- Email: [email protected]
Methodic Design of a Customized Maturity Model for Geometrical Tolerancing
Available online at www.sciencedirect.com
ScienceDirect Procedia CIRP 10 (2013) 119 – 124
12th CIRP Conference on Computer Aided Tolerancing
Methodic design of a customized maturity model for geometrical tolerancing Albert Weckenmann, Gökhan Akkasoglu* Chair Quality Management and Manufacturing Metrology, University Erlangen-Nuremberg, Naegelsbachstrasse 25, 91052 Erlangen, GERMANY
Abstract
development times and low resource consumption. The additional higher complexity of the products to be designed causes a low transparency of the development status, whereby decision-making and problem-solving become more difficult. In order to persist in a global competition, increasing effectiveness and efficiency of the development is elementary. Maturity models represent Best-Practices for a specific approach and can uncover improvement potentials in development by evaluation of defined indicators. A new approach is proposed, which allows designing customized maturity models systematically for a subject matter. By the resulting base of indicators the status of the subject matter can be determined to deduce specific operational improvement measures. The method for the design of a customized maturity model is exemplary applied in the field of geometrical tolerancing. With the help of a principle approach for the ited and subdivided into their characteristics. Requirements on these characteristics are staged and assigned to four maturity levels. The result is an evaluation basis, which allows to assess the performance of tolerancing work and to deduce improvement measures. © © 2013 2012 The The Authors. Authors. Published Publishedby byElsevier ElsevierB.V. B.V. Selection and/or peer-review under responsibility of Professor Xiangqian Jiang. Selection and peer-review under responsibility of Professor Xiangqian (Jane) Jiang Keywords: maturity model; reference model; tolerance management; decision-making
1. Current Challengesa The interchangeability of product parts has been one of the main promoters for the industrial revolution and has led to the maximum of mass production in the provided to the consumer at that time [1]. Along with the products has been increased due to the increasing demands of customers for individualized products. anyway they have to be produced industrially due to economic reasons. A smooth product realization can only be ensured, if the interchangeability,
manufacturability and testability of the workpieces are given [2]. This requires a complete and unambiguous definition of the properties and specifications of the workpieces [3] with consideration of valid standards and guidelines for a collaborative development. According to the Rule-of-ten possible faults in specifying workpieces are especially to be analyzed and prevented in early phases of product realization (e.g. by use of Failure Mode and Effect Analysis FMEA) due to the lower costs per fault elimination (Fig. 1). In late phases of product realization the elimination of detected faults causes significantly higher costs. A systematic and comprehensive approach for design and geometrical tolerancing of products can avoid failures and provide a cost-effective realization of products.
* Corresponding author. Tel.: +49-9131-85-26517 ; fax: +49-9131-85-26524 E-mail address: [email protected].
2212-8271 © 2013 The Authors. Published by Elsevier B.V. Selection and peer-review under responsibility of Professor Xiangqian (Jane) Jiang doi:10.1016/j.procir.2013.08.021
120
Albert Weckenmann and Gökhan Akkasoglu / Procedia CIRP 10 (2013) 119 – 124
Fault prevention
Developing and planning Costs per fault
Fault detection
Purchasing and producing
100.-
10.-.10 Definition
Development
1.Process planning
Manufacturing
Testing
Fig. 1. Correlation between fault prevention and fault detection of-ten [4]
Field
Rule-
For the management of design and development processes in early phases coordinating activities to direct and control the development approach [5] based on numerical evaluations are to be established. However, in these early phases primarily qualitative indicators are available instead of quantitative data [6, 7]. In order to carry out a quantified assessment, maturity models can be used [8]. They provide specific indicators with staged requirements on them, which relate to a certain number of maturity levels. Maturity models focus on different subject matter like processes, products or systems. Due to the reference-based assessment, a comparability of the investigated objects is enabled and improvement possibilities are pointed out in the next higher maturity level as assessed. An aim-oriented development approach with cost-reduced changes is facilitated. 2. Maturity models and state of the art A maturity represents the status of a considered object like process, product or system to a specific time and is to be assessed by comparison with relevant indicators and the staged requirements on them. A specific maturity level is achieved, if the requirements within this level are completely fulfilled. Accordingly, the maturity levels are gradually built on each other [9]. A maturity model summarizes these indicators and staged requirements. Thus, maturity models provide with the highest maturity level best-practices for a subject matter to be evaluated by comparison. With determining the status of the considered processes, products or systems specific improvement possibilities can be detected. In addition, maturity models enable the capturing of lessons learned by changing the currently documented requirements per maturity level. Typically, maturity models consist of four to six maturity levels.
