A bobbin change occurs when yarn
on the bobbin is fully exhausted during winding. But if a bobbin is
changed with yarn still left on it, we call it ‘Rejected Bobbin'. The
quantity of yarn on the bobbin may vary from full bobbin to only few
layers of yarn.
2. Cop Content : Depending on the spindle lift and ring diameter, the cop content (in gms) should be checked
3. Diameter of the Cop : The ‘Actual cop diameter' must be checked against ‘Standard cop diameter'. The standard cop diameter depends on the ring diameter. Standard Cop Diameter = Ring Diameter - 3mm.
4. Back Winding : The number of back winding coils should be around 1.5 to 2.5 and the maximum length of back winding should not be more than 80cms
5. Under Winding : The number of under winding coils should be around 2 to 3 and the maximum length of back winding should not be more than 20cm. As the under winding and back winding increases, more time is wasted to open them up before feeding in the magazine and also hard waste is increased.
6. Top Clearance : The clearance from bobbin tip to yarn body of a full cop should be approx 10 mm. If the top clearance is too less, it may cause slough off at the start of the bobbin unwinding.
7. Bottom Clearance : The clearance from bobbin bottom to yarn body of should be approx. 10mm. If the bottom clearance is too less, it may cause bottom spoiled bobbin.
8. Yarn Length per Chase : The length of yarn per chase should be around 3.5 to 5.5 m. If the length is too long, it may lead to slough of during high speed unwinding.
9. Bobbin Hardness : The bobbin hardness should be around 50° to 55°. Soft bobbins results slough off. Besides the above mentioned points, the cops should be also checked for long tail end, deshaped bobbin, kirchi & lapetta, ring cut, overfilled and bottom spoiled bobbin to ensure high production efficiency in winding.
Due to the ever-increasing emphasis on better quality of yarn for the competitive market and process performance, the normal parameters of yarn tenacity, unevenness and imperfections are not adequate to completely define today's quality. Besides the above mentioned traditional parameters, so many factors influence the performance of the yarn in the subsequent process such as process parameters in ring spinning & cone winding, work procedures in ring spinning & cone winding and ambient conditions. So to attain the expected quality for any applications such as weaving or knitting, one should focus mainly on the fault free feed material preparation because it contributes more than any other factor. Best winding capabilities can be achieved through best bobbin quality.
- The Various Reasons of Bobbin Rejections are as follows:
1. Bobbin Quality
- Long Tail End
- Kirchi/Lapetta
- Deshaped Bobbin
- Overfilled Bobbin
- Bottom Spoiled Bobbin
- Ring Cut Bobbin
- Soft Bobbin
- Sick Bobbin
2. Bobbin Feeding in Magazine
- Presence of under-winding and back-winding while feeding the bobbins in the magazine leads to rejection
3. Top Bunch Transfer Failure
- Top bunch position is lower with respect to bobbin tip.
- Blowing device does not come down to concentrate blow at the bobbin tip.
- Very few numbers of coils at the bobbin tip.
- Removal of top bunch due to fault in cutter at the bobbin preparatory or any other reason. Very few numbers of coils at the top bunch.
4. Fault in Winding Unit, Splicing Failure
- 5. Yarn Quality
- High degree of objectionable fault
- Count variation
- High Hairiness Bobbin
Bobbin Quality Checking for Best Winding
- Whenever there is a count change in ring frame, the cop quality should be checked. Proper quality of cop ensures higher winding efficiency. The cop quality is checked as per the following parameters:
2. Cop Content : Depending on the spindle lift and ring diameter, the cop content (in gms) should be checked
3. Diameter of the Cop : The ‘Actual cop diameter' must be checked against ‘Standard cop diameter'. The standard cop diameter depends on the ring diameter. Standard Cop Diameter = Ring Diameter - 3mm.
4. Back Winding : The number of back winding coils should be around 1.5 to 2.5 and the maximum length of back winding should not be more than 80cms
5. Under Winding : The number of under winding coils should be around 2 to 3 and the maximum length of back winding should not be more than 20cm. As the under winding and back winding increases, more time is wasted to open them up before feeding in the magazine and also hard waste is increased.
6. Top Clearance : The clearance from bobbin tip to yarn body of a full cop should be approx 10 mm. If the top clearance is too less, it may cause slough off at the start of the bobbin unwinding.
7. Bottom Clearance : The clearance from bobbin bottom to yarn body of should be approx. 10mm. If the bottom clearance is too less, it may cause bottom spoiled bobbin.
8. Yarn Length per Chase : The length of yarn per chase should be around 3.5 to 5.5 m. If the length is too long, it may lead to slough of during high speed unwinding.
9. Bobbin Hardness : The bobbin hardness should be around 50° to 55°. Soft bobbins results slough off. Besides the above mentioned points, the cops should be also checked for long tail end, deshaped bobbin, kirchi & lapetta, ring cut, overfilled and bottom spoiled bobbin to ensure high production efficiency in winding.
Due to the ever-increasing emphasis on better quality of yarn for the competitive market and process performance, the normal parameters of yarn tenacity, unevenness and imperfections are not adequate to completely define today's quality. Besides the above mentioned traditional parameters, so many factors influence the performance of the yarn in the subsequent process such as process parameters in ring spinning & cone winding, work procedures in ring spinning & cone winding and ambient conditions. So to attain the expected quality for any applications such as weaving or knitting, one should focus mainly on the fault free feed material preparation because it contributes more than any other factor. Best winding capabilities can be achieved through best bobbin quality.