Impacts of Yarn Hairiness and Voluminous on Weft Yarn Speed and Twist Loss in Air-Jet Weaving

ABSTRACT The velocity and twist loss of weft yarns in air-jet weft insertion is affected by the type of yarn used as a weft. In this work, ring- and rotor-spun yarns of 16Ne were used as weft yarns and velocity and twist loss differences between these yarns were investigated. The constant air pressures and loom speed were used to measure the velocity difference between the two yarns. For twist loss, the speed of the loom and relay nozzle pressures were varied in the range of (300–510 rpm loom speed, 2–4 bar left side relay nozzle air pressure (LSRNP) and 3–6.5 bar right-side relay nozzle air pressure (RSRNP). A full factorial design was used to design and analyze the results of the experiment for twist loss. It is observed that the average velocity (m/s) and twist loss (TPM) of the ring-spun yarns are higher than those of the rotor-spun yarns. Additionally, it has been found that for both types of yarn, the twist loss increases when the loom’s speed falls and the air pressure in the relay nozzles rises. However, the highest twist loss difference between the two yarns is observed at the highest speed of the loom.


Introduction
Air-jet weaving is one of the most widely used looms in the world due to its advancements for the production of woven fabric (Zegan and Ayele 2022;Umair et al. 2016).In this loom, the filling yarn is inserted by compressed air and it is one of the best-known and successful high-yield weaving machines (Adanur, 2020).High filling insertion rates, low noise and vibration levels, reliability and low maintenance costs, low spare parts requirements, low space requirements, relatively simple operation, reduced hazards due to few moving components, and a low initial outlay are its outstanding qualities (Adanur 2020).This feature makes it the most selective loom among others for the production of light to medium weight fabric, and its application in the textile industry is widespread (Szabó, Patkó, and Oroszlány 2010).On the other side, it has some limitations; for instance, loss of weft yarn twist during CONTACT Million Ayele milliti2000@gmail.comEthiopian Institute of Textile and Fashion Technology, Bahir Dar University, P.O.Box 1037, Bahir Dar, Ethiopia insertion and its high power consumption are the most determinant drawbacks of this loom (Göktepe and Textile 2008;Ketema, Ayele, and Million 2023).
The weft yarn is inserted by dragging air force, which applies high-pressure force to the surface of the inserted yarn for the whole insertion period and this causes the free end of the yarn to untwist (Umair et al., 2017b).As a result, twist loss is one of the biggest matters in this regard, and different factors are responsible for this.Weaving conditions and yarn characteristics are among the factors that affect insertion time and loss of twist in air-jet weaving (Erdumlu et al. 2009;Umair et al., 2017b).
Numerous scholars have proved that loom speed and applied air pressure significantly affect insertion time and twist loss.As loom speed and air pressure rise, insertion rate also increases because these two variables have a direct relationship with insertion rate (Haq and Mobarak 2017;Turel, Bakhtiyarov, and Adanur 2004).Air pressure, on the other hand, promotes twist loss, so every increase in air pressure has a significant impact on the rate of twist loss.The compressed air applies highpressure force to the yarn that enables twist loss of the weft yarn (Ketema, Ayele, and Million 2023;Yao-Qi 1984).But when the loom speed is high, there is less twist loss because the waiting time of the weft yarn in the shed that exposed for air pressure is short (Lu and Lu 2017).The second deciding element is the weft yarn characteristics.Yarn count, diameter, hairiness, and irregularity have a significant influence on the weft yarn arrival rate and twist loss (Adanur and Tacibaht 2004).
The structure of the yarn produced by the ring and rotor spinning mechanisms varies, particularly in terms of hairiness, strength, evenness, and diameter.This is a result of the different spinning methods by which the yarns are made, particularly in terms of how the fibers are arranged in the yarn and the different methods of twist insertion.For instance, in the ring spinning technique, the fibers are typically grabbed at the front roller's nip and twisted into a helix structure (approximately circular).While the core is compressed, the outermost fibers are strained into tension.This makes the ring-spun yarn stronger and smaller in diameter than OE-spun yarns (Lord 1971).While friction in the balloon controls ring and the uncontrolled passage of edge fibers during roller drafting are to blame for the increased hairiness of ring-spun yarns.Rotor spinning uses wrapping fibers that are coiled crosswise around the yarn to "bind in" loose fiber ends (Ahmed et al. 2015); however, the surface of the yarn is smothered.The yarn properties like hairiness, diameter, and evenness of the yarns have a significant effect on weft yarn velocity and twist loss in air-jet weaving.
Scholars have been arguing on the effects of yarn hairiness and voluminous on weft insertion speed and twist loss in air jet weaving process.They divide into two groups; some researcher (Mohamed, Lord, and Saleh 1975;Parkeh et al. 2011;Szabó and Szabó 2012;Vangheluwe 1999) stated that a yarn with a larger diameter will have a higher rate of insertion and twist loss than a yarn with a greater degree of hairiness this is due to the fact that as the diameter increases, the contact area between the yarn surface and air drag also increases, creating a higher frictional force between them, which results in a high insertion rate and loss of twist.The opposing scholars (Umair et al. 2016;Adanur and Turel 2004) disagree with this premise, claiming that a yarn with more hairiness will insert more quickly and loss its twist more quickly than a yarn with higher diameter.This is due to the fact that the dragging force beats the protruding fiber, carrying the weft yarn through the opening shed and onto the receiving side.The yarn to air friction is high due to hairiness of the yarn, and this results in high control of the weft yarn during insertion.The yarn, however, becomes untwisted when the fiber is beaten by the air.Consequently, this study's goal is to refute these extremely contradictory ideas.In this work, the same count of ring-and rotor-spun yarns is used and their hairiness and voluminous levels have been measured.
Twist loss of these two types of yarn at different loom speeds and relay nozzle air pressure was measured.Comparison analysis of the twist loss between ring-and rotor-spun yarn was also done.In addition, the weft yarn speed of both yarn at constant speed and air pressure has also been measured and compared.
To assess whether or not the factors have a substantial impact on the response variable, an ANOVA is used.The first hypothesis states that when the yarn type (rotor vs. ring yarns) is altered, there is no variation in the mean values of the weft yarn twist level.The alternative theory states that when there is a change in yarn type (rotor vs. ring yarns), there is a mean difference between the values of the weft yarn twist level.
A 95% confidence interval was used to evaluate whether any of the variations from the mean values are statistically significant.A 5% chance of presuming a difference when there isn't one arises when the significance level is set at 0.05.We reject the null hypothesis and come to the conclusion that not all population means are equal if the p-value is less than 0.05 (p .05).The difference between the means is not statistically significant, though, if p > .05.