Currently existing maturity models have primarily a strategic and generic focus like SPICE (Software Process Improvement and Capability Determination) of the international standard ISO 15504 [10] or CMMI (Capability Maturity Model Integration) of the Software Engineering Institute [11]. Both are focusing on software development and guide developers in improving business processes. Furthermore, there exists a multiplicity of maturity models for different matters, where determining an operational status is not regarded [12]. They have a reduced relevance to the needs of a deviating subject matter. Thus, provided improvement measures based on the determined maturity have low adaptability to the specific concerns. Creating an ability to design customized maturity models would enhance the adequacy of derived improvement actions and their acceptance within organizations. The following chapters provide a methodic design for customized maturity models and its subsequent application for the field of geometrical tolerancing. 3. Methodic Design for customized maturity models A customized maturity model creates the possibility for adequate self-assessments and shows up appropriate improvement possibilities. Thus, the status of the subject matter can be monitored and continuously improved. Approaches for the development of maturity models are discussed in different literature. Exemplary de Bruin [13] proposes generalized phases for developing a maturity model. Based on these works, Becker proposes in [14] a procedure model for the development of maturity models in IT management. Both procedures have in common that they do not provide methodic support in designing a customized maturity model. Nevertheless, a methodical approach in designing a maturity model would enhance its efficiency and usability. The proposed generic approach for designing customized maturity models in this paper has been generated and validated within the collaborative research work for the development of the novel sheet-bulk metal forming, wherein a maturity model has been created for new forming processes [15]. Initially a reference model of the subject matter is to be created, which can exemplary comprise the elementary activities of a general process for a specific aim (Fig. 2) [16]. Based on the reference model relevant maturity indicators are to be deduced and categorized, for example using the quality management technique of affinity diagrams. Afterwards the selected indicators have to be weighted comparatively with the help of a pairwise comparison. The defined indicators and their weightings as well as the hierarchically staged requirements on the indicators are captured by the Maturity Level Matrix.
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Albert Weckenmann and Gökhan Akkasoglu / Procedia CIRP 10 (2013) 119 – 124
status of a subject matter with the fulfillment of requirements on the different indicators in percent and calculation of the weighted arithmetic mean. The result quantifies the status of the subject matter, which can be classified within the intervals of the four maturity levels n
Reference Model
Sustainable
Maturity indicators Comprehensive
Level Le el 3
Appropriate
Indicator weighting Indi
Ad hoc/ unstructured
Indn
Indi
Levell 4 Lev
4. Conceptual design of a maturity model for geometrical tolerancing
Level Lev el 2
Levell 1 Lev
...
... Indn
0% - 15%
15% - 50%
50% - 85%
The introduced method in the previous chapter has been used to create a maturity model for geometrical tolerancing. The task of geometrical tolerancing is to permit interchangeability due to clear definition of properties and specifications of a workpiece. A local and temporal separated manufacturing becomes possible, which can enhance the economic efficiency of the production. Therefore, the geometrical tolerancing is part of the basics of every construction work. According to [17] the fulfillment of intended product function is influenced by uncertainties like incorrect or incomplete application of geometrical tolerancing or by measurement uncertainty and the correlation uncertainty. Therefore, the assurance of product specifications by a characteristic maturity model in the early stages of product development can avoid cost-intensive changes in later development phases and increase the fulfillment of product functions as required by the customer.
85% - 100%
Maturity M Maturity Level Matrix wi
Maturity Levels
...
