Reliability centered maintenance planning based on computer-aided fmea
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The document discusses computer-aided failure mode and effects analysis (FMEA) to improve reliability-centered maintenance planning. It proposes using an extended product model to (1) represent potential machine failures and (2) simulate machine behavior under usage conditions to detect abnormalities. This allows FMEA to be performed efficiently in a computer-aided manner. Validation experiments on mechatronics products demonstrated the proposed computer-aided FMEA method.
![The 35th CIRP-International Seminar on Manufacturing Systems, 12-15 May 2002, Seoul, Korea
1
Reliability-Centered Maintenance Planning
based on Computer-Aided FMEA
Fumihiko Kimura, Tomoyuki Hata and Noritomo Kobayashi
Department of Precision Machinery Engineering
The University of Tokyo
Abstract
For proper management of life cycle of machines and manufacturing facilities, it is important to perform
appropriate maintenance operations, and to keep machine status for better reuse and recycling opportunity.
For this purpose, a virtual maintenance system is very effective, where facility life cycle model is constructed
in computer, and reliability and availability of machines are predicted based on usage deterioration
modelling. FMEA(Failure Mode and Effect Analysis) is a powerful method to extensively investigate possible
machine failure and functional deterioration, and to predict reliability. However it is very time-consuming and
tedious to perform FMEA by conventional manual method. In this paper, computer aided FMEA is proposed,
and its theoretical basis is discussed. An extended product model is introduced, where possible machine
failure information is added to describe used machine status. By applying generic behaviour simulation to
extended product models, it is possible to detect abnormal or mal-behaviour of machines under used
conditions. Based on this behaviour analysis and extended product models, FMEA process can be
performed by computer-aided manner, and can be very efficient to avoid laborious work and possible errors.
Based on FMEA results, maintenance planning can be evaluated by simulating life cycle operations of
machines and by predicting reliability during operation. For validating the proposed computer-aided FMEA
method, several experiments are performed for mechatronics products.
Keywords: Maintenance, Reliability, FMEA
1 INTRODUCTION
In order to cope with the pressing issues of
environmental effect due to industrial production, it is
required to fundamentally reduce the environmental
burden, such as resource consumption and disposal,
while to keep the proper service level products can offer
to customers [1,2].
It is difficult to achieve this target only by optimising
individual product design towards better resource
consumption and recycling performance. It is rather
essential to design the total product life cycle as a whole
from product planning, throughout product design and
manufacturing, to product usage, maintenance and
reuse/recycling/disposal. A sound strategy for product
maintenance and improvement during product usage
should be established, and all the life cycle processes
are to be well controlled. By such approach,
reuse/recycling activities are also rationalized. A whole
product life cycle can be made visible and controllable.
We have called such approach as Inverse Manufacturing
by stressing the controllability of reuse/recycling
processes, where closed product life cycles, including
maintenance, are pre-planned and controlled [3].
For proper management of life cycle of machines and
manufacturing facilities, as required in the above
discussion, it is important to perform appropriate
maintenance operations, and to keep machine status for
better reuse and recycling opportunity. There are many
methods for maintenance operations, such as time-based
or condition-based maintenance. It is necessary to
generate rational maintenance planning for optimizing
total maintenance activity in terms of maintenance cost
and facility availability.
It is desirable to make maintenance planning
concurrently with machine design processes, and to
verify the total life cycle performance before actual facility
construction. For this purpose, a virtual maintenance
system is very effective, where facility life cycle model is
constructed in computer, and reliability and availability of
machines are predicted based on usage deterioration
modelling[4,5,6]. FMEA(Failure Mode and Effect
Analysis) is a powerful method to extensively investigate
possible machine failure and functional deterioration, and
to predict reliability. However it is very time-consuming
and tedious to perform FMEA by conventional manual
method.
In this paper, computer aided FMEA is proposed, and its
theoretical basis is discussed. For this purpose, an
extended product model is introduced, where possible
machine failure information is added to describe used
machine status[7]. By applying generic behaviour
simulation to extended product models, it is possible to
detect abnormal or mal-behaviour of machines under
used conditions. Based on this behaviour analysis and
extended product models, FMEA process can be
performed by computer-aided manner, and can be very
efficient to avoid laborious work and possible errors.
