|Overview Of A Cotton Gin
Cotton ginning systems consist of several different types of processing machines and each
is designed for specific tasks. Each machine influences several physical properties of the
cotton fiber and many of those properties must be measured with complex laboratory
instruments. The decision about the use of an individual machine involves a tradeoff,
i.e. a cleaning machine will remove foreign material but also removes some valuable cotton
and does some damage to the remaining fiber. A computerized process control system can
optimize fiber quality by "prescription" processing the cotton.
Process Control System
The first computerized process control system was installed in a small-scale research
facility at Stoneville, MS, and used special routing valves to bypass or select any
combination of four seed cotton cleaners, two multi-path driers, and three lint cleaners
as directed by a computer. The current design uses three color/trash/moisture measurement
stations in the gin system: in the feed control or module feeder, immediately behind the
gin stand (before the lint cleaning), and after the lint cleaning. Station 1 evaluates
seed cotton whereas stations 2 and 3 evaluate lint. The lint moisture, color, and trash
measurements are used to predict the value of the cotton after treatment by all combinations
of equipment which are available in the gin. Similar installations in six full-scale gins
have also been evaluated.
The gin process control system developed at the Stoneville Ginning Lab has operated successfully for
several years. Research and field experience clearly demonstrates that process control designed to
maximize farmer monetary returns will also minimize the damage to cotton fiber during gin processing.
W.S. Anthony and R.K. Byler adapted the design and coordinated the installation and validation of the
system in several commercial gins. Components of the CGPCS were initially field tested at Burdette Gin
near Leland, MS, in 1989. After successful validation, the components were installed at Westlake Gin, Stratford,
CA and Servico Gin, Courtland, AL. Excellent results have been achieved at Westlake since 1992. The Servico
system processed about 40,000 bales successfully in 1994 and improved monetary returns to the farmer as well as
provided cotton of a higher spinning quality. It also helped identify several additional opportunities for
improvements during the gin process. The CGPCS at Servico was improved and operated in 1995, yielding even better
results for the farmer and spinner. Based on the successes in 1994 and 1995, Zellweger Uster licensed several USDA
patents (with W.S. Anthony, R.K. Byler, and O.L. McCaskill inventors) to enable them to make the CGPCS available to the
cotton industry. In 1996, the CGPCS at Servico was upgraded with Zellweger Uster cameras. Again, the upgraded CGPCS was
very successful. Prior to the 1997 season, new Zellweger Uster manufactured sampling stations, flash cameras, spread spectrum
data transmission equipment, and other improvements were installed at Servico. The new system essentially operated on
"automatic pilot" during the 1997 season. Experiences with the cotton from Servico at one textile mill have been exceptionally
favorable. The same mill has purchased the entire gin production for 1998.
New beta sites were also installed prior to the 1997 season at Marianna and Dumas, AR, and were Zellweger Uster's first
installations. Additional CGPCSs are being installed for the 1998 season. Thus, this new technology is now available to the
cotton industry on a limited basis.
Evaluation of computer simulation models for process control suggest that bale values could be increased from $6.86 to $23.38
per bale (based on base price of 60.9 cents per pound for strict low middling and an initial lint moisture content of 6.0%).
Obviously, adjustments are required to reflect current market prices. Field experience at commercial gins indicate that these
numbers are reasonable and are likely too low for current raw cotton and market conditions. One commercial ginner reported farmer
profit increases of over $40 per bale using the gin process control system. He also reported dramatic improvements in fiber quality
based on HVI measurements. Mill processing experiences with the cotton produced from gins equipped with the IntelliGin have been
exceptionally good with higher quality yarn produced at lower costs.
Fiber Improvement by Process Control
Control of the cotton ginning process minimizes machinery usage as well as drying. Obvious benefits result both in
monetary rewards and fiber quality. Control of fiber moisture will: 1) increase length about 4%, 2) reduce short fibers about
47%, 3) increase seed-coat fragment size about 18% and improve removabiliy at the textile mill, 4) decrease the number of seed-coat
fragments about 36%, 5) increase measured strength by 5%, and 6) increase fiber yield about 3%.
Rapid expansion of automated and intelligent process control systems for cotton gins will vastly improve the quality of cotton.
The capability to rapidly determine the essential fiber quality features of cotton and to consider the ability of individual
cotton machines to modify those fiber quality characteristics every few seconds, and to make those measurements at multiple locations
in the ginning process and refine the machinery selection is the basis for a new frontier in cotton ginning. Armed with a full spectrum
of knowledge concerning the fiber qualities of cotton online during processing and the capabilities of gin machines to influence those
fiber qualities, this new frontier will represent many future opportunities for improved ginning processes. It will also serve
as a platform for major advancements in gin machinery, in fact, some are already in the patent process. New, less aggressive and less
damaging machines can be developed and integrated into existing gin systems that can now monitor the performance of those machines.