Staged requirements
Indi
M(t)
Evaluation 1 n wi Ind i ( t ) n wi i 1 i 1
Fig. 2. Method for the design of customized maturity models
The requirements are assigned to four maturity levels which in turn are related to certain percentage intervals. The highest maturity level up to 100% represents the best-practice for the specific indicator. The percentage intervals are designed in accordance to [10], with level 1 covering 0% to 15%, level 2 covering 15% to 50%, level 3 covering 50% to 85% and level 4 covering 85% to 100%. The maturity can be determined by comparing the Analysis and definition of requirements
Designer
Validation 2 1 Specification (Drawing)
Simulated workpiece
Simulated workpiece
Real workpiece
Inspection result
Production engineer
Metrologist
Manufacturing
Inspection
Fig. 3. Reference Model for Product Specification
Albert Weckenmann and Gökhan Akkasoglu / Procedia CIRP 10 (2013) 119 – 124
Tolerance specification (Are the tolerancing zones specified with consideration of functional properties and variances in manufacturing and testing?) Accordance with standards (Are valid standards and guidelines used for tolerancing?) Illustration of the workpiece (Are the tolerancing specifications defined complete, unambiguous, clearly and as far as possible given in one view?) Inspection of real workpiece (Is the measurement system defined and analyzed holistically?) Validation of specification (Have the specifications been validated reproducible and applicationspecific?) Coordination of specification changes (Are organizational approaches established for sustainable managed changes of tolerancing specifications?) The weighting of each indicator wi has been determined by a pairwise comparison. Requirements on each indicator are staged and linked to one of the four maturity levels (Table 1). The assessment of the maturity to a specific time t can be performed by the designer. Therefore each indicator Indi(t) is to be valued between 0% and 100% according to the existing status of the geometrical specified workpiece in relation to the designed maturity model. The evaluation of the total maturity M(t) is afterwards to be calculated by the weighted arithmetic mean
M(t)
n
1 n
Boundaries setting
Requirements setting
i 1
Tolerances indication
The design of the maturity model for geometrical tolerancing requires a reference model, which has to represent a general approach for product specification. An appropriate procedure is given in Figure 3. The product specification is initially based on the analysis and definition of requirements, whereby customer demands have to be translated into functional, manufacturable and testable product definitions. The product specification has to be performed in such way by the designer that the realized workpiece can fulfill its intended functions over the whole life cycle. The defined tolerances have to enable safe (process capable) and cost-effective manufacturing and assembly of the workpieces. Essential function and assembly properties must be testable or measurable easily and reliably by direct detection of the workpiece. Translating these requirements into a complete, unambiguous and clear drawing is the task of the designer. Adjacently the specifications are to be validated. This can happen by previous knowledge of the designer or by simulation (workflow no. 1, Fig. 3). The latter can be performed arithmetical or statistical. Another approach for validation of the designed product specification is represented by comparison to the manufactured and inspected real workpiece (workflow no. 2, Fig. 3). The approach for the step of specification in Figure 3 is in accordance to [2, 18] detailed into three typical steps, wherein the designer has initially to define the requirements on the workpiece to be constructed (Fig. 4). This includes the determination of functional relevant elements, requirements on orientation, location and run-out as well as the determination of form and surface requirements. Afterwards boundary conditions like selecting the tolerancing principle for size (e.g. principle of independency [19] or the envelope requirement [20]), defining general tolerances as well as datums and datum features are to be performed. Finally the tolerances of orientation, location, run-out, form and surface are to be indicated. Each specifying value should be as large as possible while ensuring the function. The additional use of material condition modifiers (if applicable) can provide a cost-effective specification through tolerance extension without functional losses and can also simplify the inspection of the workpiece by using gauges [21]. Based on the reference model for product specification (Fig. 3) and the approach for geometrical tolerancing (Fig. 4) following relevant indicators for maturity assessment have been determined (clarifying questions are given in brackets): Tolerancing requirements (Are the requirements defined with considerations of functionality, manufacturability and testability of the workpiece?)
Specification (Drawing)
122
wi
i 1
wi Ind i ( t )
(1)
2
Determine functional relevant elements and their purpose Determine orientation, location and run-out requirements
3
Determine form requirements
4
Determine surface requirements
5
Select tolerancing principle for size
6
Define general tolerances
7
Define datums and datum features
8
Indicate type and magnitude of orientation, location and run-out tolerances
9
Indicate type and magnitude of form tolerances
1
10 Indicate type and magnitude of surface tolerances 11 Define and indicate material condition modifiers
Fig. 4. Detailed approach for geometrical tolerancing (in accordance to [2, 18])
10%
17.5% No arrangements or definitions for the T he measuring systemto be used inspection of real workpieces. and the measurement strategy to be applied (e.g. measuring values, resolution etc.) are defined and coordinated.
17.5% No validation is performed.
10%
Illustration of the workpiece
Inspection of real workpiece
Validation of spe cification
Coordination of spe cification changes
T olerance zones are designed functional, statistically, economical and e cological with consideration of variances in manufacturing and me asurement process.
Requirements result from customer interviews and are functional as well as manufacturableoriented and consider te stability.
(85% - 100%)
Le ve l 4
A function oriented simulation of the worst-case scenario (minimummaximum-principle) in a peer-review is performed.
A complete illustration of the workpiece is regarded.
Changes on product specifications are we ll-founded in a continuous process and in agreement with neighboring business sections. A ve rsion history provides information about significant changes and are communicated to persons concerned.
A function oriented and statistical based simulation of the worst-case scenario with considering temperature effects as well as influences of the manufacturing process and the me asuring/inspection process in a peer-review is performed.
T he measuring system to be used and the measurement strategy to be applied (e.g. number of measurements, procedure, measuring values, resolution, evaluation strategy etc.) as well as an appropriate and function suitable measurement principle are defined, coordinated and documented.
A complete and unambiguous illustration of the workpiece is regarded.
Changes on product specifications are we ll-founded in a continuous process and in agreementwith neighboring business sections. A ve rsion history provides information about significant changes and are communicated to persons concerned. The e ffects of the changes are analyzed previously and are validated afterwards.
