How a Stand Mixer Works

A vertical mixer is a common type of material mixing equipment, widely used in industries such as plastics, chemicals, food, and building materials. Its core feature is a vertically arranged agitator shaft, which uses rotating components to stir and mix materials. The following is a detailed working principle:

I. Basic Structure
A vertical mixer primarily consists of a motor, a reduction gear, agitator shaft, agitator blades (or paddles), a drum (mixing barrel), an inlet, and a discharge port.

The motor provides power, which is reduced in speed and increased in torque by a reduction gear, driving the vertical rotation of the agitator shaft. The lower end of the agitator shaft is connected to agitating blades of various shapes (such as paddle, ribbon, or turbine, depending on the material characteristics).
The drum is a vertical container, where the material is mixed by the agitating blades. After mixing, the material is discharged from the bottom or side outlet.

II. Core Working Process
The operating principle of a vertical mixer is based on forced convection mixing. The rotating agitating blades create multi-dimensional motion in the material, achieving uniform mixing. The following steps are involved:

Material Addition
The material to be mixed (solid particles, powder, liquid, or paste) is added to the drum through the top or side inlet. The initial state of the material may be layered, dispersed, or contain lumps.
The rotation of the blades generates power.
After the motor is started, the agitator shaft drives the blades to rotate at high or low speed (the speed is adjusted based on the material viscosity and mixing requirements, typically ranging from tens to hundreds of revolutions per minute). The shape and mounting angle of the blades determine the material's movement:

Radial movement: As the blades rotate, they exert radial thrust on the surrounding material, causing it to disperse along the cylinder's radius and break up localized material accumulation.

Axial movement: Some blades (such as inclined paddles and spiral ribbon blades) generate axial thrust, pushing the material up and down (for example, material at the bottom is pushed upward, while material at the top falls to the bottom due to gravity), creating longitudinal convection.

Shearing movement: The relative movement between the blades and the material, and between the material and the cylinder wall, generates shear forces, breaking up agglomerates and dispersing small particles more evenly throughout the cylinder.

Uniform material mixing: The combined effects of radial diffusion, axial circulation, and shear forces create complex turbulent or convective motion within the cylinder. The different components of the materials continuously interpenetrate and intermingle, gradually achieving a uniform composition.

For example, when mixing plastic pellets and masterbatch, the rotation of the blades "envelops" the small masterbatch particles. The mixture is fed into the plastic pellets, where it is repeatedly circulated to achieve uniform color distribution.

Discharge after mixing is complete

After the set mixing time has elapsed, mixing is stopped and the evenly mixed material is discharged through a discharge valve (such as a gate valve or ball valve) at the bottom of the cylinder or a side outlet. Some models can control the blade speed during mixing to achieve simultaneous mixing and discharging (continuous production).

III. Targeted Effects of Different Blade Designs

Blade shape is a key factor influencing the efficiency of a vertical mixer, and different designs are suitable for different materials:

Paddle blades: These are simple in structure and can be straight or inclined. They are suitable for mixing low-viscosity materials (such as powders and granules), primarily generating radial and axial bulk flow.

Ribbon blades: These blades spiral around the agitator shaft, promoting strong axial circulation of the material (material at the bottom is pushed upward by the spiral, while material at the top falls along the cylinder wall). They are suitable for mixing high-viscosity materials or large volumes.

Turbine blades : The radial blades generate strong radial shear forces during rotation, making them suitable for applications requiring high-intensity dispersion (such as mixing liquids with powders and de-agglomerating).

Disperser: For materials containing liquids, high-speed rotation generates centrifugal force, breaking the liquid into small droplets and evenly dispersing them into solid materials (such as mixing coatings and adhesives).

IV. Application Characteristics

The operating principle of a vertical mixer makes it compact, requires little floor space, and has high mixing efficiency, making it particularly suitable for mixing small and medium-volume materials. However, due to the influence of gravity, materials at the bottom may require a stronger force to circulate. Therefore, for high-density and high-viscosity materials, a wall scraper or multi-layer blade design is often used to prevent material sedimentation.

In short, the core of the vertical mixer is to use vertically rotating blades to drive the material into multi-dimensional motion, utilizing convection, diffusion, and shear to break the material's initial state and ultimately achieve uniform mixing.