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During the process of five-axis free-form milling, tool orientation and surface curvature of the workpiece have significant effects on tool wear. Five-axis milling experiments are carried out on 17-4PH stainless steel using a carbide ball end mill. The influence of tool orientation on the amount of wear, cutting force, and chip morphology of the ball end cutter was investigated. The results show that tool wear is slighter at a tool inclination angle of approximately 15°, reducing tool wear by up to 29.55% compared with other angles. The inclination angle also has great effects on the milling force and torque signals, a suitable tool inclination angle makes the milling force and torque signals smooth, and the standard deviation is only 0.94 N and 0.017 N·m, respectively. In addition, the chips can reflect the stability of the machining process to some extent. On this basis, different workpiece surfaces were selected to investigate the effect of workpiece surface characteristics on tool wear. The results show that more severe tool wear and higher milling force signals on curved surfaces occurred with smaller radii of curvature. An appropriate tool orientation in relation to the curvature of the workpiece surface can significantly reduce tool wear; concave surfaces are suitable for machining with small angle of inclination, e.g., 5° ~ 10°, whereas convex surfaces are suitable for machining with larger angle of inclination, e.g., 20° ~ 25°. [ABSTRACT FROM AUTHOR]

Polishing path optimization plays a crucial role in achieving high-quality and uniform surface polishing of free-form surfaces. To address the issue of uncontrollable ripple errors caused by uneven material removal in traditional contact polishing, this paper proposes an adaptive polishing path optimization method for uniform polishing of free-form surfaces based on footprint evolution. The presented approach considers the influence of curvature on footprint evolution and seeks to dynamically optimize the spacing between adjacent paths. This optimization ensures suitable overlap between neighboring footprints, ultimately leading to the achievement of uniform depth removal. Through modeling simulations and experimental comparisons involving different contact curvatures, it has been conclusively established that surface curvature plays a pivotal role in footprint evolution. Additionally, surface polishing experiments yielded results indicating a reduction in surface waviness within the central polishing area, decreasing from a root-mean-square value of 5.1766 to 4.1448 nm. These outcomes preliminary demonstrate the effectiveness of the proposed method. This study presents an efficient curvature adaptive path planning approach based on footprint evolution, offering new insights into achieving uniform polishing and suppressing waviness errors on free-form surfaces. [ABSTRACT FROM AUTHOR]

This paper aims to explore the influence of surface curvature distribution on the mechanical properties of lattice structures. In this study, a series of typical structure types were designed to obtain lattice structures with different surface Gaussian curvatures, including BCC (body center cubic) configuration, cross-cube configuration, and diamond lattice structure. Then, the above-mentioned porous structural sample was formed by SLM (selective laser melting), and the relevant mechanical properties were obtained by simulation and experiment. In addition, a characteristic method to describe the surface curvature of discrete triangular plaques is proposed and used to calculate the curvature distribution of the designed lattice structure. The results show that the lattice structure with concentrated Gaussian curvature distribution on the surface has good mechanical properties. Especially, for the cross-cube structure, the elastic modulus of the traditional configuration lattice structure increases by 79%, and the elastic modulus of the stretched structure increases by 70% when the volume fraction increased from 10 to 15%. Meanwhile, the elastic modulus for the traditional structure and the stretched structure increases by 41% and 14%, respectively, when the volume fraction of the structure increases from 15 to 20%. It is noted that the influence of surface curvature distribution on mechanical properties is slightly inferior to the volume fraction, which provides a new idea for the quantitative evaluation and design of porous structural properties. In addition, the BCC structure with concentrated curvature distribution provides a new scheme for the protection device after the stress climb stage after the elastic stage. Furthermore, the influence of surface curvature on the mechanical properties of lattice structures described in this paper will provide new inspiration for lattice structures in the fields of biocompatibility and heat exchange. [ABSTRACT FROM AUTHOR]

