A flour mill does four jobs: store and pre-clean the wheat, clean and condition it, mill and sift it, then pack the flour. Here is every step, and the machine that does it.
Wheat arrives by truck or rail, is unloaded into an intake pit, pre-cleaned to take out straw, stones and large debris, and conveyed to the silos. A flow scale weighs it on the way to the cleaning section.
Everything that is not sound wheat comes out here: metal, stones, chaff, dust, shrivelled and discoloured grains. Clean wheat is the first condition for low-ash, white flour.
| Machine | What it removes |
|---|---|
| Magnetic separator | Iron and steel pieces, before they damage the rolls. |
| Vibro separator | Coarse and fine impurities by screen size. |
| Aspirator | Light impurities: chaff, dust, shrivelled grains. |
| Destoner | Stones and heavy particles the same size as wheat. |
| Scourer | Dust and dirt in the crease and on the surface of the grain. |
The moisture of the wheat is measured, and a dampener adds exactly the water needed. The wheat then rests 10–24 hours in tempering bins. Tough bran and a mellow endosperm separate cleanly in the mill: more flour, less bran in it.
After tempering, the wheat passes a final sifter, destoner and scourer, then a flow scale before the first break. Comparing the two scale readings shows the cleaning loss.
This is where flour is made, in many small steps rather than one. Each passage grinds a little, the plansifter grades what comes out, and each grade goes on to the next roll pair.
Fluted rolls open the grain and scrape the endosperm off the bran in 4–5 passages. Roller mills
Stacks of screens separate flour, semolina, middlings and bran after every passage. Plansifter
Air and vibrating screens take fine bran out of the semolina before it is reduced. The key to low-ash flour. Purifier
Smooth rolls reduce clean semolina to flour in 6–8 passages. Detachers loosen flakes between passages.
Recover the last flour from the bran. Bran finisher
High-pressure fans lift stock between floors through cyclones and airlocks.
How much roll and sifting area a mill needs for its capacity: sizing calculator.
Finished flour goes to flour bins, through a vibro discharger and an insect killer to the packing scales. Bran is packed separately.
Ask for a flow sheet for your capacity How a maize mill differs →