AN EMPIRICAL APPROACH ON BREAKDOWN TIME IN KNITTING ROOM TO

AN EMPIRICAL APPROACH ON BREAKDOWN TIME IN KNITTING ROOM TO
IMPROVE PRODUCTIVITY AND MINIMIZE WASTAGE & COST
Report Submitted to
M/S. APEX CLUSTER DEVELOPMENT SERVICES PVT. LTD
TIRUPUR – 641 606
K.J.SIVAGNANAM, Professor,
NIFT TEA KNITWEAR FASHION INSTITUTE
East of TEKIC, Mudalipalayam,
TIRUPUR – 641 606
CONTENT
1. Introduction
2. Statement of the problems in knitting room
3. Scope of the investigation
4. Objectives
5. Relevance of knitting room
5.1 Yarn quality
5.2 Fabric quality
5.3 Fabric faults
6. Methodology
7. Limitations
8. Details of investigation
8.1 Production of knitting
8.2 Snap study on machine stoppages
8.2.1 Production loss due to m/c stoppage:
8.3 Fabric wastage: (Areal density / gsm checking)
8.3.1. Wastage of fabric due to uneven roll weight:
8.3.2 Causes for fabric defects
9. Findings of the investigation
10. Summary and Conclusion
11. Acknowledgement
12. References
AN EMPIRICAL APPROACH ON BREAKDOWN TIME IN KNITTING ROOM TO IMPROVE
PRODUCTIVITY AND MINIMIZE WASTAGE & COST
(K.J.Sivagnanam, Professor, NIFT TEA Knitwear Fashion Institute, Tirupur)
1. INTRODUCTION:
As the demand for the knitted garment is steadily on the increase during the recent years, a large
number of knitting factories are involved in the manufacture of fabrics for knitwear industry. The present
knitting factories when compared to past decades are established with the new generation of high-speed
modern knitting machines. The present knitting industry is faced with proclaim of stiff global competitions
demanding of production of quality fabric with international level with reduced cost.
The performance of the knitting room has assumed critical importance especially with regard to the
production of quality of knitted fabrics. The profitability and sustainability of the knitting factories are
influenced and depends on various factors, such as labour productivity, machine productivity, machine
efficiency, Fabric defects and wastages in various stages.
The present study has been undertaken to investigate the knitting room and find the causes for these
issues and suggest the ways and means to improve them. Some of the relevant points have been
discussed in this report with fruitful suggestion for the implementation in the knitting company. Finally to
arrive at suitable system for knitting room to obtain fabrics having an acceptable quality with reduced
wastage and cost.
2. STATEMENT OF THE PROBLEMS IN KNITTING ROOM:
The various departments of garment industry and that of knitting in particular have many problems to be
addressed in order to improve the productivity and quality. These two are factors directly influences the
wastage and cost of knitting. The following problems have been identified for this investigation.
Machine efficiency
Machine / Operator Productivity
Fabric Wastages
Defects in fabrics
3. SCOPE OF THE INVESTIGATION:
The focus of this investigation is to understand the performance of knitting factory and identify the
factors responsible for the above stated problems. The investigation conducted a snap study to analyze
the breakage rate of knitting machine with a view to recognize the factors which need attention for
increasing the both labour and machine productivity and reduce the defects and wastages.
The investigation also reviews the role of yarn quality, knitting room procedures and functioning
documents in achieving better productivity and quality.
This study intends to provide suitable
suggestions for minimizing the wastages and cost of knitting room.
4. OBJECTIVES
1. To evaluate the knitting room and to study the extent of role played by yarn properties, machine
parameters, knitting room systems on the critical fabric quality, productivity, wastages and cost of
knitting.
2. To Investigate all the core parameters and suggest the methods to have better knitting room
management for the improvement in productivity / efficiency / defects points
5. RELEVANCE OF KNITTING ROOM
5.1 Yarn Quality:
In Knitting Room, the first and basic raw material is yarn and it mainly decides the knitting performance
and the quality of fabric produced. And the new generation of high-speed modern knitting machines
place increasingly more stringent demands on the quality and processability of the yarn. As the speed of
knitting machines increase, high quality yarn is going to become more important. Companies which are
best able to use high quality of yarn and high speed modern knitting machines are going to be
successful in an increasingly competitive market.
Therefore, a thorough knowledge on some of the important yarn properties will be helpful to knitting
industrialist to produce good quality of knitted fabric and meet the market requirements. The important
yarn properties are Yarn Count, Strength & CSP, Twist, Evenness and Hairiness..
All these properties are to be evaluated to determine its quality and important in the design of knitted
structures and they govern the fabric appearance and behaviors.