In the milling process of automobile panel mold of hardened steel, the characteristic of free-form surface is one of the dominant factors for surface topography. In this paper, the trajectory of cutting edge is firstly modeled to analyze the residual height of the free-form surface in ball-end milling of hardened steel. Furthermore, the non-uniform rational B-splines (NURBS) surface reconstruction is utilized to generate the surface topography. Subsequently, the influences of surface curvature, lead angle, milling vibrations on the machined surface topography, and residual height are investigated, respectively. Finally, the accuracy of the surface topography and the roughness prediction model are validated by the milling experiments of free-form surface, where two-dimensional contour maps could be obtained. The simulation and experimental results demonstrate that the machined surface topography of hardened steel is fitted by means of NURBS surface reconstruction. In that manner, the effects of surface characteristics on the machined surface topography can be accurately predicted. [ABSTRACT FROM AUTHOR]

Tool orientation has an important effect on the surface quality of a free-form surface during ball end milling process, and the selection of tool orientation is important to ensure the surface quality. In this work, a series of milling experiments were performed by using a carbide ball end mill on a workpiece of TC17 titanium alloy. The purpose of this study was to determine the tool orientation producing optimal surface integrity. The results showed that the surface roughness in both directions was better when the rotational angle was within the range of 0°~90° and with a constant inclination angle. In addition, inclination angle had little effect on the roughness in the feed direction, whereas a much larger or smaller angle led to greater roughness in the step direction. The tool orientation strongly affected the surface morphology. Compressive residual stress was detected on all machined surfaces. The maximum surface residual stress was obtained when the rotational angle was 90°, and the surface residual stress decreased as the inclination angle increased. On this basis, four curved surface models with different curvatures were established according to the features of a blade, and the effects of inclination angle and cutter path orientation on surface integrity were studied. The results indicated that the surface roughness produced with an upward orientation varied more than that produced with a downward orientation for a steep curved surface; the value of the roughness was small for a horizontal orientation and when the machine surface was very smooth. The machined surface for a flat curved surface was smoother, and there were no obvious differences in surface morphology between the two cutter path orientations. For steep curved surfaces, the cutter path orientation had no obvious influence on the residual stress, and a greater value was obtained when the surface was much steeper. For flat curved surfaces, the residual stress had no obvious variation resulting from small changes of the inclination angle. [ABSTRACT FROM AUTHOR]

In this paper, a predictive model of milling stability, which considers the surface curvature and the lead angle of the milling cutter, is proposed for milling of the panel die with sculptured surface. Firstly, influences of the radius of curvature and lead angle of milling cutter on uncut chip thickness are analyzed by exploring the curvature characteristics of sculptured surface. Subsequently, influence of the curvature characteristics of sculptured surface on chatter stability lobes in milling process is investigated by utilizing the full-discretization method. This analysis implies that the milling stability decreases with the increase in the radius of the die surface's curvature; the milling stability decreases with the increase in lead angle. The experimental results demonstrate that the prediction of chatter stability lobes could match well with the measured results on the change trend, where the maximum relative percent error is less than 11.1 % in stable milling. It is further validated that this method can effectively predict the chatter stability lobes of the domain in ball end milling of sculptured surface of die. [ABSTRACT FROM AUTHOR]

Complexity of sculptured surfaces has a great influence on multi-axis computer numerical control (CNC) machining performances such as processing efficiency, surface quality, and energy consumption. A term called surface machining complexity (SMC) is first presented to describe the complexity level of surface geometrical shape features, and its influence on CNC machining performance. Shape features of sculptured surfaces are classified into seven categories based on surface curvature. An innovative method for quantifying SMC using surface subdivision is proposed. Firstly, representation of sculptured surfaces is introduced. Then, three processes of surface subdivision are presented, which are surface discretization based on iso-parameter line sampling, rough partitioning based on surface shape categories, and region grouping based on two criteria. After that calculation, formulas of SMC including formulas of local SMC and global SMC are developed. The proposed formulas utilize three correction factors to describe the influences of surface size, cutter diameter, grouping order, and mode of different surface shape categories. Finally, the proposed method is applied to calculate SMC for a typical sculptured surface and multi-axis CNC machining experiments to demonstrate the ability of our method, which can form a foundation for further research. [ABSTRACT FROM AUTHOR]