Thread breakage

A thread break is in the textile technology tearing of fibers , yarns or twines . The production of the threads that have just been produced or that have already been processed must then be stopped. The tear strength then did not correspond to the standard intended for processing at one point.

The production on the ring spinning machines and weaving machines is afflicted with a high frequency of thread breaks; in both cases the thread break must be repaired manually. Thread breaks can also affect rotor spinning machines and winding machines , but here they can be fixed by robots or automatic machines. Thanks to the development of so-called relative technology , the number of thread breaks per hour compared to conventional circular knitting machines has been reduced from an average of 3 to a maximum of 1.

Ring spinning machines

Causes of thread breakage

Thread guide on the ring spinning machine

The factors that influence the frequency of thread breakage are the raw material processed, the technology, the condition of the production facilities, the climatic conditions in the production room and the personnel. The most common thread breaks occur between the drafting system (1 in the picture) and the tip of the spindle (4). When the thread breaks, the end of the finished yarn is wound onto the cop , while the fiber sliver running out of the drafting system is fed into the tube of the suction system (2).

Fix thread breakage

The machine operator stops the spindle with cops, unwinds about 0.5 meters of yarn, pulls it through the traveler (5), the thread guide (3) and executes the piecing , i.e. That is, the thread end connects to the fiber sliver just below the drafting system so that the fibers twist into the spiral together with the finished yarn. The process described takes about 1/4 minute with deviations depending on the type of material, etc. The operation of the ring spinning machine is usually organized in such a way that the worker carries out various tasks during a tour of the assigned machines Thread breakage repair is busy (approx. 120 piecings / hour). The frequency of thread breakage varies greatly from 2 to 10 cases per kilogram of thread. The specialist literature does not give any average values; the results vary particularly widely for smaller spinning lots. In many companies the necessary data is not systematically recorded.

Business aspects

If 40 million tons of yarn are produced on ring spinning machines worldwide every year, with an average of 4 yarn breaks / kg, at least 600,000 employees are exclusively engaged in yarn breakage repair. Thread breaks cause a 2–5% loss in production capacity. The proportion of yarn breaks in yarn production costs can reach up to 10% in countries with high wages.

In Germany, some prototypes of mobile piecing robots have been tested under operating conditions since the 1980s . The tests did not lead to a positive result, because currently (2012) no manufacturer offers such devices.

Looms

Causes of thread breakage

In addition to the same factors as with ring spinning machines, the properties of the yarn are by far the most important factor for the running behavior of the loom. The yarn quality features include tear resistance and elongation, which are essentially dependent on the raw material used. Carded yarns achieve a tensile strength of 5 to 7 cN / tex, combed cotton yarns three times that, and synthetic filament yarns are ten times more tear-resistant.

For these reasons, the performance parameters of the loom can practically only be fully exploited with warp threads made of synthetic fibers. Yarn evenness and cleanliness are strongly influenced by the production conditions in the spinning mill. All yarns are electronically checked on the winding machine and errors can largely be eliminated by cutting them out.

A test in which the finished yarn is electronically scanned, accurate information on uniformity, number of may thin and thick places and neps supply. On the basis of these tests, Etalons (sample pieces) have been published in Switzerland for several decades, with which each spinning batch can be compared and classified in relation to global competition (Uster Statistics).

Thread breaks can occur both in the warp and in the weft, the cause depends on the loom used. Possible causes for thread breaks in the weft are:

• Rapier loom
  • The weft thread brake was not set correctly (is closed or opened too early or too late), therefore too much or too little tension in the weft thread
  • The looper clamp is dirty and could not clamp the weft thread properly
  • Not enough clamping force in the gripper head (with strap grippers)
  • The weft guards were not set correctly
• Air jet loom
  • Too little or too much main jet pressure
  • The weft thread is not kept properly taut on the weft insertion side and jumps back into the shed
  • The stopper finger closes too early or too late
  • Too high pressure on the bristle ring on the weft storage device
  • There is no monitoring between the cheese and the weft thread storage device, thread breaks in the area can enter the shed unhindered
• Projectile loom
  • The projectile clamp does not clamp the weft thread properly
  • The weft brake has not been set correctly
  • The weft thread was too fine and broke when accelerating

Possible causes of thread breaks in the warp are:

• Rapier loom
  • The looper head rubs against the warp threads
  • The compartment opening was not coordinated with the entry and exit of the gripper
• Air jet loom
  • The air pressure can damage the warp threads
• Projectile loom
  • The compartment is opened too early or too late, causing the projectile to shoot warp threads

Fix thread breakage

Front compartment of the loom

The photo on the right shows the front compartment of the loom where most of the thread breaks occur. The warp threads (1) mainly tear between the strands (2) and the beginning of the finished fabric (3). In the event of a thread break, the machine stops immediately. The weaver has to find the end of the thread, tie up a missing piece of thread, pull it through the reed (5) and knot both thread ends. If the break occurs in front of the shaft, the thread must first go through the strand.

A small part of the thread breaks occur in the back compartment. The number of weft breaks (4) is also relatively low.

Business aspects

Some studies show that the thread breakage costs when processing staple yarns on the weaving machine are 3 to 4 times higher than on the ring spinning machine (based on 1 kg of yarn). In contrast, modern air-jet weaving machines can produce up to 3 kg of fabric from textured warp threads with just one thread break. Under these conditions, the yarn breakage costs are roughly the same as on the ring spinning machine.

Tissue defects

All products of the weaving mill are visually checked before delivery and the errors are recorded. As a rule, the proportion of fabric defects caused by thread breaks is low. The criteria for error assessment are not standardized internationally. A statistical recording as with the yarn defects is only in the test stage. In the case of expensive fabrics, mainly wool-like fabrics, defects are repaired by darning and knobs before delivery. In some weaving mills, photo-electronic controls are installed directly on the weaving machines.

literature

• Schenek: Lexicon of yarns and twisted threads . Deutscher Fachverlag, 2005, ISBN 3-87150-810-1 .
• Weaving technique. ISBN 3-926685-39-5 , employers group Gesamttextil, Frankfurt / Main 1988.
• Berner, Koslowski: Chemical fiber dictionary. ISBN 3-87150-185-9 , Deutscher Fachverlag, Frankfurt / Main 1983.

Individual evidence

1. ^ Paul-August Koch, Günther Satlow: Large Textile Lexicon. Specialized lexicon for the entire textile industry. Deutsche Verlags-Anstalt, Stuttgart 1965, Vol. A – K, p. 356.
2. ↑ Alois Kießling, Max Matthes: Textile specialist dictionary. Fachverlag Schiele & Schön, Berlin 1993, ISBN 3-7949-0546-6 , p. 110.
3. ↑ Anton Schenek: Encyclopedia yarns and threads. Properties and manufacture of textile threads. Deutscher Fachverlag, Frankfurt am Main 2006, ISBN 3-87150-810-1 , p. 138.
4. ↑ Development and future of the circular knitting machine. The costs become the decisive success factor. ( Memento from September 23, 2006 in the Internet Archive ). In: mayercie.de. April 5, 2005.
5. ↑ rieter.com
6. ↑ Page no longer available , search in web archives: zakkum.com
7. ↑ Page no longer available , search in web archives: lenzing.com (PDF)
8. ↑ Page no longer available , search in web archives: lindauer-dornier.com (PDF)
9. ↑ mittex.ch. ( Memento of March 2, 2006 in the Internet Archive ).
10. ↑ Cyclops: Functional Principle. ( Memento of May 24, 2006 in the Internet Archive ). In: barco.com.