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Richard Lindqvist and Lars Mattsson, Ph.D., of The Royal Institute of Technology: and Niclas Josefsson and Jarno Salmela of Scania CV

Richard Lindqvist and Lars Mattsson, Ph.D., of The Royal Institute of Technology: and Niclas Josefsson and Jarno Salmela of Scania CV’s default image

CMSC

Implementation of the Quality Assurance Matrix and Methodology

Quality by design

Published: Thursday, February 10, 2011 - 11:34

The purpose of this article is to present the planning of a case study performed in the field of geometrical and dimensional measurement and controllability planning (GMCP, previously abbreviated GICP). The case study is carried out at the Swedish automotive company Scania CV. This article presents the preparation of the planned implementation work of the quality assurance matrix and methodology (QAM). The QAM methodology is described and will later be implemented, evaluated, and verified.

The QAM framework is primarily being applied on complex products. In this case study a pinion and a crown wheel are being used as case study objects. These two critical components create a subassembly, i.e. conical or hypoid gearbox assembly, in the rear central gearbox of a Scania truck. Critical design and process requirements, characteristics, and parameters, and their related design classification as defined by Scania CV internal standard specification, will be presented. The design classification is a major important input to the QAM model. Historical geometrical and dimensional measurement data, and machine and process capability data from production of the pinion and crown wheel are also important inputs to the QAM matrix. Discussion of the findings and the captured results to date, along with a conclusion on the current work, is presented at the end of this article.

Introduction

This article will mainly focus on the current implementation of QAM at Scania CV, presenting an overview of the ongoing planning activities and ideas. The efficiency of the QAM implementation will be evaluated based on the number of engineering design, production engineering, and quality engineering-related issues captured in the industrialization phase of new designs and re-designs of crown wheels and pinions. The pinion and the crown wheel are critical components. From a process and operational perspective, these components must be planned for high-capability manufacturing, with the goal to reach zero defects in manufacturing, i.e. "first component through" or "first component correct."

QAM, first presented by Lindqvist, et. al.,1 is performed in integrated product-development teams in a concurrent engineering environment. The members of QAM teams are typically design engineers, production engineers, operation and process planning professionals, quality engineers, and the production engineers in metrology departments. Through the interplay between design, production, and metrology, Scania CV attempted to show that it is possible to ensure quality early in the new product development process. The future vision and state of product development, industrialization activities, quality revision system, and the overall quality assurance system are explained in figures 1, 2, 3, and 5. The use of a systematic and holistic concurrent engineering teamwork approach will demonstrate that it is possible to meet the clearly stated design engineering functional requirements (FR), design parameters (DP), and manufacturing and process parameters (MP) requirements, with the support of production's knowledge of the potential process capabilities. As seen in figures 5 and 6, the introduction and combination of a new kind of design and a process failure mode and effects analysis (FMEA) tool, along with the integrated methodology of QAM, demonstrates the intention for the preproduction planning to perform and identify a one-risk assessment and a GMCP plan.

This will probably result in:
• Changed design engineering, production engineering, and production engineering metrology, and related drawing requirement specifications, i.e., according to ISO/TC 213, "Geometrical Product Specification and Verification"
• New or changed selection of applicable measurement types, measuring method and dimensional metrology equipment (DME)
• A first proposal on a suitable sampling and measurement frequency plan based on the risk assessment and identified current available machine and process capability in production

Methods and materials

Scania CV currently employs a quality revision process, as seen in figure 1, which they want to improve to a future state along the lines seen in figure 2. The current revision process, which is an indicator on how well the company's products meet quality standards, only captures a few parts per million (ppm), and it only analyzes finished components. In other words, it captures the total production process, but not the individual machines and operations that comprise the total production process.


Figure 1: Scania CV quality assurance process, current state (click here to enlarge)


Figure 2: Scania CV quality assurance process, proposed future state (click here to enlarge)

For the machine workshop producing the pinions and the crown wheels, the implementation of the process seen in figure 3 is suggested. This process is intended to include line revisions in addition to late final component revision only on the finished and fabricated components.