Ginners will now be able to achieve the desired fiber qualities based upon guidance from the farmer or textile mill within constraints of
initial fiber quality characteristics. Farmers, ginners, gin managers, and the textile industry now have acccess to instantaneous online measurements
of cotton quality. Interactive, responsive processing at the gin can now be controlled remotely by the buyer of the cotton. Enormous
opportunities exist for re-engineering the post harvest processing of cotton to deliver textile mills precise products that meet their specifications.
With control of the cotton fiber quality characteristics comes the opportunity for improvements in the textile industry. The
stage is now set fro ginning to be the next new frontier in cotton processing.
Gin Machinery Impact on Fiber Quality
Knowledge of the performance characteristics of gin machinery is the basis for controlling
the gin process. W.S. Anthony developed the performance characteristics of each type of
gin cleaning machinery and combination of machines in terms of their effect on fiber
quality as a function of moisture and trash levels as well as cotton varieties. The study
included three moisture levels (4.1, 5.5 and 8.4%), and three trash levels (3.0, 4.1 and
7.8%) based on the Shirley Analyzer visible foreign matter.
Samples were taken before gin processing and at the feeder apron and lint slide to
determine the characteristics of the seed cotton as well as the characteristics of the lint
cotton. Foreign matter and moisture analyses were performed by the Cotton Testing
Laboratory (CTL) at Stoneville. HVI and Smith-Doxey classifications were done by the
Agricultural Marketing Service at Greenwood, MS. Neps, seed-coat fragments and short fiber
content were determined at the CTL at Stoneville, MS.
The visible and total foreign matter remaining in the ginned lint were a function of the
variety, moisture, and machinery treatments. Visible lint foreign matter ranged from 3.9%
to 6.2% as moisture increased, and from 2.0% to 7.4% as ginning machinery was changed.
Staple length ranged from 36.0 for the EFGS only to 35.1 for the 3-lint cleaner
treatment. All lint cleaner treatments decreased staple length. HVI length corresponded
directly with moisture level and was 1.10, 1.11 and 1.12 in. respectively, for the low
(4.1%), medium (5.5%), and high (8.4%) moisture levels. No difference existed in length
values for the seed cotton cleaners. However, each lint cleaner reduced the length by
Mean lengths, as measured by the Peyer 101, for machinery ranged from 0.86 in. for the
three lint cleaner treatment to 0.92 in. for a treatment with no lint cleaners. Mean
length decreased from 0.93 in. to 0.87 in. as lint moisture decreased from 8.4% to 4.1%.
The short fiber content (fibers less than 0.5 in. in length) by weight increased from 4.6%
to 8.7% as moisture decreased from 8.4% to 4.1%. Seed cotton cleaners did not increase the
short fiber content but lint cleaners did. Lint cleaners increased the short fiber content
to 6.8, 8.8 and 9.6%, respectively, as one, two and three stages of lint cleaning were used.
Length Uniformity and Strength
The uniformity was higher for the high moisture level, 82.8, than for the medium, 82.2, and low, 81.9, moisture levels. The Machinery treatments caused the mean uniformity to vary from 81.4 (three lint cleaners) to 82.8 (extractor-feeder and gin stand (EFGS) only or stick machine with EFGS) with lint cleaners decreasing uniformity about 1.0. Strength means for moisture were 28.0, 28.6 and 29.2 g/tex, respectively, for cotton processed at 4.1, 5.5 and 8.4% fiber moisture.
Seed-coat Fragments and Motes
The number of seed-coat fragments per 3 grams of lint were about 50% higher at the low moisture level than at the two higher levels. Machinery did not significantly influence the number of seed-coat fragments. The weight of seed-coat fragments was significantly influenced by Moisture and Machinery. Means for the high moisture level were significantly higher (33.8 fragments) than for the other two moistures (28.5 fragments). Machinery strongly influenced fragment weight with the seed cotton cleaners having no effect and lint cleaners decreasing the weight dramatically. The number and weight of motes were decreased dramatically by saw-type lint cleaners.
Small entanglements of cotton fibers called neps increase each time that cotton is manipulated. G.J. Mangialardi studied samples of cotton fiber collected in seven locations in a gin system and found that neps were increased from 6 to 16 per 100 in.2 of web by simply removing cotton from the trailer pneumatically. Two stages of lint cleaning increased the number of neps dramatically from 18 to 34. W.S. Anthony reported that neps averaged 13.1 and 6.7 per 100 in.2 of web for lint moisture contents of 4.1% and 8.4%, respectively, a decrease of 49% across all machines. He also reported that neps decreased by 15% and 42%, respectively, when one and two stages of lint cleaning were bypassed.