Mixing machine is the machine using mechanical force and gravity to mix two or more materials together to uniform mixture. Mixing machine is widely used in various industrial and everyday lives. Mixing machine can make various materials into a homogenous mixture, such as cement, sand, gravel and water are mixed into the wet concrete and other materials; it also can increase the contact surface area of materials to facilitate chemical reactions; and accelerate physical changes, such as granular solute added to a solvent, mechanical mixing action can accelerate the dissolution.

Four commonly used mechanical mixers: mixer for gases and low viscosity liquids, mixer for high viscosity liquids and pastes, mixer for thermoplastic material and mixer for powder and granular solid material and low viscosity liquid mixing machine is characterized by simple structure, and no moving parts, less maintenance overhaul, low energy consumption. Such mixing machine is divided into four kinds: flow mixing, mixing pipe, jet mixing and forced circulation mixer.

Mixing machines for high viscosity liquids and paste generally has a strong shearing action; Thermoplastic material mixer is mainly used for thermoplastic materials (such as rubber and plastic) mixing with additives; intermittent operation for powder granular solid material, and machine combining mechanical mixing and grinding, such as wheels rolling machine etc..

Mixing requires all involved materials uniformly distributed. There are three state of mix: an ideal mixed, randomly mixed and completely immiscible mixed. There are several factors determining the mixing state of all involved materials: Ratio of the material to be mixed, physical state and properties, mixing operation time and mixing machine etc.

Liquid material is agitated by mechanical stirrer, air and liquid jets to achieve uniform mixing. Agitation causes partial liquid flow which pushes the surrounding liquid, resulting in a recycle stream in mixing device. Arose fluid distribution is called convection-diffusion.

Partial vortex occurs when the liquid agitated at a high speed. These swirls quickly spread and more liquid involves into the whirlpool. The disorder convection formed in a small area known as eddy diffusion.

Mechanical stirrer, the moving part, creates shearing action to the liquid during rotation. Meanwhile the liquid flows through container wall and the fixed frame bearing shearing force. All these shearing actions cause numerous partial eddy diffusions.

Convection-diffusion and eddy diffusion caused by stirring increase the surface areas between molecular diffusion and reduce the distance, thereby shortening the diffusion time.

For the immiscible liquids with different density, composition, the shear force and strongly turbulent cut and shred big density liquid into small droplets and make them uniformly dispersed in the main liquid. Liquid flow rate caused by stirring must be greater than the droplets settling velocity.

The mixing mechanism for a small amount of insoluble powdered solid and liquid mixing is the same as immiscible liquids with different density, except for mixing cannot change the particle size of the powder. If the solid particles settling velocity cannot be less than the liquid flow rate, regardless of the mixing method used, a uniform suspension can not be formed.

Mixing different pastes is to repeatedly cut, press, roll and squeeze them, then to repeat combining, and kneading, finally reach the required degree of mixing. In this case, it is hard to get the desired mix, only to reach a random mix. The powder mixing with small amount of liquid is the same situation as pastes mixing.

In order to achieve a random mix, various thermoplastic materials and thermoplastic materials with a small amount of powdered solids, need to rely on strong shearing, repeatedly rubbing and kneading.

Granular solids with good fluidity mixing can be reached by container's turning or stirrers running, agitating or by airflow or turbulence flow. As it is hard to create whirlpool from airflow or turbulence flow, the mixing speed for solids is much lower than the liquid mixing, and generally getting a random mix.

Illiquid and adhesive, granular or powdered solid often requires turning and mixing machine with mechanical pressing, rolling functions.