Based on FMEA results, maintenance planning can be
evaluated by simulating life cycle operations of machines
and by predicting reliability during operation. For
validating the proposed computer-aided FMEA method,](https://image.slidesharecdn.com/reliability-centeredmaintenanceplanningbasedoncomputer-aidedfmea-130407045208-phpapp01/85/Reliability-centered-maintenance-planning-based-on-computer-aided-fmea-1-320.jpg)
![The 35th CIRP-International Seminar on Manufacturing Systems, 12-15 May 2002, Seoul, Korea
2
several experiments are performed for mechatronics
products.
2 RELIABILITY-CENTERED MAINTENANCE
Proper maintenance planning is a complicated task.
There are many causes of machine failure, and their
properties are different. Some are depending on the age
of machines, and some are purely stochastic. Monitoring
of machine operation is not necessarily effective. Often
bad maintenability is only improved by early design
changes. There are various types of maintenance, such
as time-based maintenance and condition-based
maintenance. It is complicated whether to adopt time-
based maintenance or condition-based maintenance.
Maintenance cost very much depends on required
maintenance resources and facilities.
In order to achieve rational total life cycle management, it
is strongly desired to realize a systematic planning
method of maintenance operations. Reliability-Centered
Maintenance (RCM) is one of the well-established
systematic methods for selecting applicable and
appropriate maintenance operation types[8]. In RCM,
failure consequences and their preventive operations are
systematically analysed, and feasible maintenance
planning is determined. The rough process of RCM is as
follows:
(1) Target products or systems of maintenance should
be clearly identified, and necessary data should be
collected.
(2) All the possible failures and their effect on target
products or systems are systematically analysed.
(3) Preventive or corrective maintenance operations are
considered. Selection of operations is done based
on rational calculation of effectiveness of such
operations for achieving required maintenance
quality, such as reliability, cost, etc.
The above steps are repeated to realize feasible
maintenance planning. Step (2) is the core of the RCM
process. It is generally very tedious and time-consuming,
and its contents are fundamentally the same as Failure
Mode and Effect Analysis (FMEA). In the following
sections, efficient and practical approach to FMEA based
on computer-aided technology is explained.
3 COMPUTER-AIDED FMEA
The aim of FMEA is to systematically analyse the
reliability of target systems or products based on
planning or design information, and to enhance reliability
by modifying target system or product design before
actual production. The general procedure of FMEA is as
follows:
(1) Based on the given design information about the
target products or systems, a reliability diagram is
created, where failure effects among components
are described.
(2) Known modes of failure about individual components
are applied to the reliability diagram, and failure
effects are propagated up to the total functional
behaviour of the products or systems.
(3) Criticality of the failure is evaluated based on the
probability and severity of the failure effects.
The results of the step (3) are fed back to the original
products or systems design, and they are iteratively
improved. The above FMEA steps are systematic, but
they are practically very tedious, especially step (2).
Here we introduce a computer-aided technology for step
(2), and realize efficient FMEA, which can be performed
with not much extra-effort than to use CAD systems for
product design. For this purpose, a feature-based
product modelling is considered, by which functional
behaviour and failure effects can be automatically
propagated among components. By this extended
product modelling capability, all the possible mal-
functions of target products or systems can be
enumerated. For the evaluation of the method, it is
applied to small mechatronics products. But, it can be
applied for wider range of products with addition of extra
feature and failure mode definitions.
4 PRODUCT MODELLING FOR FMEA
4.1 Feature modelling
For FMEA applications, two types of feature definition are
required for part structure description:
(1) Part/component feature: This feature describes
space occupancy or vacancy with appropriate
attributes. This includes body features, such as a
rigid body, a flexible body, a shaft and a flange. It
also includes empty space and surfaces. It contains
various attributes, such as materials.
(2) Relation feature: This feature represents semantic
relations among part/component features, such as
flexible deformation and rotational pair. This is
described by various mechanisms, such as data,
formula, logical constraints and procedures. Failure
modes corresponding to parts/components and their
relations are described by this type of features.
Simple example is shown in Figure 1, where a rotational
relation represents transfer of rotational movement and
torque between two features.