Materials
For this study, 100% cotton ring-and rotor-spun yarn with same count of 16Ne was taken, and their properties are mentioned in Table 1.The rotor-spun yarn was produced on rotor spinning machine with model of Rieter G-923, and ring-spun yarn was produced on ring frame machine with model Rieter G-35.

Sample preparation
To produce the required samples, an air-jet loom with a model OMNI PLUS-800 was used.All yarn and fabric were produced in Bahir Dar Textile Share Company.The detailed fabric properties are illustrated in Table 2.

Experimental design
Types of yarn, supply air pressure and loom speed were taken as independent variables (factors), whereas twist loss and weft yarn velocities were taken as dependent variables (response).To design the experiment and analyze the results of the experiment Design-Expert 13 software with full factorial design was employed.The coded and actual values of the factors are depicted in Table 3.For the purpose of this "−1" shows the low level and "+1" shows high levels of the factors.However, for yarn type, "−1" represents ring-spun yarn and '+1' represents rotor-spun yarns.The upper and lower levels of each factor have been selected based on the current working condition of the machine, the manual of the machine, quality of input material and different authors' recommendation (Ketema, Ayele, and Million 2023;Zegan and Ayele 2022).The experimental design with actual factor levels is revealed in Table 4. where the hairiness index value of H is the length, in cm, of every fiber end that protrudes from a yarn segment with a length of one cm.

