Weaving Shedding Control Mechanisms
Shedding is the process in weaving where the warp yarns are divided into two layers to form a gap, known as the shed, allowing the shuttle carrying the weft yarn to pass through.
Mechanism Analysis for Individual Warp Thread Control
Different shedding mechanisms provide varying degrees of control over the warp threads:
- Crank Shedding: This mechanism controls groups of warp threads simultaneously, typically used for creating simple patterns.
- Tappet Shedding: Similar to crank shedding, tappet mechanisms operate heald frames that lift groups of warp threads, suitable for basic weaves like plain and twill.
- Dobby Shedding: Offers more sophisticated pattern control than crank or tappet systems. It can manipulate combinations of warp threads to create more complex designs but generally does not control each thread independently.
- Jacquard Shedding: This advanced mechanism is specifically designed to control each individual warp thread independently. By using a system of hooks and lashes, controlled by punched cards or digital data, the Jacquard loom can raise or lower any specific warp thread, enabling the creation of intricate and complex patterns.
Therefore, the Jacquard shedding mechanism is the one that provides control of individual warp threads.
Important Questions from FABR Loom Mechanisms Shedding
- Group I lists the components of the weaving machine and Group II lists their functions. Match the component with its function.
Group I Group II P Conjugate/matched cams 1 Driving the cloth roller with slip
driveQ Worm and worm wheel 2 Continuous positive take up
motionR Friction clutch device 3 Motion of sley in rapier loom S Lease rod 4 Separation of the warp sheet
forming the shed Amongst the following, the correct condition(s) that will reduce bumping during weaving is/are
- Group I lists weaving machine related parameters and Group II contains the shortcomings of these parameters. Match the machine related parameter with its shortcoming.
Group I Group II P. Variable heald staggering 1. Not favourable for heavy fabric Q. High eccentricity ratio 2. Reduction in shed height R. Fixed heald staggering 3. Reduction of sley dwell S. Late shedding 4. Higher vibration in weaving machine Group I gives a list of loom motions and Group II contains loom systems. Match the motion from Group I with the corresponding system from Group II.
Group I Group II P. Shedding 1. Matched cam Q. Picking 2. Seven wheel R. Beat-up 3. Rapier S. Take-up 4.Jacquard Determine the correctness or otherwise of the following Assertion [a] and Reason [r]
Assertion: In shuttle loom, late shedding is preferred for filament weaving.
Reason: In late shedding, the timing of shed dwell matches with the timing of shuttle travel through the shed, and therefore, it minimises the rubbing of warp yarns.
