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Features

Rieter's C 60: Meeting Customers' Needs

New card provides improved efficiency, quality and flexibility.

TW Special Report

T he development of cards in recent decades directly illustrates considerable advances in production performance. New card models have been based primarily on detailed improvements to existing products.

With Switzerland-based Rieter Textile Systems' C 60 card, a high-performance card is now available that has been reconceived and developed from scratch. The new dimensions, therefore, refer not only to its geometric characteristics.

rieter
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Sliver count can be maintained by using Rieter’s C 60 card in conjunction with its RSB drafting mechanism and a card autoleveler.

Requirements

As early as the conceptual phase, the requirements were discussed and initial ideas for the design of the CX card were outlined in an introductory discussion workshop with experienced customers from the United States, Europe and Asia. Three main points emerged:

Cost: By reducing the capital and operating costs of the carding process in a spinning mill (cash per kilogram per hour [kg/h]), the emphasis was placed on the price of the system and overall operating costs rather than on the price of the machine.

Quality
: In the keenly contested yarn market, manufacturers are being confronted with demands to meet ever higher quality standards. At the same time, according to Rieter, cotton - the principal raw material - is tending to reach spinning mills in increasingly poorer quality. Higher demands on the technological qualities of cards, and especially their ability to reduce trash content, are therefore understandable.

Flexibility
: If they are to be successful in the future, a large proportion of spinning mills will need to offer a flexible product range, while also using the least expensive raw materials in the interests of profitability.

With regard to flexibility, Rieter reports it has already successfully met this requirement for some years in the case of its blowroom with the VarioSet concept.

Higher Output

The C 60 card enables output to be increased by some 50 percent compared to the C 51 Hi•Per•C ard, depending on raw material and yarn type. This is the most important - although not the only - response to the demand for a reduction in the cost of carding. The alternative approach to achieving the required card output - by means of an appropriate number of small, cheap and thus correspondingly low-performance cards - was dropped at an early stage.

Development in the direction of high output per machine only became interesting after initial basic experiments and design sketches showed that this could be achieved on the basis of the space requirements of a C 51 card. The high production performance has been achieved through the following features, among others:
•    increase in working width by 50 percent to 1,500 millimeters;
•   reduction in cylinder diameter and increase in take-off roll diameter; and
•    improved preparation for carding by means of an opening unit in the chute and the use of a triple licker-in.

Boosting output by increasing working width means there is no reduction in carding quality. The amount of material laid down on the cylinder is exactly the same on the C 60 at 150 kg/h as on a conventional card at 90 kg/h.

On conventional cards with a working width of 1 meter, high sliver weights have to be run at high production rates in order to keep the delivery speed within permissible limits (sliver weights greater than 6.6 ktex at 120 kg/h). High sliver weights mean high material density on the take-off, which has a negative impact on quality. By its very nature, so to speak, the C 60 delivers a 50-percent-heavier sliver with the same amount of material laid on the cylinder. Initial experience has shown that in most cases, the usual sliver coiler (CBA-4) can be used and the weight of the sliver can be reduced again to the customary level in the sub-sequent drafting passage. If a lighter sliver (3.5 to 6ktex) has to be delivered for any reason, even at high production rates, a coiler with an integrated non-leveling drafting system (SB module) can be used. The autoleveler version (RSB module) is used for the open-end (OE) direct process application described below.

Consistent High Quality

Not only high quality, but, above all, consistent quality is important. This is made possible by means of Rieter's pioneering developments and mill-oriented products, such as IGS-classic and IGS-top for automated grinding of the cylinder. Equipment of this kind can, to a large extent, correct the negative influence of clothing wear.

However, conceptual and design measures that keep the quality of output high and stable are just as important. The following features of the C 60 are among those that help maintain quality:
•    a complex chute-feed system with an opening roller and infeed via a feed trough;
•    uniform lap feed by means of active compression of the material; and
•    small cylinder diameter, which reduces the effect of temperature fluctuations on the size of the carding gap, thus permitting narrower settings without running any risk.

The high precision and, in some respects, innovative manufacture of the machine provides a further basis for stable and reliable operation.

