Loom Timing of Weaving Machine (cotton fabric)

Loom Timing for Cotton Fabric

 

 

(𝟎°→𝟑𝟔𝟎°)1 Pick Insert

𝟎°−𝒃𝒆𝒂𝒕 𝒖𝒑 𝒑𝒐𝒊𝒏𝒕

𝑎𝑡 0°− 𝑇ℎ𝑒 𝑟𝑒𝑒𝑑 𝑖𝑠 𝑎𝑐𝑡𝑢𝑎𝑙 𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑓𝑟𝑜𝑛𝑡 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛 

𝑎𝑡180°−𝑇ℎ𝑒 𝑟𝑒𝑒𝑑 𝑖𝑠 𝑎𝑐𝑡𝑢𝑎𝑙 𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑏𝑎𝑐𝑘 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛

𝟑𝟎°−𝟏𝟓𝟎°(𝑫𝒘𝒆𝒍𝒍 𝒕𝒊𝒎𝒆) 

𝑎𝑡 30°−𝑇ℎ𝑒 𝑚𝑜𝑣𝑒𝑚𝑒𝑛𝑡 𝑜𝑓 ℎ𝑒𝑎𝑙𝑑 𝑠ℎ𝑎𝑓𝑡 𝑖𝑠 𝑠𝑡𝑎𝑟𝑡𝑒𝑑 𝑓𝑜𝑟 𝑠ℎ𝑒𝑑𝑑𝑖𝑛𝑔

𝑎𝑡 150°−𝑇ℎ𝑒 𝑚𝑜𝑣𝑒𝑚𝑒𝑛𝑡 𝑜𝑓 ℎ𝑒𝑎𝑙𝑑 𝑠ℎ𝑎𝑓𝑡 𝑖𝑠 𝑠𝑡𝑜𝑝𝑝𝑒𝑑 & 𝑡𝑎𝑘𝑒 𝑎 𝑝𝑎𝑢𝑠𝑒 𝑓𝑜𝑟 𝑖𝑛𝑠𝑒𝑟𝑡𝑖𝑜𝑛 𝑜𝑓 𝑤𝑒𝑓𝑡 

𝟏𝟏𝟎°−𝟐𝟑𝟎°(𝑷𝒊𝒄𝒌 𝒊𝒏𝒔𝒆𝒓𝒕𝒊𝒐𝒏)

𝑎𝑡 110°−𝑠ℎ𝑢𝑡𝑡𝑙𝑒 𝑒𝑛𝑡𝑟𝑒 𝑖𝑛𝑡𝑜 𝑠ℎ𝑒𝑑 𝑓𝑜𝑟 𝑤𝑒𝑓𝑡 𝑖𝑛𝑠𝑒𝑟𝑡𝑖𝑜𝑛 𝑝𝑢𝑟𝑝𝑜𝑠𝑒 

𝑎𝑡 230°−𝑠ℎ𝑢𝑡𝑡𝑙𝑒 𝑒𝑥𝑖𝑡 𝑓𝑟𝑜𝑚 𝑡ℎ𝑒 𝑠ℎ𝑒𝑑 𝑎𝑓𝑡𝑒𝑟 𝑝𝑖𝑐𝑘 𝑖𝑛𝑠𝑒𝑟𝑡𝑒𝑑 

270°−𝐵𝑜𝑡ℎ ℎ𝑒𝑎𝑙𝑑 𝑠ℎ𝑎𝑓𝑡 𝑎𝑟𝑒 𝑙𝑒𝑣𝑒𝑙𝑙𝑒𝑑 𝑎𝑛𝑑 𝑎𝑓𝑡𝑒𝑟 𝑡ℎ𝑎𝑛 𝑠𝑡𝑎𝑟𝑡𝑖𝑛𝑔 𝑚𝑜𝑣𝑒𝑚𝑒𝑛𝑡 𝑓𝑜𝑟 𝑠ℎ𝑒𝑑 𝑐𝑙𝑜𝑠𝑖𝑛𝑔 𝑝𝑢𝑟𝑝𝑜𝑠𝑒. 

The Timing of Shedding and Other Primary Motion

            The timing of the shedding motion varies considerably for different kind of cloth but it should always be such that the traverse of the shuttle through the shed should be a clear one. If the picking is too early the shuttle will have to force its way into a partly opened shed and yarn breakage may take place. For this reason the shed should be in a substantially open condition when the picking takes place.

            It is usual to time the picking to confirm to the shedding and nit vice versa. For cotton weaving looms, the shedding motion is generally set in such a way that the heald are leveled when the crank reaches at . This is shown in timing diagram fig.

            The tappet has dwell of one third pick. The shed is fully open from point  in crank cycle. The shuttle enter the shed at about bottom center. The normal setting is that reed is about 80mm away from the cloth fell.

·     Normal Shedding

If the heald shaft are at same level when the crank comes to the top center, that is 270 degree, then it is known as normal shedding.

·    Early Shedding

A shed is said to be early when the pick insertion is effected after the shed is completely open. If the heald shaft are at the same level when the crank come to 265 degree or 5 degrees before the top center, then it is known as early shedding.  

Advantages of early shedding

• Fabric cover is improved, because during beat-up, the warp yarn are evenly distributed.
• It assists in clearing the shed while weaving fibrous warp like woolen and worsted so entanglement are avoided.
• Heavy weft yarn can be easily inserted. So hard weave like corkscrew weave can be woven.

Disadvantage

• As the warp yarn are open widely during beat-up, strain on the warp yarn is high.
• Early shedding causes chaffing of warp yarn (yarn abrasion) and end breakage may occur.

·    Late Shedding

If the heald shaft are at the same level when the crank comes to 5 degree after top center, then the shedding known as late shedding.

Advantages of late shedding 
Late shedding allows the weft to get beaten up before the shed has been properly crossed. During beat-up, opening of the shed is minimal. So strain on the warp yarn is low

• Late shedding can be used for weak warp yarn.
• It allow greater time for shuttle passage so it is suitable for synthetic yarn.
• It is useful if pick of low strength is used.

Disadvantages

• It causes a very weak fell of the cloth because the weft may roll back.
• It causes less distribution of yarn. So it is not suitable for fibrous warp.
• As the warp yarn are not distributed evenly during beat-up, fabric cover low.    

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