Available online at www.sciencedirect.com
Procedia CIRP 00 (2012) 000–000
8th CIRP Conference on Intelligent Computation in Manufacturing Engineering
Adaptation of the Value Stream Optimization approach to collaborative company networks in the construction industry Dominik T. Matta,b, Daniel Krausea,*, Robert Raucha b
a Innovation Engineering Center, Fraunhofer Italia Research, Schlachthofstr. 57, 39100 Bozen, Ialy Faculty of Science and Technology, Free University of Bolzano, Piazza Università 5, 39100 Bozen, Italy * Tel.: +39-0471-1966914; fax: +39-0741-1966949.E-mail address:
[email protected]
Abstract
While in the automotive or aerospace industry the use of automation technology and processes and the application of lean manufacturing methods are common nowadays, the construction industry is lagging behind these developments. In this context, with the help of value stream design, largely known in mass production but recently also in variant intensive manufacturing, the process flows within single companies but especially amongst the partners in such a collaborative network can be designed in a highly customer-oriented and efficient way [1]. Therefore, this paper describes in detail a methodology to design an integrated and customized value stream map for construction industries requirements. The approach was developed and verified based on a collaborative project of applied research with the acronym “build4future”. © 2012 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of CIRP Keywords: Production; Process; Customization
1. Introduction Already in the early 60’s the target of an industrialized construction value chain was followed in order to be more competitive against the growing low cost countries in Europe. Efficiency and construction costs were drastically reduced by rationalizing the construction process, pre-fabrication of construction elements and the development of innovative construction machines [2]. Later, with the development of the Lean Thinking approach derived from the Toyota Production System [3], new organizational methodologies even for the construction industry were available. Despite these construction optimization activities, which were actively pushed by research as well as industry, only a few punctual projects could be realized. In this context, a significant margin of labor productivity can be detected for the construction industry. This margin amounts in Italy to about 15% from 1995 to 2007 [4]. Also in the fields of occupational
safety and supply-chain and materials management significant deficiencies can be detected, which are compounded by the declining skills in the labor market [5]. A recent study has proven potential cost and time savings trough process optimization of about 30% as realistic for the construction industry. As a consequence, it is not surprising that more than 30% of the people involved in construction business are unhappy with the processes they work with [6]. Another fundamental problem of the construction industry consists in the competition for projects that is mainly cost focused: the cheapest bid wins and the very conservative industry invests little time, money or energy in innovation and thus realizes only incremental changes. The co-acting of the aforementioned factors leads to a negative spiral, which creates an increasing competitive pressure especially on small and medium sized enterprises (SME) in the construction sector and construction-related industries. Due to these problems, the cooperative and interdisciplinary research project “build4future” aims to
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develop and implement a cooperative project platform for an industrialised, integrated and intelligent construction [7]. The “build4future”-consortium is cofunded by the Italian province of Bolzano and is coordinated by Fraunhofer Italia (IEC Innovation Engineering Center). It involves 12 Italian SMEsa from construction and construction related industries as well as an interdisciplinary research team formed by Fraunhofer Italia, the Free University of Bolzano, the South Tirolean CasaClima Agency and the TIS Innovation Park. The main objective of “build4future” is to rethink and redesign the entire value chain for customized construction involving a discrete number of different players, and to reach a level of efficiency and industrialization known from other industries. 2. The value stream engineering approach A value stream can be defined as the sum of every specific action within the manufacturing of a certain product [8]. In this context, the physical transformation of raw materials to a finished product as well as the therefore needed information management must be considered for the value stream. In order to be able to see and in particular to understand the value stream, a lean production [3] method called value stream design was developed for the description and optimization of production processes. Value steam design supports the process engineer to visualize the value stream and the waste within a process: it’s “like wearing lean glasses”, as the workbook “Learning to See” [9] shortly sums it up. Within this publication the authors propose guidelines to eliminate waste increasing simultaneously the value added share of a process. The concept of value stream mapping was first implemented by the automotive industry especially for series production with limited variant number [10]. Later it was expanded to various industries and branches. On this basis, the Fraunhofer Institute for Industrial Engineering (IAO) adapted the value stream design methodology to the specific needs of the single-part and small batch production with high diversity of product typologies and variants. The resulting approach, called value stream engineering, uses process patterns [11], which are first developed methodically, then standardized and finally projected. Thus, in industrial enterprises implemented process patterns are frequently projected according to the operational situation. This approach makes it possible to represent every step of the
