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Peanut butter milling

Product analysis: the peanut butter mill

The market
Almost all households in Migori and surrounding areas produce peanut butter. As a result, there is a large potential market for the peanut butter mill.

Technical specification
Motor: 3 horse-power, high-speed, 3000 rpm (usually bought from China or the Czech Republic)
Starter: 9-13 amps with a single-phase electricity supply suitable for use in a house. An overload system automatically stops the mill
Base plate: 230mm diameter x 6mm thickness. This is permanently attached to the frame, to make the machine stable
Grinding container: made from heavy 0.5 gauge stainless steel, 260mm diameter x 260mm height. A mesh allows the ground butter to drop into an outlet chute
Blades: two blades, 220mm x 25mm x 5mm, driven by a stainless steel rotor shaft
Outlet chute: 180mm x 95mm, with a 25mm flap on each side
Bucket: to catch the butter, made from 0.5 gauge stainless steel, 220mm diameter x 1230mm height
Frame: made from heavy gauge square steel and one inch round black tube, finished in metallic blue paint

Product function
Peanuts, including their skins, are poured from a cup into a small hole in the lid of a grinding container. They slowly drop through the hole, where the blades rotate and crush them into a fine semi-liquid. This falls through a mesh, down a chute and into a container below. The new machine can make 90 kilograms of peanut butter in eight hours.

Extruding peanut butter from the mill Practical Action/Zul

Now that George Omondi has standardised the design, the peanut butter mill can be mass produced. However, at the moment, just five are made each month.

Frame materials are cut using a hacksaw and are arc-welded. A fixture jig is used to maintain the correct angles. Welded parts are ground smooth before being spray primed and painted. The motor is bolted to the frame and then three bolts (machined on the lathe) and a screw are added as the seat for the base plate. A template is made to align the base to the bolts and container. The bolts are welded to prevent the container detaching.

The rotor is attached to the motor key. The blades are correctly aligned, one twisted at a 20 degree angle to press down on the peanuts; the other horizontal to continue milling. Blades are spot-welded to the rotor. The container is bolted to the base plate and its lid is adapted to house a brazed stainless steel funnel made from a metal cup. Wiring is completed and the machine is tested.

George Omondi with a peanut butter mill Practical Action/Zul

The machine is fitted with a standard plug, can be powered by a standard socket and is fitted with a power overload. A lid means that operators don't come into contact with the blades. A coupling key-way has been added to prevent the blades flying off. The frame has been reinforced and the machine is stable, although it could still be knocked over if it was roughly handled. The blades need to be cleaned carefully.

A user guide is sent out with each mill.

Operators sit at the mill but need to bend to retrieve the butter bucket. The top of the grinding container is at a convenient height for feeding the machine.

The machine is primarily functional. However, it is finished with metallic paint and there are plans to add a brand name to make it easier to market the mill.

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Practical Action - Technology challenging povertyEuropean Commission - Department for International Development

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