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Loepfe's solutions for spinning needs

Feb 01, 2015

Loepfe Brothers is a manufacturer of sensors and monitoring equipment for yarn spinning and fabric weaving processes.
Loepfe Brothers Ltd was founded in 1955 by the brothers Helmut and Erich Loepfe. The company´s electronic control systems are used with success in spinning mills, weaving mills and other textile industries. All Loepfe products are 100 per cent produced in Wetzikon/Switzerland facilities with the most modern production technologies. The company´s technical competence in the textile, electronics and information technology areas as well as the intensive personal contact with our customers all over the world make our products innovative and trend-setting. The high benefit provided by Loepfe products secures leading market positions for our customers and partners.

YarnMaster P-Sensor
The problem

Yarn contamination by white or transparent polypropylene causes production and quality losses. The contamination of cotton with synthetic foreign matter results mainly from contaminated cotton fields and packaging remnants. During processing in the spinning preparatory mill they become smaller and are evenly distributed during folding. Foreign matter elimination when opening the bale can reduce the cut numbers in the winding process by only 10 percent. Experience shows that every fifth machine stop during sectional warping and beam warping is due to polypropylene contamination. Yarn strength is reduced because there are fewer fibres in the cross-section. In addition, hooking can cause machine standstills. The later the standstills occur in the process, the higher the costs incurred.

White polypropylene becomes visible only after dyeing. Clearing improves the yarn standard considerably and prevents costly complaints concerning the dyed end product.

The solution
Polypropylene Detection:
Polypropylene (PP) and other synthetic foreign matter that is transparent and identical in color with cotton/wool can hardly be detected with conventional, optical foreign fibre clearing.

Loepfe has developed the P-Sensor to overcome these problems. This sensor detects synthetic foreign fibres:

  • Irrespective of the color of the yarn and the foreign matter, for example, white and transparent polypropylene in raw-white yarn
  • Even the finest foreign fibres
  • With highest reliability thanks to many years of practical experience

Operating principle: While the yarn passes the P-Sensor, the fibres exchange electrons with the sensor. This effect is referred to as ´triboelectric effect´. It is continuously measured with the latest state-of-the-art electronics. When a synthetic fibre passes the electrode of the sensor, it is detected because of the triboelectric voltage difference. The YarnMaster ZENIT FP yarn clearer thus detects synthetic foreign matter, such as polypropylene, polyethylene, polyamide (nylon), etc


  • Efficiency of downstream processes of the spinning mill is clearly increased.
  • Complaints because of foreign matter in the finished, dyed fabric are reduced. In this stage, undyed yarn particles would result in costly faults.
  • The door to the most demanding market segment is opened. In this segment, yarn cleared from polypropylene is the basic prerequisite.
  • Higher margins can be achieved for yarn with a high quality standard.


Loepfe provides optimum solutions with the optical and triboelectric measuring processes. Using a measuring system with limited capability and low reliability is unnecessary and not economical.
Optical: Detection and clearing of yarn faults as well as f