Wednesday, 2 June 2010

Warp Knitting | Spandex Fiber Handling and Warping Processing

Opening cases
Take care not to damage the thread with any sharp instrument that may be used to cut  open the carton.
Once opened - pull the plastic bag liner over the sides of the case to prevent contact of the spandex liner, which could disturb the wind and affect the performance in knitting.
Although not an absolute requirement, some users of spandex fibers prefer to open cartons in the same environment in which it will be processed for a period of 24 hours prior to its use.
Removal of packages
Remove the returnable black separator tray by grasping the handle holds and pulling straight up to prevent contact with the layer of spandex packages below.
Grasp the spandex package by positioning the thumb (not thumb nail) in the top center of the package with one or more of the remaining fingers placed inside the tube, again avoid contact with the edges or shoulders of the package.
Handle only one package at a time. Stacking, cradling or otherwise transporting more than one tube or cone at a time dramatically increases the likelihood that the package may be bumped and the wind may be disturbed causing running tension variation and breaks.
The use of a tray, pin truck or other suitable carrier is recommended for handling multiple packages by one operator.
Briefly inspect the package for "fall-overs" (spandex ends fallen off the edge of the package). If "fall-overs" are found, clear by lightly pinching the top center of the package with the thumb and forefinger (do not pinch with fingernails) and pulling the spandex over the edge of the package until a single end remains, or gently roll the "fall-off" ends back onto the surface of the package using the fleshy part of your palm, which must be free of
callouses or skin burns.

Thread up
Remove empty spandex packages from the let-off rolls and place them aside leaving the threaded spandex end in machines. Place the new full package on the let-off rolls. Tie the threaded end to the loose end on the new package. A square knot is commonly used but other knots are adequate.
Once positioned and tied, adjust the tension on the spandex so as to ensure "enough" tension to prevent the spandex from back winding on the let-off rolls, but not an "excessive" amount that would result in breaks due to exceeding the ultimate elongation of the spandex.
A good spandex stretch ratio1 starting point is 3 to 1 (200%), however higher stretch ratios are likely and will be dictated by fabric requirements (stretch, density, % components etc.)
When practical, jog knots slowly through before increasing to full speed.
The following recommendations are suggested  to maximize warping efficiency:
Yarn Conditioning
Condition the yarn for 24 hours in the same room or climate where warping will take place. The temperature in the warping room should be 68 to 72° F (20 to 22° C) and relative humidity of 60 to 65%.
The yarn should be used first in, first out as supplied. Do not use packages of different weights, sizes or age.
The yarn tubes should be handled very carefully so that outside yarn layers are not disturbed. Outside yarn layers should not be touched.
The yarn should be loaded randomly in such a manner that tubes from the same box do not lie next to one another in the warp.
If the creel is scheduled to be down for any length of time, then the tubes must be stored back in the original shipping cartons out of light and protected from atmospheric fumes.
Pre-tension Elongations - For those warping machines using a pre-tension feature, pretension is a function of the desired final warp beam elongation.
Raschel Fabric - For 25% final elongation on beams, use a 70% to 100% pre- tension. For 50% final elongation on beams, use a 100% to 150% pre-tension.
For warping machines without a pre-tension feature, a standard level of final elongation is 40 to 50%.
Tricot Fabric - On 40 denier  spandex, recommended warping stretch should be 50% to 100% depending upon customer preference.For 70 denier and higher it is recommended to use 50% to 100% final stretch.
Care and Handling of Warp Beams
After warping, beams should be wrapped carefully with cellophane or other BHT –free nonporous film to protect the  spandex from contaminants during storage and handling. Beams should be kept wrapped and stored in shipping racks until ready for use.
General Precautions
Beams left on the knitting machine for any extended downtime should be wrapped in BHT-free nonporous film to protect  the spandex  from contamination and discoloration.
Storage of beams at temperatures above 95° F (35° C) or below 20° F (-7° C) should be avoided. These temperatures could cause adverse effects on processing performance.
source: radici spandex