(A) Experimental set-up. The cylindrical drum attached to the rotary table is characterized by the diameter D = 184 mm and width W = 95 mm. (B) Binarized image of the pile surface. Red dashed line indicates the linear fit for the margin, from which θ is obtained. (C)–(G) Illustrations of five types of beads, namely steel, ABS, glass, 3D-printed plastic (3DP), and 3D-printed plastic with bumpy surface (BUMP) in sequence. They all possess 50:50 bidisperse diameters d = 5/6 mm.