Development of the Saw Gin

When Eli Whitney invented the saw gin in 1794, America, especially the cotton-producing southern states, eagerly welcomed its arrival. Although growing conditions for cotton were favorable in the South, and the demand for cotton fiber was great in the U.S. and abroad, farmers produced only what they could gin by hand or with the Churka gin. Whitney's saw gin, which removed the seeds from the cotton fibers with a spiked cylinder that pulled the lint through wooden slots too narrow for the seeds to pass through, was 50-100 times faster than hand ginning. It was especially effective in separating the hard-to remove seeds in Upland cottons, making these short-staple cottons more economical to produce than before. With Whitney's saw gin, farmers were finally able to mass produce Upland cottons to satisfy consumer demand, and the South had a new export commodity that contributed to the economic development of this nation.

Modern research has improved on an old concept, and saw ginning remains the most efficient way to gin cotton. The spikes in Whitney's saw gin have been replaced with circular serrated saws that have made it even more effective for separating seed and fiber. Today's saw gin can produce up to 15 bales of lint an hour per stand.

Research Programs in Saw Ginning

Research programs in saw ginning at the Southwestern Cotton Ginning Research Laboratory aim to develop more efficient seed cotton cleaning and conditioning methods, as well as safer ginning and lint cleaning devices. Other programs focus on finding ways for gins to combat air pollution and deal with the problems of ginning "sticky cotton," a condition caused by deposits of sugar from the feeding activity of insects.

One major project we are currently working on is a combination saw ginning and lint cleaning method called the Coupled Saw-Lint Cleaner. By combining all ginning and lint cleaning in one machine, the Coupled Saw-Lint Cleaner decreases fiber damage and does away with the conveying air used to transport the cotton from one ginning stage to the other. Gins, therefore, will be able to produce a longer, higher quality fiber, reduce cotton dust emissions, and save in energy costs.

Although highly effective in removing fine trash from lint, saw-lint cleaners can also damage the quality of the fiber and make it less efficient to process at the textile mill by shortening its staple or length, and by creating knots of fibers called neps, which show up as imperfections in the finished textile product. Saw-lint cleaners also remove good fiber in the process, lowering the weight of the cotton bale, and cutting into the farmer's profits. To reduce the damage and loss of good fiber, gins can base their lint cleaning on the amount of trash in the seed cotton. But knowing how much trash is in the lint is sometimes difficult for gins to determine. Another major research project currently underway at the Southwestern Cotton Ginning Research Laboratory is a trash imaging system. This system is designed to help gins limit the adverse effects the serrated saws in saw-lint cleaners have on the cotton fiber. With this computer system, gins will finally be able to measure accurately the trash amount in the seed cotton to determine how much lint cleaning it will require. For example, cotton with a low trash content can be run through only one of the saw-lint cleaners, instead of two or even three of these machines.