Conventional three-probe method of artifact roundness and spindle error measurements is subjected to the trouble of harmonic suppression, which is also mathematically complicated due to complex ...transformation processing. A novel three-probe method by solving system of multivariable equation (SSME) method is presented in this paper. The presented method simplifies the mathematical processing and has good robustness to the measurement angles which are difficult for conventional three-probe method. This paper gives mathematical models, detailed theoretical derivations, and numerical simulations. Selection criteria of the optimal measurement angle combinations can be determined in accordance with rank and condition number of the coefficient matrix. Then, to validate the feasibility and repeatability of the proposed method, experimental measurements are performed on a vertical machine tool spindle by using nanometer-resolution capacitive displacement sensors, high-precision indexing table, and professional data acquisition system. Artifact roundness error and spindle radial error are tested to validate separation accuracy by specialized instruments. The comparisons demonstrate that the proposed method has good feasibility and repeatability (the maximum deviations of spindle error and roundness error are 9.62 and 3.86%). SSME method, due to its simplicity in computation and the uniqueness of the solution provided, is more suitable to separate spindle radial error from the artifact roundness error.
The double-disc straight-groove (DDSG) grinding method is a new precision machining method for the rolling surface of bearing cylindrical rollers by using a flat grinding disc and a straight-groove ...grinding disc as machining tools. The machining principle of bearing cylindrical rollers based on the DDSG grinding method is experimentally investigated in this study. A circulating grinding platform has been constructed. The grinding test of the cylindrical rollers was performed with W40 white corundum abrasive. Under the experimental conditions of the grinding disc rotation speed of 7.5 rpm, the machining load of 110 N, and the eccentricity of the straight groove of 6 mm, 2000 cylindrical rollers (AISI 52100) were synchronously ground by the DDSG grinding method. The average diameter, surface roughness, and roundness of the ground rollers were investigated. Experimental results show that the material removal rate of the rollers is uniform. After 270 grinding cycles, the average diameter decreased from 5.99082 to 5.94135 mm, with an average material removal rate of 0.183 microns per cycle. The average roundness of ground cylinders reduced from 9.64 to 2.78 μm. The diameter variation decreased significantly from 14.5 to 6.0 μm. The average roughness reduced from 0.258 to 0.137 μm, and the fluctuation range of the roughness decreased from 0.143 to 0.033 μm. Experimental results demonstrate that the DDSG grinding method can improve the bearing cylindrical rollers’ dimensional consistency, roundness, and surface quality.
A novel pure rotary actuator with a double-layer flexible mechanism (RA-DFM), which is driven by a single piezoelectric ceramic in the lower mechanism and generates rotational motion in the upper ...mechanism, is proposed in this paper. The output of piezoelectric ceramic is successively amplified using an enhanced double Scott–Russell mechanism and two lever-type mechanisms to obtain a large rotation range. The static, kinematic and dynamic properties of the RA-DFM are numerically analyzed, and the actual output of the piezoelectric is analyzed considering the input stiffness. The geometric parameters of the RA-DFM are optimized based on the constructed numerical models. Finite element analysis has been implemented to validate the correctness of the theoretical models and further evaluate the output property. The simulation results show the maximal rotation angle of the RA-DFM is 15.14 mrad with 0.44% center drift.
Ultrasonic elliptical vibration-assisted cutting (UEVC) has been successfully applied in the precision and ultra-precision machining of hard and brittle materials due to its advantages of a low ...cutting force and minimal tool wear. This study developed a novel double-excitation ultrasonic elliptic vibration-assisted cutting (D-UEVC) device by coupling ultrasonic vibrations in orthogonal dual paths. A two-degree-of-freedom vibration system of the D-UEVC was modeled, form which the elliptical trajectory of the end under different phase angle φ values was derived. The initial dimensions of the D-UEVC device were obtained through theoretical calculations. Subsequently, with the aid of finite element analysis methods, structural dynamic analysis of the device was conducted to obtain the elliptical vibration trajectory under different phase differences of the excitation source. In order to verify the cutting trajectory and cutting performance of the D-UEVC device, a prototype of the device was developed, and a series of vibration performance tests as well as the Inconel 718 cutting experiment were conducted. The experimental results illustrated that the D-UEVC device can achieve the elliptical vibration trajectory at the tool tip with a resonant frequency of 36.5 KHz. The adjustable elliptical vibration trajectories covered a range of ±4 μm in the axial and radial directions. Compared with the surface roughness Ra = 0.36 μm under the conventional cutting, the surface roughness of Inconel 718 under D-UEVC was Ra = 0.215 μm. Thus, the surface quality can be significant improved by utilizing the D-UEVC device.