Figure 1: Feature modelling of a motor-gear pair.
4.2 Function representation
For representing functional behaviour, three levels of
model description framework are introduced, as shown in
Figure 2:
(1) Function structure: Targeted functions of products or
systems are described from an abstract level to
more concrete levels. Those functions are
Motor
Rigid
Term.
Lead
Term.
Shaft
Gear
Rigid
Hole. Tooth
Rotational
Pair](https://image.slidesharecdn.com/reliability-centeredmaintenanceplanningbasedoncomputer-aidedfmea-130407045208-phpapp01/85/Reliability-centered-maintenance-planning-based-on-computer-aided-fmea-2-320.jpg)
![The 35th CIRP-International Seminar on Manufacturing Systems, 12-15 May 2002, Seoul, Korea
6
6 CONCLUSION
As a basis for systematic computer support for RCM
planning and FMEA, a feature-based product modelling
is introduced, by which semantic description and analysis
of product behaviour is realized. By applying various
failure phenomena of individual component to product
representation, total malfunctions and functional defects
are predicted. FMEA is a core part of RCM, and
computer-aided FMEA is expected to be very effective for
total maintenance planning throughout the whole life
cycle of target products and systems.
7 REFERENCES
[1] Alting, L., Legarth, J.B., 1995, Life Cycle
Engineering and Design, Annals of CIRP, 44/2:569-
580.
[2] Westkaemper, E., Alting, L., Arndt, G., 2000, Life
Cycle Management and Assessment: Approaches
and Vision Towards Sustainable Manufacturing,
Annals of CIRP, 49/2:501-522.
[3] Kimura, F., 1999, Life Cycle Design for Inverse
Manufacturing, Proc. EcoDesign'99, IEEE, Tokyo,
995-999.
[4] Van Houten, F.J.A.M., Kimura, F., 2000, The Virtual
Maintenance System: A Computer-based Support
Tool for Robust Design, Product Monitoring, Fault
Diagnosis and Maintenance Planning, Annals of
CIRP, 49/1:91-94.
[5] Kimura, F., Hata, T., Suzuki, H., 1998, Product
Quality Evaluation Based on Behaviour Simulation
of Used Products, Annals of CIRP, 47/1:119-122.
[6] Hata, T., Kobayashi, N., Kimura, F., Suzuki, H.,
2000, Representation of Functional Relations
among Parts and its Application to Product Failure
Reasoning, Proc. Int. CIRP Design Seminar, ed.
Shpitalni, M., Haifa, 393-398.
[7] Kobayashi,N., 2002, Machine Failure Analysis using
Feature-Based Product Modelling, Ms.Thesis, The
University of Tokyo.
[8] Kumar,U., Crocker,J., Knezevic,J. and El-
Haram,M., 2000, Reliability, Maintenance and
Logistic Support, Kluwer Academic Publishers.](https://image.slidesharecdn.com/reliability-centeredmaintenanceplanningbasedoncomputer-aidedfmea-130407045208-phpapp01/85/Reliability-centered-maintenance-planning-based-on-computer-aided-fmea-6-320.jpg)
Reliability centered maintenance planning based on computer-aided fmea
- 1. The 35th CIRP-International Seminar on Manufacturing Systems, 12-15 May 2002, Seoul, Korea 1 Reliability-Centered Maintenance Planning based on Computer-Aided FMEA Fumihiko Kimura, Tomoyuki Hata and Noritomo Kobayashi Department of Precision Machinery Engineering The University of Tokyo Abstract For proper management of life cycle of machines and manufacturing facilities, it is important to perform appropriate maintenance operations, and to keep machine status for better reuse and recycling opportunity. For this purpose, a virtual maintenance system is very effective, where facility life cycle model is constructed in computer, and reliability and availability of machines are predicted based on usage deterioration modelling. FMEA(Failure Mode and Effect Analysis) is a powerful method to extensively investigate possible machine failure and functional deterioration, and to predict reliability. However it is very time-consuming and tedious to perform FMEA by conventional manual method. In this paper, computer aided FMEA is proposed, and its theoretical basis is discussed. An extended product model is introduced, where possible machine failure information is added to describe used machine status. By applying generic behaviour simulation to extended product models, it is possible to detect abnormal or mal-behaviour of machines under used conditions. Based on this behaviour analysis and extended product models, FMEA process can be performed by computer-aided manner, and can be very efficient to avoid laborious work and possible errors. Based on FMEA results, maintenance planning can be evaluated by simulating life cycle operations of machines and by predicting reliability during operation. For validating the proposed computer-aided FMEA method, several experiments are performed for mechatronics products. Keywords: Maintenance, Reliability, FMEA 1 INTRODUCTION In order to cope with the pressing issues of environmental effect