Validation of specification is done with a sufficient sample of workpieces, which are manufactured, measured and functionally tested under production conditions.
T he measuring system to be used and the measurement strategyto be applied (e.g. number of measurements, procedure, measuring values, resolution, evaluation strategy etc.) as well as an appropriate and function suitable measurement principle are defined, coordinated and documented. The measurement uncertainty is determined and indicated with the measurement result.
A complete, unambiguous and cle arly arranged illustration of the workpiece is regarded.
T olerances are designed in accordance T olerances are designed in accordance T olerances are designed in most to national standards and to international standards and accordance with the Geometrical guidelines. guidelines. Product Specification Matrix.
Changes on product specifications are Changes on product specifications are done ad-hoc and without we ll-founded in a continuous process communication to anyone. and in agreement with neighboring business sections.
Illustration of the workpiece is not reviewed.
No standards and guidelines are used for tolerance design.
10%
Accordance with standards
Requirements result from customer interviews and are functional as well as manufacturable oriented.
(50% - 85%)
Le ve l 3
T olerance zones are designed T olerance zones are designed functional and based on knowledge. functional and statistically with consideration of variances in manufacturing process.
17.5% T olerance indication is done knowledge based.
(15% - 50%) Requirements result from customer interviews and are functional oriented.
Tolerance specification
(0% - 15%)
17.5% No requirements on tolerancing defined.
wi
Le ve l 2
Tole rancing requirements
Indicators - Ind i
Le ve l 1
Maturity Le vels
Albert Weckenmann and Gökhan Akkasoglu / Procedia CIRP 10 (2013) 119 – 124 123
Table 1. Designed maturity model for geometrical tolerancing
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Albert Weckenmann and Gökhan Akkasoglu / Procedia CIRP 10 (2013) 119 – 124
n represents the number of evaluated indicators. The quantified status of an existing geometrical tolerancing can be assigned to one of the intervals of the four i potentials can be uncovered by analyzing the deviations of each indicator from the maximum possible value (100%). 5. Conclusion and outlook Geometrical tolerancing provides in early development phases the design and specification of workpieces with consideration of requirements for functionality, manufacturability and testability. According to the Rule-of-ten, an insufficient definition of specifications can lead to cost-intensive changes later on. For preventive failure avoidance, a maturity model for geometrical tolerancing has been designed based on a given method. With the help of a reference model for geometrical tolerancing maturity relevant indicators have been derived and weighted by a pairwise comparison. Hierarchically staged requirements on the indicators have been defined and related to certain maturity levels. The assessment of the maturity is carried out by the designer and calculated by a weighted arithmetic mean. With the appliance of the maturity model for geometrical tolerancing and the assessment and improvement of the status, valid specifications can result. This reduces the risk for cost-intensive changes in later product development phases. For a continuous improvement, lessons learned can be integrated easily in the maturity model after its application by extending the base of indicators or the requirements defined for them. 6. Acknowledgement This article is based on work within the Transregional Collaborative Research Centre (Transregio) 73 funded by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG). The authors thank the German Research Foundation. 7. References [1] [2] [3] [4] [5] [6]
Koren, Y., 2010. The Global Manufacturing Revolution. John Wiley and Sons, New York. Klein, B., 2006. Toleranzmanagement im Maschinen- und Fahrzeugbau. Oldenbourg, Munich. Trumpold, H. et al., 1997. Toleranzsysteme und Toleranzdesign Qualität im Austauschbau. Hanser, Munich. Ross, J.E., 1995. Total quality management: text, cases, and readings. St. Lucie Press, Michigan. ISO 9000: Quality management systems Fundamentals and vocabulary, Geneva, 2005. Weckenmann, A., Akkasoglu, G., 2012. Maturity Determination of New Forming Processes considering Uncertain Indicator Values, Key Engineering Materials 502, p. 97-102.
