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ESTIEM Lean Six Sigma Green Belt Project at YIT - Airport Extension


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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:

Published in: Engineering
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ESTIEM Lean Six Sigma Green Belt Project at YIT - Airport Extension

  1. 1. European Students of Industrial Engineering and Management www.estiem.org1 Decreasing Structural Frame Assembly Time Lean Six Sigma Green Belt Project - Educational Case Site visualizations: PES-Arkkitehdit Oy and 3Drender Oy
  2. 2. European Students of Industrial Engineering and Management The Project Was Conducted As a Part of Helsinki-Vantaa Airport Expansion 2 Site visualizations: PES-Arkkitehdit Oy and 3Drender Oy
  3. 3. European Students of Industrial Engineering and Management The Goal of the Project Was to Reduce the Leadtime of the Structural Frame Assembly 3
  4. 4. European Students of Industrial Engineering and Management  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. 5. European Students of Industrial Engineering and Management 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. 6. European Students of Industrial Engineering and Management 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. 7. European Students of Industrial Engineering and Management 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. 8. European Students of Industrial Engineering and Management 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. 9. European Students of Industrial Engineering and Management 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. 10. European Students of Industrial Engineering and Management 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. 11. European Students of Industrial Engineering and Management 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
  12. 12. European Students of Industrial Engineering and Management 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. 13. European Students of Industrial Engineering and Management 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
  14. 14. European Students of Industrial Engineering and Management 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. 15. European Students of Industrial Engineering and Management 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