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Weak spot tester

The importance of detecting weak spots in yarns

DYNAJET
DYNAJET
When yarns are processed on winding-, twisting-, weaving-, or knitting machines, they are subjected to tensile forces at different levels. If those forces exceed the breaking strength of the yarn, breakage occurs. Yarn breakages result in down time and may cause faults in the end product.

As a rule, the average breaking strength as measured with a conventional static tensile tester is clearly higher than the tensile forces in the manufacturing process. On the other hand, staple fibre spun yarns inevitably contain weak spots, for example very thin places, yarn segments with inclusions of foreign matter, sections with thermal damage, or else, whose strength falls under the tensile forces of the manufacturing process leading to yarn breakage.

Conventional tensile tests are normally not suitable for detecting weak spots with sufficient statistical probability as the tested yarn length is very small compared to the large distance of hundreds or thousands of meters between individual weak spots.

DYNAJET 

In the development of this tester a new path has been pioneered, which is distinguished by formerly unattained efficiency. At the DYNAJET the yarn passes with high speed of up to 1000 m/min through a test section and thereafter through a nip roller/apron feeding device into a suction orifice. Within the test section the yarn is subjected to a tensile force which remains absolutely constant throughout the test. The level of this tensile force can be freely selected to simulate actual manufacturing process conditions. In case of yarn rupture the tester stops immediately for subsequent manual rethreading.

The fully automatic version of the tester (DYNAJET PLUS) employs a rotating arm which rethreads the yarn into the test section after breakage.

Beside its very high level of efficiency this test method is characterized by its particular simulation of manufacturing processes. In both cases the yarn runs with high speed into a zone with high tensile stresses, resulting in extremely high rates of loading. A further interesting feature is the collection of broken yarn ends, which enables to analyze whether yarn breakages were due to raw material or defects of the spinning process.

Control of the test process as well as measured data evaluation including number of yarn breaks and statistical analysis is provided by the Textechno TESTCONTROL system, consisting of  PC and Textechno software.

Technical data

  • Yarn feed by nip roller/apron delivery device with automatic traversing motion,
    speed range 10...1000 m/min,
    suction clearing of waste yarn
  • Tensile-force generation by motor-driven godet controlled via downstream force sensor,
    max. tensile force 1000 cN;
  • Base cabinet with waste yarn collecting chamber (optional).

Further technical data

Mains supply:

230 V, 50 (60) Hz, current requirement approx. 1 A

Compressed-air supply:

6 bar, 150 l/min

Lacquer finish:  

RAL 9006/5002

Dimensions :

Height 300 mm, width 650 mm,  depth 550 mm, weight (without base cabinet): approx. 45 kg

The above technical contents can be subject to changes by Textechno.

 
 
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