Banbury Mixer Lab Report

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MOW 217: group assignment Banbury mixer
Design report

Graeme Garcia Menendez
Bradley Burrell
Alex Jackson
Joshua Elphinstone
Murray Smith

Background:
The Banbury mixer is a tangential type of mixing machine, in which two spiralled rotors turn side by side toward each other within a chamber. The chamber has an opening at the top called the hopper that the material is pushed into, the chamber also has a bottom gate used to drop out the material after mixing. Banbury mixes can operate at different temperatures and pressures for mixing different solutions. A common use of a Banbury mixer is to mix the rubber compound used in the tyre industry.

Problem statement:
When designing a Banbury mixer one must get acquainted with the full spectrum
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Some of these standards include:

Feed hopper: Rigid mechanical design allows for a longer lifespan. Large air cylinder allows for rapid pressurization of batch.
Chamber assembly: Dust stops are needed to ensure that no dust enters the chamber, the dust stop standards are FYH and FH. Rotors need to be precisely machined to make sure no cavities form during the mixing process, this also improves the lifespan of the machine.
Discharge area: Toggle latches are needed to ensure positive locking of the drop door. Rack and pinion rotary actuators are used because they can withstand the force of sudden pressure changes.

The expected life of the mixer was assumed to be 2000 hours. As it is a machine tool and machine tools generally have a life of around 2000 hours.
The Banbury mixer designed by the ACME group of engineers chose deep groove ball bearings rather than vesconite bearings. The deep groove ball bearing chosen had the code 6820 as it met the requirements of the shaft diameter, rotational speed, rotational and axial loads aswell as the expected
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The chain length was calculated to be 90 pitches.
System-level diagram:

Functional analysis:
The rotors:
These are the main mixing elements of the machine and are responsible for the mixing of the raw material which happens between the blades. The shape of these ‘wings’ is very important to ensure smooth fluid flow through the machine.
An optimal length to diameter ratio helps mix more efficiently.
Mixing quality is also greatly influenced by the speed of the rotors, too fast and the fluid will develop cavities, too slow and the mixing process will be too inefficient.
Temperature inside needs to be carefully controlled and the friction between the fluid and blades increases the temperature rapidly thus a cooling system is required, this takes the form of complex geometric paths within the rotors.
High tensile steel is generally used.

Sides:
The sides of the banbury mixer is lined with cooling/heating systems so that heat is evenly transferred to prevent scorching.

Dust stops:
These are hydraulically operated and prevent batch contamination.

Feeding hopper:
The feeding hopper door is also operated using

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