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Assembly Line Balancing
Gonca Karaarslan
Ali Galip Matlar
PROBLEM DEFINITION
Line Balancing Problem at Indesit Industrial and Trade Inc. Company
in refrigerator factory for Lines 6 & 7
Two Sided
AssemblyPre-Assembly
Takt Time: C = 86 sec (Polyurethane Machine)
MM _ D _ S2 (I)*
Straight-2 Sided Line
Multi Model DeterministicType-I: Min # Stations given C
CLASSIFICATION
GOLDEN & STRIKE ZONEAnalysis of work operations in the area
that favors the handling in order to
minimize movement and reduce fatigue.
Mechanic Shop Plastic Shop Paint Shop
Door FoamingPre-Assembly
Assembly
Quality Control Packaging Delivery
MANUFACTURING PROCESSES
SETST: Set of tasks
S: Set of stations
SL: Left side of stations; SL
SR: Right side of stations; SR
SE: Set of stations that can be used for operations
which required zoning restriction; SE
TL: Set of tasks that can be assigned to left side; TL
TR: Set of tasks that can be assigned to right side; TR
β : Set of concurrent task groups
TC : Pair of tasks belonging to concurrent task group c
that must be performed simultaneously, c ∈ β
ℸ : Set of marriage tasks groups
Tα : Set of tasks belonging to group α that must be
assigned to same station, α ∈ ℸ
Pi : Set of immediate predecessors of task i, i ∈ T
⊂S
⊂ S
⊂S
⊆
⊆ T
T
TB : Set of tasks that can be assigned to both sides; TB
TE : Set of tasks belonging to operations
which required zoning restriction; TE T
RightLeft
S5
S3
S1
S6
S2
S4
T1.1 T1.2
T1
T2
T3
Reducing Non-Value AddedOperations
Decreasingthe number of
stations
Improvementof total workload
Minimizing theIdle Time =
Maximizing the station utilization
Decreasing the number of workers =
Reduction of labor cost
KEY PERFORMANCE INDICATORS
Min 𝒋∈𝑺𝒚𝒋
𝒋∈𝑺𝑳
𝒙𝒊𝒋 = 1 , ∀𝒊 ∈ 𝑻𝑳
𝒋∈𝑺𝑹
𝒙𝒊𝒋 = 1 , ∀𝒊 ∈ 𝑻𝑹
𝒋∈𝑺𝒙𝒊𝒋 = 1 , ∀𝒊 ∈ 𝑻𝑩
𝒊∈𝑻𝒕𝒊 𝒙𝒊𝒋 ≤ 𝑪 𝒚𝒋 ∀𝒋 ∈ 𝑺
1+ 𝒋∈𝑺𝑳
𝒋 𝒙𝒊𝒋 = 𝒋∈𝑺𝑹
𝒋 𝒙𝒌𝒋
∀𝒊 ∈ 𝑻𝑳 ∩ 𝑻𝑪 , 𝒌 ∈ 𝑻𝑹 ∩ 𝑻𝑪, 𝒄 ∈ 𝜷
𝒋∈𝑺𝑬
𝒙𝒊𝒋 = 1 ∀𝒊 ∈ 𝑻𝑬
𝒙𝒊𝒋 ∈ {0,1}
𝒚𝒋 ∈ {0,1}
ASSIGNMENT
Each task must be assigned
to an eligible station
CYCLE TIME
Total duration of tasks assigned
to a station cannot exceed cycle time
PRECEDENCE
A task can be assigned to a station
if all predecessors are assigned
previously
SIGN RESTRICTIONS
Binary decision variables
CONCURRENT TASKS
A concurrent task must be performed
simultaneously in different sides of
same physical station
ZONING RESTRICTIONS
Certain tasks can only be
assigned
to specific stations
OBJECTIVE FUNCTION
Minimizing number of stations}
}
}
}
}
}
𝒋∈𝑺
𝒋 𝒙𝒊𝒋 ≤
𝒋∈𝑺𝑹
𝒋 𝒙𝒌𝒋 +
𝒋∈𝑺𝑳
𝒋 + 𝟏 𝒙𝒌𝒋
∀𝒌 ∈ 𝑻 , 𝒊 ∈ 𝑷𝒌
}
Decreasing the number of stations
Decreasing non-valueadded operations
⊆T
⊆
CURRENT SYSTEM IMPROVED SYSTEM IMPROVEMENTS BY NVA OPERATIONS
Decision Variables
xij=1 if task i is assigned to station j, 0 otherwise
yi=1 if station j is used, 0 otherwise
Parameters
