Jan 17, 2011
Positive pattern beam drive (PPD) - for maximum efficiency and first-class fabric quality. Lace fabrics want to do one thing above all else
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 (Fig. 1), 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.