Therefore, the testing becomes
necessary to ensure the quality of raw materials. A good Knitting yarn should have the following
qualities.
Better evenness
Soft twist
Less count variation
Free from thick, thin, Neps and undrafted places
Better elasticity and elongation
Resistance to friction
5.2 Fabric Quality
The term “fabric quality” in knitting can describe the nature of the fabric density (tightness factor) and the
number or types of faults within the fabric;
Fabric Density
The structure of a knitted fabric has a large influence on the fabrics’ characteristics and can make them
better or worse. Stitch density is directly related to the “loop length”, which is the length of yarn
contained in one complete knitted loop, and this is adjusted on the knitting machine. Loop length
affects:-
• Stitch density/fabric density
• Fabric weight and fabric cost
• Fabric dimensions and panel size; shaped knitwear
• Dimensional stability; relaxation and shrinkage
• Physical performance; pilling, burst strength
There is a definite correlation between the yarn count and loop length of a fabric and this can be defined
as the “cover factor”. The cover factor hence determines the handle, drape and performance of the
fabric. Just as the yarn type dictates the optimum loop length, this in turn dictates the gauge or knitting
machine required to knit the yarn
5.3 Fabric Faults
Fabric faults can be attributed not only to the knitting, but also the quality of yarns and dyeing and
finishing. Typical fabric faults found in knitted fabrics are:• Cockling or loop distortion
• Fabric Spirality
• Yarn irregularity and neps create small lumps like knots.
• Barrè
• Contaminated yarns (colored fibre/vegetable matter)
6. METHODOLOGY:
As a first step the factors contributing to the performance of knitting room were studied.
The knitting process is observed and the number of machine stops, yarn breaks, and holes are
recorded. The results of experiments are evaluated by charts and statistical analyses.
Thirdly the fabrics after knitting were examined to understand the quality level
After that the employee skill level, knitting room procedures, and functioning documents are
investigated.
In the next stage suitable procedures and systems were established and given to factory for
implementation, after conducting training classes to the employees. The study makes use of both
primary and secondary data. Specific information’s relating to defects was obtained.
7. LIMITATIONS:
The company prefers to maintain the secrecy of their details of knitting room performance and hence
there is considerable apprehension in taking information to this report on their activity. As the number of
factory taken for this investigation is just one in tirupur, care should be taken while implementing the
same in other factories.
8. DETAILS OF INVESTIGATION
8.1 PRODUCTION DETAILS OF KNITTING ROOM:
The details about the gauge, dia, count and actual production of single jersey machines are collected on
sample basis. The details are given below.
Fig: 1(a) Showing Production details of factory producing Single Jersey
Sl.
GG
Dia (in)
No. of feeders
Speed (RPM)
Count (Ne)
Avg. Prod.
Kgs.
1.
20 /24
18
54
38
20
70
2.
20 /24
18
54
38
30
45
3.
20 /24
18
54
38
40
36
4.
20 /24
32
96
22
20
135
5.
20 /24
32
96
22
30
84
6.
20 /24
32
96
22
40
65
Fig: 1(b) Details for 18 Dia.
Fig: 1 (c) Details for 32 Dia.
8.2 MACHINE EFFICIENCY DETAILS OF KNITTING ROOM
Fig: 2 Showing Machine efficiency details of factory producing Single Jersey
Speed
Ct.
Avg. Prod.
Avg. Prod.
(rpm)
(Ne)
(Actual)
(Calculated)
54
38
20
70
111
63.1 %
32
96
22
20
135
203
66.5 %
24
18
54
38
30
45
74
60.8%
4.
24
32
96
22
30
84
135
62.22%
5.
24
18
54
38
40
36
55.5
64.8 %
6.
24
32
96
22
40
65
102
63.7 %
Sl.
GG
Dia (in)
Feeders
1.
24
18
2.
24
3.
Efficiency
8.2 SNAP STUDY ON MACHINE STOPPAGES
An attempt was made to determine the knittability of a yarn before knitting. Different yarns are knitted
into jersey structures at different loop length values. The knitting process is observed, and the number
of machine stops, yarn breaks, and holes are recorded, using the template given below. The results of
our experiments are evaluated.
Sl
Total
Stoppage
Reason
Average no. of stoppages
Total Time to
rectify
=
%
3- 4 per machine / hour.
Time taken to restart the machine after rectification =
2 mins
Total number of machines
=
19 over all
Actual Work Hours per shift
=
7 hrs
Total hours of production
=
7 x 19 machines = 133 hrs
Machine idle time due to stoppage
=
6 - 8 min per hour per machine.
Total time loss due to stoppage
=
6 - 8 x 7 x 19
=
798 - 1064 mins.
