The project was conducted during an internship by a student who had attended ESTIEM Lean Six Sigma Green Belt Course. More information about about the course and opportunities can be found here: https://www.estiem.org/default.aspx?PageId=3824

1. European Students of Industrial Engineering and Management
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Decreasing Structural Frame Assembly Time
Lean Six Sigma Green Belt Project - Educational Case
Site visualizations: PES-Arkkitehdit Oy and 3Drender Oy

2. European Students of Industrial Engineering and Management
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The Project Was Conducted As a Part of
Helsinki-Vantaa Airport Expansion
2
Site visualizations: PES-Arkkitehdit Oy and 3Drender Oy

3. European Students of Industrial Engineering and Management
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The Goal of the Project Was to Reduce the
Leadtime of the Structural Frame Assembly
3

4. European Students of Industrial Engineering and Management
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 A Finnish construction company is building an extension to the Helsinki-Vantaa airport. Over 300 meter
long new terminal is being built in the center of a fully functional airport.The project schedule is tight and
the process owner wants to deliver the project as soon as possible to minimize the disturbance to the
airport operations.The work phases can be roughly divided to groundwork, structural frame assembly,
facades, interior work, and HVAC.The process owner wants to focus on the frame assembly as it is on the
critical path of the project.The process improvement project is scoped in this example to the most
repeatable process step, hollow-core slab assembly.The quantity of hollow-core slabs is especially large in
this project and the estimated performance is 30 slabs per day.The project execution including all other
concrete and steel components is is scheduled to take 10 months.
 A local manufacturer provides the hollow-core slabs from Otaniemi.The manufacturer has its own logistics
and the assembly itself is done by a subcontractor specialized in structural frame assembly.The material
loading in the factory to the trucks takes approximately 30 minutes.The crane used for lifting the hollow-
core slabs on the site is provided by the main contractor.The assembly also requires two workers to install
the slabs and two workers to unload the truck. A supervisor form the subcontractor is also always present.
The site provides a logistical problem, as the trucks have to cross the airport ramp in order to get to the
site.The entry to the airport ramp is prevented if planes are moving on the ramp.
 The measurements of the slab assembly were conducted using two time-lapse cameras taking pictures with
a 1-minute interval.The cameras were positioned in two of the cranes. Crane 1 (STT1330) was close to the
actual assembly and crane 2 (STT753) was further away giving an overview.The measurements present the
time interval between two consecutive assemblies.
Project Information*
*The case is modified for educational purposes

5. European Students of Industrial Engineering and Management
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S I P O C CTQ
Structural frame
assembly
Delivery of
materials
Lifting of
components
Fixing of
components
Delivery of
assembled
frame
Concrete
Columns
Beams
Hollow-core
slabs
Casting material
Steel
Columns
Beams
Braces
Fixings
Element suppliers
Steel supplier
Logistics
Crane & operator
Additional lifting
devices
Workers
Designers
Concrete frame
Steel frame
Frame assembly
lead time
Airport owner
Contractor
Management
and workers of
the superseding
tasks
Supplier Input Process Output Customer Key metrics
SIPOC

6. European Students of Industrial Engineering and Management
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http://peikkousa.blogspot.fi/2016/09/peikko-frame-alternative-to-post.html
Hollow-core slab assembly
Element
manufacturer
Truck
driver
Crane
operator
Site
workers
Site
Managers
Truck drives the
elements next to
the crane
Lifting bar is
connected to
crane
Slabs are
connected to
crane
Slabs are
lifted into
place
Slabs are
aligned and
disconnected
Process repeats
until truck is
unloaded
Elements are
manufactured
and transportedLifting bar →
Process of Hollow-Core Slab Assembly

7. European Students of Industrial Engineering and Management
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Site Layout & Logistics
A B C D E
Runway
Truck route to siteCrane
Top view of building (sections)
150 Slabs per segment
2 levels
Single truck holds 4-5 slabs
Travel time from
slab factory to site
is 30min per
direction

8. European Students of Industrial Engineering and Management
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Data Collection
 Data was collected from video
filmed with two cameras
attached to the crane
 Start of an observation is
when previous slab is on place

9. European Students of Industrial Engineering and Management
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756045301 50-1 5
LSL 0
Target 7
USL 15
Sample Mean 10,4144
Sample N 222
StDev(Overall) 10,1731
StDev(Within) 7,8664
Process Data
Pp 0,25
PPL 0,34
PPU 0,15
Ppk 0,15
Cpm 0,22
Cp 0,32
CPL 0,44
CPU 0,19
Cpk 0,19
Potential (Within) Capability
Overall Capability
PPM < LSL 0,00 152984,37 92766,38
PPM > USL 144144,14 326083,25 279969,23
PPM Total 144144,14 479067,62 372735,61
Observed ExpectedOverall ExpectedWithin
Performance
LSL
Target
USL
Overall
Within
2211 991 771 551 331 1 1896745231
80
60
40
20
0
Observation
IndividualValue
_
X=10,41
UB=15
LB=0
Count 1 1 1 1 1 1 21 7 1 1 3 2 2 2 1 1
Percent 2 2 2 2 2 2 436 23 6 4 4 4 2 2
Cum% 85 87 89 91 94 96 1 0036 60 66 70 74 79 81 83
Delay cause
O
ther
Truck
late
+
oth er+
w
o rkers
Truck
late
+
other+
unknow
n
Tru ck la te +
other +
B ig/sm
allsla b
Tru ck
la te
+
Big/sm
all slab
Truck
change
+
w
o rkerslate
O
the r
+truck
blocked
M
a
npow
er
Break
+
truck
late
U
n know
n/break
Truck
change
M
en
had
to
m
o ve
Big/sm
a ll slab
Truck
late
+
other
Truck
late
40
30
20
1 0
0
1 00
75
50
25
0
Count
Percent
31302932
80
60
40
20
0
Day (May)
Duration
1
1
1
1
1
1
1
11
1
1
9,48989,09259
12,3171
10,1892
11,561
Process Capability Report for Slab Assembly Duration
I Chart of Slab Assembly Duration
Pareto Chart of Delay causes Boxplot of Slab Assembly Duration By Day
14.4 % of
assemblies
are out of spec
Lot of special cause variation,
low standard variation
Low day-to-day variation
Truck scheduling
major issue
Exploratory Data Analysis (EDA)

