A Must-know Guide to Roving Frame

The roving frame is the main equipment of cotton spinning, and it is also one of the most complex equipment. The quality of the roving frame directly affects the physical performance of the yarn, such as evenness, weight unevenness, strength, and yarn defects. It also plays a decisive role in spinning output, energy consumption, labor, materials, labor productivity, cost, benefit, and floor area.

Roving, sliver and yarn

A roving frame, also known as a roving machine or fly frame, produces roving from a sliver. The sliver is created in a draw frame, which is located upstream of the yarn manufacturing process. The roving is the raw material used to make yarn, such as in a ring spinning machine. As a result, the roving is much thicker than yarn yet much thinner than a sliver.

Tasks for roving frame

There are three tasks on the roving frame, namely drafting, twisting and winding.
  • Drafting: lengthen and thin the cooked sliver, improve the parallelism and separation of fiber straightening;
  • Twisting: add proper twisting to increase the strength, facilitate winding and unwinding, and facilitate the drafting of spun yarn;
  • Winding: Winding into packages, convenient for transportation and storage, suitable for feeding into spinning frame.

Drafting

The main task of the roving frame is to further draft the sliver into finer count fiber bundles, so-called rovings. This intermediate production step is necessary because the ring spinning machine cannot process coarse slivers into fine yarns. Furthermore, the handling of sliver in ring spinning machines remains unresolved.
This is because, due to the poor strength of the sliver, there is not enough space in the ring spinning frame to store the bulky sliver box that holds the sliver.

Twisting

Another task of the roving frame is to insert a protective twist in the roving to strengthen the textile fiber bundle so that it can be transported without being damaged, since the sliver as well as the fine-count roving are produced from the roving. Without a protective twist, the sliver has little coherence.
Protective twist is a slight twist that is only used to give the roving sufficient (tensile) strength, ie stability for transport. Protecting the twist is again taken care of in the drafting unit of the ring spinning frame.

Winding

The roving is helically wound around the cylindrical winding surface of the bobbin, and the height of the yarn layer decreases from the inside to the outside, forming a shape with truncated cones at both ends and a cylinder in the middle. Therefore, the roving winding movement includes two parts:
  • Circumferential movement of the yarn relative to the bobbin.
  • The axial movement and moving distance of the yarn relative to the bobbin decrease layer by layer.
Winding should have appropriate tightness to increase the volume of the package. At the same time, it is required that the yarn loops are arranged neatly, with clear layers, no loose loops, and no edge collapse, so that the unwinding can be smooth.

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