[7]
[8] [9]
[10] [11] [12] [13] [14] [15]
[16] [17]
[18] [19] [20] [21]
Weckenmann, A., Akkasoglu, G., 2010. Managing the challenges in development processes with the maturity method, in AIMTDR 24/1 B. Satyanarayana, K. Ramji, Editors. Andhra Univ., Visakhapatnam, p. 3-10. Weckenmann, A., Werner, T., Akkasoglu, G., 2012. Facing the challenges of engineering in quality management. Quality Access to Success 13, p. 72-78. Ahlemann, F. et al., 2005. Kompetenz- und Reifegradmodelle für das Projektmanagement. Grundlagen, Vergleich und Einsatz, in ISPRI-Work Report F. Ahlemann et al, Editors. University of Osnabrück, Osnabrück. ISO 15504-2: Information technology - Process assessment - Part 2: Performing an assessment, Geneva, 2003. SEI (Software Engineering Inst.): CMMI for Development v1.3, Carnegie Mellon University, 2010. Berg, P. et al. 2001. Assessment of quality and maturity level of Intl. Conf. on Management of Engineering and Technology PICMET. Portland, USA. de Bruin, T. et al., 2005. Understanding the Main Phases of Develop 16th Australasian Conference on Information Systems. Sydney, Australia. Becker, J. et al., 2009. Developing Maturity Models for IT Management. Wirtschaftsinformatik 51, p. 249-260. Weckenmann, A., Akkasoglu, G., 2012. Maturity Model for the development of new forming processes applied to the Sheet-Bulk Metal Forming. Key Engineering Materials 504-506, p. 10111016. Weckenmann, A. et al., 2012. Methodengestützte Referenzvorgehensweise für neue Umformverfahren. Zeitschrift für wirtschaftlichen Fabrikbetrieb 1-2, p. 43-47. Srinivasan, V., 2003. An Integrated View of Geometrical Product Specification and Verification, Geometric Product Specification and Verification: Integration of Functionality Bourdet et al., Editors. Kluwer Academic, London, p. 1-12. Jorden, W., 2007. Form- und Lagetoleranzen. Hanser, Munich. ISO 8015: Geometrical product specifications (GPS) Fundamentals - Concepts, principles and rules, Geneva, 2011. DIN 7167: Relationship between tolerances of size, form, and parallelism; envelope requirement without individual indication on the drawing, Geneva, 1987. Schütte, W., 1995. Methodische Form- und Lagetolerierung. University of Paderborn, Paderborn.
ScienceDirect Procedia CIRP 10 (2013) 119 – 124
12th CIRP Conference on Computer Aided Tolerancing
Methodic design of a customized maturity model for geometrical tolerancing Albert Weckenmann, Gökhan Akkasoglu* Chair Quality Management and Manufacturing Metrology, University Erlangen-Nuremberg, Naegelsbachstrasse 25, 91052 Erlangen, GERMANY
Abstract
development times and low resource consumption. The additional higher complexity of the products to be designed causes a low transparency of the development status, whereby decision-making and problem-solving become more difficult. In order to persist in a global competition, increasing effectiveness and efficiency of the development is elementary. Maturity models represent Best-Practices for a specific approach and can uncover improvement potentials in development by evaluation of defined indicators. A new approach is proposed, which allows designing customized maturity models systematically for a subject matter. By the resulting base of indicators the status of the subject matter can be determined to deduce specific operational improvement measures. The method for the design of a customized maturity model is exemplary applied in the field of geometrical tolerancing. With the help of a principle approach for the ited and subdivided into their characteristics. Requirements on these characteristics are staged and assigned to four maturity levels. The result is an evaluation basis, which allows to assess the performance of tolerancing work and to deduce improvement measures. © © 2013 2012 The The Authors. Authors. Published Publishedby byElsevier ElsevierB.V. B.V. Selection and/or peer-review under responsibility of Professor Xiangqian Jiang. Selection and peer-review under responsibility of Professor Xiangqian (Jane) Jiang Keywords: maturity model; reference model; tolerance management; decision-making
1. Current Challengesa The interchangeability of product parts has been one of the main promoters for the industrial revolution and has led to the maximum of mass production in the provided to the consumer at that time [1]. Along with the products has been increased due to the increasing demands of customers for individualized products. anyway they have to be produced industrially due to economic reasons. A smooth product realization can only be ensured, if the interchangeability,
manufacturability and testability of the workpieces are given [2]. This requires a complete and unambiguous definition of the properties and specifications of the workpieces [3] with consideration of valid standards and guidelines for a collaborative development. According to the Rule-of-ten possible faults in specifying workpieces are especially to be analyzed and prevented in early phases of product realization (e.g. by use of Failure Mode and Effect Analysis FMEA) due to the lower costs per fault elimination (Fig. 1). In late phases of product realization the elimination of detected faults causes significantly higher costs. A systematic and comprehensive approach for design and geometrical tolerancing of products can avoid failures and provide a cost-effective realization of products.
* Corresponding author. Tel.: +49-9131-85-26517 ; fax: +49-9131-85-26524 E-mail address: [email protected].