Figure 3: Scania CV applied quality revisions, current and future state proposal (click here to enlarge)

A number of design and manufacturing process engineering parameters have been identified. According to data gathered from Scania, there are 36 pinion-related design DPs and 20 crown-wheel-related DPs with classification of requirements (COR).2 There are also 19 pinion-related MPs and 10 crown-wheel-related MPs identified. All of these parameters are also related to geometrical, dimensional, and surface structure requirements, and will be used as an important input to the QAM matrix. Figure 4 shows a typical hypoid gearbox assembly, which demonstrates how the crown wheel and the pinion are oriented to each other.


Figure 4: The principal design and configuration of a representative hypoid gearbox assembly

Figure 5 presents the contextualized and closed-looped product realization process. An overview of the QAM process and working methodology has previously been described by Lindqvist, et. al.1,3 A draft activity model based on geometrical and dimensional measurement and controllability planning was first developed using the ASTRAKAN modeling language. This activity model was later simplified according to the developed QAM Microsoft Excel software application, as seen in figure 6.


Figure 5: The main activities in product realization, industrialization and reuse of production knowledge data and results (click here to enlarge)


Figure 6: A simplified ASTRAKAN activity model for performing and using the QAM methodology (click here to enlarge)

From an engineering development point of view, the GMCP and QAM process and methodology should be performed in concurrent engineering teams and be accomplished, according to experiences gained from Volvo CE, within a typical three- to four-hour workshop window for every new component. The team should include at a minimum a workshop leader, one design engineer, one production engineer, one process and operation planning engineer, and one production engineering metrology engineer. Figure 7 displays the interaction and interplay between the addressed engineering disciplines in a typical manufacturing company.


Figure 7: The interplay and probable iterations between different disciplines in concurrent engineering work

The first key issue is to break down the design requirements4 and intents into requirements that are manageable, producible, and measurable from the perspective of design, production, and metrology. As seen in figure 8, according to ISO/TC 213, there is a defined relationship which breaks down the functional point of view into design and drawing specifications. Then the actual manufacturing is carried out, a physical component is produced, and a real work piece is fabricated. After the fabrication process, the actual measurement and/or inspection is carried out to compare the result (verification operators) gathered from the measuring equipment and compare it to the specification operator.

Figure 8: Functional requirement relationship to specification and verification requirements

In figure 9, a more detailed description of the specification operator relationship to the verification operator, i.e. measurand, is highlighted. In this case the specification operator generally contains a skin model, which contains different operations and relates to a measurand. The verification operator generally contains a real surface, which contains different operations, and which ends in a measured value. The specification operators' measurand is validated and compared with the actual measured value, and a conformance check is thereby carried out. Figure 9 thereby attempts to explain the complexity of conformance in production engineering metrology measurements.5


Figure 9: Specification operator vs. Verification operator4

The developed QAM matrix and methodology is performed in a Microsoft Excel application. QAM contains the following worksheets in the Microsoft Excel application.

In worksheet 1 the user fills in general information about the component to be planned and prepared for production. A 2-D or 3-D model-based drawing should be attached and linked to this specific Excel file. In worksheet 2 the main work is carried out. Here the user and workshop group fill in the classification template. The classification template itself contains of the following topics to be performed:
1. Preconditions for operation and process planning
2. A preliminary operation and process plan for the component to be manufactured; the main part includes the measurement and controllability of the component, where controllability is a key principle
3. The impact matrix, which means identification of the different process steps and identification of what process step or steps significantly affect the design or manufacturing specification operator
4. In the final step, the team develops a detailed GMCP plan for the component based on the previous working steps

Figures 10 to 15 show screen prints taken from the actual QAM application starting with worksheet number 1, which is the introductory/general information page.


Figure 10: The QAM application introductory or "Information" page and worksheet (click here to enlarge)


Figure 11: The QAM application "Classification Template" worksheet (click here to enlarge)


Figure 12: The QAM application log or "Change trace template" worksheet (click here to enlarge)


Figure 13: The QAM application measurement classes and explanation worksheet (click here to enlarge)


Figure 14: The QAM application measurement report/plan protocol worksheet (click here to enlarge)


Figure 15: The QAM application follow-up template worksheet (click here to enlarge)

In summary, the QAM methodology and process could be simplified and explained by figure 16, in which the main process steps are presented. In a real world workflow, more extensive processes with more complex questions and issues to solve will be present.