due to industrial production, it is required to fundamentally reduce the environmental burden, such as resource consumption and disposal, while to keep the proper service level products can offer to customers [1,2]. It is difficult to achieve this target only by optimising individual product design towards better resource consumption and recycling performance. It is rather essential to design the total product life cycle as a whole from product planning, throughout product design and manufacturing, to product usage, maintenance and reuse/recycling/disposal. A sound strategy for product maintenance and improvement during product usage should be established, and all the life cycle processes are to be well controlled. By such approach, reuse/recycling activities are also rationalized. A whole product life cycle can be made visible and controllable. We have called such approach as Inverse Manufacturing by stressing the controllability of reuse/recycling processes, where closed product life cycles, including maintenance, are pre-planned and controlled [3]. For proper management of life cycle of machines and manufacturing facilities, as required in the above discussion, it is important to perform appropriate maintenance operations, and to keep machine status for better reuse and recycling opportunity. There are many methods for maintenance operations, such as time-based or condition-based maintenance. It is necessary to generate rational maintenance planning for optimizing total maintenance activity in terms of maintenance cost and facility availability. It is desirable to make maintenance planning concurrently with machine design processes, and to verify the total life cycle performance before actual facility construction. For this purpose, a virtual maintenance system is very effective, where facility life cycle model is constructed in computer, and reliability and availability of machines are predicted based on usage deterioration modelling[4,5,6]. FMEA(Failure Mode and Effect Analysis) is a powerful method to extensively investigate possible machine failure and functional deterioration, and to predict reliability. However it is very time-consuming and tedious to perform FMEA by conventional manual method. In this paper, computer aided FMEA is proposed, and its theoretical basis is discussed. For this purpose, an extended product model is introduced, where possible machine failure information is added to describe used machine status[7]. By applying generic behaviour simulation to extended product models, it is possible to detect abnormal or mal-behaviour of machines under used conditions. Based on this behaviour analysis and extended product models, FMEA process can be performed by computer-aided manner, and can be very efficient to avoid laborious work and possible errors. Based on FMEA results, maintenance planning can be evaluated by simulating life cycle operations of machines and by predicting reliability during operation. For validating the proposed computer-aided FMEA method,
- 2. The 35th CIRP-International Seminar on Manufacturing Systems, 12-15 May 2002, Seoul, Korea 2 several experiments are performed for mechatronics products. 2 RELIABILITY-CENTERED MAINTENANCE Proper maintenance planning is a complicated task. There are many causes of machine failure, and their properties are different. Some are depending on the age of machines, and some are purely stochastic. Monitoring of machine operation is not necessarily effective. Often bad maintenability is only improved by early design changes. There are various types of maintenance, such as time-based maintenance and condition-based maintenance. It is complicated whether to adopt time- based maintenance or condition-based maintenance. Maintenance cost very much depends on required maintenance resources and facilities. In order to achieve rational total life cycle management, it is strongly desired to realize a systematic planning method of maintenance operations. Reliability-Centered Maintenance (RCM) is one of the well-established systematic methods for selecting applicable and appropriate maintenance operation types[8]. In RCM, failure consequences and their preventive operations are systematically analysed, and feasible maintenance planning is determined. The rough process of RCM is as follows: (1) Target products or systems of maintenance should be clearly identified, and necessary data should be collected. (2) All the possible failures and their effect on target products or systems are systematically analysed. (3) Preventive or corrective maintenance operations are considered. Selection of operations is done based on rational calculation of effectiveness of such operations for achieving required maintenance quality, such as reliability, cost, etc. The above steps are repeated to realize feasible maintenance planning. Step (2) is the core of the RCM process. It is generally very tedious and time-consuming, and its contents are fundamentally the same as Failure Mode and Effect Analysis (FMEA). In the following sections, efficient and practical approach to FMEA based on computer-aided technology is explained. 