2212-8271 © 2013 The Authors. Published by Elsevier B.V. Selection and peer-review under responsibility of Professor Xiangqian (Jane) Jiang doi:10.1016/j.procir.2013.08.021
120
Albert Weckenmann and Gökhan Akkasoglu / Procedia CIRP 10 (2013) 119 – 124
Fault prevention
Developing and planning Costs per fault
Fault detection
Purchasing and producing
100.-
10.-.10 Definition
Development
1.Process planning
Manufacturing
Testing
Fig. 1. Correlation between fault prevention and fault detection of-ten [4]
Field
Rule-
For the management of design and development processes in early phases coordinating activities to direct and control the development approach [5] based on numerical evaluations are to be established. However, in these early phases primarily qualitative indicators are available instead of quantitative data [6, 7]. In order to carry out a quantified assessment, maturity models can be used [8]. They provide specific indicators with staged requirements on them, which relate to a certain number of maturity levels. Maturity models focus on different subject matter like processes, products or systems. Due to the reference-based assessment, a comparability of the investigated objects is enabled and improvement possibilities are pointed out in the next higher maturity level as assessed. An aim-oriented development approach with cost-reduced changes is facilitated. 2. Maturity models and state of the art A maturity represents the status of a considered object like process, product or system to a specific time and is to be assessed by comparison with relevant indicators and the staged requirements on them. A specific maturity level is achieved, if the requirements within this level are completely fulfilled. Accordingly, the maturity levels are gradually built on each other [9]. A maturity model summarizes these indicators and staged requirements. Thus, maturity models provide with the highest maturity level best-practices for a subject matter to be evaluated by comparison. With determining the status of the considered processes, products or systems specific improvement possibilities can be detected. In addition, maturity models enable the capturing of lessons learned by changing the currently documented requirements per maturity level. Typically, maturity models consist of four to six maturity levels.
Currently existing maturity models have primarily a strategic and generic focus like SPICE (Software Process Improvement and Capability Determination) of the international standard ISO 15504 [10] or CMMI (Capability Maturity Model Integration) of the Software Engineering Institute [11]. Both are focusing on software development and guide developers in improving business processes. Furthermore, there exists a multiplicity of maturity models for different matters, where determining an operational status is not regarded [12]. They have a reduced relevance to the needs of a deviating subject matter. Thus, provided improvement measures based on the determined maturity have low adaptability to the specific concerns. Creating an ability to design customized maturity models would enhance the adequacy of derived improvement actions and their acceptance within organizations. The following chapters provide a methodic design for customized maturity models and its subsequent application for the field of geometrical tolerancing. 3. Methodic Design for customized maturity models A customized maturity model creates the possibility for adequate self-assessments and shows up appropriate improvement possibilities. Thus, the status of the subject matter can be monitored and continuously improved. Approaches for the development of maturity models are discussed in different literature. Exemplary de Bruin [13] proposes generalized phases for developing a maturity model. Based on these works, Becker proposes in [14] a procedure model for the development of maturity models in IT management. Both procedures have in common that they do not provide methodic support in designing a customized maturity model. Nevertheless, a methodical approach in designing a maturity model would enhance its efficiency and usability. The proposed generic approach for designing customized maturity models in this paper has been generated and validated within the collaborative research work for the development of the novel sheet-bulk metal forming, wherein a maturity model has been created for new forming processes [15]. Initially a reference model of the subject matter is to be created, which can exemplary comprise the elementary activities of a general process for a specific aim (Fig. 2) [16]. Based on the reference model relevant maturity indicators are to be deduced and categorized, for example using the quality management technique of affinity diagrams. Afterwards the selected indicators have to be weighted comparatively with the help of a pairwise comparison. The defined indicators and their weightings as well as the hierarchically staged requirements on the indicators are captured by the Maturity Level Matrix.
121
Albert Weckenmann and Gökhan Akkasoglu / Procedia CIRP 10 (2013) 119 – 124
status of a subject matter with the fulfillment of requirements on the different indicators in percent and calculation of the weighted arithmetic mean. The result quantifies the status of the subject matter, which can be classified within the intervals of the four maturity levels n
Reference Model
Sustainable
Maturity indicators Comprehensive
Level Le el 3
Appropriate
Indicator weighting Indi
Ad hoc/ unstructured
Indn
Indi
Levell 4 Lev
4. Conceptual design of a maturity model for geometrical tolerancing
Level Lev el 2
Levell 1 Lev
...
... Indn
0% - 15%
15% - 50%
50% - 85%
The introduced method in the previous chapter has been used to create a maturity model for geometrical tolerancing. The task of geometrical tolerancing is to permit interchangeability due to clear definition of properties and specifications of a workpiece. A local and temporal separated manufacturing becomes possible, which can enhance the economic efficiency of the production. Therefore, the geometrical tolerancing is part of the basics of every construction work. According to [17] the fulfillment of intended product function is influenced by uncertainties like incorrect or incomplete application of geometrical tolerancing or by measurement uncertainty and the correlation uncertainty. Therefore, the assurance of product specifications by a characteristic maturity model in the early stages of product development can avoid cost-intensive changes in later development phases and increase the fulfillment of product functions as required by the customer.