Figure 16: The simplified and general QAM process and related questions and issues to be solved and managed (click here to enlarge)

The QAM management and progress reporting could fairly easy be carried out in the Microsoft Excel application. The user can compile data from all ongoing QAM development application projects and design a substantial management report. As an example, Volvo CE used the following reporting format, seen in figure 17.


Figure 17: QAM management tool for progress reporting (click here to enlarge)

Figure 17 presents an example of Volvo CE management reports, in which the total number of QAMs that have been carried out so far is displayed. The figure reveals how many actions have been started and which actions are now ongoing activities. They are also related to the actual engineering discipline, weather it is design engineering, production engineering, production engineering metrology, or quality engineering.

Results

Scania CV introduced and combined a new kind of design and process FMEA tool and the integrated QAM methodology and evaluated it on two complex components. In this case study a pinion and a crown wheel are used for the evaluation of the QAM methodology. The methodology and working process for QAM has been presented and scheduled for implementation and evaluation at Scania CV.

Discussion

Does the presented QAM process and methodology answer the important questions one should ask when performing GMCP planning? The following questions should be considered:
• What should be measured, controlled, and monitored? How important are the specification operator and verification operator? Have design and manufacturing classifications been performed?
• Why is each specific measurement performed? What is the level of its importance?
• Is the specific operation in close range to the machine or in a separate measuring room?
• How is measurement performed? Manually, semi-automatic, or fully automatic?
• What tools are used for measurement: CMMs, portable CMMs, hand gauges, and/or some combination of the above?
• When is the measurement supposed to happen? (i.e., production pace and planned tact times)
• How often should measurement happen, and for what sample size?
• Who does the measurement? How is their competence analyzed, and what is the requirement in terms of education and the need for certification?

In our opinion the QAM process and methodology as presently constituted can help answer all of these questions. However, it can and should be further developed, improved, validated, and evaluated. The QAM tool will be further explored in other Swedish companies engaged in the SIMET research project to validate and improve the methodology and process.

Disclaimer

The name and vendors products are used in this article solely for descriptive purposes only. This does not imply any endorsement or recommendation of any vendors' products by the authors.

Acknowledgements

We would like to acknowledge the Swedish Vinnova and the FFI research program for funding and supporting our research.

References

1 Lindqvist, R.; Lundgren, M.; Hedman, S.; Lindahl, P.; Vångell, T.; and Mattsson, L.; "An Information Model Approach for Systematic and Holistic Geometrical Inspection and Control Planning (GICP)," The Journal of the CMSC, Vol. 4, No.2, pp. 20–26, 2009.
2 Classification of Requirements – COR, Scania CV internal standard, STD3944, revision 7, 2007-10-24.
3 Lindqvist, R.; Lundgren, M.; and Mattsson, L.; "Geometry Assurance By Systematic Geometrical Inspection and Control Planning", Proceedings from the annual Swedish Production Symposium, Gothenburg, Sweden, Dec. 2009.
4 Zheng, L.Y., et. al., "Key Characteristics Management in Product Lifecycle Management: A Survey of Methodologies and Practices," Proc IMechE, Vol.222, Part B, 2008, DOI:10.1243/09544054JEM1045
5 Humienny, Z., "State of the Art in GPS Area," CIRP Journal of Manufacturing Science and Technology 2, 2009, DOI:10.1016/j.cirpj.2009.06.007

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About The Author

Richard Lindqvist and Lars Mattsson, Ph.D., of The Royal Institute of Technology: and Niclas Josefsson and Jarno Salmela of Scania CV’s default image

Richard Lindqvist and Lars Mattsson, Ph.D., of The Royal Institute of Technology: and Niclas Josefsson and Jarno Salmela of Scania CV

Richard Lindqvist is a Ph.D. student in geometry assurance-geometry inspection and control planning at the Royal Institute of Technology in Stockholm, Sweden. Lars Mattsson, Ph.D., is the head of the Royal Institute of Technology's department of production engineering. Niclas Josefsson is a project manager at Scania CV. Jarno Salmela is a quality technician at Scania CV.