Influence of the mechanical harvesting method on ring and rotor
up to the end product
by Harald Schwippl, Head
Technology, After Sales.
In a joint cooperation between the Cotton Institute
of South Africa and Rieter, the two commonly used methods of
mechanical cotton harvesting were compared with each other. The
comprehensive test and its results are available in a special
print (see QR code for entire report). We are pleased to
present some of the interesting extracts from the project.
Cotton is still the dominant staple fibre in
Africa, and almost 1.4 million tons of cotton were produced
2013. That corresponds to about 5% of global production. In
South Africa, approx. 9000 tons of cotton are harvested
Two different methods of cotton harvesting were
each examined at two different farms. The comparison was carried
out through to the knitted fabric, whereby carded ring and rotor
yarns with various counts were spun. Not only the yarns and
knitted fabrics were tested but also interim products, to be
able to better interpret the effects on the yarn and the knits.
Today there are two common mechanical methods for
harvesting cotton – the spindle method and the stripper method.
Fig.1: The mechanical cotton harvesting methods currently
in use are the
spindle and the stripper methods.
These two methods differ in productivity and
quality. The stripper method has many advantages, such as lower
investment costs, lower fuel consumption and higher harvest
yields, which, however, can increase the proportion of immature
fibres. Also known is that the cotton harvested with the
stripper picker exhibits a higher seed coat content. (Fig.
Fig. 2 The cotton harvested by the spindle method (left)
contains fewer trash particles than the cotton harvested
by the stripper method (right).
The fibre length, in particular, short fibre ratio
and mean fibre length, have a strong influence on the yarn
Across the process line, a mean staple 1 to 2 mm
longer is seen with the spindle method compared to the stripper
method. Thus, as far as evenness is concerned, a positive result
in the yarn and in the knitted fabric is also to be expected.
Also decisive here is, however, how great the influence is of
the two yarn structures, ring, and rotor as seen in the figure.
Fig. 3 Across the process stages, the spindle method
exhibited a 1 – 2 mm longer mean staple.
The quality criteria of the ring yarn show that the
spindle method gives somewhat better yarn results than the
stripper method. With rotor yarn, no evident differences between
the two harvesting methods are detectable.
Knitted fabric comparisons
The knitted fabrics made of rotor yarn have a far
better evenness than those made of ring yarn. This means that
the influence of the end spinning system on the knitted fabric
quality is far higher than the influence of the harvesting
method. Nevertheless, the positive influence of the spindle
method, at least with one farmer, is recognizable even in
knitted fabric made of rotor yarn
Fig. 4: Knits from rotor yarn, 100% cotton, Ne 24, 4.2 αe.
in the special print
The special print includes the complete,
comprehensive data and detailed explanations and background
information. It can be ordered under email@example.com.
Electronically, the special print can be downloaded with the
given QR code (Fig.5).
Fig. 5 QR code for scanning and downloading the special