Rieter

Automatic piecing after ends down and quality stops

Index

After an end down or quality stop, sliver feed to the spinning position is discontinued immediately (signal from yarn monitor disconnects feed cylinder) in order to prevent the rotor from being overloaded with fiber material. The package is lifted off the winding cylinder to prevent damage to the layers of thread. The operating robot is called up via the machine control system.

Spinning positions that have been stopped due to quality alarm or maintenance and reported to the machine control system are not re-started when the cause of the fault has been remedied manually. Spinning positions that are stationary due to the absence of sliver are detected by the robot by means of sensors and are not served until a new sliver has been fed in.

After the robot has been positioned precisely, the piecing process starts with the end of the sliver waiting between the feed trough and the feed table being moved briefly into the opening roller zone in order to comb out short and damaged fibers. Immediately after this the sliver is withdrawn again in order to prevent renewed damage of the fibers in the end of the sliver.

As the next step the inside wall of the rotor and the rotor groove are thoroughly cleaned pneumatically by means of a precise current of air, and if necessary the rotor groove is additionally cleaned by means of scrapers. The deposits removed in this way are blown out and extracted by means of compressed air.

The thread end is taken off the package and fed back into the rotor housing through the draw-off tube (Fig. 55 – step A). At the same time the sliver feed is started and the fibers are fed under control (depending on rotor speed) into the rotor. In the rotor groove the end of the thread is joined to the fibers fed in. The rotation of the rotor inserts twist into the overlapping zone and the fibers fed subsequently into the rotor. Synchronized thread take-off from the rotor then commences (step B). How long the thread remains in the rotor and how much twist is thus to be inserted in the piecing zone can be determined by the timing of the thread take-off.

After the piecing has been formed, the rotor is accelerated to full spinning speed and the piecing process is thus concluded. Each piecing is examined electronically with regard to mass (capacitive) or diameter (optical) before it is wound onto the package (step C). If a piecing exceeds the preset limits the spinning process is interrupted again (sliver feeding is discontinued) and the piecing process is repeated.

The success rate of piecings produced automatically is almost 100%, with a success rate between 80 and 90% for the first piecing cycle, while the remaining spinning positions can usually be re-started in a second piecing process (the number of piecing attempts can be set between 1 and 3). Unsuccessful piecing attempts are on the order of no more than 1% and are indicated by a signal lamp on the spinning position.

Fig. 55 – Automatic piecing after an end down or quality stop; A The end of the thread is taken off the package and inserted in the rotor at the same time as starting fiber feed; B The piecing is formed under processor control and thread take-off is started; C The piecing is examined electronically and then wound onto the package