working principle scutching line

Bast fibres are the family of plants consisting of a wooden core with bast around it, in which fibre supports the plants. The best-known bast fibre plants are flax, hemp, kenaf, ramie and nettle.

After the harvesting of the plant, one let stay the plant on the field for the retting process. This retting process is a chemical process, which solves the pectin’s sticking the fibres together with the bast and the wooden core. Once the plant is sufficiently retted it will be baled and stored.

The bast fibres are the most suitable and stable natural fibres for automotive industries, insulation materials and for making composites (composite carbon – natural fibre and plastics).

A scutching line is a process unit in which the bast fibre plant is transformed or split into his basic parts: the wooden core named shives, the fibres and seeds. While transforming the plant, the fibres are kept at full length so at the end they can be cut on the length needed for the further processing (length needed for paper making, for making composites, for making non-woven).

The scutching lines produced by Demaitere are based on the very old manual principle: the "Flemish Scutching mill", in which a person by means of wooden flaps scrapes on the manually presented flaxstraw.

This principle has been automated by Julien Demaitere and has been redesigned to obtain the actual industrial equipment.

This industrial equipment contains the following parts:

• Opening the bales

To make it possible to process the straw, one has to open the bales. This is done automatically by a bale breaker followed by an opener-divider, which makes a continuous layer of straw.

• Breaking or crimping the straw

Breaking or crimping the straw is crimping the wooden core of the plant in parts of about 2 cm without damaging the fibre.

• Scutching

The scutching unit is a processunit in which the layer of straw is presented through retaining rolls to a rotating drum with spring steel blades mounted on its outline.

These steel blades on the outline of the drum have a speed of about 120 km/hour and are scraping off the broken wooden parts (shives) from the fibres. In this process the fibre is kept at full length and is not damaged. The minimum length of the straw that can be processed is 5 cm; the maximum length is about 120 cm.

The capacity of a line is determined by the number of drums in the processing line and the grade of cleanness of the fibre that has to be obtained.

• Rough scutching

In the first stage of a processing line we are using a drum with a width of 1.7m, capable to transform max. 4 tons straw/ hour.

In this drum the distance between the retaining point and the blades on the drum is about 3 cm. This means we can process a big layer of straw with loosing the largest part of the wooden shives, shives that are scraped off of the fibre.

• Fine scutching

In the second stage of a processing line we are using a drum with a width of 1.2m.

The fibres are presented to the drum between a retracting roll and a retracting blade. The distance between the retaining point and the blades on the drum is adjustable between 5 mm and 12 mm. This means that the steel blades are passing very close to the layer with the result that the fine layer is scraped completely.

• Shaking screens

Between the scutching drums we are using shaking screens. On this shaking screens we are shaking up the fibres while transporting. The transporting is a kind of pelgrimswalk with the result that loose shives are falling out of the layer of material.

 

• Cutting and baling

At the end of the line we obtain a cleaned fibre (cleanness is balance between capacity of the line and quality to be obtained).

While transforming the plant, the fibres are kept at full length so at the end they can be cut on the length needed for the further processing (length needed for paper making, for making composites, for making non-woven). After cutting the fibres are baled in by an automatic hydraulical baling press and stored.

 

 

Throughout the world, bast fibres are grown commercially for industry.  The fibres after processing are then used by a diverse range of industrial sectors ranging from textiles to the automotive industry.  As a raw material, the processed bales are a valuable commodity and are also speculated on world markets.

Please feel free to contact us for further information.

See also www.vandommele.be, this is a collaborating company that manufactures bale openers, bale presses, industrial dedusting and shives treatment.