a
Alpi Fenster GmbH, Studio Arch. Ralf Dejaco, Erlacher Innenausbau KG, Euroclima AG, Eurotherm AG, EXPAN GmbH, Frener & Reifer Metallbau GmbH, Glas Müller Vetri AG, Lanz Metall GmbH, Plattner Bau AG, Tecno Spot GmbH
workflow, even preceding indirect activities (e.g. development), from customer to customer. Furthermore, value stream engineering enables the process engineer to not just visualize and analyze the value stream for a certain product group, but also for different product groups in one process map. Beside this, even different customer groups are considered. Thereby resources used by different product and/or customer groups can be identified and scheduled in an easier way. Thus, the value stream engineering approach is tailored for the single-part and small batch production with high diversity of product typologies and variants. 3. Customized methodology for construction process design on the basis of value stream engineering In construction projects, a process map needs to integrate various different craft trade businesses along the value chain based on concepts optimizing the building process and organization. Such concepts may be existing lean management [12] or lean construction [13] methodologies as well as innovative contractual approaches [14, 15] promoting cooperative project handling. Additionally, in contrast to other industries, the mapping of a holistic construction process has to be highly flexible and adaptable in terms of product and process as construction firms are not able to operate on basis of a fixed target process because of the changing customer requirements from one project to the next. Therefore, the ideal mapping process for cooperative construction projects is a customized integration of different lean trade processes, compounded and designed according to individual needs of a certain construction project. The value stream engineering approach for modeling and representing strongly structured business processes [16] covers mainly the gap from customized manufacturing to series production [10]. As this represents a preliminary stage from the series production to the one-of-a-kind production, as we have in the building sector, the value stream engineering has been taken as a basis for the development of the new customized mapping methodology described in the following sections. 3.1. Requirements definition for classified customer scenarios As various building projects can be very different (e.g. industrial buildings compared to private residential buildings), the building characteristics take a considerable influence on the individual construction process and thereby on the trades executing the processes [17]. In order to make this specific characteristic of the building industry clearer, figure 1
Author name / Procedia CIRP 00 (2011) 000–00 exemplary illustrates three different customer scenarios and their direct implication on the three main targets of project management that are quality, cost and time.
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The single requirements can now be weighted according to their relevance for the investigating customer scenario. Therefore, the method of paired comparison [19] is used to rank alternative solutions regarding predefined criteria by directly comparing every single alternative with every other alternative. After having ranked the alternatives, they can be weighted to afterwards carry out a scoring model analysis [19]. The ranking and weighting of the ten identified requirements is shown for an exemplary customer scenario in figure 2.
Fig. 1. Different customer scenarios implicate different construction processes
The illustration demonstrates the different implications of individual building projects on the construction process. These very different project conditions complicate the internal elaboration of an efficient template process for every single trade. Thus, the mostly small and medium sized craft trade businesses (about 90% of the European construction industry [18]) collaborating simultaneously in different typologies of projects need to perform on a very high flexibility level. In order to introduce a classification of construction projects, the most significant characteristics having impact on the process and their possible specifications were brainstormed within the “build4future”-project. In order to combine these specifications to coherent customer scenarios, the morphological box [19] was introduced as a scientific methodology. On this basis, customer scenarios, especially for the local market were defined. As an example for such a customer scenario the typical South Tyrolean wooden house, following a modern and individual design can be named. The requirements, distinguishing different customer scenarios, are defined on the basis of the three primary objectives in project management. According to this, primarily low costs, low project lead time and at the same time high quality are the crucial requirements a customer demands. Beside the initial determination of those three project objectives trough planning, even the compliance during execution is fundamental for the customer. Thus, three more requirements were defined: cost compliance, construction time compliance and quality compliance. Furthermore, the cost aspect is divided into investment cost and operating costs. Quality is in addition divided into ecological usage of resources, living comfort, architecture and mutability. Altogether, there are ten customer requirements.
