Vibrating flip-flow screens (VFFS) are widely used to separate high-viscosity and fine materials. The most remarkable characteristic is that the vibration intensity of the screen frame is only 2–3 g (g represents the gravitational acceleration), while the vibration intensity of the screen surface can reach 30–50 g. This effectively solves the problem of the blocking screen aperture in the screening process of moist particles. In this paper, the approximate state of motion of the sieve mat is realized by setting the discrete rigid motion at multiple points on the elastic sieve mat of the VFFS. The effects of surface energy levels between particles separated via screening performance were compared and analyzed. The results show that the flow characteristics of particles have a great influence on the separation performance. For 8 mm particle screening, the particle’s velocity dominates its movement and screening behavior in the range of 0–8 J/m² surface energy. In the feeding end region (Sections 1 and 2), with the increase in the surface energy, the particle’s velocity decreases, and the contact time between the particles and the screen surface increases, and so the passage increases. When the surface energy level continues to increase, the particles agglomerate together due to the effect of the cohesive force, and the effect of the particle’s agglomeration is greater than the particle velocity. Due to the agglomeration of particles, the difficulty of particles passing through the screen increases, and the yields of various size fractions in the feeding end decrease to some extent. In the transporting process, the agglomerated particles need to travel a certain distance before depolymerization, and the stronger the adhesive force between particles, the larger the depolymerization distance. Therefore, for the case of higher surface energy, the screening percentage near the discharging end (Sections 3 and 4) is greater. The above research is helpful to better understand and optimize the screening process of VFFS.

Double-deck vibrating flip-flow screens have been widely used for the repurposing of decoration waste; however, the influence of shear spring stiffness on the screen’s vibration characteristics is under-researched. The shear spring stiffness affects the amplitude–frequency characteristics, phase–frequency characteristics, screening performance and processing capacity of the screen. In this paper, a mathematical model of the double-deck vibrating flip-flow screen is proposed based on a vibrating system with three degrees of freedom. Based on the experiments of the industrial screen, the amplitude–frequency and phase–frequency characteristics of the double-deck vibrating flip-flow screen were studied. Within the range of 25 to 75 rad/s, the amplitude of the main screen frame decreased gradually, the floating screen frames decreased at first and then increased and the amplitudes of the main and floating screen frames were dependent on the stiffness of the isolation springs and shear springs. When the frequency was 75 rad/s, the stiffness of the upper and lower shear springs was 11,440 kN/m, respectively, and the screening efficiency reached 97.09%.

Deep dry screening is the key unit in mineral processing. A vibrating flip-flow screen (VFFS) can provide effective solutions for screening fine-grained minerals, and it has been extensively used in many industrial fields. An accurate dynamic model of VFFS considering the influence of materials is significant for its dynamic analysis and screening process research, but it has rarely been studied in detail. In this paper, an improved dynamic model of VFFS is proposed and its dynamic equations are solved to find the reasonable operating condition, and experiments are carried out to verify the reasonability of the proposed model under no-load and loading materials conditions. Furthermore, the method of multistage sampling and multilayer screening is also applied to evaluate the screening performance of iron ore at 3 mm cut size on VFFS. Results show that when the mass of materials, relative amplitude, and operating frequency have values of 107 kg, about 6 mm and 80.79 rad/s, respectively, the screening efficiency gradually increases with an increase of screening length, reaching 89.05%; however, it does not change much when the screening length exceeds 1900.8 mm. Additionally, the misplaced materials of coarse particles will continue to increase as the screening length increases. This provides theoretical and technical support for the optimization of the length of the VFFS.

Moisture content has an important influence on the stratification and screening of materials on the surface of screens, and materials with different external moisture concentrations present different screening characteristics. A vibrating flip-flow screen (VFFS) is a two-body vibration system with a high-vibrating-strength screen surface developed based on a circular vibrating screen (CVS), which offers significant advantages in terms of handling sticky fine particles. To better understand the difference in screening performance between a VFFS and CVS under different external moisture concentrations, it is necessary to conduct a comparative study on the distribution characteristics of materials on the screen’s surface. In this paper, a CVS dynamic model considering the stiffness force and position of the damping spring is proposed, and the influence of different arrangements of damping springs on the amplitude and angular displacement of the screen is analyzed. Under different external moisture concentrations, the screening percentages of the 3–1 mm sized fractions in sections I–IV of a VFFS and a CVS are greater than those of 1–0 mm sized fractions. The screening efficiencies of CVSs and VFFSs are 92.54% and 92.19%, respectively, at an external moisture content of 4.30%, so the screening effect of a low-vibration-intensity screen surface is better in the case of better material stratification. When the external moisture content of the material was increased from 4.30% to 8.19%, the screening efficiency of the VFFS and the CVS decreased by 33.85% and 41.32%, respectively. The screening efficiency of the CVS is more sensitive to the external moisture content of a material.

Vibrating flip-flow screens are widely employed in the deep screening processes of coal washing, solid waste treatment, metallurgy, and other fields, playing a crucial role in enhancing product quality and production efficiency. The screen surface and material movement of vibrating flip-flow screens are highly complex, and there is currently insufficient understanding of their screening mechanism, limiting further optimization and application. In this paper, the Discrete Element Method (DEM), Finite Element Method (FEM), and Multi-Body Dynamics (MBD) were integrated to establish a numerical coupling model for vibrating flip-flow screens, considering material loads, screen surface deformation, and screen machine dynamics. The Response Surface Method was utilized to analyze the significant impact of relative amplitude, tension amount, amplitude of driving screen frame, vibration frequency, and screen surface inclination on screening efficiency and material velocity. The results indicate that the most significant factor influencing the screening of flip-flow screens is the screen surface inclination. Based on a BP neural network, a five-degree-of-freedom inclination surrogate model for flip-flow screens was established. The whale algorithm was employed for multi-objective optimization of the surrogate model, resulting in a screen surface inclination distribution that meets the requirements of different operating conditions.

The vibrating flip-flow screen (VFFS) is a high-efficiency device currently used for deep screening of moist fine-grained materials. During VFFS operation, the normal operation of the screen is affected by fatigue damage to the shear springs arranged symmetrically on both sides of the screen, leading to equipment failures and disruption production. In this paper, the shear spring’s static and dynamic characteristics in different operation conditions were studied using the INSTRON 8801 fatigue test system and Dynacell dynamic sensors. Using an experimental test of shear spring stiffness and damping coefficients, the effects of some factors, i.e., temperature, hardness, amplitude and frequency, were studied. The results show that the temperature of the shear spring on the left side of the flip-flow screen was higher than that of the right side (driving side). With an increase in temperature, the stiffness of the shear spring decreased. With the increase in amplitude, the dynamic stiffness decreased and the damping coefficients did not change; with the increase in frequency, the dynamic stiffness increased and the damping coefficient decreased. At the same amplitude, with the increase in hardness of the shear spring, the dynamic stiffness increased. Finally, the stiffness and damping coefficients of the shear spring before and after tearing were obviously reduced. These research results reveal the relationship of the characteristics of a shear spring with operational conditions, and could provide a theoretical reference for the design of the VFFS and the selection of the shear spring.