3 COMPUTER-AIDED FMEA The aim of FMEA is to systematically analyse the reliability of target systems or products based on planning or design information, and to enhance reliability by modifying target system or product design before actual production. The general procedure of FMEA is as follows: (1) Based on the given design information about the target products or systems, a reliability diagram is created, where failure effects among components are described. (2) Known modes of failure about individual components are applied to the reliability diagram, and failure effects are propagated up to the total functional behaviour of the products or systems. (3) Criticality of the failure is evaluated based on the probability and severity of the failure effects. The results of the step (3) are fed back to the original products or systems design, and they are iteratively improved. The above FMEA steps are systematic, but they are practically very tedious, especially step (2). Here we introduce a computer-aided technology for step (2), and realize efficient FMEA, which can be performed with not much extra-effort than to use CAD systems for product design. For this purpose, a feature-based product modelling is considered, by which functional behaviour and failure effects can be automatically propagated among components. By this extended product modelling capability, all the possible mal- functions of target products or systems can be enumerated. For the evaluation of the method, it is applied to small mechatronics products. But, it can be applied for wider range of products with addition of extra feature and failure mode definitions. 4 PRODUCT MODELLING FOR FMEA 4.1 Feature modelling For FMEA applications, two types of feature definition are required for part structure description: (1) Part/component feature: This feature describes space occupancy or vacancy with appropriate attributes. This includes body features, such as a rigid body, a flexible body, a shaft and a flange. It also includes empty space and surfaces. It contains various attributes, such as materials. (2) Relation feature: This feature represents semantic relations among part/component features, such as flexible deformation and rotational pair. This is described by various mechanisms, such as data, formula, logical constraints and procedures. Failure modes corresponding to parts/components and their relations are described by this type of features. Simple example is shown in Figure 1, where a rotational relation represents transfer of rotational movement and torque between two features. Figure 1: Feature modelling of a motor-gear pair. 4.2 Function representation For representing functional behaviour, three levels of model description framework are introduced, as shown in Figure 2: (1) Function structure: Targeted functions of products or systems are described from an abstract level to more concrete levels. Those functions are Motor Rigid Term. Lead Term. Shaft Gear Rigid Hole. Tooth Rotational Pair
- 3. The 35th CIRP-International Seminar on Manufacturing Systems, 12-15 May 2002, Seoul, Korea 3 connected by relations, such as dependency or decomposition. Each function is defined by its physical input-output relations. (2) Function-dependency path: This representation is a key for failure diagnosis, and is automatically generated by comparing (1) and (3). For some functional description in (1), behaviour of physical attributes is detected, and it is related with part structure description via physical attributes. The same procedure is repeated to propagate functional dependency. (3) Part structure: This corresponds to the feature description of part/component in section 4.1. Figure 2: Function representation. 4.3 Failure analysis process Based on the knowledge of individual component failure, possible failure reasons are assigned to respective components in part structure. There may be many failures due to environment, time, statistics, wear/fatigue, etc. As shown in Figure 3, failure phenomena are propagated by tracing function-dependency path. The results are reflected in function structure, and failure effects of individual component over total product/system behaviour can be analysed. All the results are summarized in tabular form called an FMEA table. Figure 3: Propagation of failure. In order to show the criticality of the failure, Risk Priority Number (RPN) is used. Here RPN is computed by two factors: probability of occurrence of failure and severity of failure. Those factors also can be generated by the models described in sections 4.2 and 4.3. 