Rotor spinning mills with 40, 50 or even more machines in a single spinning installation are by no means rare. These machines are often processing a wide range of different yarns. This inevitably increases the demands on efficient production and quality monitoring. In contrast to this, however, personnel numbers have steadily decreased in modern, thoroughly rationalized spinning mills (higher numbers of machines allocated to operating and maintenance personnel, leaner administration, etc.).
The higher the number of machines and the more complex the logistics in a spinning mill in terms of raw material and product diversity, the more important is comprehensive production monitoring (independent of personnel). This in turn is only assured if machine, production and quality data are available at all times, up-to-date and complete. Omissions in this context have serious effects: every undetected malfunction in the production process results in reduced machine efficiency, loss of output and thus directly in higher production costs. If not identified immediately, the production of defective yarn at the high output rates of modern rotor spinning machines results very quickly in enormous quantities of unusable or severely devalued yarn. If the faulty yarn is delivered and the defect only identified in the finished fabric, this results in additional compensation claims for the finished goods.
Systems for monitoring production have been on the market for some years and are offered by both machinery manufacturers and other suppliers. They usually consist of a central process computer with the relevant peripherals (printer and monitor) for data output. Each rotor spinning machine, or any other machine in the spinning mill equipped with the required sensors, is directly linked with the process computer via cable (see Fig. 47). All signals from the machine and the spinning positions are scanned, stored and processed at very short intervals. In contrast to the production machine, the storage capacity of the central computer permits long-term analysis of production and quality data.
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All essential machine production and quality data are available in tabular and graphic form. These include speeds, efficiency, stoppages and their causes, and many other data.
Printed reports are available both for individual machines and for groups of machines, organized according to the above-mentioned criteria. Reports are printed out automatically at the end of the shift or on request. Machines or spinning positions that fail to achieve the specified reference efficiency or exceed certain preset criteria (ends down, quality stops, etc.) are listed separately.
Mill management can use this information to analyze output, productivity and quality as a basis for decision-making on the deployment of personnel and technical aspects of production, such as changes in machine allocation when order bottlenecks arise, adjustments to machine settings in response to sudden changes in raw material quality and the relevant action in spinning preparation operations, etc.
Information is available to the Material Planning Department, for example for purchasing raw material (selecting raw material quality on the basis of cost/benefit criteria), planning material flow in accordance with productivity in the spinning mill, specifying spinning parameters (rotor speeds, yarn twist, etc.) according to the required yarn quality and monitoring order processing (number of kg produced, number of packages completed, etc).
Data on those machines that fail to achieve the required efficiency or exceed a certain ends down rate or a certain number of quality-related stops are available at all times to foremen or shift foremen. The foreman or mechanic can therefore concentrate solely on machines and spinning positions that are not running satisfactorily, and take the appropriate action without delay.
Maintenance personnel receive reports on spinning positions that are at a standstill, running unsatisfactorily or out of action, inadequate robot efficiency, etc., and can then immediately take the action they consider necessary. Periodic maintenance for machines and robots can be planned, performed and monitored on the basis of the operating hours of the rotor spinning machines.
Fig. 47 – System diagram of production monitoring; central computer with peripherals and connected production machines