=
13.3 hrs to 17.73 hrs per day.
Percentage of idle time = 10 - 13.33 %
Sl.
Breakages per hour
Percent idle time per 8 Hrs
1.
3
10.00
2.
4
13.33
Fig.: Higher the stoppages- More Idle time
Fig.:
Causes for Machine idle time
8.2.1 Production loss due to M/C stoppage:
Total no. of machines (S/J)
=
11
Average production per machine per shift
=
150 kgs. Apx.
Total production
=
1650 kgs per day
Avg . Loss of production @ 12%
=
200 kgs per day.
Money [email protected] Rs 10 /Kg.
=
Rs 2000.
Money loss per year of 300 days
=
2000.00 x 300 days.
=
Rs. 6 Lacks. Apx.
8.3 FABRIC WASTAGE: (AREAL DENSITY / GSM CHECKING)
During the investigation, it has been noticed that the company is taking care to ensure that the customer
is supplied with the fabric having correct GSM and hence have a practice of checking the GSM on every
alternate roll. It is calculated to be more wastage of fabric in subsequent processes, as every point of
GSM testing would damage at least 0.5 mtr of fabric, which can not be used for cutting the garment.
For example,
Average Production per day
=
160 kgs apx.
Total machines
=
11 machines
Total production per day
=
1760 kgs
Total number of fabric rolls produced
=
88 rolls (considering apx. 20 kgs / roll)
Fabric wastage in GSM checking per roll
=
0.5 mtrs
Fabric GSM
=
160 avg.
Total fabric wastage
=
160 gms X 22 rolls = 3.50 kgs
(Taking into account that minimum of 25 % of the rolls are checked for GSM)
Fabric wastage percentage
=
Cost of wastage material
= 3.50 kgs X Rs. 200/Kg
Total loss per year of 300 days
3.50 / 1760 = 0.2 %
=
Rs. 700.00 per day
=
Rs. 700.00 x 300
=
Rs. 2.1 Lacks
8.3.1 Wastage of fabric due to uneven weight of rolls cut:
For instance, a case is presented here.
Number fabric rolls produced per day @ 20 kgs. weight
=
88 rolls
Fabric wastage (unusable fabric) per roll
=
1 mtr.
Due to maximization / standardization / optimization of roll weight, number of rolls can be
minimized and thereby fabric wastage can be reduced as follows,
Sl.
Roll weight
No. of rolls
% reduced
1
21
84
04.5
2
22
80
09.0
3
23
77
12.5
4
24
74
16.0
5
25
71
19.5
Standardisation of roll weight v/s Wastage %
Series1
Roll wt. & Wastages
Series2
30
25
20
15
10
5
0
9
25
24
23
22
21
12.5
16
19.5
4.5
1
2
3
Roll
4
5
8.3.2 Causes for fabric defects
Poor Yarn quality
-
83%
Unskilled Operator
-
8%
Poor maintenance
-
7%
Poor M/c condition / setting
-
2%
9. FINDINGS OF THE INVESTIGATION:
9.1 General Findings: The knittability of a yarn determines if knitting it will be easy or not, and many
descriptions of knittability can be found. Probably knittability is the most surprising property which we
don't measure directly. Knittability should be divided into three groups.
The first group would include factors affecting the running of the yarn from the package to the feeder,
the way in which the yam is guided, the elements guiding the yarn, and the yarn variables. The second
group would include factors affecting knitting performance, i.e., yam, knitting machine, and fabric
properties. The third group would include yarn faults that do not affect knitting performance.
Ideally, the knitting performance of a yarn should be assessed by knitting it under carefully controlled
conditions, and then counting the number of yarn breaks (holes in the fabric) that can be specifically
attributed to the physical properties of the yarn. Various machine settings have important effects on the
knitting performance. The control of loop length during knitting is of paramount importance.
Control of Yarn tension affects the fabric quality,
•
Too much tension leads to yarn break or holes in fabric
•
Less tension leads to snag and snap and drop stitches
Yarn tension depends mainly, Yarn variable and Machine variable. Yarn variable includes, Yarn color
Yarn count, Yarn twist, Moisture content, Yarn lubrication and Package hardness. Machine variable
includes, Stitch cam setting, Take down tension, Stretcher board and Machine gauge.
9.2 Specific Findings: Through the snap study, the knitting process was observed, and the number of
machine stops, yarn breaks, and holes are recorded, using the standard template developed for the
study. The results of our experiments revels that the average percentage of machine idle time is in
between 10 - 13.33 % and estimated Production loss due to M/C stoppage (Loss of production @ 12%)
was around 200 kgs per day, which in turn comes to a monthly loss of approximately Rs.6 Lacks (at 300
working days, calculated based on average production of the company).
