that leads to poor machining precision and surface quality of workpiece. The gray cast iron, as the typical material of a machine tool, exhibits poor dynamic suppression of vibration that its processing yield and quality can no longer satisfy the product demand of current market. Consequently, in this study, we proposed granite composite material (GCM) in place of gray cast iron for the structure of machine tool, which would be mixed with main ingredients of high-strength epoxy resin and cemented carbon fibers and fillers to maximize the structural properties of the machine tool. The sample of granite composite material would first be tested for its mechanical properties. The results showed that the GCM cast with only 1/3 density of gray cast iron could withstand a maximum compressive stress of 125.8 MPa. With this granite composite material used in a digitally controlled machine tool bed, the maximum stress and the maximum strain exerted on the machine tool were reduced by 68.93% and 72.6%, respectively, when compared with the cast iron, while the 1st to the 6th-order natural frequencies of the machine tool of mineral composite was significantly increased by 20% to 30%, giving it more resistance to vibration than the gray cast iron. The stability and precision of the machine tool were shown to have been drastically improved by using the granite composite material.

Influence of Setup and Kinematic Parameters on the Shape Precision of Workpieces

Influence of Setup and Kinematic Parameters on the Shape Precision of Workpieces

Online Remaining Useful Life Prediction of Milling Cutters Based on Multisource Data and Feature Learning

A milling cutter is one of the most important parts of machine tools. Its working status significantly influences the precision of workpiece. Due to the complex wear mechanism, the single sensor may be difficult to acquire the complete degradation information of milling cutters. Therefore, in this article, a feature learning based method is proposed to automatically extract features from multisource data and predict the remaining useful life of cutting tools in real time. First, a statistic-based method is constructed to detect and delete the outliers hidden in the monitoring data. Second, the clean data are input into a multiscale convolutional attention network (MSAN) to learn features and fuse multisource data. At last, the fused data are used to predict the remaining useful life of cutting tools in a regression layer. Compared with traditional tool life prediction methods, the proposed method is able to fuse multisource data through an attention feature learning model to conduct the life prediction of tools. Additionally, the data cleaning and model optimization methods are also proposed to promote engineering practicability. To validate the effectiveness of such method, the life testing experiments on milling cutters are conducted to obtain run-to-failure data. In those experiments, multisensor monitor data are acquired, which are used to conduct validation experiments testing the effectiveness of the proposed method. The results indicate the superiority of the proposed method in remaining useful life prediction milling cutters.

Study on the micro through holes machining using the electrochemical machining (ECM) method with a graphite electrode

Electrochemical machining is widely used in biomedical, aerospace, automotive, and other fields. The development of electrochemical machining (ECM) is restricted by many factors such as the difficulty of preparing micro-electrode, large machined gap and serious stray corrosion. In this paper, we present a method to fabricate micro-holes by combining micro-graphite electrode with hollow structure. Firstly, a sealed graphite electrode was proposed to guarantee that the sediment can be fully removed by the flowing electrolyte. Then, the effect of machined parameters such as the pulse frequency, machined voltage, electrode feeding speed, and electrolyte concentration on machining quality was studied. By optimizing the machined parameters, the minimum value of micro-hole taper with 0.07 could be obtained. To improve the shape precision of workpiece, this paper designed the hollow structure inside the electrode. With the increasing of the pulse frequency, the machining accuracy of micro-holes increased. The results suggested that the pulse frequency of 100 kHz, the machined voltage of 18 V, the feeding speed of 1 µm/s, and electrolyte concentration of 5% were more suitable for micro-holes machining with ECM.

Gearbox Production Using Distortion Controlled Inductive Fixture Hardening*

Abstract Fixture-hardening, also known as quench-press hardening, is a widespread process mainly for the automotive industry. This paper introduces a new inductive hardening and tempering process that combines the well-known advantages of induction heating and hardening with the advantages of a fixture hardening process to obtain highly precise workpieces with enormously reduced or even without rework. The main component is a new hardening machine with implemented fixture hardening assembly and integrated induction coil, all in a protective gas atmosphere. Induction as electrical energy source can be used for heating up workpieces prior to fixture hardening and for tempering, which allows to simultaneously draw out the calibration mandrel without any abrasive wear on its surface. In certain applications, an expanding mandrel can be used in order to relieve the workpiece.

Fabrication and Automation of Drilling Machine by Using Arduino

For precision workpiece manufacturing, the system should have good dimensional accuracy and surface finish. In applications such as drilling, punching, marking, boring, tapping, etc., the workpiece is first positioned, and then the tool executes its action while the moving axis remains stationary. In the traditional method of such applications, manufacturers use very expensive CNC machines to program the cycle and perform the same work. Large manufacturers can afford such expensive machines, but for the small machinery manufacturing industry, we must consider low-cost solutions that can provide high-quality output. In this study, we tried to propose a low-cost design that can be used to achieve functions similar to CNC. By applying this machine in industry, multiple generations can be obtained in a short time. It is very difficult to estimate the drilling depth when manually drilling with a traditional drilling machine, and the work will usually fail due to over-drilling. In many cases, it is difficult to measure the depth after the drilling is completed; especially the depth of the fine hole cannot be measured. Therefore, an automatic drilling machine that performs the drilling function according to the generated drilling depth and transmitted to the control circuit is indispensable; therefore, undertaking the study, it exposed the technology of the dedicated drilling machine. The automatic drilling machine designed here is very useful for the mechanical workshop. The machine is built with power feed technology and is designed to drill the job to a certain specified depth.