Manufacturing Rotor-Spun Yarn

The C 60 is an excellent card for the rotor-spun yarn process, where primarily low trash and dust content in the card sliver affect not only yarn quality but also the productivity of the rotor spinning machine. With the opening unit in the chute and the triple licker-in referred to above, trash and dust are exposed and, for the most part, already removed in the licker-in zone. In the carding zone (cylinder/flats), much more intensive trash removal takes place than in cards of conventional design. This is due to the influence of the 50-percent increase in centrifugal forces resulting from the smaller cylinder diameter and higher cylinder speeds (See Figure 1).

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With the RSB coiler, a carding system with short-term leveling is now available from Rieter. This special coiler is essentially a complete autoleveler draw frame from the well-known RSB series. It is the result of close cooperation between Rieter's drafting and carding specialists. Maintaining counts at the beginning and end of a can is ensured virtually to the last centimeter by the integrated automatic control of the card and the coiler.

Since the C 60 delivers a 50-percent heavier sliver than conventional cards of the same quality, it is ideally suited for the direct process, because it makes technologically optimum drafts (2 to 2.5-fold) possible without any difficulty. Drafts at this level would result in sliver weights of 8 to 12 ktex on other cards, in conjunction with a corresponding loss of quality. Rotor-spun yarns can thus be manufactured in accordance with the requirements imposed using different processes.

Production Costs

All spinning mills are under severe, and in most cases global, competitive pressure. Rieter says its customers obtain products that give them a lead through quality improvements and innovations, such as COM4® yarn, as well as a succession of machines and equipment, such as the VarioSet blowroom, which enables the cost of manufacturing yarn to be reduced.

Rieter claims the C 60 card is not only the world's fastest card, but is also the most economical. Relative to its production rate, it has the following distinguishing features:
•    reasonable capital costs;
•    low energy consumption;
•    reduced maintenance and operating effort; and
•    reduced wear on the technology components.

These results are the outcome of clearly defined development targets. The goal of a 50-percent increase in the production rate compared with conventional cards was linked to the overall proviso that the floor space occupied could be no greater.

Meeting the requirement for the maximum possible service life of the costly clothing resulted almost as a side effect of the multiple material opening processes used for other reasons (chute, triple licker-in). Together with IGS-classic, the outcome is considerably higher output before reclothing is necessary. Rieter expects to obtain more exact quantitative results from ongoing experience with this new card.

An inherent problem of machines with high production rates is their major impact on the overall productivity of an installation. Whereas 15 cards were required for an output of 600 kg/h 20 years ago, only 4 or 5 are required today.

Instead of losing output of 7 percent when a card fails, today this figure is 20 to 25 percent. This was an important point both for Rieter and its key customers at the beginning of the conceptual phase of the C 60. The consequence is a strictly modular design with the following features:
•    A simple device enables the licker-in to be replaced as a unit.
•    The entire set of flats can be removed and replaced as a whole, or the flats can be removed individually from the machine.
•    The delivery unit can be completely removed from the machine.

Initial Experience

The time for market launch comes when a sufficient number of machines have been producing for many months with good results for customers in different regions. The results of a trial with an American customer, where older cards with short-term leveling attachments were to be replaced, were of special interest.

The output of these cards was 60 kg/h. This application is critical insofar as card sliver quality has a direct impact on yarn quality. The C 60 with the RSB module fulfilled this task so convincingly that the customer immediately ordered a large installation, which is now operational. The yarn values (IPI, CVm, elongation, strength) are all equal or better at a production rate of 150 kg/h on the C 60.

Production increases of 50 percent or greater also have been achieved with cotton/polyester blends, 100-percent polyester and various regenerated materials (See Figure 2).

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Conclusion And Thanks

Rieter wishes to thank its customers for the opportunity to test the new card in their mills. These field trials are enormously important for the everyday operating capability of Rieter's machines.

Operating reliability can only be verified in daily mill use, and this is one of the most important criteria for a machine featuring such high productivity. Field trials of this kind often disturb production in a mill, and the owners' willingness to cooperate cannot therefore be taken for granted.

March 2003



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