C: Cycle Time
ti: Duration of tasks i; i∈ T
LINECURRENT
SYSTEM
MODEL
RESULT
HEURISTIC
RESULT
ALGORITHM
RESULT
IMPROVEMENT
(%)
LINE 6
PRE-ASSEMBLY14 11 11 11 21,43%
LINE 6
ASSEMBLY14 9 9 9 35,71%
LINE 6
TOTAL28 20 20 20 28,57%
LINE 7
PRE-ASSEMBLY13 10 10 10 23,08%
LINE 7
ASSEMBLY18 14 14 14 22,22%
LINE 7
TOTAL31 24 24 24 22,58%
LINE 6 PRE-ASSEMBLY
OLD NEW %
Station 1 81.72 79.90 2.23%
Station 2 79.20 73.30 7.45%
Station 3 43.40 43.40 0.00%
Station 4 76.68 73.60 4.02%
Station 5 60.50 58.60 3.14%
Station 6 70.30 67.60 3.84%
Station 7 68.70 63.10 8.15%
Station 8 64.44 62.60 2.86%
TOTAL 544.94 522.10 4.19%
LINE 6 ASSEMBLY
OLD NEW %
Station 1 78.08 69.90 10.48%
Station 2 75.60 70.20 7.14%
Station 3 84.06 79.20 5.78%
Station 4 86.00 86.00 0.00%
Station 5 85.77 85.77 0.00%
Station 6 34.56 34.00 1.62%
Station 7 51.66 47.00 9.02%
Station 8 65.34 61.38 6.06%
Station 9 64.14 63.50 1.00%
TOTAL 625.21 596.95 4.52%
LINE 7 PRE-ASSEMBLY
OLD NEW %
Station 1 61.92 59.76 3.49%
Station 2 63.18 62.80 0.60%
Station 3 75.24 75.06 0.24%
Station 4 76.86 72.20 6.06%
Station 5 60.48 58.70 2.94%
Station 6 63.00 59.60 5.40%
Station 7 82.84 76.40 7.77%
Station 8 78.12 74.32 4.86%
TOTAL 561.64 538.84 4.06%
LINE 7 ASSEMBLY
OLD NEW %
Station 1 76.10 69.44 8.75%
Station 2 71.82 71.82 0.00%
Station 3 67.32 65.34 2.94%
Station 4 64.98 64.98 0.00%
Station 5 68.58 66.80 2.60%
Station 6 63.90 63.90 0.00%
Station 7 61.20 61.20 0.00%
Station 8 32.50 32.50 0.00%
Station 9 67.86 67.86 0.00%
Station 10 63.40 63.40 0.00%
Station 11 65.52 63.70 2.78%
Station 12 64.55 64.55 0.00%
Station 13 50.76 49.90 1.69%
Station 14 48.60 47.50 2.26%
TOTAL 867.09 852..89 1.64%
0
20
40
60
80
100
S 1 S 2 S 3 S 4 S 5 S 6 S 7 S 8 S 9 S 10 S 11 PU S 13 S 14
Station Time(sec) Idle Time
0
20
40
60
80
100
S 1 S 2 S 3 S 4 S 5 S 6 S 7 S 8 PU S 10 S 11
VA NVA idle
LINE 6 PRE-ASSEMBLY WORKLOAD & IDLE TIMELINE 6 PRE-ASSEMBLY WORKLOAD & IDLE TIME
(sec) (sec)
(sec) (sec)
0
20
40
60
80
100
S 1 S 2 S 3 S 4 S 5 S 6 S 7 S 8 S 9
0
20
40
60
80
100
S 1 S 2 S 3 S 4 S 5 S 6 S 7 S 8 S 9 S 10 S 11 S 12 S 13 S 14
LINE 6 ASSEMBLY WORKLOAD & IDLE TIMELINE 6 ASSEMBLY WORKLOAD & IDLE TIME
LINE 7 PRE-ASSEMBLY WORKLOAD & IDLE TIME LINE 7 PRE-ASSEMBLY WORKLOAD & IDLE TIME
LINE 7 ASSEMBLY WORKLOAD & IDLE TIME LINE 7 ASSEMBLY WORKLOAD & IDLE TIME
S 11S 14
S 14
0
20
40
60
80
100
S 1 S 2 S 3 S 4 S 5 S 6 S 7 S 8 PU S 9 S 10
S 9
0
20
40
60
80
100
S 1 S 2 S 3 S 4 S 5 S 6 S 7 S 8 S 9 S 10 S 11 PU S 12 S 13S 13
36%
IMPROVEMENT
0
20
40
60
80
100
S 1 S 2 S 3 S 4 S 5 S 6 S 7 S 8 S 9 S 10 S 11 S 12 S 13 S 140
20
40
60
80
100
S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18S18
LINE 6
TOTAL
LINE 7
TOTAL
M MT
MTM is a method for determination of duration.Main purpose of MTM-UAS:
Standardization of every movements
and process time in operations.
