Agro-Tech Book - Agriculture Support Programme

HAMMER MILL PROCESSING and COSTS
Introduction
Processing maize into Roller Meal provides a good opportunity for increasing income from
maize production and from other people’s maize.
Roller meal is the product obtained when whole maize grain is milled by any process. “Breakfast
Meal” is the product obtained from maize after most of the germ and seed coat has
been removed. This process requires a more sophisticated machine or set of machines.
There are roller mills on the market which can produce a product very similar to commercial
breakfast meal but they cost much more than a “Hammer Mill” and require a high standard
of management for successful operation.
The hammer mill is a simple robust machine which consists of a set of “hammers” which are
attached to a steel shaft which rotates very fast so that it smashes the maize grains. The
smashed pieces then pass through a “screen” or sieve. Eventually all the maize is smashed
suf�ciently that all of it is able to pass through the screen. These particles after passing
through the screen are called “roller meal”.
Roller meal is more nutritious than breakfast meal as a signi�cant part of the protein and
minerals is removed as “maize bran” during the processing of breakfast meal.
DESIGNS of HAMMER MILLS
Most hammer mills are based on the same simple principle – maize is fed into a chamber in
which a row (or rows) of hammers rotate at approximately 3,600 rpm. This requires a motor
of 5.6 kilowatt or 7.5 horse power (HP) for a throughput of 200kg/hr. The motor can be
fuel driven – usually diesel (D), or electrically powered (E) which is cheaper to buy and to
operate.
Common hammer mill sizes and capacities are;
OUTPUT MOTOR SIZE Litres of diesel/hr Cost of Mill($)
200kg/hr 7.5HP 1.3 2,111(E); 2,328(D)
E.E.O.A.
400kg/hr 15-16HP 2.6 2,715(E); 5,563(D)
600-700kg/hr 25HP 6.1 3,700(E);7,100(D)
DECIDING TO BUY and OPERATE A HAMMER MILL
The �rst consideration is: “is there suf�cient market?” This entails looking at the “competition”,
the population and their ability/willingness to buy roller meal or milling services and
for how much of the year. Normally it is not worthwhile buying maize, transporting it to the
mill, processing it and then transporting any signi�cant distance to market.
The next decision is the size (capacity of the mill) – this will depend on the expected market
demand. The choice of motors is the next decision – electric motors are cheaper but there
AGRO-TECHNOLOGY: Farming and Processing Equipment 17