Test 2 Example_Keys
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North Carolina State University *
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252
Subject
Industrial Engineering
Date
Dec 6, 2023
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5
Uploaded by MasterFreedom8483
1
TT 252 FORMATION AND STRUCTURE OF TEXTILE FABRICS
Example of Test 2
Yarn Preparation
Name:
ID:
Question 1
a)
What are the objectives of the sizing process?
(4 points)
The primary objective of the sizing process is to prepare warp yarns to withstand the
stresses of the weaving process.
A secondary objective is to modify the characteristics (such as weight, stiffness, or hand)
pf the woven fabric.
b)
Define the following terms:
(4 points)
Size penetration:
size penetration is measure by the distance that the size material
penetrated through the yarn (expressed as % of yarn radius)
Waiting for service (stop time) in winding:
one of the downtime items when the service
station can only serve one position at a time while keeping other positions waiting to be
served
Creel capacity in warping:
defined as the maximum number of supply packages that the
creel can hold
Splicing:
the forming of a joint between two yarns or two parts of the same yarn by
partly untwisting (usually with air) and then entangling fibers together, without making
a knot
c)
Mention one function for each of the following:
(4 points)
Heating zone in sizing machine:
drive the water away and leave the solid
material with the yarn
Yarn tension device in winding:
break the yarn at weak spots
Creel of a warping machine:
to hold and supply wound packages
Lubricant in a size mix:
to reduce the coefficient of friction and therefore the
surface frictional force of yarn
d)
Mention two differences between:
(4 points)
Manual and automatic drawing-in
Manual drawing-in is slow and time consuming.
While, automatic drawing-in is more efficient.
Manual drawing-in is mainly done when the plant does not run a broad range of
styles. Automatic drawing-in machine is expensive but it is necessary when dealing
with frequent style changes.
Drawing-in and tying-in processes
Drawing-in process is performed in drawing-in room.
While, tying-in process is performed at the loom.
Drawing-in is performed if a new style is to be woven.
While, tying-in is performed if the style running on the machine is to be continued.
2
Question 1 (continued)
e)
Draw the following graphs:
(5 points)
i.
Effect of size encapsulation on number of warp yarn breaks during weaving
ii.
Effect of % size add-on on number of warp yarn breaks during weaving
f)
The graph below shows the effect of % size penetration on number of warp yarn
breaks during weaving. Explain why the number of warp breaks increases with too low
or too high % size penetration. (4 points)
When the % size penetration is too low, the size material will fall off from the yarn, which
defeated the purpose of sizing. All the hairiness and entanglements will appear and yarns
will break more frequently.
When the % size penetration is too high, with the % size add-on fixed, the size
encapsulation will decrease which will lead to more breaks due to more hairiness. The high
% size penetration will also make sized yarns too stiff, causing the elongation to be low.
Stiff yarns tend to break more during weaving as a certain level of elongation is usually
required for weaving.
20
15
10
5
0
0
10
20
30
40
50
Size Penetration, %
Number of Warp Breaks
3
Question 2
(50 Points)
For the following statements, circle T (for true) or F (for False):
T
F
Spindle drive winders use a reciprocating guide for yarn traverse.
T
F
One objective of the warping process is to inspect yarns and remove weak
spots and defects.
T
F
The mode of yarn traverse during winding dictates the package shape.
T
F
In cross winding, packages with flanges are required to prevent slough off.
T
F
Yarn clearing refers to removing yarn defects (such as thin places, thick places,
and slubs) during the winding process.
T
F
Cross winding is produced by very low yarn traversing speed.
T
F
The indirect warping process is slower than the direct warping process.
T
F
Direct warping process is used for short runs.
T
F
A warper with a duplicate creel is less efficient than a warper with a single creel.
T
F
In warping, using a movable headstock is almost as efficient as using a truck
creel, but takes up 1/3 less space.
T
F
Direct warping process is faster than indirect warping process.
T
F
Direct warping process produces a warp section beam in two steps.
T
F
A complete warp beam contains part of the total number of warp yarns
required to weave the fabric.
T
F
The sizing process is performed on all types of yarns.
T
F
Sizing prevents clinging of warp yarns caused by yarn hairiness during weaving.
T
F
Too high % size add-on on warp yarns reduces warp breaks during weaving
due to increased yarn brittleness.
T
F
The lubricant is used in sizing to increase warp yarns coefficient of friction a
matter that decreases the frictional forces on the yarns during weaving.
T
F
Cylinder dryers are Teflon-coated to prevent the sticking of the sizing material.
T
F
Weaving efficiency increases with increasing size encapsulation.
T
F
The tying-in process is much faster and less-costly than the drawing-in process.
T
F
In the tying-in process, each warp yarn is threaded through a drop wire, a heddle
wire, and a reed dent.
T
F
Tying-in is performed if a new style is to be woven.
T
F
Drawing-in machines are expensive, but they are must when dealing with
frequent style change.
T
F
A reed dent is the space between two neighboring wires of the reed.
T
F
In the drawing-in process, each end from the new warp beam is tied or pieced to
an end of the old warp beam.
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