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بافندگی اتری پودی Weaving

312Textile Technology

Reference:S. Adanur, Handbook of weaving. CRC Press, Boca Raton, 2001.

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BASIC WEAVING MOTIONS• warp let-off• shedding• filling insertion• beat-up• fabric take-up

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Warp Let-offThe let-off mechanism applies tension to the warp yarns by controlling the rate of flow of warp yarns.

Let-off mechanisms can be classified as:negative and positive.

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Warp Shedding

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Filling Insertion

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Yarn feeders or accumulators

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Beat-Up

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Beating mechanism of a projectile machine.

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Early shed timing

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Take-Up

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Temple function in weaving

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Selvages

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Shedding Systems

There are four systems used to provide manipulation to the warp yarns:

• crank shedding• cam (tappet) shedding• dobby shedding• jacquard shedding

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Characteristics of shedding mechanisms

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CAM SHEDDING

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Schematic principle of negative cam shedding

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Positive cam system with two negative cams

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Weaving possibilities with cams

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DOBBY SHEDDING

Dobby mechanisms are more complicated than cam systems. They usually have higher initial and maintenance costs. They are normally built to control up to 30 harnesses. Picks per repeat are virtually unlimited in dobby shedding.

Basically there are two separate functions in a dobby mechanism: 1) power transmission, 2) connection and disconnection of the harnesses to and from the power source at the proper time.

Dobby mechanisms are classified as negative, positive and rotary dobbies, they can be mechanical or electronic.

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Schematic of a negative dobby mechanism

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Motor driven card cutting and copying machine

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Functional principle of double lift open shed positive dobby

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Functional principle of rotary dobby

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JACQUARD SHEDDING

Jacquard shedding offers unlimited patterning possibilities. Jacquard machines can be mechanical or electronic with single or double lift mechanisms; the new machines are all double lift.

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Schematic principle of single lift,single cylinder jacquard machine.

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Functional principle of electronically controlled, double lift jacquard machine

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