Preparation Requirements for Weaving Yarns Warp Yarns
Yarns must be aligned properly
Yarn strength must be increased
Yarn hairiness must be decreased
Yarn smoothness must be increased
Yarn elongation and flexibility must be sustained
Filling Yarns
Yarn must be wound properly and on a suitable package for high speed unwinding
Preparation Requirements for Knitting Yarns Weft Knitting
Yarn friction must be decreased Fiber shedding must be decreased Yarn smoothness must be increased
Warp Knitting
Yarn friction must be decreased
Fiber shedding must be decreased
Yarn smoothness must be increased
Yarns must be properly aligned for introduction to knitting needles
Yarn Preparation For Weaving And Knitting
Winding
Materials Processed
Input - Yarn (spinning bobbins)
Output - Yarn (large cones, tubes, etc.)
Objectives of the Process
· Inspect the yarn
· Clearing of defects
· Lubricate the yarn
· Package the yarn
Elements of Winding
· Yarn withdrawal
· Yarn tensioning
· Yarn clearing
· Stop motion
· Take up
Figure 8-1 Open Wind Coner
Yarn Preparation for Weaving
L Warping
A. An operation where yarn is transferred from single packages of yarn to an even sheet of yarn representing hundreds of ends and then wound onto a warp beam.
H. Producing An Even And Uniform Sheet Of Warp Yarn
A. The packages in the warper creel must be uniform in density, size, and wind configuration.
B. Tension applied in warping must be uniform throughout.
• C. Contact surfaces which the yarn passes must be smooth and must not impede the progress of the yarn.
D. The speed of the warper must not exceed that at which the yarn can be withdrawn from supply packages without undue strain.
E. Warp winding speed must be controlled and maintained at a constant rate throughout.
III. Direct Versus Indirect Warping
A. Direct Warping
1. Warp is wound directly onto section beams.
2. Used predominantly in preparing yarn for warp knitting and weaving.
B. Indirect Warping
1. Warp is wound in bands onto pattern drum and then transferred onto a beam in a separate operation.
2. Used for fancy pattern warps or where creel capacity is limited.
Figure 8-2 Single End Creels
Figure 8-3 Traveling Package Creel
Figure 8-4 Indirect Warping: Drum Warper
Slashing
L Objectives
A. Strengthen the yarn
B. Make outer surface of yarn smoother
C. Lubricate the yarn
D. Have no effect on subsequent processes or resulting fabric IL Why Warp Yarns Need To Be Strengthened
A. To overcome tension levels in the warp
1. Constant average tension determined by:
a. rate of take-up of cloth and let-off of warp
b. contraction of warp due to crimp
c. stretch of warp due to tension
2. Cycling variations in tension
a. due to shedding
b. due to beat-up
c. higher level in dense fabric
d. highest tension in cycle is where a weak yarn will break
3. Random variations in tension
a. due to large, badly shaped knot
b. yarn and fiber entanglements c. knot tails entangling
B. To overcome weaknesses in the yarn created by:
1. Yarn damage caused by the machine
2. Weak places in the yarn supplied
3. Inadequate distribution of load over all warp ends
4. Inadequate knotting or joining
III. Sections Of The Slasher
A. Beam creel
B. Size box
C. Drying unit
D. Warp separation
E. Headstock
IV. Size Add-On
V. Factors Affecting Size Add-On
A. Yarn characteristics
B. Number of ends and tension of warp
C. Squeeze roll control and conditions
D. Residence time of yarn in size box E. Viscosity of mix
VI. Important Ingredients In A Size Mix
A. Adhesives
B. Lubricants
C. Additives
D. Water or solvent
VII.Parameters Controlled In The Size Box
A. Level of size solution
B. Temperature
C. Concentration of size liquor
D. Squeeze roller pressure E. Yarn speed
VIII.New Sizing Techniques
A. High pressure squeezing
B. Hot melt sizing
C. Foam sizing
IX. Slashing Calculations
Figure 8-5 Slashing - Preparatory To Weaving
Requirements For A Quality Warp Beam
Objective: To Make A 'More Perfect Warp Beam"
· Ends wound straight and parallel to one another from beginning of beam to the end with each end holding its relative position in the warp with no "Rolled", "Crossed", "Stuck", or "Lost Ends".
· Tension uniform on all ends.
· Density of the warp is uniform from beginning of beam until full beam.
· . Selvage ends flat with the rest of the warp.
· Size added is uniformly applied on all ends and improves warp weaveability.
Warp Preparation
Drawing-In
Provides each warp yarn with its drop wire, heddle, and reed dent. Tying-In
When mass producing the same fabric by simply typing each end of a new beam to its corresponding end of the old beam
Side View Of A Loom
This sketch shows why the yarn must be flexible and lubricated to withstand the weaving operation. The warp sizing material must impart flexibility, elasticity, lubricity and abrasion resistance to the yarn.