85% - 100%
Maturity M Maturity Level Matrix wi
Maturity Levels
...
Staged requirements
Indi
M(t)
Evaluation 1 n wi Ind i ( t ) n wi i 1 i 1
Fig. 2. Method for the design of customized maturity models
The requirements are assigned to four maturity levels which in turn are related to certain percentage intervals. The highest maturity level up to 100% represents the best-practice for the specific indicator. The percentage intervals are designed in accordance to [10], with level 1 covering 0% to 15%, level 2 covering 15% to 50%, level 3 covering 50% to 85% and level 4 covering 85% to 100%. The maturity can be determined by comparing the Analysis and definition of requirements
Designer
Validation 2 1 Specification (Drawing)
Simulated workpiece
Simulated workpiece
Real workpiece
Inspection result
Production engineer
Metrologist
Manufacturing
Inspection
Fig. 3. Reference Model for Product Specification
Albert Weckenmann and Gökhan Akkasoglu / Procedia CIRP 10 (2013) 119 – 124
Tolerance specification (Are the tolerancing zones specified with consideration of functional properties and variances in manufacturing and testing?) Accordance with standards (Are valid standards and guidelines used for tolerancing?) Illustration of the workpiece (Are the tolerancing specifications defined complete, unambiguous, clearly and as far as possible given in one view?) Inspection of real workpiece (Is the measurement system defined and analyzed holistically?) Validation of specification (Have the specifications been validated reproducible and applicationspecific?) Coordination of specification changes (Are organizational approaches established for sustainable managed changes of tolerancing specifications?) The weighting of each indicator wi has been determined by a pairwise comparison. Requirements on each indicator are staged and linked to one of the four maturity levels (Table 1). The assessment of the maturity to a specific time t can be performed by the designer. Therefore each indicator Indi(t) is to be valued between 0% and 100% according to the existing status of the geometrical specified workpiece in relation to the designed maturity model. The evaluation of the total maturity M(t) is afterwards to be calculated by the weighted arithmetic mean
M(t)
n
1 n
Boundaries setting
Requirements setting
i 1
Tolerances indication
The design of the maturity model for geometrical tolerancing requires a reference model, which has to represent a general approach for product specification. An appropriate procedure is given in Figure 3. The product specification is initially based on the analysis and definition of requirements, whereby customer demands have to be translated into functional, manufacturable and testable product definitions. The product specification has to be performed in such way by the designer that the realized workpiece can fulfill its intended functions over the whole life cycle. The defined tolerances have to enable safe (process capable) and cost-effective manufacturing and assembly of the workpieces. Essential function and assembly properties must be testable or measurable easily and reliably by direct detection of the workpiece. Translating these requirements into a complete, unambiguous and clear drawing is the task of the designer. Adjacently the specifications are to be validated. This can happen by previous knowledge of the designer or by simulation (workflow no. 1, Fig. 3). The latter can be performed arithmetical or statistical. Another approach for validation of the designed product specification is represented by comparison to the manufactured and inspected real workpiece (workflow no. 2, Fig. 3). The approach for the step of specification in Figure 3 is in accordance to [2, 18] detailed into three typical steps, wherein the designer has initially to define the requirements on the workpiece to be constructed (Fig. 4). This includes the determination of functional relevant elements, requirements on orientation, location and run-out as well as the determination of form and surface requirements. Afterwards boundary conditions like selecting the tolerancing principle for size (e.g. principle of independency [19] or the envelope requirement [20]), defining general tolerances as well as datums and datum features are to be performed. Finally the tolerances of orientation, location, run-out, form and surface are to be indicated. Each specifying value should be as large as possible while ensuring the function. The additional use of material condition modifiers (if applicable) can provide a cost-effective specification through tolerance extension without functional losses and can also simplify the inspection of the workpiece by using gauges [21]. Based on the reference model for product specification (Fig. 3) and the approach for geometrical tolerancing (Fig. 4) following relevant indicators for maturity assessment have been determined (clarifying questions are given in brackets): Tolerancing requirements (Are the requirements defined with considerations of functionality, manufacturability and testability of the workpiece?)
Specification (Drawing)
122
wi
i 1
wi Ind i ( t )
(1)
2
Determine functional relevant elements and their purpose Determine orientation, location and run-out requirements
3
Determine form requirements
4
Determine surface requirements
5
Select tolerancing principle for size
6
Define general tolerances
7
Define datums and datum features
8
Indicate type and magnitude of orientation, location and run-out tolerances
9
Indicate type and magnitude of form tolerances
1
10 Indicate type and magnitude of surface tolerances 11 Define and indicate material condition modifiers
Fig. 4. Detailed approach for geometrical tolerancing (in accordance to [2, 18])
10%
17.5% No arrangements or definitions for the T he measuring systemto be used inspection of real workpieces. and the measurement strategy to be applied (e.g. measuring values, resolution etc.) are defined and coordinated.
