In the final analysis, it is the grid or a grid-like structure under the opening assembly that determines the level of waste and its composition in terms of impurities and good fibres. Grids are segment-shaped devices under the opening assemblies and consist of several (or many) individual polygonal bars or blades (i.e. elements with edges) and together these form a trough. The grid encircles at least 1/4, at most 3/4 and usually 1/3 to 1/2 of the opening assembly.
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| Two-part Grid |
The influence of the grid on cleaning efficiency?
The grid has a major influence on the cleaning effect via:
• the section of the bars;
• the grasping effect of the edges of the polygonal bars;
• the setting angle of the bars relative to the opening elements;
• the width of the gaps between the bars;
• the overall surface area of the grid.
Elements of the Grid?
The following elements can be used in the grid:
• slotted sheets (a): poor cleaning;
• perforated sheets (b): poor cleaning;
• triangular section bars (c): the most widely used grid bars;
• angle bars (d): somewhat weak;
• blades (e): strong and effective.
The following elements can be used in the grid:
• slotted sheets (a): poor cleaning;
• perforated sheets (b): poor cleaning;
• triangular section bars (c): the most widely used grid bars;
• angle bars (d): somewhat weak;
• blades (e): strong and effective.
These elements can be used individually or in combination. Modern grids are mostly made up of triangular bars. They are robust, easy to manipulate and produce a good cleaning effect. The same is true of blade-grids. Blades have been used as grid elements for a long time (the mote knife), almost always in combination with triangular section bars.
What are the Grid adjustments?
Three basic adjustments:
• Distance of the complete grid from the beater;
• Width of the gaps between the bars (a=closed, b=open);
• Setting angle relative to the beater envelope.
Degree of opening, degree of cleaning and fibre loss are influenced by-
- Type of opening roller
- Speed of the opening roller
- Degree of penetration
- Type of feed
- The spacing of the feed from the opening device
- Type of grid
- Area of the grid surface
- Grid settings
- Airflow throw the grid
- Condition of pre-opening
- The thickness of the feed web
- Material throughput
- Position of the machine in the machine sequence.