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The Manufacturing Process

Some manufacturers spin the bales of cotton delivered to the manufacturer.Others purchase the yarn already spun on spools. This section will describe the process of making 100% sheeting from bales of cotton delivered to the plant which are not yet spun.

Procuring the cotton

1 Bales of cotton weighing about 480 lb (217.9 kg) are purchased and shipped to the sheeting manufacturer.

2 Bales are laid out side by side in a blending area. The bales are opened by a Uniflock machine that removes a portion of cotton from the top of each bale. Next, the machine beats the cotton together, removing impurities and initiating the blending process. The fibers are then blown through tubes to a mixing unit where the blending continues.

Carding

3 Once blended, the fibers move through tubes to a carding machine, which aligns and orients the fibers in the same direction. Cylinders with millions of teeth pull and straighten the fibers and continue to remove impurities.

Drawing, testing, and roving

4 Here, the cotton fibers are further blended together and straightened as many strands of fibers are drawn together into one strand by a roving frame. The frame twists the fibers slightly and winds a cotton roving onto bobbins.

Spinning

5 The rovings are spun on a ring spinner, drawing the cotton into a single small strand and twisting it as it spins. The yarn is then wound onto bobbins and the bobbins are placed onto winders that wind the thread onto section beams that will eventually fit onto a loom for weaving.

Warping a section beam

6 It takes between 2,000-5,000 warp (lengthwise yarns) to make up a single width of sheet. Thus, the warping beam, which holds all of the yarns, is very large and cannot be loaded at once. So 500-600 ends of yarn from spools are pulled onto a single section beam, thus warping it. Later, several section beams will be loaded onto the large warping beam, each contributing a portion of the warp.

Slashing

7 Each section beam goes through a slasher—a machine that coats the yarn with starch or sizing to protect the ends and makes the yarn easier to weave.

Warping the beam

8 Once coated with sizing, several section beams are loaded onto a single large loom beam. As many as 6,000 yarns are automatically tied onto old yarns by a machine called a knotter in just a few minutes. The knots are pulled through the machine and the weaving can begin.

Weaving

9 The weaving, in which the weft or filler threads interlock with the warp or vertical threads, is done on high-speed automatic air jet looms. The filler threads are transported across the warp threads at a rate of 500 insertions per minute, meaning that a filler thread runs across the warp thread about every one-tenth of a second. It takes about 90 insertions to weave an inch of sheeting. Thus, about 5.5 in (14 cm) of sheeting is woven per minute—10 yd (9.14 m) per hour are woven. Typically, 8,000 yd (7,312 m) of sheeting is woven on a loom and wound up in rolls and shipped for further processing.

Cleaning and bleaching

10 The fabric, called greige, is gray in color. It is further finished by singeing—a process in which bits of yarn are burned off of the surface. Then, the sheeting is ready to be bleached. This is done in three steps. First, it is desized by bathing it in water and soaps that removes contaminants. Next, caustic chemicals are applied to get rid of dirt and remnants of debris found in cotton yarn. The caustic is washed out and concentrated bleaches (chlorine and/or hydrogen peroxide) are applied to dissipate the gray color. Now whitened, the sheeting is rolled into a rope and put into a dryer which takes the moisture out prior to dyeing.

Weaving is done on high-speed automatic air jet looms. Typically, 8,000 yd (7,312 m) of sheeting is woven on a loom and wound up in rolls and shipped for further processing. Once woven, the sheeting is bleached, rolled into a rope and dried, dyed, and rolled. Automatic cutting equipment cuts the roll into standard sheet lengths and the sheet hems are sewn. 

Dyeing 

11 All sheeting is dyed. Even sheeting sold as white must be dyed to become a truly white sheet. In order to give the gray-colored sheets color, pigments are applied to the sheeting in color vats that use large rollers to press the dyestuff into the material. Once dyed, the sheeting is steamed to set the color. Next, a resin is applied to the sheeting to control shrinkage. The sheeting is rolled onto huge rolls and is ready to be cut and sewn.
 

Cutting and sewing

12 Automatic cutting equipment pulls the cloth off the rolls as it automatically cuts the sheeting to the requisite length. The rolls are transferred to a sewing machine that sews top and bottom hems.

Packaging

13 The sewn sheet is either folded by 1 3 hand or machine. Machine-folded sheets are ejected, shrink wrapped, and individually packaged for sale.

Quality Control

Sheeting manufacturers carefully choose cotton bales. Cotton is classified by length (staple) and by quality (grade). Shorter staples are used for batting, while longer staples are used to make higher quality products. Egyptian cotton is made from longer staples. Medium staples is considered standard. There are nine grades used to classify cotton from middling to good. Cotton with much debris and residue would be of a lower grade than that with less impurities. The lower grade bales tend to slow down the processing of the cotton into spool yarn and may never render a quality product. Thus, many plants will purchase bales based on test data received from the U.S. Department of Agriculture to ensure the bales are fairly clean. Many weaving facilities perform their own tests on bales to be purchased to assess quality and cleanliness.

Rovings—the rope-like strand that is spun into yarn—generally undergoes quality control inspection prior to spinning. At major points in the production of yarn and sheeting, statistical samples are taken and tested in the laboratory. Physical tests are run on the completed products. Because the bleaching and dyeing processes include a number of chemicals that must be mixed exactly, the chemical solutions are monitored. Furthermore, employees within the plant carefully monitor the process and visually inspect the product at each manufacturing stage.