Sley eccentricity? On a Double width loom sley eccentricity ratio is keep higher or lower ?why

Sley Eccentricity refers to the lateral displacement of the sley (the part of a loom that holds the reed and beats the weft into place) during weaving. It is an important factor in loom dynamics that affects fabric quality and loom efficiency.


Causes of Sley Eccentricity:


1. Mechanical Defects – Wear and tear in loom components like crankshafts, bearings, or reed holders.



2. Improper Settings – Incorrect alignment of the sley or unbalanced beat-up motion.



3. Uneven Force Distribution – Irregular movement in the crankshaft or the drive mechanism.



4. High Loom Speed – Excessive loom speed can cause vibrations, leading to eccentric sley movement.




Effects of Sley Eccentricity:


Uneven beat-up, leading to fabric defects like reed marks or irregular picks per inch (PPI).


Increased loom vibrations, causing mechanical wear and reduced loom efficiency.


Potential breakage of warp or weft yarns, especially in high-speed looms.



Ways to Reduce Sley Eccentricity:


Regular maintenance of loom parts (crankshaft, bearings, reed holder, etc.).


Ensuring proper balance of sley motion during loom setup.


Using dampers or shock absorbers to minimize vibrations.


Avoiding excessive loom speeds that might amplify eccentric motion.



pecific aspect of sley eccentricity?



 In a plain power loom, when using a double-width reed, the sley eccentricity ratio should be kept low.


Why Should the Sley Eccentricity Ratio Be Low?


1. Increased Inertia of the Sley


A double-width reed increases the weight and inertia of the sley.


If the eccentricity ratio is too high, the sley motion will become more abrupt, causing excessive vibrations and uneven beat-up.


A low eccentricity ratio ensures smoother acceleration and deceleration of the sley, preventing mechanical stress.


2. Avoiding Excessive Loom Vibrations


Higher eccentricity means a more aggressive beat-up, which can create excessive loom vibrations, affecting fabric quality and machine longevity.


A lower ratio provides a more controlled beat-up, reducing stress on the crankshaft and bearings.


3. Ensuring Uniform Beat-up Across the Double Width


With a wider fabric width, uniform force distribution is critical.


A high eccentricity ratio can cause non-uniform beat-up, leading to reed marks or variations in pick density (PPI).


A lower ratio helps maintain consistent impact across the full width of the fabric.


4. Minimizing Warp and Weft Breakages


If the eccentricity is too high, the aggressive beat-up can increase warp and weft breakages, especially in fine or delicate yarns.


A lower eccentricity ratio ensures a gentler and controlled beat-up, reducing breakages.


Conclusion:


For a double-width reed on a plain power loom, keeping the sley eccentricity ratio low is ideal. This ensures smooth beat-up, reduced vibrations, even fabric formation, and longer loom life.


Q. For double width loom Sley eccentricity ratio is how to adjust.


To adjust the sley eccentricity ratio in a plain power loom, you need to modify the sley drive mechanism, particularly the crankshaft, sley cam, and pitman rod length.



How to Adjust Sley Eccentricity Ratio?


1. Adjusting Crankshaft or Crank Radius


Increase Crank Radius → Higher Eccentricity (More aggressive beat-up)


Decrease Crank RadiusLower Eccentricity (Smoother beat-up)


In a double-width loom, keeping a moderate or lower eccentricity is preferred to prevent excessive vibrations.



2. Changing the Pitman Rod Length


Shorter Pitman Rod → Increases Eccentricity Ratio


Longer Pitman Rod → Decreases Eccentricity Ratio


A longer pitman rod helps in reducing aggressive sley motion, making the beat-up more uniform across a wider reed.



3. Modifying the Sley Cam Profile (For Cam-Driven Looms)


Steeper Cam Profile → Higher Eccentricity (Faster acceleration and impact)


Gentler Cam Profile → Lower Eccentricity (Smooth and controlled beat-up)


For a double-width loom, using a more gradual cam profile is recommended to distribute force evenly.



4. Adjusting Sley Weight and Counterbalance


Increase Weight on Sley → Reduces Eccentricity (Smooth motion)


Decrease Weight on Sley → Increases Eccentricity (More aggressive motion)


Adding counterweights on the sley can stabilize motion and prevent excessive vibrations.



5. Regulating Loom Speed


Higher Loom Speed → Increases Eccentricity Effect (More impact force)


Lower Loom Speed → Reduces Eccentricity Effect (Smoother beat-up)


Operating at optimum speed prevents sudden impacts that may cause fabric defects.


Recommended Settings for a Double-Width Loom


✅ Lower Sley Eccentricity Ratio is preferable.

✅ Longer Pitman Rods for smoother motion.

✅ Gentle Sley Cam Profile for uniform force.

✅ Counterweights or Balancing Mechanism to prevent excessive vibrations.



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