5 FMEA EXAMPLES In order to show the feasibility of the method, mechatronics products are selected: a computer mouse and a portable CD player. Figure 4 shows an example mouse. Its part structure is shown in Figure 5. A part of its function structure is described as in Figure 6, and its function-dependency path is generated as shown in Figure 7. A part of a resultant FMEA table is shown in Figure 8. This example is simple, but almost exhaustive enumeration of possible failures can be realized, which includes rather unusual phenomena. Figure 4: A computer mouse. As a more complicated example, a portable CD player, as shown in Figure 9, is successfully analysed. The proposed method is basically feasible for such types of products. However for the comprehensive analysis of all types of mechanical/electrical analysis, substantial extension of feature description is necessary. Function Structure Function-Dependency Path Part Structure
- 4. The 35th CIRP-International Seminar on Manufacturing Systems, 12-15 May 2002, Seoul, Korea 4 Figure 9: A portable CD player. Cover body Human Mouse Pad screw_fix hold rotation_pair rotation_pair rotation_pair rotation_pair Frame shaft body catchhole1 hole2 photo_pass photo_pass frict_wheel frict_wheel Circuit body solder solder soldersolder Ball body surface shaft flange hole H_Roller V_PDiode body terminal H_LDiode body terminal H_PDiode body terminal term_fixterminal V_LDiode body terminal term_fix PC friction_rolling frict_wheel photo_pass photo_pass Base body hole1 hole2 hole3 hole4 catch3 catch4bottom_surface put fit fit hang rotation_pair rotation_pair rotation_pair rotation_pair hang spring Lead lead terminal1 terminal2 Roller body surface hole fit shaft Shaft Box body hole1 hole2 catch1 catch2 catch3 Spring shaft flange hole V_Roller terminal1 terminal2 terminal3 terminal4 Parts Feature Parts Group Parts Relation Function PositionButton y-Positionx-Position Ball Rotation x-Roller Rot. y-Roller Rot. Ball Support Left Button Right Button x-Lazor Det. y-Lazor Det. Figure 5: Part structure of a computer mouse. Figure 6: Function structure of a computer mouse.
- 5. The 35th CIRP-International Seminar on Manufacturing Systems, 12-15 May 2002, Seoul, Korea 5 Wear Dust Wear Dust Input Failure Wear Upper Function Failure Reason Failure Parts Failure Feature Relation causing Failure RPNFailure Function Figure 7: Failure analysis based on function-dependency path. Figutre 8: FMEA table for a computer mouse.
- 6. The 35th CIRP-International Seminar on Manufacturing Systems, 12-15 May 2002, Seoul, Korea 6 6 CONCLUSION As a basis for systematic computer support for RCM planning and FMEA, a feature-based product modelling is introduced, by which semantic description and analysis of product behaviour is realized. By applying various failure phenomena of individual component to product representation, total malfunctions and functional defects are predicted. FMEA is a core part of RCM, and computer-aided FMEA is expected to be very effective for total maintenance planning throughout the whole life cycle of target products and systems. 7 REFERENCES [1] Alting, L., Legarth, J.B., 1995, Life Cycle Engineering and Design, Annals of CIRP, 44/2:569- 580. [2] Westkaemper, E., Alting, L., Arndt, G., 2000, Life Cycle Management and Assessment: Approaches and Vision Towards Sustainable Manufacturing, Annals of CIRP, 49/2:501-522. [3] Kimura, F., 1999, Life Cycle Design for Inverse Manufacturing, Proc. EcoDesign'99, IEEE, Tokyo, 995-999. [4] Van Houten, F.J.A.M., Kimura, F., 2000, The Virtual Maintenance System: A Computer-based Support Tool for Robust Design, Product Monitoring, Fault Diagnosis and Maintenance Planning, Annals of CIRP, 49/1:91-94. [5] Kimura, F., Hata, T., Suzuki, H., 1998, Product Quality Evaluation Based on Behaviour Simulation of Used Products, Annals of CIRP, 47/1:119-122. [6] Hata, T., Kobayashi, N., Kimura, F., Suzuki, H., 2000, Representation of Functional Relations among Parts and its Application to Product Failure Reasoning, Proc. Int. CIRP Design Seminar, ed. Shpitalni, M., Haifa, 393-398. [7] Kobayashi,N., 2002, Machine Failure Analysis using Feature-Based Product Modelling, Ms.Thesis, The University of Tokyo. [8] Kumar,U., Crocker,J., Knezevic,J. and El- Haram,M., 2000, Reliability, Maintenance and Logistic Support, Kluwer Academic Publishers.
- 7. The 35th CIRP-International Seminar on Manufacturing Systems, 12-15 May 2002, Seoul, Korea 7