Machinery  >>  Mixer

Internal Mixer

Rubber Mixer is a mixing machine, designated to create a mixture of rubber raw materials and ingredients, which is also known as the rubber compound.

The main body of the mixer is actually a chamber comprised  of two counter-rotating heavy mixing rotors with small clearance between themselves and the enclosing walls. The mixing chamber is jacketed and may be heated or cooled, as may be the rotor.

Basically, all mixers are aiming to emulate the mixing action of a mill. The main features of a mill are:

·         High intensity shear in the nip

·         As the material enters the nip, the rollers pull down the sheet and extending it while creating shear on the edges

·         Cutting and folding of the sheet on the mill roll by the operator with the assistance of a  traveling stockblender


Although the designs of tangential and intermeshing rotors vary from manufacture to manufacture, some components are identical on each mixer as follows:

·         A chamber with a feed hopper and a discharge door

·         Rotors for producing shear rates to the material in order to form good distributive and dispersive mixing

·         A ram that exerts pressure on the material being mixed in the chamber.

·         A cooling/heating system which is responsible for manipulating the temperature of the rotors, ram, chamber walls and the drop door.


There are two basic designs of rotors for internal mixer; the non-intermeshing also called tangential type and the intermeshing type. Tangential rotors are able to rotate independently and hence, if required at different speeds. The same principle is in rolls of a mill for instance. Intermeshing rotors have to rotate at the same speed.

In an intermeshing process, emphasis is placed on the cutting and folding, enforced by the impingement of the radius of rotation of one rotor within the other and the Archimedean screw shape of each rotor driving the material in opposite directions. The nip of the mill, and the friction ratio of the rolls is simulated by the nip between the rotors being offset from the centerline of the machine, causing a difference in the surface speeds of the tip of the wings and the root of the rotor and hence the simulation of the friction ratio.


There are few other differences between both typs

         ·           Generally, intermeshing rotors are bigger and therefore take up    more of the mixing chamber space. Hence, the batch size in tangential rotors is greater for equal chamber sizes.

·         Intermeshing has more intensive mixing action and thus are able to achieve a better dispersion in a given mixing time.

·         Tangential rotors accept the ingredients more easily and discharge them faster. This means that for shorter cycle times, tangential rotors are preferable.


Intermeshing 3 - wing rotors                Tangential 4 wing rotors

Pelmar has a variety of used, refurbished and renewed rubber mixers on stock ranging from 1.5 liter laboratory rubber mixers to 690 liter for preparation of master or final batch.

Click here for the catalog


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