Experimental investigation of recoating forces in sand binder jetting

Additive manufacturing of sand molds using binder jetting enables production of geometrically complex castings. Process parameters during recoating significantly affect and impair part quality. While recoating forces have been studied extensively through simulations for metal powder bed fusion, experimental quantification for sand binder jetting is lacking. The transferability of existing models to sand systems with larger, irregular particles remains unclear. This work presents systematic experimental quantification of both tangential and normal recoating forces in sand binder jetting. A dual load cell measurement system was developed to simultaneously capture both force components during recoating. The two most common industrial recoater geometries (blades and rollers) were investigated. Blade angles (70°-92°), roller circumferential speeds (0-500 mm/s), and recoating velocities (100 mm/s and 300 mm/s) were systematically studied using GS14RP sand. Additionally, force differences at transitions between unprinted and printed areas were examined. Blade recoaters showed minimum forces at angles of 88°-90°, while 92° blade angle produced sharply increased forces and a visible displacement of the printed region in the powder bed. Roller recoaters achieved stable conditions at circumferential speeds above 200 mm/s. Blade recoaters exhibited decreasing forces with increasing recoating velocity, whereas roller recoaters showed the opposite trend. Force differences at part boundaries were significantly higher for rollers than for blades, particularly at elevated recoating velocities. This study provides experimental data for recoating forces in sand binder jetting, complementing particle-scale force chain frameworks from the DEM literature and establishing a foundation for future process optimization. From our results, we identified the configurations that minimize the recoating forces.