Yarn arrival rate measurement
The arrival rate of ring-and rotor-spun yarn in an air-jet loom has been measured at constant supply air pressure and loom speed.By measuring the length of yarn inserted in a second, the speeds of both yarns were assessed.Four trials were conducted for each yarn, and the average outcome was taken for analysis.

Characterization of yarns
Yarn diameter and hairiness.The diameter and hairiness of the yarn are measured according to the USTER® TESTER 5 modular laboratory system.The yarn moves through an optical field consisting of two parallel light beams that illuminate the yarn from two sides.It is equipped with an optical sensor that can measure the diameter, diameter variation, roundness, and hairiness of yarns (Kretzschmar and Furter 2009).And for the minimization of errors, five replicates were taken.
Twist loss.The number of turns in a particular length of yarn is known as a twist.The traditional untwisting method, which entails unwinding the yarn until it has no twist and counting the number of turns, can be used to measure the average twist of yarns.Unraveling the weft yarn from the body of the fabric in accordance with ISO 2016:2015 with a gauge length of 500 mm and using a quadrant-type tester with untwist-retwist procedures allowed for the measurement of the number of twists lost during the weaving process.The 500 mm length of yarn was cut 150 mm away from the selvage on both sides of the fabric, as advised by.Each experiment contains ten replications, and an average value has been taken for analysis.

Effects of yarn hairiness and diameter in weft yarn arrival rate
The yarn's hairiness, which is a numerical way of representing the surface roughness of a cottonspun yarn, is the property of the yarn that is believed to have the greatest impact on weft yarn velocity.It is measured by how many broken fibers stick out from the surface of the yarn, giving it a fuzzy appearance (Patil et al. 2016).In the other principle, weft yarn velocity is a function of its diameter, meaning that the yarn with a higher diameter, like rotor yarn, has a higher velocity than that of ring yarn of the same count.As illustrated in Table 1, the diameter of rotor yarn is 0.388 mm and that of ring yarn is 0.35 mm, whereas the hairiness of rotor yarn is 6.73 and that of ring yarn is 8.57.In this research, the velocity of these two yarns of the same count is analyzed.There is a noticeable velocity variation between these two types of yarn, as can be seen from Figure 1.The length of ring-spun and rotor-spun weft yarn inserted per second was measured.All conditions, like the speed of the loom and air pressure were kept constant for both yarns.
In all experiments, the speed of ring-spun yarn was greater than that of rotor-spun yarn.We can also look at their average speed, and it shows that ring-spun yarn has a speed of 11.58 m/s, which is higher than the speed of the rotor, which is 11.48 m/s.The structural characteristics of the yarns account for this distinction.It can be stated with certainty that the impact of yarn hairiness on the insertion speed is bigger than the impact of rotor-spun yarn with a slightly larger diameter.This is caused by the protruding fiber of ring-spun yarn which increases the surface friction between the weft yarn and the dragging air, and this phenomenon significantly affects the insertion rate.While the diameter of the rotor-yarn is sufficiently big to have strong contact between its surface and the dragging air, as its surface is more uniform and smoother than that of ring-yarns, the friction between the yarn and the dragging air is less than that of ring-yarns.And this is also in agreement with various researchers like Umair et al. (2017a;Adanur and Turel 2004).

Yarn twist loss
Weft yarn woven in air-jet loom loses its twist for a variety of reasons, for instance, yarn diameter, smoothness, hairiness, loom speed, and air pressure (Lu and Lu 2017;Yao-Qi 1984).The structure of the yarn produced by the ring and rotor spinning mechanisms varies, particularly in terms of hairiness, evenness, diameter, and strength.Yarn, diameter hairiness, and irregularity have a significant influence on the weft yarn twist loss (Adanur and Tacibaht 2004).This section of this research also reveals the variation in twist loss between ring-spun and rotor-spun yarn of the same count.Based on the planned combination in the experimental design, yarn type, loom speed, and air pressure were taken as factors, and 60 fabric samples were produced on an air-jet weaving machine.
The twist loss of both ring-and rotor-spun yarn in an air-jet loom was determined.The measured values of each yarn type were then assessed using design expert software (full factorial design).Table 5 illustrates the result of ring-and rotor-spun yarn twist loss at various combinations of factor levels.

