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How to solve the problem of uneven twist in two-for-one twisting machine

January 03,2024

Uneven twisting of the two-for-one Twisting machine will cause different fiber cohesion forces in each segment of the strand and inconsistent inclination of the surface fibers, which will affect the physical and mechanical properties and appearance characteristics of the strand such as strength, elasticity, elongation, gloss and wear resistance, and affect The style and quality of the fabric. For the problem of uneven twisting of the two-for-one twisting machine, please read below.

1. Cause

Uneven tension of dragon belt

Since the two-for-one twisting machine relies on the dragon belt friction to drive the spindle to twist the strands, the tension of the dragon belt directly affects the spindle speed of the entire machine. Because the dragon belt itself has a certain degree of elasticity, its tension is greatly affected by climate. In autumn and winter and when the machine is parked for a long time, the dragon belt shrinks greatly, causing the tension to increase and the spindle speed to increase. The opposite is true in spring and summer.

Tension wheel entry and exit position deviation

The entry and exit position of each tension wheel will directly affect the spindle speed of the two adjacent spindles. The equipment technical conditions have strict requirements on the entry and exit position of the tension wheel. Practice has found that the deviation of each adjustment unit will affect the proximity between the dragon belt and the spindle, causing the spindle speed deviation to increase.

Insufficient lubrication of the spindle

When the spindle rotates at high speed under the friction transmission of the dragon belt, it acts on two torques at the same time. One is the rotational torque caused by the friction of the dragon belt, and the other is the resistance torque caused by the friction between the spindle and the spindle foot bearing. The magnitude of these two moments directly affects the spindle speed. The function of the spindle oil is to form an oil film between the spindle tip and the spindle bladder to reduce the frictional resistance of the bearing to the spindle. Therefore, the lubrication of the spindle directly affects the spindle speed. Changes in spindle speed will inevitably cause uneven twist in the strands, and the uneven twist will increase with the increase in the difference rate of spindle speed changes.

Large and small chuck bearings are not flexible

The large and small chucks of the two-for-one twisting machine rely on the rotation of two small bearings to realize the rotation and winding of the bobbin. If the chuck bearings rotate inflexibly or the cradle's clamping force on the bobbin is insufficient, the normal yarn take-up speed may be affected. The speed of the yarn take-up speed will inevitably cause uneven twist of the strands, and the greater the difference in the yarn take-up speed, the more serious the uneven twist of the strands.

Improper operation of spindle flyer

If the production environment of the two-for-one twisting machine is not good, such as lint flying around or the machine is not clean properly, lint will be trapped between the spindle flyer and the spindle tube, causing frustration when the spindle flyer rotates, resulting in uneven twist.

Improper setting of tension spring parameters

In the early stages of production of the TDN-120 double-twisting machine used by our company, the twist unevenness rate of several double-twisting machines was always high, once exceeding 3.5%. Later research found that the main reason was that the tension spring in the spindle tensioner was set to a small value, resulting in high uneven twist.


FH230A high speed yarn twisting machine(big roll)

2. Solutions

Technological design

Adjustment of spinning tension. Different varieties require different spinning tensions. The basis for determining the tension is that it is more appropriate to wind the yarn around the spindle wheel for 1.5 to 2.0 turns, and the maximum should not exceed 2.5 turns.

Reasonably determine the spindle speed. Under normal circumstances, it should be determined based on the number of broken ends per thousand spindles. End-breaks of fine yarns and high-end varieties are controlled within 5 yarns per thousand spindles, and medium-thick yarns are controlled within 10 yarns. On the basis of meeting output and quality requirements, the spindle speed is maximized. After random sampling inspection, the twist unevenness can be controlled within 5%, and the unevenness rate of the entire vehicle can be controlled within 2.5%.

Choose the correct overfeeding rate. Changes in the overfeed rate affect the winding tension, thereby changing the winding density of the bobbin. Under the condition that the forming is satisfied, the overfeed rate is selected according to the fineness of the yarn. It is generally controlled at around 160% to reduce the increase in breakage caused by the winding tension and reduce the chance of uneven twisting.

Equipment status maintenance

Ensure the tension of the dragon belt. Replace the dragon belt that is inflexible or jumpy in operation, and adjust its tension to ensure that the tension of the dragon belt meets the specified standards and that the tension between the machine and the spindle is consistent. When calibrating with special rules, ensure that the distance between the tangential belt and the spindle wheel is about 2 mm or more, and the distance between the tangential belt and the tension roller is about 2 mm or more.

Adjust the pressure the dragon brings to the spindle wheel. High tension of the dragon belt can increase the contact surface with the spindle wheel and reduce uneven twisting, but at the same time it will increase the loss of the spindle belt. Therefore, on the premise of satisfying the quality, the pressure on the spindle wheel of the tungsten belt should be kept small to extend the service life of the tangential belt.

Check the tensioning device. For the peak twist of a single spindle on the machine, it is necessary to promptly check the wear and tear of the tension head, tension rod and tension head seat in the tension device. Tension heads that are inflexible and retractable must be replaced and repaired in time; damaged tension rods, tension head seats and other components must be replaced to ensure that the tension difference between each spindle is minimal, and the position of the spindle must be adjusted in time to make it contact with the dragon belt. The surface is in a more reasonable position.

Check the spindle bearings. Check and refuel the spindle transmission bearings of the two-for-one twisting machine, and replace the inoperable or damaged spindle bearings when the machine is stopped to ensure that the difference in spindle speed between spindles is controlled within the internal control indicators and reduce the chance of weak twist. Strengthen the inspection of spindle operation, eliminate deteriorated spindles, reduce the spindle speed difference and yarn tension difference of the entire machine, and ensure the consistency of the entire machine.


Twisting and Doubling machine

3. Operation management

The doubling process reflects the setting of fixed length. According to user requirements, the overall yarn loading and overall doffing modes are adopted to reduce the number of joints in the double twisting process.

Strictly implement the operation method. Improper control of the brake release time will also cause local unevenness, and avoid untwisted yarn and weakly twisted yarn caused during the splicing process. When the operator discovers a broken end during the tour, he steps on the brake disc joint. When the joint is completed, he twists the joint with his hands and releases the brake disc for 5 s to 10 s. When the yarn section in the untwisted area is fully twisted Then release your hand and wind it onto the bobbin. The time from releasing the brake disc to winding the knotted yarn onto the bobbin is selected according to the twist, 7 s to 10 s for a large twist, and 5 s to 7 s for a small twist.

The operator should do a good job in cleaning after doffing, and the residual yarn on the spindle wheel should be disposed of in time to eliminate the reduction in spindle speed caused by yarn wrapping and reduce the chance of weak twist.

Stopping and restarting the equipment after a power outage has a great impact on the twist. During production, it was found that the twist unevenness of the machine before the power outage was 2.9%, and in the test after the power outage was restarted, it was 4.3%. Therefore, the time and frequency of stopping the twisting machine should be minimized. When you need to park during holidays, you must ask for the empty truck to be delivered, then drive again and try driving again.