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Geometric error is a crucial factor influencing the spatial accuracy of CNC machine tools. A novel methodology for modeling, measuring, and identifying geometric errors in multi-axis machine tools is proposed in this paper. Firstly, a synthetic volumetric error model is established by utilizing dual quaternions for multi-axis CNC machine tools. To characterize the relative position relationship between the tool and the workpiece, the kinematics model automatically incorporates the complex coupling between position and orientation motion in an implicit way, enabling a concise and compact representation of the kinematics. Secondly, measure path planning includes candidate measurement positions which are screened to obtain the optimal position group by using observation indices and the modified Detmax method. Thirdly, a parametric modeling method based on exponential cosine fitting is proposed for representing both angular and linear errors, and an improved sparrow search algorithm and nested parameter uncertainty optimization are established to process curve fitting–based optimization of the geometric error term. The fitting of the exponential cosine model is quantified with model uncertainty, and the nested uncertainty optimization method is employed to improve geometric error terms with a poor fitting effect. Finally, the effectiveness is demonstrated through experimental comparisons. The geometric error of a single axis has an average decreased of 69.7%, and the compensation rate of roundness driven by two-axis synchronization is an average of 68.7%. This method offers the advantage of quantifying the minimum optimal number of measurements and positions, improving the efficiency of parametric modeling. [ABSTRACT FROM AUTHOR]

The WC/Ni coatings were prepared by the laser cladding of Ni-based powders containing nano-WC particles with different contents. The effect of nano-WC particles on the wear resistance and impact resistance of Ni-based coatings were studied. The SEM and XRD were used to analyze the microstructure of the composite coating. The wear tester and charpy impact tester were used to test the wear resistance and impact resistance of the composite coatings. The microstructure of the coating is refined by nano-WC. The wear rate of the nano-WC coating was 53.43% lower than that of the Ni45 coating. The impact toughness of the coating was 13.37% higher than that of Ni45 coating. The nano-WC hinders the crack propagation in the grain boundary and eutectic region. Thus, the nano-WC can increase the impact energy required for coating fracture and significantly improve the impact toughness of the coating. Nano-WC can reduce the uneven slip of dislocations and alleviate the accumulation of dislocations by the analysis of the finite element. Nano-WC can effectively disperse the stress concentration formed in the impact process of the coating. Nano-WC can significantly improve the impact resistance of the composite coating. The results show that nano-WC can improve the wear resistance and impact resistance simultaneously. [ABSTRACT FROM AUTHOR]

Geometric error is the main obstacle that affects the quasi-static accuracy of horizontal boring machine tools. To improve quasi-static performance, the error terms of all position-independent geometric errors (PIGEs) and position-dependent geometric errors (PDGEs) must be measured and identified precisely. This study proposes a novel method for measuring and identifying the above two types of geometric errors based on double ballbar for the rotary axis. The error terms of the linear axis are identified from the measurement model based on the exponential product method and a preset measure trajectory, and the measure coordinate system is combined with the reference coordinate to lower the uncertainty in the identification accuracy. Then, the elastic net method and improved weight function IGG3-LTS method are established to identify the PIGEs and PDGEs of the rotary and linear axes, respectively. This method has the advantage that measurement with the built-in sensor method synchronously does not interfere with the running state of the machine tool, and neither the inaccuracy of reference-frame misalignment nor installation error of the measuring instrument affects the geometric error identification results of the linear axis. Moreover, all PIGEs and PDGEs, particular to the rotary axis of the horizontal boring machine tool, are determined accurately. The measurement and identification strategy is demonstrated by experimental comparison on a four-axis precision horizontal boring machine tool. The minimum compensation rate of each precision index of the test specimen is 40.0%, the average compensation rate is 52.7%, and the maximum compensation rate is 62.5%. [ABSTRACT FROM AUTHOR]

Owing to such advantages as long transmission distances and compact structures, flexible rope-sheave lifting mechanisms are important for applications in disaster relief, emergency treatment, high-altitude operations, and robot transmission. Despite their long research history and wide range of applications, the mechanical properties of the interactions between flexible ropes and sheaves have been investigated by few studies, most of which rely on experience and experimental test results for design. The present study developed a mathematical model for the mechanical characteristics of a hoisting mechanism that was composed of a sheave with gear teeth, pressure wheels, and a flexible rope. The critical value for the hoisting mechanism's slippage was analyzed, and the parameters that affected the lifting performance, such as the sheave groove angle and gear teeth, were simulated and optimized. The results were consistent with the experimental test data. The optimized rope-sheave lifting mechanism was further applied to the design and development of rope-climbing robots, and its lifting performance was experimentally tested. The research results presented in this paper described the mechanical characteristics of the flexible rope-sheave lifting mechanism, combined the mechanical model with the optimized design, and verified them through experiments; this provided guidance for more precise and quantitative applications of flexible rope-sheaves. [ABSTRACT FROM AUTHOR]