29 Questions
What is the primary function of the hook in the jacquard shedding mechanism?
To lift the harness
What is the purpose of the spring on the left side of each needle?
To push the needles against the pattern card
In a single cylinder jacquard, how many operating cylinders are available?
One
What is the purpose of the dead weights attached to the harness in the jacquard shedding mechanism?
To lower the harness
How many needles are there in a single lift jacquard for each end in the repeat?
One
What is the direction of the curved or kinked needle around the vertical hook?
Vertical
What is the function of the double roller or pulley system?
To move the harness up and down
What is the purpose of the retaining hooks (d) and (e)?
To catch the hooks depending on the weave design
What happens when the right-hand solenoid (H) is energized?
The retaining hook (d) does not catch the hook (b)
What is the position of the harness at point (1)?
Bottom position
What happens to the hook (c) and its knife (g) at point (3)?
They reach the top position
What happens to the harness at point (3)?
It remains in the bottom position
What is the formula to calculate the number of repeats handled by a jacquard?
Jacquard capacity/(Ends per repeat)
What is the utilization of jacquard capacity in terms of ends per repeat?
Number of repeats handled by jacquard x Ends per repeat
What is the purpose of casting out in jacquard shedding mechanisms?
To achieve a warp thread density less than harness density
What is the maximum ends per inch achievable on a loom with a jacquard shedding mechanism?
Harness density
What is the formula to calculate the width of a repeat?
Ends per repeat/Ends per inch
What is the effective jacquard capacity after casting out?
Jacquard capacity - Number of ends cast out
What is the total number of ends in a fabric with a width of 60 inches and 60 ends per inch?
3600
How is the number of repeats handled by a jacquard calculated?
Jacquard capacity / Ends per repeat
What is the utilized jacquard capacity in a fabric with 3 repeats handled by the jacquard and 200 ends per repeat?
600
How are harnesses per hook calculated in a jacquard loom?
Total ends / Utilized jacquard capacity
In the example given, what is the number of harnesses per hook?
6
What is the rate of the cylinder's rotation in a DLSC jacquard loom that produces 300 picks per minute?
300 times per minute
What is the advantage of DLSC jacquard over SLSC jacquard?
It produces a semi-open shed
What happens when an end has to remain in the bottom position for two consecutive picks in a DLSC jacquard?
It remains at the bottom without any intermediate movement
In a DLDC jacquard, how many hooks are controlled by each harness or end?
Two hooks
What is the purpose of the two cylinders in a DLDC jacquard?
One cylinder carries the pattern card for odd numbered picks and the other for even numbered picks
How many hooks are there in a 400 capacity DLDC machine?
800 hooks
Study Notes
Jacquard Shedding Mechanism
- Single Lift Single Cylinder (SLSC) Jacquards have one operating cylinder, whereas Double Cylinder Jacquards have two cylinders, one for odd picks and one for even picks.
SLSC Jacquard Mechanism
- The mechanism completes its cycle once in every pick, being single lift and negative in action.
- Lifting of harness is achieved through jacquard hooks, while lowering is done by dead weights attached to the harness.
- Each hook is connected to a harness after passing through a grate.
- A double roller or pulley system is used to move the harness up and down.
Operating Cycle
- The initial position has hook (b) and its knife (f) in the uppermost position, while hook (c) and its knife (g) are in the lowermost position.
- The harness is at the bottom position at the initial stage.
- To remain lowered in the next pick, the right-hand solenoid is energized, and the retaining hook (d) does not catch hook (b).
- The knife (g) will then go up, taking hook (c) up, and the knife (f) will go down, taking hook (b) down.
Jacquard Capacity and Utilization
- Jacquard capacity = 10 x 40 = 400
- Total ends = 60 x 50 = 3000
- Number of repeats handled by jacquard = Jacquard capacity / (Ends per repeat) = 400 / 150 = 2.66 or 2
- Utilized jacquard capacity = Number of repeats handled by jacquard x Ends per repeat = 2 x 150 = 300
- Harnesses per hook = Total ends / Utilized jacquard capacity = 3000 / 300 = 10
- Width of repeat = (Ends per repeat) / (Ends per inch) = 150 / 60 = 2.5"
- Height of repeat = (Picks per repeat) / (Picks per inch) = 300 / 60 = 5"
Casting Out
- Warp thread density can be controlled by changing the reed count and reed plan in shedding mechanisms other than jacquard.
- However, every jacquard has a specific harness density, and the maximum ends per inch achievable on the loom is equal to the harness density.
- Casting out is used to achieve warp thread density less than harness density.
DLSC and DLDC Jacquards
- In Double Lift, Single Cylinder (DLSC) jacquard, the cylinder turns once, but the knives reciprocate (rise and fall) half the time.
- This is an advantage of DLSC jacquard over SLSC jacquard.
- DLSC jacquard produces a semi-open shed.
- Double Lift, Double Cylinder (DLDC) jacquard has two cylinders, one for odd picks and one for even picks, each carrying a pattern card.
- A 400 capacity machine will have 800 hooks and 800 needles.
This quiz tests your understanding of jacquard loom calculations, including total ends, repeats, and harnesses per hook. It's an essential concept in textile engineering and fabric weaving.
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