A Must-know Guide to Roving Frame

HINA, HEFEI (December 1, 2023)-The primary and most intricate piece of equipment used in cotton spinning is the roving frame. The roving frame's quality has a direct impact on the yarn's physical properties, including strength, evenness, and uneven weight distribution. Additionally, it has a significant impact on energy usage, labor, materials, labor productivity, cost, benefit, and floor area in addition to spinning production.https://fyitester.com/roving-frame/
Roving, sliver and yarn
A roving frame creates roving from a sliver. It is sometimes referred to as a roving machine or fly frame. A draw frame, which is situated ahead of the yarn production process, is where the sliver is made. The raw material called roving is what's utilized in ring spinning machines and other yarn-making processes. The result is that the roving is both much thinner than a sliver and much thicker than yarn.

Tasks for roving frame
There are three tasks on the roving frame, namely drafting, twisting and winding.
 Drafting: extend and thin the cooked sliver, enhance parallelism and fiber separation;
 Twisting: appropriately apply twisting to fortify, ease winding and unwinding, and ease drafting of spun yarn;
 Winding: Suitable for feeding into a spinning frame, winding into packages makes it convenient for storage and transit.

Drafting
The roving frame's primary function is to further draft the sliver into bundles of finer-count fibers, or "rovings." Because coarse slivers cannot be turned into fine yarns by the ring spinning machine, an intermediate production step is required. Moreover, there is still uncertainty around the management of sliver in ring spinning machines.
This is because the sliver's weak strength makes it impossible to fit the large sliver box that contains the sliver inside the ring spinning frame.

Twisting
Since both the fine-count and sliver roving are made from the roving, the roving frame's second job is to create a protective twist in the roving to strengthen the textile fiber bundle during transportation. The sliver lacks cohesiveness in the absence of a protective twist.
Protective twist is a little twist that is solely applied to provide the wandering with enough stability for transportation, or enough tensile strength. The ring spinning frame's drafting mechanism once more takes care of protecting the twist.

Winding
Helically wrapping the roving around the bobbin's cylindrical winding surface causes the yarn layer's height to fall from the interior to the outside, creating a shape with a cylinder in the center and truncated cones at both ends. Consequently, there are two components to the wandering winding movement:
 The yarn moves in a circular motion in relation to the bobbin.
 Layer by layer, the yarn's axial movement and moving distance from the bobbin diminish.

The right amount of winding tightness is necessary to boost the package's volume. Simultaneously, a smooth unwinding depends on the yarn loops being placed in an orderly manner with distinct layers, no loose loops, and no edge collapse.

Process flow of roving frame
The four primary functions of the roving frame are feeding, drafting, twisting, and winding. The sliver is fed into the drafting device by the guiding roller after being removed from the sliver container at the back of the machine. The sliver output from the front roller's nip is too weak after drafting, thus the spinning flyer adds the proper twist (30~65 twist/m) to create a roving.
The roving thread winds through the flyer's top and side holes, enters the yarn guide arm, emerges from the bottom end of the guide arm, winds many times on the pressing palm's crank arm, and ultimately reaches the pressing palm leaf before winding on the bobbin. The bobbin rotates faster than the flyer on one hand, moves up and down with the dragon tendon on the other, and finally winds the roving in a helical pattern on the bobbin's surface in order to wound it on the bobbin on a regular basis.

Roving tension and roving elongation
Roving tension
The term "tension" describes the tensile force applied to the sliver's axial direction; it is expressed as the sliver's tension. The sliver must be taut and provide tension during the roving winding process in order for the roving to wind smoothly on the bobbin. This is achieved by the bobbin winding speed needing to be somewhat greater than the front roller's output speed.
Each part of the sliver from the front roller to the bobbin has a variable tension because it must overcome frictional resistance at the hollow arm, the presser palm, and the flyer's top sleeve throughout the advancing process. The highest tension comes from winding from the presser palm to the bobbin tube; the next largest tension comes from the hollow arm; the smallest tension comes from spinning from the front roller to the flyer's top tube.

Roving elongation
When the tension on the sliver is high, the sliver will elongate due to the relative displacement between the internal fibers, and the degree of elongation can be expressed by the elongation ε.
Ε=(l1+l2)/l2*100%
In the formula: l1 - the measured length of bobbin winding (m);
l2--the calculated length of the front roller (m).
The twist is little and erratic as the spinning region is where the sliver is formed. The spinning part is the simplest to stretch, while having the least tension. As a result, the sliver tension in this area is sometimes referred to as roving tension. Tiny adjustments to the roving tension will have a sensitive impact on the elongation, which will modify the roving's unequal weight and evenness. In order to prevent harming the output sliver's homogeneity, the roving tension must be maintained at a certain level during spinning. Making ensuring there is enough winding density is also essential.

The relationship between roving tension and elongation
By looking at the spinning section, one may ascertain the roving's tension. There will be a high tension if the sliver is tight and a low tension if it is loose. Elongation can be utilized to subtly indicate the stress of roving in production, as visual inspection is only useful for qualitative analysis and not quantitative analysis.
Raw material, spinning type, flyer structure and material, use of false twister and its structure and material, machine section size, winding size, process speed, workshop temperature, humidity, etc. are some of the factors that influence the relationship between tension change and elongation change. The roving elongation may be utilized as an indirect way to determine the roving tension in the workshop if a certain false twist method is adopted and the temperature and humidity levels are normal. This means that the elongation should be regulated between 1.5% and 2.5% at this point, with a maximum of 3% and a minimum variation of 1.5% in elongation.

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