Effects of yarn type on weft yarn twist loss
The yarn feature is one of the key elements that influence the degree of twist loss in air-jet weaving weft insertion.The level of twist loss in woven fabric after air-jet weaving is different for every spinning method (Vangheluwe 1999;Yao-Qi 1984).The weft yarn twist loss of ring and rotor-spun yarns woven under identical weaving conditions on an air-jet loom is shown in Figure 2.For instance, run 1 indicates that ring-and rotor-spun yarn twist losses was woven at 510 rpm speed of loom, 2 bar left-side relay nozzle air pressure and and 3 bar right-side relay nozzle air pressure.Run 2 shows ring and rotor yarn twist losses, which were produced at a 510 rpm loom speed with a left-side relay nozzle of 4 bar and a right-side relay nozzle of 6 bar.These circumstances are maintained up to run eight, as shown in Figure 2. As we go from run one to run eight for both yarns, there is a significant twist loss (for rotor yarn, it raises from 19 to 121 TPM, and for ring yarn, it raises from 52 to 123 TPM as the loom speed decreases from 510 rpm to 300 rpm).This is because as the loom speed decreases from 510 rpm to 300 rpm, the period of time the weft yarn stays in the shed increases, leaving the weft yarn exposed to air pressure for a longer period of time.On the other hand, the first two runs had the biggest twist loss differences between ring-and rotor-spun yarn, and run 8 showed the lowest twist loss differences.In runs 1 and 2, even though the insertion time is too short compared to other runs, ring-spun yarn still loses more twists than rotor-spun yarn (the difference in runs 1 and 2 is 33 and 32, respectively).This is because greater speed creates a much higher contact between the yarn and drag air than the slow speed does for ring-spun yarn, that is uneven and hairy.In addition to the effects of its hairiness and surface roughness, the twisting technique used in ring-spinning has a significant impact on the loss of twist.In ring spinning, the outermost fibers experience more stress while twisting (Erdumlu et al. 2009;Lord 1971).This highly stressed fiber will be relaxed simultaneously when it is free to rotate.Furthermore, higher air pressure with high protruding fibers will increase the coefficient of friction between air and yarn, resulting in higher twist loss.Contrarily, in rotor spinning, twist is formed in the center and moves out to the surface; as a result, the highly stressed fibers are located at the core and are covered by loosely bound fiber (Lord 1971).The yarn is further shielded from the impacts of yarn untwisting during the insertion procedure by the fact that it is coiled with wrap fiber.Figure 3 also demonstrates that considerable twist loss exists between ring-and rotor-spun yarns.It shows that rotor-spun yarn (coded as + 1) has a lower twist loss than ring-spun yarn (coded as −1) does.This suggests that for twist loss, hairiness has a more significant effect than yarn diameter.Though the speed of ring-spun yarn is faster than that of rotor-spun yarn, as illustrated in Figure 1, these protruding fibers have a greater impact on the loss of weft yarn twist than that of smoother yarn with a higher diameter.This result is also confirmed by scholars such as Umair et al. (2017) and Adanur and Turel (2004).

