Lace fabrics want to do one thing above all else — and that is to please people. The knitting yarns
interact artistically with each other to create eye-catching, delicate pattern details and
attractive grounds.
The expertise and know-how of specialists are needed to efficiently produce these delicate
knitted fabrics with their many different patterns.
The lace raschel machines used must be able to work a wide range of different lappings and
process a variety of different materials – and this must be done at top speed. This is the ultimate
challenge, especially when it comes to feeding-in the yarn to the knitting point. It is
particularly difficult to reliably knit fancy yarns, such as Lurex, bourdon or viscose yarns, at
high machine speeds. This becomes even more difficult when these yarns are used as the pattern
yarns, because the yarn consumption fluctuates. A large amount of yarn is used to produce the
actual design elements, whereas less yarn is used when working the transition zones between them.
Yarn feed systems
In general, there are two ways of feeding pattern yarns on lace raschel machines. On the one
hand, creels having a large number of bobbins can be used, which is ideal for conventional,
standard production. On the other hand, pattern beams can be used, and these are particularly
beneficial when producing small- and medium-sized runs. The advantages of these include their low
space requirements, short setting-up times, low capital outlay and high level of flexibility.
Because of the nature of the technology, the yarn paths are short when using pattern beams, and
this is a prerequisite for processing more difficult fancy yarns, such as Lurex, bourdon or viscose
yarns. The yarns may become twisted when the yarn feed paths are long. However, in the past, the
use of pattern beams was restricted by the yarn feed being controlled passively. During the
knitting process, the yarn needed was taken off from the pattern beams and subjected to extreme
stress at high speeds. This meant that the speed had to be reduced to 600 min-1. KARL MAYER has
therefore developed active pattern beam drives to enable the efficiency potential of high-tech lace
raschel machines to be fully exploited. The positive pattern beam drive (PPD) has already been used
successfully on the JL 42/1 machine, among others, and presented in ‘Kettenwirk-Praxis’ 2/2010, pp.
38-39. The second generation of PPD, with his new features and customer-oriented improvements, is
now available.
PPD increases efficiency
An electric motor at every beam is responsible for delivering different amounts of yarn
accurately, even at high operating speeds. The drives are computer-controlled and guarantee
constant yarn tension levels, which are measured constantly in order to do this.
This allows lace raschel machines to achieve their top speed potential of up to 850 min-1 and
show that they are first-class machines. When processing different materials, the distortion and
looping that used to be visible to a greater or lesser extent are now minimised. A fabric with a
perfect appearance is produced.The positive, slip-free drive also means that time-consuming
balancing and re-balancing of the pattern beams are no longer necessary, which is an advantage in
terms of manpower requirements, storage and machine availability compared to operating with disc
brakes.
The construction of the pattern beams that can now be produced is also an additional benefit.
With package diameters of 14 cm, these yarn carriers have increased the running time by about 50
percent and make full use of the warping length, thus reducing downtimes compared to the old
system.
The actively driven pattern beams can also be used, for example, to work separating lines and
panel borders, even when the number of repeats is small. The version fitted with disc brakes needs
at least 10 to 12 threads for the yarns to run off. Compared to delivering yarns from the creel,
the changeover times for pattern beams are generally shorter when processing short runs and when
the yarn has to be changed frequently. The capital outlay is also lower and the storage
requirements are minimal.
User friendliness and machine availability
When developing the active pattern beam drive system for lace raschel machines, KARL MAYER
paid particular attention to the aspects of ergonomics and reliability. For example, all the
operating commands and relevant parameters are input at the Operator Interface (OI). The customer
can also allocate the pattern beam drives to the individual string bars at the OI.
KARL MAYER also thought of the user as far as the care and maintenance of this new system are
concerned. The drive unit consists of exceptionally high, maintenance-free components and can be
exchanged easily by the user. And last but not least, the entire concept makes it easier to change
the pattern beams.
PBW and PPD – a dual system that provides additional benefits
Another member of the machine range that enables the potential of high-tech lace raschel
machines to be fully exploited is the PBW 130/2 pattern beam warping machine.
This machine produces precision-wound pattern beams with an optimum biconical structure, and
thus guarantees perfect yarn running – even when processing difficult yarns. With their neat edges
and perfect wind, these precision-warped yarn carriers can be let-off perfectly at lace raschel
machines using the pattern beam drives. However, the PBW 130/2 not only operates with a high degree
of precision, it is also extremely fast. The warping speed of this pattern beam warping machine is
60% higher than that of the HDSM version.
Posted on January 21, 2011
Source: Karl Mayer Textilmaschinenfabrik GmbH