Oerlikon Schlafhorst Express - Oerlikon Schlafhorst - Oerlikon Textile

Technology
PreciFX successful in application
for S-twist yarns
Bigger format – better unwinding behaviour – less handling
We reported on the advantages of processing S-twist yarns with
PreciFX on the Autoconer in Oerlikon Schlafhorst Express 3/2009. In
this issue, we will demonstrate these advantages once again with
reference to results obtained in practice.
Increasing efficiency in the knitting mill
The challenge for the Oerlikon Schlafhorst technologists was to
produce packages of the same format for customers both for
S-twist and Z-twist yarns. To achieve top quality and dimensional
stability of knits, the knitting machine is supplied alternately with
S-twist yarns and Z-twist yarns during the knitting process in these
applications. This should effectively prevent twisting and the tendency
of the knit to twist.
The problem up to now lay in the limiting of the package diameter
for the S-twist yarns due to the deterioration in unwinding behaviour
in larger diameter ranges. The package weight limit for S-twist yarns
was 985 g compared with a weight of 1.89 kg for packages with
Z-twist yarn.
Thanks to the optimised package build, large-format packages for
S-twist yarns with the same weight of 1.89 kg as the packages of
Z-twist yarns could be produced successfully using PreciFX. 100% CO
of a count of Ne 60 was processed.
The following winding parameters were set:
PreciFX Package Plus
“PreciFX number of groove turns”: 3.5gg
Yarn tension (Autotense FX ): 16 cN
Cradle contact pressure: 30 N
Winding speed: 1,200 m/min
Oerlikon Schlafhorst Express 13
The customer was extremely satisfied with the result. The handling
times in the knitting process were dramatically reduced, as feeding
of the S-twist yarn packages is no longer necessary. This means
shorter downtimes for the knitting machines. And the S-twist packages
run smoothly.
Less handling during winding - maximised take-up speeds
For another customer there were two reasons why the processing of
S-twist yarns was very uneconomical.
• First, the limited take-up speed in downstream processing of
S-twist yarns on account of entanglements due to compromises
in package build with the drum winding system
• Second, the excessive amount of handling involved including
hardware exchange and the change from right-hand to left-hand
winding cradle for processing S-twist yarns
PreciFX is the solution to both these problems. Due to the softwarecontrolled
yarn placement and the individual parameter selection
(angle of wind, edge and flank configuration, taper and position of
crossing point), the package build could be designed so specifically
that it proved possible for the first time with this optimised PreciFX
package structure to wind the S-twist yarns even in right-hand
winding (thus p-winding). The result is that these S-twist yarn packages
run smoothly even at considerably increased take-up speeds of e.g.
300-400 to 900 m/min. The customer established delightedly that
he has virtually limitless flexibility in the winding mill product
programme, as a switch from S-twist to Z-twist yarn or vice-versa is
achieved at lightning speed and without much handling effort. And
productivity increased dramatically in downstream processing.
These results were achieved with a wide variety of yarns e.g. CO,
CO compact, modal in various count ranges.