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.
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.
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.
What are the general factors influencing opening and cleaning performance? 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.