During the investigation, it has been noticed that the company is having a practice of checking the GSM
every alternate roll and hence leads to a damage of at least 0.5 mtr. in every testing, leaving a total
wastage of approximately equal to Rs. 2.1 lacks per year. It is also noticed to have wastage of fabric
due to uneven weight of rolls cut after knitting.
10. SUGGESSTIONS AND CONCLUSION:
The main purpose of this investigation has been to explain and give examples of how the knitting room
could be effectively managed for better result. Knitted fabric room is described and discussed.
The profitability and sustainability of knitting room in the future would be defined for decrease in
machine idle time, increase in machine & labour productivity, decrease wastages of fabric and lower
points in fabric rejection. These parameters plays vital role and will reduce the cost of knitting room to a
greater extent. Of course, the yarn quality should meet such demands and it found to be major aspects
that influence the machine idle time and fabric wastages. The tools & systems required to assess them
could be developed and used effectively.
It is concluded that the knitting room can effectively be managed by properly taking measures on proper training to operators & floor supervisors, implementation of system for testing and approval of
yarn, knitting room management as per GFAR (given in annexure) developed under this project. The
Feedback reports are to be continuously for initiating corrective and preventive actions. By all these
means, the company will be able to progress towards minimizing all the above losses and it is
accepted by the industry that the productivity of the room will increase with lesser wastage and cost of
knitting.
11. ACKNOWLEDGEMENT
The author wishes to record his sincere thanks to M/S. Small Industries Development Bank of India
(SIDBI), M/S. Apex Cluster Development Services Pvt. Ltd and NIFT TEA Knitwear Fashion Institute for
their large support in completing this industrial project successfully. The author specially thanks
Mr.P.P.Gopalakrishnan, Professor, NIFT TEA, without his support this project could not have been
finished.
12. REFERENCES:
1. D.B.Ajgoankar, Knitting Technology, Universal Publishing Corporation, Mumbai (1998).
2. David.J Spencer, Knitting Technology, Wood Head Publishing Ltd. – Second Edition,
3. Mowbray J. A Quest for Ultimate Knitwear. Knitting International 2002;109 (1289):22-24.
4. Knitting Ability, Sayed Ibrahim JiříMilitký, Textile Faculty, Technical University of Liberec
5. www.autexrj.org
Annexure
GREY FABRIC APPROVAL REGISTER
(GFAR)
Order
Details
XYZ Firm
Customer Name :
Qty. of order
Delivery Date
Fabric
Machine / GG
Design details
Ref:
Yarn Mill :
Grey GSM :
Loop length:
Others details:
Knitting
Programming
Ac. – Actual / No. – Nominal
Dia
(“)
Total
(kgs.)
Roll
Wt.(Kg)
(X)
L.L
(cm)
(L)
No. of
Rolls
Feeders
(F)
CL (Mtrs.)
=
L X N/100
Needles
(N)
KNITTING DIVISION
Date:
Testing Report Approvals
Details
Ac. No.
Report
Count Ne
CSP
TPI
Yarn Approved by
…………………………………
Total Yarn /
Rev. (Ty)
= F X CL
(mtrs.)
Wt. of Fabric
Produced / Rev.
WFPR (g) =
0.59xTy/Ac.Ne
Revolutions
Required for
roll
= X x 1000 /
WFPR(g)
Note
Fabric Inspection as per 4 POINT SYSTEM
Fabric c Approval Process
12
11
10
09
08
07
06
05
04
03
Linear Defect: up to 3” = 1 point;
3 to 6 “ = 2 points;
6 to 9” = 3 points ;
9 & above = 4 points.
Areal Defects: Less than 1” = 2 pts.; More than 1” = 4 pts.
Pts/
Acc.
Tot.
Pts./
Result
100
TSM
Diff.
Note
pts
100SM
sm
02
(X –X)2
01
Roll
No.
Roll
Weight
(Kgs.)
X
1
2
3
4
5
6
7
8
9
10
Avg. Wt x =
Note: TSM: Total square meter of the fabric inspected & Acceptable Points Level (APL) shall be decided by
company based on its standard .
S.D.(σ) = √(X – X)2 / n
=
CV % of roll wt =
{σ
/ x ] x 100
Due to Yarn Fault
Due to Operator fault
Due to Machine fault
Due to other faults
Summary of Points:
: (Blue)
: …… / ... ..(%)
: (Red)
: …… /…...(%)
: (Black) : …… /…....(%)
: (Green) : …… /…....(%)
Over all comments :
……………………………………………………………………………………..
Lower cv % is better
Delivery Remarks:
Checked by
Approved by
Manager
`