Fig. 2. Weighting of the customer requirements
3.2. Development and modeling of lean-optimized process patterns The development of process patterns was done based on a problem analysis in construction industry also carried out within the “build4future”-project. These analyses lead to a better understanding of the process organization of the small-structured and highly fragmented construction industry. Thus, four main fields of action could be identified: 1. Optimization of management and control during construction execution (organization and information technology) 2. Optimization of construction site logistics (interface between production and construction site) 3. Linkage of planning and execution (strengthening of the conceptual phase or “Frontloading”) 4. Intelligent Change Management These fields of action were taken as a starting point for the development of process patterns. Starting there, a catalogue of measures was defined, which enables the research team to systematically improve the fields of action using lean principles. An example for a measure optimizing the planning and control during construction execution (field 1), the implementation of the “Last
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Planner” process pattern (Figure 3) can be named. The Last Planner System®” [20] is a control system, which promotes the implementation of execution planning and is particularly helpful for interdisciplinary on site management and organization. An example for optimizing the construction site logistics (field 2) is a lean logistics process pattern for construction sites, called “Milk Run”. So far the material supply for the construction site could be delivered in an innovative, building phase-related way. Another logistics measure implements a “Just-in-time” process pattern for a rational prefabrication of client-specific products inside the enterprise with a timely supply on the construction site [7]. The representation of the process pattern is done according to the standardized value stream engineering notation. However, adapting the value stream engineering approach to construction, several notation standards needed to be changed or added in order to be able to describe the construction processes in a suitable way. A further adaption to the construction industry will be worked out when necessary, considering project-, product- and contract-related framework conditions.
Pre-assembly and final-assembly by the supplier Commissioning and final-assembly trough the supplier “Milk-Run” with several suppliers and construction sites
In order to be able to select the right process pattern of a functional cluster, the process patterns need to be evaluated regarding their field of application. In this context, for cluster 2 needs to be evaluated the applicability for pre-fabrication or pre-assembly and construction site fabrication or construction site assembly. For cluster 4 the applicability of the process pattern for different types of material (building materials, building elements, indirect materials and operating materials) [21] and means for work need to be evaluated. After having developed lean process patterns deriving from the catalogue of measures, their applicability for the investigating customer scenario (see 3.2) needs to be evaluated. Therefore, the following four-staged scale evaluation is applied for the ten customer requirements introduced in section 3.1: Table 2. Description of the four-staged scale evaluation Evaluation
Description
Suitable
The requirement is fulfilled by the process pattern without any significant restriction
Partial suitable
The requirement cannot be fulfilled by the process pattern without any significant restriction
Not suitable
The requirement cannot be fulfilled by the process pattern; the process pattern is contradictory to the process pattern
Not relevant
The requirement is not influenced by the process pattern and is thus not relevant
Fig. 3. “Last Planner” process pattern with timeline visualization
Until the actual stage of the research, the following four functional clusters of process patterns have been determined: Table 1. Functional clusters and developed process patterns Functional cluster
Process pattern
Order fulfillment
Engineer-to-Order Configure-to-Order
Organizational form of production
Construction site production Workshop production Flow production
Project control
Central push-project control trough the site foreman Decentralized pull-project control with Last Planner
Procurement logistics
Reorder point controlled direct delivery Planning controlled direct delivery Project plan determined direct delivery
3.3. Selection of process patterns according to the customer requirements In this section, the matching of the requirements derived from individual customer scenarios with the lean-optimized process patterns will be described. The selection approach uses the scoring model [19] to select the appropriate process pattern from the four functional clusters to afterwards design the investigating construction process map. The scoring model determines first the single values of benefit based on the weighted paired comparison of the project requirements and the evaluated process patterns. The ideal process pattern results from the highest value of benefit reached and is thus suitable to be used for mapping the construction process. Using this approach for every cluster of process patterns, an