The rotational performance of the spindle-bearing system has critical influence upon the geometric shape and surface roughness of the machined parts. The effects of preload and preload method on the ...rotational performance of the spindle-bearing system is explored experimentally to reveal the role of preload and preload method in spindle rotational performances under different speeds. A test rig on which both the rigid preload and elastic preload can be realized, equipped with variable preload spindle-bearing system, is developed. Based on the mechanical model, the relationship of the axial preload and negative axial clearance of the spindle-bearing system is provided. Rotating sensitive radial error motion tests are conducted for evaluating synchronous and asynchronous radial errors of the variable preload spindle-bearing system under different rotating speeds and preload methods. The change regularity of synchronous and asynchronous radial errors with preloads under different rotating speeds are given. The results show that the preload plays an important role on the rotational performance of spindle-bearing system. The rigid preload is more efficient in achieving better rotational performance than elastic preload under the same rotating speed. Furthermore, this article significantly guides the preload designing and assembling of the new spindle-bearing system.
In the field of precision machining, the spindle-rolling bearing (SRB) system is widely used on the machine tool as one of the most fundamental and important components. The rotational error motions ...of the SRB system have significant effects on the machining accuracy (contour accuracy and surface roughness). Over the past decades, much work has been focused on the measurement of spindle balancing and rotational error motions, the vibrations response induced by the nonlinear stiffness and surface waviness of the bearing. However, the formative mechanism of the rotational error motions for the SRB system is not well understood. In this paper, the dynamic model of the SRB system considering the bearing nonlinearity is established. Seeking to reveal the effects of surface waviness of the bearing raceway, unbalance mass and disturbance force on the dynamic rotational error, the modeling method and formative mechanism of the dynamic rotational error for the SRB system is explored both theoretically and experimentally. Then, numerical simulation is performed to analyze the influence of the bearing raceway waviness, unbalance mass and disturbance force on the dynamic rotational error. An experimental setup is established based on a typical SRB system and a series of experiments are carried out. The experimental results are in good agreement with the theoretical and simulation results, which can demonstrate the feasibility and validity of the modeling method. Furthermore, this method can be effectively applied to the design and development phases of an SRB system to improve dynamic rotational accuracy.
Predicting and avoiding the onset of milling chatter are desirable to reduce its harm to machine tools, workpieces, and cutters. This paper presents an updated method to complete the stability ...prediction for the milling process with multiple and distributed time delays. After the dynamic of the combination milling process with variable helix cutter (VHC) and variable spindle speed (VSS) is modeled as linear delay differential equations with multiple and distributed time delays, the presented method is applied to carrying out its stability prediction for the first time. By comparing with the existing researches and time-domain simulations, the effectiveness of the presented method has been validated. The influence and feasibility of the combination process on chatter suppression are explored and investigated for the associated one- and two-degree-of-freedom systems. Results show that the application of the combination process can realize a further suppression of milling chatter in practice. It can result in nearly 2-fold as high as the minimum depth of cut for the traditional milling or VSS milling and about 1.3-fold for VHC milling for some special domain, and can respectively lead to the average increase of stable area by 30.4%, 23.5%, and 1.5% for the adopted simulations. However, consider the contribution, the combination process is actually one process in which VHC plays an absolutely leading role but VSS plays an auxiliary role, in terms of milling stability.
