Purpose: Additive manufacturing (AM) is a promising alternative to the conventional production methods (i.e., machining), providing the developers with great geometrical and topological freedom during the design and immediate prototyping customizability. However, frictional characteristics of the AM surfaces are yet to be fully explored, making the control and manufacturing of precise assembly manufactured mechanisms (i.e., robots) challenging. The purpose of this paper is to understand the tribological behavior of fused deposition modeling (FDM) manufactured surfaces and test the accuracy of existing mathematical models such as Amontons–Coulomb, Tabor–Bowden, and variations of Hertz Contact model against empirical data. Design/methodology/approach: Conventional frictional models Amontons–Coulomb and Tabor–Bowden are developed for the parabolic surface topography of FDM surfaces using variations of Hertz contact models. Experiments are implemented to measure the friction between two flat FDM surfaces at different speeds, normal forces, and surface configuration, including the relative direction of printing stripes and sliding direction and the surface area. The global maximum measured force is considered as static friction, and the average of the local maxima during the stick-slip phase is assumed as kinematic friction. Spectral analysis has been used to inspect the relationship between the chaos of vertical wobbling versus sliding speed. Findings: It is observed that the friction between the two FDM planes is linearly proportional to the normal force. However, in contrast to the viscous frictional model (i.e., Stribeck), the friction reduces asymptotically at higher speeds, which can be attributed to the transition from harmonic to normal chaotic vibrations. The phase shift is investigated through spectral analysis; dominant frequencies are presented at different pulling speeds, normal forces, and surface areas. It is hypothesized that higher speeds lead to smaller dwell-time, reducing creep and adhesive friction consequently. Furthermore, no monotonic relationship between surface area and friction force is observed. Research limitations/implications: Due to the high number of experimental parameters, the research is implemented for a limited range of surface areas, which should be expanded in future research. Furthermore, the pulling position of the jaws is different from the sliding distance of the surfaces due to the compliance involved in the contact and the pulling cable. This issue could be alleviated using a non-contact position measurement method such as LASER or image processing. Another major issue of the experiments is the planar orientation of the pulling object with respect to the sliding direction and occasional swinging in the tangential plane. Practical implications: Given the results of this study, one can predict the frictional behavior of FDM manufactured surfaces at different normal forces, sliding speeds, and surface configurations. This will help to have better predictive and model-based control algorithms for fully AM manufactured mechanisms and optimization of the assembly manufactured systems. By adjusting the clearances and printing direction, one can reduce or moderate the frictional forces to minimize stick-slip or optimize energy efficiency in FDM manufactured joints. Knowing the harmonic to chaotic phase shift at higher sliding speeds, one can apply certain speed control algorithms to sustain optimal mechanical performance. Originality/value: In this study, theoretical tribological models are developed for the specific topography of the FDM manufactured surfaces. Experiments have been implemented for an extensive range of boundary conditions, including normal force, sliding speed, and contact configuration. Frictional behavior between flat square FDM surfaces is studied and measured using a Zwick tensile machine. Spectral analysis, auto-correlation, and other methods have been developed to study the oscillations during the stick-slip phase, finding local maxima (kinematic friction) and dominant periodicity of the friction force versus sliding distance. Precise static and kinematic frictional coefficients are provided for different contact configurations and sliding directions.

中文翻译：

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Fusion Deposition Modeling (FDM) 制造表面的摩擦特性

目的：增材制造 (AM) 是传统生产方法（即机械加工）的一种有前途的替代方案，为开发人员在设计和即时原型定制过程中提供了极大的几何和拓扑自由度。然而，增材制造表面的摩擦特性尚未得到充分探索，这使得精密组装制造机构（即机器人）的控制和制造具有挑战性。本文的目的是了解熔融沉积建模 (FDM) 制造表面的摩擦学行为，并根据经验数据测试现有数学模型（例如 Amontons-Coulomb、Tabor-Bowden 和 Hertz 接触模型的变体）的准确性。设计/方法/途径：传统的摩擦模型 Amontons-Coulomb 和 Tabor-Bowden 是为 FDM 表面的抛物线形表面形貌开发的，使用赫兹接触模型的变化。实施实验以测量不同速度、法向力和表面配置的两个平面 FDM 表面之间的摩擦，包括打印条纹的相对方向和滑动方向以及表面积。全局最大测量力被视为静摩擦力，粘滑阶段的局部最大值的平均值被假设为运动摩擦力。频谱分析已被用于检查垂直摆动的混沌与滑动速度之间的关系。结果：观察到两个 FDM 平面之间的摩擦与法向力成线性比例。然而，与粘性摩擦模型（即 Stribeck）相反，摩擦在较高速度下逐渐减小，这可归因于从谐波振动到正常混沌振动的过渡。通过光谱分析研究相移；主要频率以不同的拉速、法向力和表面积呈现。据推测，更高的速度会导致更小的停留时间，从而减少蠕变和粘附摩擦。此外，没有观察到表面积和摩擦力之间的单调关系。研究局限性/意义：由于实验参数数量众多，研究是在有限的表面积范围内实施的，应在未来的研究中扩大。此外，由于接触和牵拉电缆的柔顺性，钳口的牵拉位置与表面的滑动距离不同。使用非接触式位置测量方法（例如激光或图像处理）可以缓解此问题。实验的另一个主要问题是牵引物体相对于滑动方向的平面方向和切线平面中的偶尔摆动。实际意义：根据这项研究的结果，可以预测 FDM 制造表面在不同法向力、滑动速度和表面配置下的摩擦行为。这将有助于为完全 AM 制造的机构和装配制造系统的优化提供更好的预测和基于模型的控制算法。通过调整间隙和印刷方向，可以减少或缓和摩擦力，以最大限度地减少粘滑或优化 FDM 制造接头的能源效率。了解更高滑动速度下混沌相移的谐波，可以应用某些速度控制算法来维持最佳机械性能。原创性/价值：在这项研究中，理论摩擦学模型是为 FDM 制造表面的特定地形开发的。已经针对广泛的边界条件实施了实验，包括法向力、滑动速度和接触配置。使用 Zwick 拉伸机研究和测量扁平方形 FDM 表面之间的摩擦行为。光谱分析，自相关，已经开发了其他方法来研究粘滑阶段的振荡，找到局部最大值（运动摩擦）和摩擦力与滑动距离的主要周期性。为不同的接触配置和滑动方向提供精确的静态和运动摩擦系数。