Effects of loom speed and air pressure on weft yarn twist loss in air-jet weaving
In this study, the level of twist loss was determined by calculating the difference between the level of twist before and after weaving.Weft yarn twist loss has been studied in relation to the effects of loom speed and relay nozzle air pressure.The importance of each factor and how they interact are displayed in Table 6 in detail.It shows that the model is significant with a p-value of 0.004.The main factors, such as A (yarn type), B (loom speed), C (right-side relay nozzle), and D (left-side relay nozzle) and interaction effects BD (interaction effect of loom speed and right-side relay nozzle air pressure), CD (interaction effects of right and left-side relay nozzle), have a significant effect on the weft yarn twist loss.
To predict the level of weft yarn twist loss for the two types of yarn, loom speed, left-side relay nozzle and right-side relay nozzle, a regression model has been developed.After removing nonsignificant factors, the regression model equation is given in Equation (1).
Twist loss ¼ þ81:81 À 10:81A À 17:56B þ 6:44C þ 12:31D À 4:81BD À 9:06CD À 6:94BCD (1) The regression equation shows that right-and left-side relay nozzle air pressures have a positive correlation with loss of twist, whereas loom speed, yarn type, the interaction effect between yarn type and loom speed, the interaction effect between loom speed and right-side relay nozzle air pressure, the interaction effect between right-and left-side relay nozzle air pressure, and the interaction effect between loom speed and left and right-side relay nozzle air pressure have a negative correlation.The model with a coefficient of determination (R 2 ) value of 0.975 shown in Table 7 is the best fit for the twist loss of weft yarn.This implies that the investigated factor accounts for 97.5% of the twist loss for 16 Ne weft yarn.Moreover, since the difference between the predicted R 2 of 0.825 and the adjusted R 2 values of 0.938 is less than 0.2, they are reasonably in agreement.
How well the model works is seen by the scattered graphs of the actual vs. predicted values in Figure 4.The y-axis displays the predicted values of twist loss, while the x-axis displays the actual values.Points around the diagonal line reflect the results of 16 experimental twist loss values, while the diagonal line represents the estimated regression line.The model is well-fitted, as the values are near the diagonal line.There is a good correlation between the predicted and actual values of twist loss, as seen by the fact that nearly all points are closest to the line, which indicates the error or residual is very small.

Effects of loom speed on weft yarn twist loss
Loom speed in air-jet weaving is another determinant factor for loss of weft yarn twist.Weft insertion time lowers as weaving speed rises, and the yarn twist loss also goes down (Ketema, Ayele, and Million 2023;Lu and Lu 2017).Figure 5 illustrates the phenomenon of loom speed on weft yarn twist loss.It shows that as the loom speed increased from 300 to 510 rpm, the weft yarn twist loss reduced.This is because the weft yarn stays for a shorter period of time in the opened shed at a higher speed, and the time the yarn is exposed to air pressure is shorter.Due to the twist holding the fibers in the yarn during spinning, the yarn stores more potential energy during weft insertion and this energy is released with pressure, resulting in the untwisting of the yarn.The effect is more prominent in ring-spun yarn.This is also agreed upon by different scholars (Lu and Lu 2017;Zegan and Ayele 2022).Therefore, loom speed and twist loss have a negative relationship.

Effect of air pressure on weft yarn twist loss
The weft yarn insertion medium of an air-jet loom is compressed air, and this highly pressurized air beats the yarn to move it forward in the shed.This beating (drugging) force led the yarn to   untwist.So, as the amount of applied air pressure increases, yarn twist loss also increases (Umair et al., 2017b).
The impact of air pressure on loss of twist is illustrated in Figure 6.As the left-side relay nozzle air pressure increased from 2 bar to 4 bar, the loss of twist increased slowly, whereas as the right-side relay nozzle air pressure increased from 3 bar to 6.5 bar, the loss of twist increased rapidly.This is because the yarn on the left side is clamped and moves a shorter distance than on the right side, which has a free end to untwist.In addition, to complete the full insertion process, the applied air pressure on the right side is higher than on the left, which is another factor in loss of twist.This is confirmed by different scholars (Ketema, Ayele, and Million 2023;Zegan and Ayele 2022).

Factors interaction effect on weft yarn twist loss (3D surface graph)
The interaction effects of different parameters at various levels on weft yarn twist loss are clearly displayed in a 3-D graph.The 3-D interaction effects graph in Figure 7a demonstrates that reducing the loom speed from 510 rpm to 300 rpm and increasing right-side relay nozzle air pressure from 3 bar to 6.5 bar increase the twist loss from 52 TPM to 120 TPM for a constant LSRN air pressure of 2 bar.This significant twist loss has been observed as a result of the fact that when the loom speed is reduced to its minimum value, the waiting time of weft yarn in the shed is longer, giving it more time to release its stored potential energy, and it is also exposed to the highest air pressure.The interaction effect of left and right-side relay nozzle air pressure on the loss of twist is depicted in Figure 7b.As the left and right-side relay nozzle air pressure increased from 2 to 4 bar and 3 to 6.5 bar, respectively, the twist loss increased from 52 to 96 TPM for a ring yarn at a constant speed of 510 rpm.This is because, at the maximum value of both relay nozzle air pressure, the weft yarn is exposed to the highest air pressure from the place of insertion up to the rightmost side of the shed.Furthermore, by keeping one constant while changing the other, a considerable twist loss change is found.This suggests that weft yarn twist loss is more sensitive to changes in applied air pressure.

