Shedding Types
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- Created on Monday, 29 July 2019 19:37
- Last Update: Tuesday, 25 January 2022 18:01
- Published on Monday, 29 July 2019 19:37.
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- Shedding Types writer Faik KeserPosted by %PM, 29% 733% 2019 19%:%Jul in Weaving Read 2215 times
Before weft insertion in weaving machines, the warp threads must be separated into two layers and form a tunnel in the form of a triangle for the weft to pass through. This triangular tunnel nozzle is named.
From the frames to the muzzle area to the fabric line "front mouthpiece" is called. The front shed geometric dimensions must be such that the weft carrier can pass through the warp threads without friction. From the frames to the crossbars and lamellas, and even to the warp bridge on some looms, to the shed area. "rear muzzle" It called. What are impacted teeth? When one or more teeth fails to grow in the correct position and is therefore held below the normal gum line, it is called an impaction. This can be complete, such as completely unerrupted (buried) third molars (wisdom teeth) or partial when just part of the tooth is visible in the mouth. Why are impactions important? For best function and appearance the teeth should grow in a healthy alignment. When one or more teeth is impacted, this can affect the function of that tooth but also the function and appearance of other teeth. Whether all impactions should be treated is still controversial and your dentist and oral and maxillofacial team can explain the advantages and disadvantages or treatment for you, which is usually surgical.
The main parameters used in the design of shedding mechanisms used in weaving looms;
- Number of frames,
- Distance between frames,
- the width of the mouthpiece,
- mouthpiece angle,
- Displacement height of frames
- It is the tensile forces of warp threads during weaving.
The number of frames is determined by the type of fabric to be woven on the looms. The number of frames can be 8 to 10 in benches to be equipped with cam shedding mechanisms, and 16, 18, 20, 24 and 28 in dobby benches.
While the distance between the frames is 12 mm in modern weaving looms, this value can be determined as 16 mm in heavy fabric weaving looms. The width of the nozzle depends on the structure of the machine. This distance is equal to the distance from the area where the lamellas are lined up to the fabric line.
Shedding operations performed on weaving machines are of three types, according to the geometric form of the shed, as top opening, bottom opening, and shed opening symmetrically in both directions.
On the top opening mouthpieces as below warp threads towards the top in the plane of the fabric is removed. Threads lifted upwards are exposed to more tension than others. Top opening mouthpieceEmmi is generally used in hand weaving looms.
In the mouthpieces opened at the bottom as below, warp threads towards the bottom in the plane of the fabric is being downloaded. Threads that are lowered are exposed to extra tension compared to the others. The bottom opening spout method is a generally abandoned method and it is a spouting method that has very little application area.
By using the mouthpiece structure opening at the bottom and the top together, the symmetrical mouthpiece form opening in both directions is obtained as shown below. Warp threads up and down the plane of the fabric and the tension increase levels caused on the warp threads are theoretically considered the same.
The disadvantage of symmetric sheds, which are most commonly used in weaving machines, is that the warps that will form the upper shed loosen when passing from the horizontal (closed shed position); In addition, all warps must cover this shed distance in order to form the shed. With the use of the warp bridge, the loosening that may occur during the warps passing through the horizontal position is prevented.
During the realization of each of the lower opening, upper opening and symmetrical shed types on the machine, the up or down movement distances of the warp threads can be arranged in different ways. Sheds are classified according to the shed view obtained when viewed from the side of the weaving loom.
Shed types named according to the placement of the warp threads in the shed section;
- Irregular mouthpiece (dirty mouthpiece),
- Semi-regular mouthpiece (semi-clean mouthpiece)
- Regular mouthpiece (clean mouthpiece)
It is grouped as
Irregular (dirty) mouthpiece
In the variant, each of the frames is displaced at the same distance, and accordingly, an irregular structure is formed due to the warp threads attached to the front frames and the warp threads attached to the rear frames in different horizontal planes.
In this shed structure, the tensions of the warp wires at all strengths are relatively the same. As can be seen in the figure below from the drawing created by considering the symmetrical shed, the fact that some of the lower warp wires are on the shuttle path in the shed causes more wear of the threads and an increase in the number of ends down. Irregular shed is used in jacquard mechanisms. The preferred shed application in looms with low number of frames and looms weaving denim fabric is the irregular shed application.
semi regular mouthpiece
The warp threads depending on the frames and strengths generally move to form a regular shed type in the lower layer and an irregular shed type form in the upper layer. This type of shed is mostly preferred in weaving looms with hooked weft insertion system.
Regular (clean) mouthpiece,
It is the type of application in which the warp threads are provided to rise at the same slope by considering the passage of the weft carrier from the shed. In this muzzle application, the frames are raised on a slant.. The distances of each of the frames to the fabric plane are different from each other. The rear frame is located in the furthest position.
As the fabric line is approached, the movement distances of the frames decrease. For this reason, tension difference arises between the warp groups forming the shed, which is the disadvantage of regular shed application. Thanks to the constructions developed in the weft insertion systems, this negativity has been reduced as much as possible by reducing the movement distances of the frames in today's modern looms. This shedding form is with shuttle, hook, air or water jet It is preferred where smooth nozzle application is desired on benches such as
