In the apparel business, before accepting the finished goods from the manufacturer buyer do inspection of goods. As whole lot of goods inspection is not viable, also not advisable, inspection is done on sampling basis. In inspection how much percentage of defective pieces will be accepted depends on acceptable quality level. In the following table a sampling plan is given for final shipment inspection
4 Point System
4 Point system for fabric inspection is widely used in
apparel industry for fabric quality inspection. To use this system you have to
know following things.
- Fabric inspection method or
preparation
- Criteria of giving penalty
points based on defects and defect length.
- Calculation method of total
penalty points for total defects found in a fabric roll
- A Check sheet or format for
recording data
- Knowledge of different types of
defects (how a defect looks and its appearance)
Criteria
for giving penalty points
In the following table the penalty
evaluation points has been given for different length of fabric defect and
dimension of holes.
|
Size of Defect
|
Penalty
Points
|
|
Length
of defects in fabric (either length or width)
|
|
|
Defects up to 3 inches
|
1
|
|
Defects > 3 inches <
6 inches
|
2
|
|
Defects > 6 inches <
9 inches
|
3
|
|
Defects > 9 inches
|
4
|
|
Holes
and openings(largest dimension)
|
|
|
1 inch or less
|
2
|
|
Over 1 inch
|
4
|
Calculation
of total points per yards
In 4 point system fabric quality is
evaluated by unit points/100 sq. yds.
Example: A fabric roll 120 yards long and 46 inch wide contains
following defects.
|
4 defects
up to 3 inch length
3 defects
from 3 to 6 inch length
2 defects
from 6 to 9 inch length
1 defect
over 9 inch length
1 hole
over 1 inch
|
4 x 1
3 X 2
2 X 3
1 X 4
1 X 4
|
4 points
6 points
6 points
4 points
4 points
|
|
Total
defect points
|
24 Points
|
|
Points/100 sq Yds =
Points/ 100 sq.
yards = (24 X 3600)/(100 X 46)
= 18.78
points
Fabric Wise
Acceptable Points:
|
Fabric Type
|
Acceptable Points
|
|
Denim
|
28
|
|
Silk
|
50
|
|
Carded Basic Knit
|
40
|
|
Combed Basic Knit
|
30
|
|
Synthetic
|
20
|
|
Linen Blends
|
40
|
|
Plain Cotton
|
28
|
Acceptable Quality level (AQL):
. The AQL
level varies process to process, product to product and even buyer to buyer.
Definition
of AQL:
The AQL (Acceptable Quality Level) is the maximum per cent defective that for
the purpose of sampling inspection can be considered satisfactory as a process
average.
|
Lot or Batch size
|
Sample size Code Letter
|
Sample Size
|
Acceptable Quality
level
|
|||||
|
2.5
|
4
|
6.5
|
||||||
|
Accept
|
Reject
|
Accept
|
Reject
|
Accept
|
Reject
|
|||
|
2 – 8
|
A
|
2
|
0
|
1
|
0
|
1
|
0
|
1
|
|
9 – 15
|
B
|
3
|
0
|
1
|
0
|
1
|
0
|
1
|
|
15 – 25
|
C
|
5
|
0
|
1
|
0
|
1
|
0
|
1
|
|
26 – 50
|
D
|
8
|
0
|
1
|
1
|
2
|
1
|
2
|
|
51-90
|
E
|
13
|
1
|
2
|
1
|
2
|
2
|
3
|
|
91-150
|
F
|
20
|
1
|
2
|
2
|
3
|
3
|
4
|
|
151-280
|
G
|
32
|
2
|
3
|
3
|
4
|
5
|
6
|
|
251-500
|
H
|
50
|
3
|
4
|
5
|
6
|
7
|
8
|
|
501-1200
|
J
|
80
|
5
|
6
|
7
|
8
|
10
|
11
|
|
1201-3200
|
K
|
125
|
7
|
8
|
10
|
11
|
14
|
15
|
|
3201-10000
|
L
|
200
|
10
|
11
|
14
|
15
|
21
|
22
|
|
10001-35000
|
M
|
315
|
14
|
15
|
21
|
22
|
21
|
22
|
|
35001-150000
|
N
|
500
|
21
|
22
|
24
|
25
|
24
|
25
|
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