A roving frame draws carded sliver through two or three roller pairs to between a fifth and a tenth of its weight per length, adds 2-5 twists per inch so the strand can be handled, and winds it on a bobbin as the feed for the spinning frame. The roving must be even in weight, because every flaw in it is drafted 10-30 times longer in the yarn.
Part of Spinning Frame
The intermediate stage that thins sliver and gives it enough twist to be wound and drafted again.
Roving Is The Spinning Frame’s Feedstock
The overview puts the roving frame between the card and the spinning frame. The sliver is too thick and loose for direct spinning, so the roving frame draws it through 2-3 roller pairs, reducing it to a fifth to a tenth of the thickness, adds slight twist of 2-5 per inch, and winds it on bobbins. The roving then goes on the creel at the back of the spinning frame.
Evenness matters more here than at any other stage. The overview gives the spinning draft as 10:1 to 30:1, and a thick place in the roving is drafted along with the rest, so a thick place of 1 m becomes one of 20 m at a 20:1 draft, and a thin place of the same length becomes a weak place in the warp that will break on the loom.
What You Need
- A drafting system like the spinning frame’s, with the same fluted bottom and leather top rollers (Roller Construction) set to the longer staple of the sliver (Roller Spacing and Gauging).
- Flyers and bobbins like the spinning frame’s, though larger.
- Even sliver from the card (Mechanical Carding).
Method: Making Roving
Step 1: Choose the target. Roving weight follows the yarn count and the draft: roving tex = yarn tex × draft. For Ne 20 yarn at 20:1, roving is 29.5 × 20 = 590 tex.
Step 2: Set the roving draft by the same method as the spinning frame (Drafting). A sliver of 3-6 g per metre at 5-10:1 gives roving of about 590 tex.
Step 3: Set the twist low, within 2-5 per inch. Too little and the roving falls apart on the bobbin; too much and it will not draft in the spinning frame.
Step 4: Wind on at very low tension. Roving is weak and soft, so the winding in Winding On must be gentle. As the bobbin fills the wind-on speed must fall; a roving frame is where this matters most, because the roving cannot take any pull. (Historical roving frames used a differential gear train for this, recalled and not from the corpus.)
Step 5: Check evenness by weighing a metre at the start, middle and end of several bobbins.
Worked Example
Ne 1.0 is 590.5 tex (the conversion is in Thread Count System). Drafting 5-10 times from a sliver of 590.5 × 5 = 2,952 to 590.5 × 10 = 5,905 tex, 3-6 g per metre, gives that roving. At 3 twists per inch (inside 2-5) and an assumed 500 rpm flyer, a roving spindle delivers 500 ÷ 3 = 167 inches a minute, 4.2 m a minute, about 254 m an hour. At 590.5 g per km that is 254 ÷ 1000 × 590.5 = 150 g of roving an hour per roving spindle. A yarn spindle at 152.4 m an hour and 29.5 g per km uses 4.5 g an hour. One roving spindle therefore supplies about 150 ÷ 4.5 = 33 yarn spindles: roving is a small part of the plant, which is why the frame count matters less than the spinning frame count.
Common Mistakes
- Uneven sliver from a poorly set card, which the roving frame cannot cure.
- Roving twisted hard enough to resist drafting. The yarn then draws unevenly.
- Winding roving tight. Stretched roving is thin and weak, and thin places are exactly what the draft will magnify.
Safety
The roving frame has the same nips and flyers as the spinning frame
Roller nips draw in fingers; flyer arms strike hands; hair and sleeves wrap on bobbins. Stop and let everything halt before clearing a break or doffing. The line-shaft and belt hazards in Drive System apply. This is adult work; children are kept away from running machinery (Task Assignment by Age).
What’s Next
- Learn next: Spindle and Flyer Design — the mechanism that twists and winds the yarn itself
- Combine with: Multi-Spindle Frame Assembly — the creel where roving bobbins feed the frame