Roller mill

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Modern roller mill in a flour mill (Newtronic model from Bühler )

A roller frame is a size reduction machine ( grinding mill ) in which the material to be ground is broken up and ground between rotating rollers. This type of mill is the most common in industrial flour mills today.

Apart from the use in mills, roller mills are used in calendering .

functionality

Grinding in the modern mill involves two processing steps that are repeated several times: crushing and sieving . The roller mill does the grinding. The kernel is gently removed from the shell parts in several steps. The resulting mixture is passed to a plansifter for separation . The coarse particles that are not yet flour are returned to the roller mill by means of pneumatics or mechanical means of transport. A passage through the roller mill and plansifter is called a passage . When grinding, the grains are broken up by corrugated rollers, when dissolving (by smooth rollers) the flour and shell parts are separated from each other and when grinding the last flour particles are detached from the shell. The grain goes through eight to twelve passages before the flour is loosened from the shell.

In a closed housing, the grain falls into the upper end of the roller frame. There a feed roller feeds it to the grinding gap while ensuring a constant volume flow. This is formed by two horizontally or diagonally arranged rollers that rotate in opposite directions (like gears ).

The miller has various setting options:

  • Distance between the rollers (grinding gap)
  • Differential speed (advance for corrugated rollers 1: 2.5 and for smooth rollers 1: 1.25)
  • Number of corrugations
  • Corrugation angle (twist)
  • Position of the corrugations to each other (back: back, back: cutting edge, cutting edge: cutting edge, cutting edge: back)

Roller mills are now electronically controlled and monitored.

  • Corrugated rollers for a roller mill

  • Roller mills in a flour mill

  • Historic roller mill

Feed

In a modern roller mill, the speed of the feed roller is regulated according to the specifications of a weight sensor in the pre-depot. In slightly older versions, a plate in the pre-depot controls the supply by acting on a mechanism. Here the speed of the feed roller is set with a lever by the miller. The speed of the feed roller and the opening of the feed is very important for the grinding and the downstream machines, as these can be overloaded if the load is too high.

Web links

Commons : roller mills  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ Historical representation from Lueger, Otto: Lexicon of the entire technology and its auxiliary sciences, Bd. 9 Stuttgart, Leipzig 1914., p. 836.