Systems for automating the operation of rotor spinning machines have been integral parts of high-performance rotor spinning machines for some years. Automated systems have been developed for all manual operations in several stages:
- automatic gripping and introduction of the sliver end from a new can into the spinning box (implemented only in certain cases to date);
- automatic cleaning of rotor, draw-off nozzle and draw-off tube after ends down, quality stops or package changes;
- automatic removal of full packages upon reaching the preset yarn length, and replacement with empty tubes
- automatic feeding of empty tubes to the operating robot for package change;
- programmable batch phase-out/batch change;
- automatic deposit of removed packages at the end of the machine;
- automatic or semi-automatic filter cleaning.
Machine automation reduces manual operations to a minimum and replaces them by monitoring tasks and interven tion in the event of malfunction. However, the importance of automation is by no means confined to economies in operating personnel and labor costs. Automation also has a major influence on product quality, i.e. yarn quality, for example through automated piecing after ends down:
- Manual piecing is no longer possible at high rotor speeds (> 100 000 rpm).
- Manual piecings have an average tenacity of no more than 40%, whereas automated piecings have a yarn tenacity of up to 100%.
- Since electronic yarn clearers are standard equipment on rotor spinning machines nowadays, it is only worth clearing yarn defects as long as they are not replaced by a piecing of inferior quality (thick and of lower strength) than the cleared defect, as a result of being produced manually. Only piecing systems featuring controlled fiber feeding and synchronized yarn take-off can produce piecings that are virtually invisible in the yarn and the end product and thus permit fine clearer settings.
- Consistent piecing quality is essential for economical downstream processing of rotor-spun yarns, and this can only be assured by piecings produced with process control and reproducible setting parameters.
- Last but not least, thorough cleaning of the rotor groove inevitably takes place on automated machines after each end down or package change, thus reducing the risk of a creeping decline in yarn quality.
Machine automation is represented in practice by two different concepts:
- Integrated automation, in which all operating functions (rotor cleaning, repairing ends down, package change) are combined (integrated) in a single robot (Fig. 48). Package changing and the subsequent re-start of the spinning position occur as a single process.
- Automation by means of units operating separately, with the operating functions of spinning start-up (after ends down or package changes) being performed by a piecing robot, and the transport of starter bobbins (instead of empty tubes) and package change by a second robot. There is no system-imposed link between robots which operate separately and the use of starter bobbins, but the greater technical complexity this concept entails in connection with the pre-wound starter bobbin (additional starter bobbin unit, starter bobbin transport, etc.) is system-imposed. This is probably also the reason why manufacturers which previously supplied robots operating separately have switched to the integrated automation system on their machines. Operating robots are powered and controlled either mechanically/ electronically or pneumatically/electronically. Robots of modular design significantly simplify maintenance. The modular structure of pneumatically controlled operating robots permits synchronized functional processes in package change and the subsequent re-start of spinning. The entire piecing process after ends down or quality stops is completed after less than 25 seconds. The operating robots travel at a speed of some 0.4 m/sec.