Author name / Procedia CIRP 00 (2011) 000–00 individual value stream according to the lean thinking principles can be designed. Selecting a process pattern from functional cluster 2 and 4, also their field of application is decisive. Thus, only the process patterns applicable for the investigating case are considered. 4. Case Study The applicability of the customized methodology was verified on a first prototype value stream for the customer scenario of wooden houses in the medium price segment. 4.1. Introduction of the customer scenario “middle class wooden house” The investigating customer scenario represents a prefabricated residential wooden house with post-and-beam construction technique. The customer type sets a high value on turn-key order handling (general contractor), price guarantee and ecological construction [22]. The building technique enables an individual prefabrication of the various construction elements, which are subsequently assembled on the construction site. The pre-fabricated elements are thereby customized based on standardized construction configurations. The project handling process for the given customer scenario starts at the entrance of a customer order and precedes with the conceptual design and the sampling trough the constructor. Afterwards, the production drawings for the various construction elements are designed and sent to the internal and external fabrications. After the final assembly of the construction elements on the construction site, the project is accepted by the constructor and ready to be occupied. In order to get a better understanding of the processes, expert interviews and on-site analysis of the pre-fabrication and the construction site assembly have been carried out at Rubner Haus AG, an internationally well known Italian wooden house manufacturer. 4.2. Selection of suitable process patterns and design of the value stream map Based on the weighted requirements for the customer scenario “middle class wooden house”, the values of benefit for the single process patterns are calculated. For every functional cluster of process patterns, the process pattern showing the highest value of benefit has to be chosen to design the value stream. This selection is shown for the four functional clusters of process patterns in the following:
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Table 3. Selected process patterns Functional cluster
Process pattern
Order fulfillment
Configure-to-Order
Organizational form of production
Pre-fabrication: flow production
Project control
Decentralized pull-project control with Last Planner
Procurement logistics
Building materials: Daily external “MilkRun”, internal Milk-Run with supermarket
Final-assembly: construction site production
Building elements: Planning controlled direct delivery (Just-in-Time) Means for work: Commissioning and finalassembly trough the supplier Indirect and operating materials: Reorder point controlled direct delivery combined with “Milk-Run”
The integration of the above selected process patterns into a customized prototype process map is illustrated in figure 4. This step has to be done manually, to really be able to customize the interface between the process patterns. In order to keep the mapping simple and understandable it is done on a maximum A3 page size using MS Power Point templates.
Fig. 4. Prototype value stream for customer scenario “middle class wooden house”
Beginning on the right on top of the map, the constructor places an order and the planning phase begins. According to the selected Configure-to-Order project handling, the drawings are distributed from the technical office to the internal and external pre-fabrications. The production control for the pre-fabrication and the assembling on the construction site are carried out collaboratively according to the Last Planner process pattern. Construction elements, such as wall elements or pre-fabricated ceilings, are fabricated industrialized according the flow production principle. The finalassembly of the construction elements is carried out using construction site production. Regarding the procurement logistics, primary “Milk-Run” concepts for the delivery of construction material, such as wood, are selected. For the internal logistics, a supermarket
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concept combined with a “Milk-Run” is implemented. Building elements, such as windows, doors or facades are suggested to be delivered planning controlled to the usage places according to the Just-in-Time principle. Other commissioning materials, needed for the finalassembly, are commissioned and delivered by the supplier/trade to the construction site.
[6] Matt DT, Krause D. Schlanke Prozesse in Baunetzwerken (unpublished survey); Fraunhofer IEC; 2012. [7] Matt DT, Benedetti C, Krause D, Paradisi I. “Build4future” – interdisciplinary design: from the concept trough production to the construction site. Proceedings of the First International Workshop on Design in Civil and Environmental Engineering, KAIST Korea; 2011, p. 52-62 [8] Schoenberger R, Elbert R. Dimensionen der Logistik:
5. Conclusion
Funktionen, Institutionen und Handlungsebenen. Gabler Verlag; 2010.
The developed methodology has demonstrated how to design an integrated and customized value stream map for construction industry. Up to now, only a limited selection of process patterns has been developed and tested within a case study. Further research particularly aims to develop and upgrade process patterns strengthening the conceptual phase during the construction of a building. Thus, process patterns describing “Frontloading”-strategies and new cooperative models for bidding and awarding of a construction performance will be studied. Additionally process patterns will be developed to be able to handle or even better to avoid the numerous planning changes during construction, causing building freezes and delays. Therefore, process patterns including a well-thought-out change management will be elaborated. To this end, process maps for various customer scenarios should be designed and thereby verified the plausibility of the methodological approach described in the paper. Another future aim of the research team is to adapt and implement the methodological approach of customized value stream design to other similar branches. These are one-of-a-kind production related branches, such as shipbuilding or plant engineering.
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