17.5% No validation is performed.
10%
Illustration of the workpiece
Inspection of real workpiece
Validation of spe cification
Coordination of spe cification changes
T olerance zones are designed functional, statistically, economical and e cological with consideration of variances in manufacturing and me asurement process.
Requirements result from customer interviews and are functional as well as manufacturableoriented and consider te stability.
(85% - 100%)
Le ve l 4
A function oriented simulation of the worst-case scenario (minimummaximum-principle) in a peer-review is performed.
A complete illustration of the workpiece is regarded.
Changes on product specifications are we ll-founded in a continuous process and in agreement with neighboring business sections. A ve rsion history provides information about significant changes and are communicated to persons concerned.
A function oriented and statistical based simulation of the worst-case scenario with considering temperature effects as well as influences of the manufacturing process and the me asuring/inspection process in a peer-review is performed.
T he measuring system to be used and the measurement strategy to be applied (e.g. number of measurements, procedure, measuring values, resolution, evaluation strategy etc.) as well as an appropriate and function suitable measurement principle are defined, coordinated and documented.
A complete and unambiguous illustration of the workpiece is regarded.
Changes on product specifications are we ll-founded in a continuous process and in agreementwith neighboring business sections. A ve rsion history provides information about significant changes and are communicated to persons concerned. The e ffects of the changes are analyzed previously and are validated afterwards.
Validation of specification is done with a sufficient sample of workpieces, which are manufactured, measured and functionally tested under production conditions.
T he measuring system to be used and the measurement strategyto be applied (e.g. number of measurements, procedure, measuring values, resolution, evaluation strategy etc.) as well as an appropriate and function suitable measurement principle are defined, coordinated and documented. The measurement uncertainty is determined and indicated with the measurement result.
A complete, unambiguous and cle arly arranged illustration of the workpiece is regarded.
T olerances are designed in accordance T olerances are designed in accordance T olerances are designed in most to national standards and to international standards and accordance with the Geometrical guidelines. guidelines. Product Specification Matrix.
Changes on product specifications are Changes on product specifications are done ad-hoc and without we ll-founded in a continuous process communication to anyone. and in agreement with neighboring business sections.
Illustration of the workpiece is not reviewed.
No standards and guidelines are used for tolerance design.
10%
Accordance with standards
Requirements result from customer interviews and are functional as well as manufacturable oriented.
(50% - 85%)
Le ve l 3
T olerance zones are designed T olerance zones are designed functional and based on knowledge. functional and statistically with consideration of variances in manufacturing process.
17.5% T olerance indication is done knowledge based.
(15% - 50%) Requirements result from customer interviews and are functional oriented.
Tolerance specification
(0% - 15%)
17.5% No requirements on tolerancing defined.
wi
Le ve l 2
Tole rancing requirements
Indicators - Ind i
Le ve l 1
Maturity Le vels
Albert Weckenmann and Gökhan Akkasoglu / Procedia CIRP 10 (2013) 119 – 124 123
Table 1. Designed maturity model for geometrical tolerancing
124
Albert Weckenmann and Gökhan Akkasoglu / Procedia CIRP 10 (2013) 119 – 124
n represents the number of evaluated indicators. The quantified status of an existing geometrical tolerancing can be assigned to one of the intervals of the four i potentials can be uncovered by analyzing the deviations of each indicator from the maximum possible value (100%). 5. Conclusion and outlook Geometrical tolerancing provides in early development phases the design and specification of workpieces with consideration of requirements for functionality, manufacturability and testability. According to the Rule-of-ten, an insufficient definition of specifications can lead to cost-intensive changes later on. For preventive failure avoidance, a maturity model for geometrical tolerancing has been designed based on a given method. With the help of a reference model for geometrical tolerancing maturity relevant indicators have been derived and weighted by a pairwise comparison. Hierarchically staged requirements on the indicators have been defined and related to certain maturity levels. The assessment of the maturity is carried out by the designer and calculated by a weighted arithmetic mean. With the appliance of the maturity model for geometrical tolerancing and the assessment and improvement of the status, valid specifications can result. This reduces the risk for cost-intensive changes in later product development phases. For a continuous improvement, lessons learned can be integrated easily in the maturity model after its application by extending the base of indicators or the requirements defined for them. 6. Acknowledgement This article is based on work within the Transregional Collaborative Research Centre (Transregio) 73 funded by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG). The authors thank the German Research Foundation. 7. References [1] [2] [3] [4] [5] [6]
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