The passivation process of a tool is a necessary step in the manufacturing process, which could improve tool life and machining efficiency by removing microscopic defects of in tool surface (such as burrs and micro cracks) after grinding or polishing. The abrasive water jet passivation (AWJP) is one of the most commonly used processes for carbide, ceramic and steel materials tools. Nevertheless, the complex action law from passivation to machining performance is indistinct, which makes passivation parameters rely on empirical summaries. To fill this gap, this paper concentrates on the detailed review of AWJP and comprehensive assessment between machining performance and AWJP parameters. Firstly, the mechanism of AWJP is analyzed, and the influence law of jet parameters on the tool nose radius is investigated. Secondly, the effect of tool nose radius on the force in turning and milling are summarized and analyzed. The jet pressure, abrasive concentration and jet time are positively correlated with the tool nose radius. Additionally, then the tool nose radius is positively and negatively correlated with cutting force and tool wear, respectively. Finally, future directions regarding the different parameters in AWJP and the machine tool for tool passivation are proposed: to reveal the complex nonlinear relationships between the parameters in AWJP. Develop economical, practical and efficient tool passivation machine tools to improve passivation efficiency and passivation accuracy and apply them to domestic tool passivation technology.
Gear is one of important transmission components in mechanical devices.How to correctly produce gears that meets the transmission requirements has always been the research focus in the mechanical industry.Among processing methods of gears,gear hobbing is the one of the most important processing methods because of its high production efficiency and strong universality.However,due to the influence of machining process,various errors will inevitably appear in the gear hobbing process.Therefore,the analysis of hobbing error modeling,detection and compensation are very vital to improve gear accuracy.This paper summarizes researches and developments of the above three aspects,and puts forward the direction and content that need to be further studied:constructing a closed-loop hobbing machining system of "tooth surface error modeling-tooth surface error tracing-error compensation".
In machining operations, the misalignment of the bearing assembly or imbalanced load often leads to deflection and failure of the tool spindle. The use of single feature information does not accurately monitor the complex working conditions. Considering this, this paper proposes a rolling bearing running condition monitoring method which is based on multiple feature information. Firstly, a multi-dimensional feature matrix is obtained by extracting the features of a single type of raw data in the time domain, frequency domain, and time-frequency domain, and then the dimensionality of the matrix is reduced by principal component analysis (PCA). An entropy weight improved the D-S(EWID-S) evidence theory is proposed. By updating the initial evidence source, and applying the Euclidean distance of the spatial centroid, the fusion results were evaluated. Finally, a test rig for eccentric bearing load operation is developed to obtain the vibration signals at two distinct locations and to confirm the proposed method. The test results show that the condition monitoring method based on the PCA and EWID-S evidence theory can effectively identify the bearing operating at different degrees of deflection. At the same time, by comparing with other improved D-S evidence theory methods, it is verified that this method has more advantages in information fusion and bearing condition monitoring.
The slow-wave structure (SWS) working in the terahertz frequency band features large aspect ratio and long span with characteristic dimensions of tens of microns. The development of micro-manufacturing technology for the high-quality fabrication of terahertz SWS is technically essential to promote the advancement of terahertz radiation source devices. In this work, micro-milling approaches were devised to process the 0.34 THz folded waveguide SWS with particle-reinforced metal matrix composite material. The causes of shape error and position error, especially within the arc-shape region, were analyzed in detail, considering the influence from the following error of machine tool and the unfavorable rigidity of milling tools. The optimization of regionalized cutting parameters was achieved, and two productive tool-path-planning schemes were conceived according to the structural features within the processing areas, attempting to minimize the external impact on the shape accuracy of SWS. A practical tool replacement scheme with the orthometric setting slots as a reference for resetting after tool replacement was determined, in order to avoid misalignment at the junction of adjacent units. In consideration of the structural complexity of SWS and the position specificity of burrs, the tool path in the horizontal plane was designed in the way of alternately milling of S-shape slot and straight slot, with cutting parameters adaptable to the depth of the processing subregion, which shows excellent suppression effect of burrs. The proposed micro-milling process strategy offers promises to improve the fabrication quality of high-aspect-ratio SWSs with the minimum structure size of ~50μm.
Electroosmosis is one of the most used actuation mechanisms for the microfluidics in the current active lab-on-chip devices. It is generated on the induced charged microchannel walls in contact with an electrolyte solution. Electrode distribution plays the key role on providing the external electric field for electroosmosis, and determines the performance of electroosmotic microfluidics. Therefore, this paper proposes a topology optimization approach for the electrodes of electroosmotic microfluidics, where the electrode layout on the microchannel wall can be determined to achieve designer desired microfluidic performance. This topology optimization is carried out by implementing the interpolation of electric insulation and electric potential on the specified walls of microchannels. To demonstrate the capability of this approach, one typical electroosmotic device, i.e., electroosmotic micropump, is modeled with several electrode layouts derived. And this approach permits potential applications in chemicals and biochemistry due to its outstanding capability on determining the performance of electrokinetic microfluidics.