Rieter

Correction length

Index

Fig. 17 – The correction length

If there is a sudden deviation from the set volume as the material passes through, a corresponding signal is sent to a regulating device to correct the fault. Owing to the mass inertia of the system, compensation cannot be effected suddenly, but must be carried out by gradual adjustment. A certain time (the correction time: in Fig. 17, I ) elapses before the sliver delivered has returned to the set volume. During this time, faulty sliver is still being produced, although the deviation is being steadily reduced. The total length that departs from the set value is referred to as the correction length (I). In closed-loop systems, the correction length is further increased by the dead time. In this case it depends upon the dead time (II) and the correction time (III). The correction length depends upon the system and the speed of operation, and therefore varies considerably.

The term “correction length” is used to describe the efficiency of a leveling device. However, this term is used in different ways and sometimes also incorrectly. The current interpretation is: “The correction length is the length of the product which would be produced when leveling a rectangular deviation of the product.“ The length therefore refers to an amplitude of the fault of 1%. The term “correction length” is therefore a theoretical value, since in practice rectangular faults do not occur. As they cannot be checked in the spinning mill, the quality of the delivered sliver is usually taken as the standard of comparison, and sliver evenness can be determined by any evenness tester.