Characteristics of MTM-UAS:• Analyzing by UAS
• No appreciation of tempo
• Hints for time improvement
27 Stations
123 Operations
1,124 MTM Codes
Pre-Assembly Assembly
32 Stations
118 Operations
1,006 MTM Codes
2,130Total
Coding
5 Days MTM Training
Main Operations of UAS:
A Get and Place
P Place
B Operate V Visual Control
Z Motion CyclesK Body Motions
A Approximate
B Loose
C Tight
Changeable Factors of UAS:
Distance Range of UAS:
1 0 cm ≤--≤ 20 cm
2 20 cm <--≤ 50 cm
3 50 cm <--≤ 80 cm
Distance Range
Main Operation
BA 3
Handle Tool, Get Place and Place AsideH
LINE 6 & 7
S18
S 10
S14
76%
24%YES
NO
81%
19%
71%
29%
81%
19%
IMPROVEMENTS
BY STRIKE ZONELINE 6 LINE 7
IMPROVED S. IMPROVED S.
CURRENT S. CURRENT S.
.
Head Count: Blue Collar:927, White Collar:73
Industrial Site: Manisa Organized Industrial District
Products
GENERAL INFORMATIONIncorporation: 1987
Commercial Office: Istanbul
Merged at Whirpool Corpoaration Group: 2014
Consolidated Net Sales: $265Million
Levent Kandiller
Hande Öztop
GOLDEN ZONE
AA
60
A
B
C
D
Not Ergonomic
Ergonomic
Not Ergonomic
1500mm
600mm
43 2 1
Arm Forearm Wrist Hand
STRIKE ZONE
22%
IMPROVEMENT
23%
IMPROVEMENT
21%
IMPROVEMENT
(%)
Machine
400 cm
700 cm
21.43%
35.71%
28.57%
23.08%
22.22%
22.58%
IMPROVEMENT
MATHEMATICAL MODEL
5% 10%
(OPTIMAL)(%)
𝒙𝒊𝒋 𝒙𝒌𝒋 ∀𝒊 ∈ 𝑻𝜶 , α ∈ ℸ, 𝒋 ∈ 𝑺
(single variable)
𝒊∈𝑻𝜶 𝒕𝒊 𝒕𝒌 ∀𝒊 ∈ Tα , α ∈ ℸ
(single duration parameter)
TASK MARRIAGE
Certain tasks must be performed
together at the same station.
}
63%38%
STRIKE ZONE
YESNO
41%
24%
18% 18%
0%0%
10%
20%
30%
40%
50%
AA A B C D
GOLDEN ZONE
Indesit Company.(2003,May 29).
Boysen, N., Fliedner, M., Scholl, A. (2007).
European Journal of Operational Research, 183, pp.674-693.
International MTM Directorate. Introduction to MTM-UAS.Retrieved from the International MTM Directorate website:
“MTM UAS Üniversal Analiz-Sistemi El Kitabı”,2008
http://mtm-international.org/introduction-to-mtm-uas/
Kim, Y.K., Song, W.S., Kim, J.H. (2009).A mathematical model and a genetic algorithm
Computers and Operations Research, 36 (3), pp.853-865.
REFERENCES
1.
5.
2.
4.
3.
ALGORITHM
for two-sided assembly line balancing.
A classification of assembly line balancing problems.
Indesit History,Retrieved from August 10
Changable Factors
INPUTSDECISION SUPPORT SYSTEM
Initial scheduling according to model output.
Improvements on the basis of station respect to side restrictions.
Operations which exceed takt time(86 sec.) are assigned to next station.
FEASIBLE
1st combination
Both operations
2nd combination
Both operations
Whichever gives the minumum number of stations.
Right RightLeft Left
Right Right
Left Left
1.
2.
1.
2.
(To make use of existing idle times)
Successful, continuous and applicable to other factories’ assembly lines
Can be implemented to different industrial areas such as automotive, electronic
Feasible and applicable for firms which aims to be active against to industrial revolution
APPLICABILITY OF DSS
Qualified for adapting to Industry 4.0 revolution easily
OUTPUTS
If two stations are assigned to the same side and summation of
their operations’ duration does not exceed cycle time,
these stations can be combined regarding to
precedence relations.
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