10. European Students of Industrial Engineering and Management
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P
Manpower Machinery Mother nature
MaterialsMeasurementMethods
Money
What causes
Delay in element
assembly ?
Weather conditions:
-Wind speed
-Fog
Crane availability
Crane operator:
unclear instructions
and multiple requests
Workers:
Wrong place, wrong time
Material delivery
Method of
measurement
Amount of data,
sample size
Quality of data
Non standardized work
Additional mobile
cranes
Material manufacturing
Insufficient
funds/unwillingness
to support
increased
schedule
Not enough space
for trucks
Unloading materials
to ground
Other tasks during
assembly
Repeatability &
Reproducibility (project business)
Faulty elements
(Size)
Airport operations &
limited space
Circled factors
were keys for
improvement!
Fishbone

11. European Students of Industrial Engineering and Management
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Process Capability & Analysis
4137332925211713951
90
80
70
60
50
40
30
20
10
0
Observation
IndividualValue
_
X=11,56
UB=20
LB=0
1
1
I Chart of Slab Assembly Duration
Results include rows where day =2. (2.5.2017)
Manpower
Truck change
Truck late + other
Truck late
Truck late + other tasks+ workers
Truck late
Truck late
Truck late + other
Break + truck late
Truck late
Single truck
(Single Day)
Truck Arrival Interval
1 6:02
2 6:41
3 7:39
1 8:25 2:23
2 9:15 2:34
3 10:23 2:44
1 11:27 3:02
2 11:30 2:15
3 12:48 2:25
1 13:40 2:13
2 14:18 2:48
• Rotation of 3 trucks
• 2,5 hour interval
• (one truck every 50
minutes)
• 30 minutes interval
needed
Significant Special CauseVariation Within a Day

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Implemented Improvements
12
Increase number of trucks
Prioritize slab assembly
• Resource efficiency vs. Flow
efficiency!
• Truck waiting costs only 50€/h
• No other work started if truck is
couple of minutes late
• 4 truck schedule is possible in theory
but 5 or 6 truck schedule is required
Layout for slab delivery (5S)
1. Truck arrives and assembly starts
2. Second truck arrives to queue
3. First truck moves away after the assembly
4. Trucks turn around and leave
Buffer inventory located next to crane

13. European Students of Industrial Engineering and Management
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Improvement Risk Analysis
Task Potential
problem
Effect Likely cause S
E
V
O
CC
Preventive actions Contingent
actions
Triggers for
contingent
All Increase in
cycle time
Truck
queue &
waiting
Issues in
assembly
2 3 Preparatory work Unload truck to
buffer inventory
Assembly lasted
over 30 mins or
multiple trucks in
queue
All Rework Truck
queue &
waiting
Defective part,
careless
assembly
4 2 Alignment done
right the first time,
necessary
measurements
Unload truck to
buffer inventory
When need for
rework is noticed
All Buffer
inventory
full
No room
for
errors/truc
k unloading
Issues in
assembly
3 1 Assemble
elements from
buffer between
trucks when
possible
Continue
assembly to time
buffer (11.00-
13.00)
Over 6 elements in
the buffer
All No
material
available
Increase in
lead time
Error in truck
schedule/truck
s late
4 2 Load buffer at the
end of the shift
Call the supplier
for ETA →start
other tasks
Buffer empty &
truck late over 10
minutes
All Man lift
failure
Assembly
stopped
Man lift not
loaded
4 4 Make sure man
lifts are loaded on
the previous day
Use secondary
man lift
As soon as failure
occurs

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Leveraged Improvements to the
Whole Structural Frame Assembly
14
Schedule fast tracking based on
measured cycle times and known
variation
The slab assembly was only a small part
of the project
Small improvements on each
type added up to significant
savings
30% reduction on planned
assembly time
Elements Columns*
Beams* Trusses*
Reliable
measurement
Standardized
work
Reduced uncertainty & risk
*Both, Concrete & Steel parts

15. European Students of Industrial Engineering and Management
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Not a common practice in the construction industry
 Easy to find small wins as use of data is not common – Huge potential!
 Few references on how long-term improvements have succeeded
 Bottom-up initiatives are difficult (green belt) – Management support needed
Project based business
 Changing work during different work phases – measurement and implementation
needs to be fast
 Repeatability between unique projects (high sigma levels are hard to obtain)
 Use of sub-contractors makes implementation difficult
 Cost-plus pricing gives low incentives for process improvement
 Sub-contractor contract clauses are not effective to motivate for collaboration
Stagnant culture
 Change initiatives are extremely difficult without good management support
Lean Six Sigma in Construction Industry