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Warp knitting machines can be built with one or with two needle bars, thus, forming one
or two stitch courses per main shaft revolution. This fact often results in confusions when describing the productivity and fabric parameters of these machines.
A standardized definition of the relevant technical criteria is meant to remedy this matter.




Fig:Knitting elements of Karl Mayer
double needle bar

Rack
The only meaning of one "Rack" is : 480 main shaft revolutions. In other words: a warp knitting machine with one needle bar produces 480 stitch courses per Rack, at 480 main shaft revolutions, whereas a double-bar warp knitting machine produces 960 stitch courses during this cycle: i.e. 480 stitches on the front needle bar and 480 stitches on the rear needle bar. Thus, one guide bar can form max 960 stitches per Rack.

Yarn run-in

The yarn required during this cycle represents the "yarn run-in" value.
The unit of measure is "mm/Rack" and refers to 480 main shaft revolutions on double-bar machines.
This means: for the same lapping, the yarn run-in of a single-bar warp knitting machine can be compared to that of a double-bar machine working on one needle bar only.

Knitting line (ZLN)

The designation "knitting line" can also be used for one main shaft revolution. Thus,one knitting line for double-bar machines consists of one stitch-forming cycle, to from a course on the front and on the rear needle bar.
Nevertheless, special attention should always be paid to the type of stitch notation to be worked. If a thread should be interlaced by one needle bar only or should be kept as weft construction (inlay lap), it has to float on the opposite needle bar. Later on this float lap does not appear in the fabric, thus, not requiring any additional yarn run-in.
Connecting spacer/pile threads are always interlaced on both needle bars.
In this way,a stitch is usually formed on the front needle bar, underlap to the rear
needle bar, one stitch on the rear needle bar and the underlap back again to the front
needle bar.
In most cases, it is sufficient to use the term "knitting line" for
defining the yarn run-in value for double-bar Raschel machines. In special cases, however, this yarn run-in value has to be specified per stitch, separately for each needle bar, for which a sequential yarn feeding system is required. KARL MAYER's new computer generations will make it possible to enter an exact yarn feeding value to match the stitch courses. The input of this parameter can be done via a sub-menu on the
control panel of the MSM configuration (Multi Speed Motion) (in this context, please also
see the example given below.) This system will result in identical yarn run-in values on double-bar machines, regardless of the yarn feeding type.


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Repeat-length

The description of a pattern is done by means of the term "repeat length".
For electronically controlled machines, the repeat length is defined by knitting lines. The shortest repeat length is one course, consisting of one stitch-forming cycle each on the front needle bar and on the rear needle bar (for double-bar warp knitting machines).

Number of stitches
The number of stitches is a measure for the quality of the knitted fabric, having a direct influence on the productivity of the warp knitting machine.
KARL MAYER will specify this no. of stitches also for double-bar machines in such a way that the set number of stitches per centimeter on the fabric take-up will coincide with the number of stitches per centimeter on one fabric face.

Machine speed

The machine speed will only be specified as main shaft revolutions per minute.
Based on the same number of stitches, an identical calculation of the machine performance is possible for single-bar and double-bar machines.
This standardized denomination of the technical details will surely facilitate the exchange of information,helping to avoid misunderstandings.
It will be part of KARL MAYER's new development and use for all warp knitting machines equipped with the new electronic concept starting from 01.01.2005.This definitions have been discussed and agreed upon with LIBA Maschinenfabric GmbH in Naila and with members of Standards Committee for Textile Machinery.Nevertheless,this nomenclature is not yet part of new ISO standards.