Conclusion
In this work, the effect of yarn type on weft yarn speed and twist loss in air-jet weaving is investigated.Weaving conditions and yarn characteristics are among the factors that affect insertion time and loss of twist in air-jet weaving.Air pressure, on the other hand, promotes twist loss, so every increase in air pressure has a significant impact on the rate of twist loss.In addition, yarn diameter, hairiness, and irregularity have a significant influence on the weft yarn arrival rate and twist loss.
It is observed from the experiment that the diameter of rotor yarn is 0.388 mm and that of ring yarn is 035 mm, whereas the hairiness of rotor yarn is 6.73 and that of ring yarn is 8.57 for the same count of yarn (16Ne).The average speed shows that ring-spun yarn has a speed of 11.58 m/s, which is higher than the speed of the rotor-spun yarn, which is 11.48 m/s.It can be stated with certainty that the impact of yarn hairiness on the insertion speed is higher than the impact of rotor-spun yarn with a slightly larger diameter.
While the speed of the loom decreases from 510 rpm to 300 rpm, the twist loss increases from 19 TPM to 121 TPM for rotor-spun yarn and from 52 TPM to 123 TPM for ring-spun yarn.On the other hand, the highest twist loss differences (33 TPM) between ring-and rotorspun yarn are observed at the highest speed of the loom.Reducing the loom speed from 510 rpm to 300 rpm and increasing right-side relay nozzle air pressure from 3 bar to 6.5 bar increased the twist loss from 52 TPM to 120 TPM for a constant LSRNP of 2 bar.In addition, as the left-and right-side relay nozzle air pressure increased from 2 bar to 4 and 3 bar to 6.5 bar and bars, respectively, twist loss increased from 52 TPM to 96 TPM for a ring yarn at a constant speed of 510 rpm.

Highlights
• Scholars have been arguing about the effects of yarn hairiness and voluminous on weft insertion speed and twist loss in the air jet weaving process.Some of them stated that a yarn with a larger diameter will have a higher rate of insertion and twist loss than a yarn with a greater degree of hairiness.The opposing scholars disagree with this premise, claiming that a yarn with more hairiness will insert more quickly and lose its twist more quickly than a yarn with a higher diameter.Consequently, this study's goal is to refute these extremely contradictory ideas with evidence.• It is observed from the experiment that the diameter of rotor yarn is 0.388 mm and that of ring yarn is 035 mm, whereas the hairiness of rotor yarn is 6.73 and that of ring yarn is 8.57 for the same count of yarn (16Ne).• The average speed of ring-spun yarn is higher than the speed of rotor-spun yarn for the same count of yarn and the same conditions on the loom.• The highest twist loss differences (33 TPM) between ring-and rotor-spun yarns are observed at the highest speed of the loom.• While the speed of the loom decreases, the twist loss increases significantly for both yarns and as the left-and rightside relay nozzle air pressure increased, twist loss increased for both ring and rotor yarns.

Figure 3 .
Figure 3. Impact of yarn type on weft yarn twist loss.

Figure 4 .
Figure 4. Actual vs predicted value of graph for twist loss.

Figure 5 .
Figure 5. Impacts of loom speed in weft yarn twist loss.

Figure 6 .
Figure 6.Effect of air pressure on twist loss.

Figure 7 .
Figure 7. Interaction effects of loom speed with right side relay nozzles air pressure (a) and Interaction effects of right and left side relay nozzles air pressure (b) on yarn twist loss.

Table 1 .
Characteristics of yarns measured before weaving.

Table 3 .
Coded and actual level values of the factors.

Table 4 .
Experimental design with actual value of factors.

Table 5 .
Ring and rotor-spun yarn twist loss results from different combinations of factors.

Table 6 .
ANOVA for weft yarn twist loss for rotor-and ring-spun yarns at various loom speeds and air pressure.