The working principle of mung bean specific gravity machine

The mung bean specific gravity machine is an automated device that separates mung beans from impurities (or mung beans of different quality) based on material density differences. It is widely used in the pre-treatment links of mung bean processing (such as cleaning and grading). The core is to remove gravels, soil blocks, empty shell beans, moldy beans, etc. through physical methods to improve the purity and commodity value of mung beans.

The working principle of mung bean specific gravity machine
The core logic of the mung bean specific gravity machine is: the density of different materials (mung beans, impurities) is different. Under the combined action of “vibration + airflow”, different motion trajectories will be generated on the inclined screen plate (or separation bed), and ultimately layering and separation will be achieved. The specific process can be decomposed into 3 key steps:
1. Material pretreatment and uniform feeding
The mung beans to be treated are first screened (such as removing large grained straws and weeds), and then evenly transported by feeding mechanisms (such as screw conveyors, vibrating feeders) to the “separation bed” of the equipment (core working parts, usually inclined porous screen plates).
The feeding speed needs to be precisely controlled (can be adjusted through the inverter) to ensure that the material thickness on the separation bed is uniform (usually 3-5cm) and avoid local accumulation and incomplete separation.
2. Layering under the dual action of vibration + airflow
There are two key devices under the separation bed: a vibrating motor and a fan, which jointly realizes material layering:

Vibration effect: The vibrating motor drives the separation bed to perform “reciprocating inclination vibration” (usually front-back or left-right directions), forcing the material to slowly move downward along the inclined surface of the screen plate. At this time, materials with high density (such as gravel, plump mung beans) will “squeeze” to the lower layer of the screen plate (directly in contact with the screen plate); materials with low density (such as empty shell beans, soil blocks, and crushed powder) will be “lifted” to the upper layer.
Airflow function: The fan bulges in a uniform airflow from the bottom of the separation bed, and the airflow passes through the small holes of the screen plate (the aperture is smaller than the particle size of the mung beans to prevent the mung beans from leaking), creating “upward buoyancy” on the material. Light impurities with low density (such as dust, empty shells) will be blown directly by the airflow and discharged from the “light impurity outlet”; at the same time, the airflow can also assist in adjusting material layering – plump mung beans (density about 1.2-1.3g/cm³) remain in the lower layer because the buoyancy is insufficient to offset gravity, while empty shell beans (density about 0.6-0.8g/cm³) are supported by the airflow and maintained in the upper layer.
3. Separation and collection after stratification
After the combined action of vibration and airflow, the material forms a clear “three-layer structure” on the separation bed (from top to bottom):

Upper layer: light impurities (empty shells, dust, broken leaves) → blown by airflow to the “light miscellaneous outlet” to collect;
Middle layer: secondary mung beans (semi-full, mildly moldy beans, with density between full beans and impurities) → discharge along the “secondary outlet” on the middle side of the separation bed;
Lower layer: high-quality plump mung beans (largest density, close to the screen plate) → discharge along the “main material outlet” at the lowest end of the separation bed;