The spindle rotational accuracy is an important indicator to evaluate the characteristic of a machine tool. In this article, an easy-to-use measuring module is proposed based on virtual instrument ...platform. A new method for measuring rotational speed and angular orientation using an adaptive filtering method to processing the target installation eccentricity is proposed, instead of using the encoder. This method can reduce the measuring cost and make the measurement more convenient, without affecting the measuring accuracy. Meanwhile, the selective principle of target installation eccentricity for rotating sensitive direction is investigated by theoretical analysis and numerical simulation. Based on the proposed method, measuring module is developed. National Instruments data acquisition card and capacitive sensors are used to acquire the displacement signals of the spindle rotational error motion. Contrast experiments with the commercial measuring software are performed to validate the feasibility and repeatability of the proposed measuring module. The experimental results demonstrate that the developed measuring module can reach the same precision using less test parameters.
Integrated studies of accumulated data can be performed to obtain more reliable information and more feasible measures for investigating potential diagnostic biomarkers of gastric cancer (GC) and to ...explore related molecular mechanisms. This study aimed to identify microRNAs involved in GC by integrating data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus. Through our analysis, we identified hsa‐miR‐17 (miR‐17) as a suitable candidate. We performed a meta‐analysis of published studies and analyzed clinical data from TCGA to evaluate the clinical significance and diagnostic value of miR‐17 in GC. miR‐17 was found to be upregulated in GC tissues and exhibited a favorable value in diagnosing GC. In addition, we predicted that 288 target genes of miR‐17 participate in GC‐related pathways. Enrichment of Kyoto Encyclopedia of Genes and Genomes pathway, Gene Ontology analysis, and protein–protein interaction analysis of the 288 target genes of miR‐17 were also performed. Through this study, we identified possible core pathways and genes that may play an important role in GC. The possible core pathways include the cAMP, phosphoinositide‐3‐kinase–Akt, Rap1, and mitogen‐activated protein kinase signaling pathways. miR‐17 may be involved in several biological processes, including DNA template transcription, the regulation of transcription from RNA polymerase II promoters, and cell adhesion. In addition, cellular components (such as cytoplasm and plasma membrane) and molecular functions (such as protein binding and metal ion binding) also seemed to be regulated by miR‐17.
The present study identified hsa‐miR‐17 as a suitable candidate microRNA involved in gastric cancer (GC) by integrating data from TCGA and GEO databases. We performed a meta‐analysis of published studies, analyzed clinical data from TCGA, and predicted 288 target genes of miR‐17. In addition, enrichment of KGEE pathway, GO analysis and protein–protein interaction analysis of the 288 target genes of miR‐17 were also performed. In conclusion, miR‐17 may serve as a promising diagnostic marker for GC.
This study employs grand canonical Monte Carlo (GCMC) simulations to investigate the impact of functional group modifications (CH3, OH, NH2, and OLi) on the adsorption performance of CH4/N2 on ...Ni‐MOF‐74. The results revealed that functional group modifications significantly increased the adsorption capacity of Ni‐MOF‐74 for both CH4 and N2. The packed methyl groups in CH3‐Ni‐MOF‐74 create an environment conducive to CH4, leading to the highest CH4 adsorption capacity. The electrostatic potential distribution indicates that the strong electron‐donating effect introduced by the alkali metal Li results in the highest electrostatic potential gradient in Li‐O‐Ni‐MOF‐74, leading to the strongest adsorption of N2, this is unfavorable for CH4/N2 separation. At 1500 kPa the selectivity order of adsorbents for mixed gases was as follows: CH3‐Ni‐MOF‐74 > NH2‐Ni‐MOF‐74 > OH‐Ni‐MOF‐74 > Ni‐MOF‐74 > Li‐O‐Ni‐MOF‐74. This study highlights that CH3‐Ni‐MOF‐74 possesses optimal CH4 selectivity and adsorption performance. Given the current lack of research on functionalized MOF‐74 for the separation of CH4 and N2, the findings of this study will serve as a theoretical guide and provide references for the applications of CH4 adsorption and CH4/N2 separation.
PDF