Design and Development of a Three Component Milling Dynamometer

The cutting forces that are generated during metal cutting influence the work piece precision, tool wear, the nature of the machined surface, and heat generation. These cutting forces can be measured analytically however; precise outcomes may not be expected due to its included stresses, parameters of cutting, and the perplexing tool geometry. Henceforth the exploratory estimation of cutting forces is fundamental. For this reason, a milling dynamometer of three-segment is structured, created, and tried to gauge the three cutting forces which are produced during the operation of milling strain gauges can be utilized to quantify dynamic and static cutting forces through milling dynamometer. During the process of metal cutting, a dynamometer that is based on strain gauge is fit for estimating three-force segments. The dynamometer was designed based on the octagonal ring principle. The octagonal rings orientation and location of strain gauges have resolved to expand affectability and to limit cross-affectability.

STUDY OF THE DEFORMED STATE CONNECTION OF THE PISTON WITH THE ROD OF THE UNREGULATED PISTON PUMP

The technological processes of cold rolling of precision workpieces and ring parts, rolling of pipes, rolling of piston-connecting rod axial-rotor piston pump, which are a kind of processing of metals by pressure and contain changes in the shape of workpieces according to performing relative to the axis of the workpiece radial rotational motion. The workpiece can remain stationary or rotate. It is shown that by means of technological process of rolling of pipes, unrolling of preparations various hollow axisymmetric metal products receive, the specified processes are combined by the mechanism of deformation, namely: at them two deformations of compression and one - tension are realized. This mechanical deformation scheme creates favorable conditions for plastic deformation, because intercrystalline displacements are difficult, leading to the violation of mechanical bonds, and plastic deformation occurs mainly due to intracrystalline displacements. It is shown that in the process of connecting the piston-connecting rod in compliance with the process parameters (output supply pressure, feed rate, leaving time) the value of the specified gap either exceeds the maximum value or decreases to the value at which the next operation of the piston-connecting rod spell. The deformed state in the technological operation of rolling the piston-connecting rod pair at different stages of shape change is studied, the process control mechanism is revealed, which prevents the defect in the form of deviation from the regulated gap after rolling between the piston and the connecting rod. The used resource of plasticity at different stages of rolling is calculated, the deformability of the piston workpiece in the rolling process is estimated.

Experimental Study on Investigating the Influence of Combination Combining Eccentricity with Different Orientations for Process System of Milling Center

There are several critical factors which have adverse effects on the workpiece surface finish, dimensional accuracy, tool life, etc. Eccentricity is one of them which can be manipulated when the spindle, tool holder and milling cutter revolve around the line parallel to their cutting axes and crop up due to clamping deviation and geometric imperfections. This work was driven by the observation that there should an approach through which final eccentric error can be reduced as other researchers only displayed the effects of eccentricity on cutting forces, etc. This task was carried out through performing numerous experiments on the CNC milling center and measuring geometric imperfections from the whole body of machining elements at different orientations with dial gauge to find out whether different orientations of elements have effects on the eccentricity. If they have noticeable effects then such orientations of elements exhibiting the minimum eccentricity can be selected which in turn may improve the accuracy and precision of workpieces and reduce the final cutting edge error. Our observation showed that orientations have remarkable effects on the eccentricity pretending lowest final eccentric error which is unable to be ignored.

The influence of manufacturing errors of cases on their assembly

The authors of the article propose a way to increase the accuracy of processing pipe casings included in special products. Currently, in the current production of these products, there is a need to increase the accuracy of manufacturing cases, so it was decided to conduct research work. The article discusses the process of processing long bodies from thick-walled workpieces using hoods, which ensures high precision workpieces and minimal impact on the properties of the initial type of workpiece. As a result of the research, the significance of the geometric errors of the component pipes of the product on its functionality is analyzed. The achieved accuracy of the manufacture of base surfaces and the parameters of their possible distribution are shown. The similarity of the parameters of the initial part and further assembly is determined, it is also shown that the runout of the end surfaces of the part has a significant effect. The optimal basing scheme for finishing the end surfaces of long bodies is shown.

A new approach to identify geometric errors directly from the surface topography of workpiece in ultra-precision machining

Geometric errors are caused due to the inaccuracy of machine components’ manufacturing and assembling, and significantly impact the dimensional precision of workpieces. Many researches have researched the methods of inversely identifying geometric errors of multi-axis milling machines from the workpiece profile, but those methods are inapplicable to identify geometric errors of ultra-precision lathe. This paper presents a new approach to research the inverse identification of geometric errors from the surface topography of workpiece for an ultra-precision lathe. First, a volumetric error model is built to analyze tool position errors caused by geometric errors. Next, a matrix decomposition method is put forward to simplify the calculation of tool position errors and describe the propagation process of geometric errors during the manufacturing process. This method decomposes final tool position errors into a sum of three components, and each has a definite geometric meaning. Then, an equivalent machining model is constructed to identify crucial geometric errors from the surface topography of workpiece. Geometric errors in this model can be worked out precisely through topography data sampled along a radial path on workpiece surface. Finally, some simulation experiments are implemented to verify the precision of matrix decomposition method and one plane surface is machined to validate the effectiveness of equivalent machining model.