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Non-woven defect detection

This article highlights the main defects that are identified from non-woven inspection.

Non-woven fabric is a fabric-like material made from long fibres, bonded together by chemical, mechanical, heat or solvent treatment. The term non-woven comes from the fact that the fabrics are neither woven nor knitted.

A non-woven production process using the spun bonding method is widely used and accepted. One of the most widely used systems is a Reicofil system. In this system, a raw material is melted in an extruder and pushed through a spinneret to create a strand. Then, the strand is cooled in a chamber by passing through cold air, which flows into the system. The cooled strand is then formed to be non-woven fabric on a belt. The non-woven fabric is entered in a bonding process, wound, and then stored at a winder unit.

In this production process the majority of defects can be classified into 2 main groups:

  1. Appearance defectives - These are defects whose appearance do not fit customer requirements. The main types of apperance defects are: Filaments, holes, dust and lumps. 
  2. Non-appearance defectives - These are defects whose properties are out of specifications. 

Root cause defect determination

To determine the root cause of non-woven defects the 4M analysis is accepted among experienced operators in the non-woven production process. The 4M analysis approach focuses on:

  • Man
  • Machine
  • Material
  • Method 

This above approach involves analyzing each stage and element involved in the non-woven production process. Each individual stage will have different circumstances that interfere with the material and can lead to the introduction of defects. The above approach can be used to determine the cause of filament break, hole, dust and lumps. The defects share a common root cause and usually occur due to spinning conditions. These three defects may often be combined into one group as they can be solved by adjusting the same parameter condition. 

Some of the key causes of defects that can be identified from the 4M analysis are:

  • Cabin pressure - This is a parameter which affects AirFlow. AirFlow can be increased in a spinning region by increasing cabin pressure. 
  • Die temperature - This is used to heat up polymer before the material is sent to a spinning zone. Die tempature can be used to adjust melt tempature, however it might cause polymer degradation if the tempature is set too high. 
  • Cooling air temperature - This is used to transfer melted polymer to solid polymer. This heat exchange between melted polymer and cooling air affects impacts the strength of the polymer. 
  • Suction speed - This is used to balance air-to-polymer during the spinning process.

The image below shows an example of a non-woven material going through a production line. 

Non-woven production line

Some of this article was referenced from 'Apperance Defective Reduction in Nonwoven Process' written by Worapot Rodraksa and Wipawee Tharmmphornphilas for the International MultiConfrence of Engineers and Computer Scientists 2013, which took place in HongKong. This article was later published by INDA, Association Of The Non-woven Fabrics Industry. 

Conclusion 

In the non-woven production process the majority of the waste produced come from appearance defects. The major appearance defects to represent this waste are; filament breaks, holes and lumps. OneBoxVision's 100% inspection solutions for non-woven are completely configurable to detect both appearance and non-appearance defects. Contact us today to learn more about our non-woven inspection.

Follow the link below to download our whitepaper on specifying your non-woven inspection system. 

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Topics: Vision system solutions Vision network Surface inspection systems 100% Inspection ImageFlow