Jacquard Machine Components Explained
Understanding the terminology is key to solving this problem:
- Ends: Refers to the individual warp threads in the fabric.
- Hooks: The components directly responsible for raising or lowering the warp threads according to the design.
- Needles: Used in the selection mechanism (especially in older mechanical jacquards) to determine which hooks operate for each weft shot.
- Double-lift: A type of jacquard mechanism where two sets of harness cords (lifts) are used, enabling more complex shedding patterns.
- Single-cylinder: Refers to the type of card cylinder or electronic selection mechanism used.
Calculating Hooks and Needles
For a 500-end double-lift, single-cylinder jacquard machine:
- Number of Hooks: In a double-lift system, each 'end' requires two hooks to manage the two lifts. Therefore, the total number of hooks is twice the number of ends.
Number of Hooks = Number of Ends $\times$ 2
Number of Hooks = 500 $\times$ 2 = 1000 hooks
- Number of Needles: In a typical single-cylinder jacquard mechanism, the number of needles is usually half the number of hooks, as each needle often selects two hooks (one for each lift).
Number of Needles = $\frac{\text{Number of Hooks}}{2}$
Number of Needles = $\frac{1000}{2}$ = 500 needles
Thus, the machine has 1000 hooks and 500 needles.
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.
