Roving Frame Workflow and Related Calculation

 

As an important production equipment of cotton mill, roving frame belongs to the preparation process from combed sliver to spinning into yarn in the production process. Roving production is the last of the preparatory stages for spinning.
The tasks of the roving production
 (1) Drafting the sliver to a finer one whose weight per unit length is made to allow a draft at the ring frame in the approximate range of 4 to 12;
(2) Using two suspended flyers to inserting few twists to the roving to make it strong enough to sustain the tension in further processing;
(3) Winding roving into the bobbin in proper way.

Drafting

The drafting system is the key to the rubbed roving frame, which adopts 3- roller -2-apron drafting arrangement can make the friction boundary distribution reasonable, the floating zone is small, can effectively control the fiber movement, the total draft multiple is high, and the roving eveness is good.
The bottom rollers are fluted steel and the top rollers are covered with synthetic rubber. When the top pendulum is latched down, springs are, compressed to apply pressure on the top rollers for good, strong contact with the bottom rollers. Located in the front draft zone are top and bottom aprons, necessary to suppress drafting waves caused by roller drafting.
Drafting roller spacing is the distance between the nip lines of successive roller pairs. This distance, as with all roller drafting systems, is adjustable to accommodate the fiber length to be drafted. Total draft is determined by the surface speeds of the back and front roller pairs. The draft in the back zone is referred to as break draft, and it should be as low as feasible so that the largest portion of the total draft will take place in the front zone where apron control of fiber movement is located. Most roving frames are designed to allow a large range in total draft from 4 to 20 and above. A more practical range 4 to 12 has been found to yield a better quality product.

Twisting

The suspended flyer is a twisting mechanism, and the suspended flyer turns once and adds a twisting. Doffer does not need to pull out the flyer, easy to operate, reduce the work intensity, is conducive to automation. Good rigidity, high rotation stability, suitable for high speed and large roll.
Twist multiple in roving should be sufficient to prevent stretching of the strand in normal handing and in its travel in the spinning creel. The method of calculating the twist in roving is to relate flyer speed to the velocity of the strand exiting the front roller:
In roving production, a combined twist insertion and bobbin build device is used to insert twist to the attenuated strand, and wind the roving into the bobbin.
More information about the roving frame can be found here.

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