Technology for sliver weight regulation on the carding machine is commonly used in cotton processing for long (greater than 10 meters) incremental lengths of sliver. The engineering challenge is to maintain sliver uniformity over relatively short lengths by the application of modern control technology. With current technology, the sliver mass is usually monitored by measuring the thickness of compressed sliver as it passes between a set of tongue and groove rollers or by using a sensor to determine pressure or sound changes at the trumpet. These changes are caused by the fluctuations in sliver linear density. Using one of these two levelling methods the input speed of the batt is then varied at the feed roll. The draft of the carding machine is about 120, which produces a lag time between the sliver that is going through the trumpet and the batt of fibers input at the rear of the card. Due to this lag time, only long term autolevelling can be accomplished.

Other methods and technologies need to be considered for sliver weight control on the cotton card in order to affect changes over shorter lengths. This would increase overall uniformity, especially in the shorter wavelengths. The elimination of roller drafting in the sliver weight regulation process needs to be thoroughly investigated. This study involved using a mechanically isolated trumpet sensor to sense sliver uniformity and a torque meter on the feed roll to sense input batt thickness. These measurements were combined mathematically to create two control loops for regulating sliver weight uniformity by regulating the feed roll. A third control loop monitors and controls the speed of the doffer using the same inputs to improve sliver evenness. This approach eliminated the drafting waves imparted to the sliver through roller drafting and used the high speed response of a microcomputer control system coupled with a heavy duty inverter. These components allowed precise control of both speed and acceleration of the feed roll and doffer motors on the cotton card.

Using these control systems the coefficient of variation for sliver density was reduced from 8 to 4% a significant improvement in uniformity.