Fred Schenkelberg

Getting started is not about just a list of tasks, it's about creating value with each task. A short paper introducing reliability engineering and laying out a way to get started.

Two accelerated life tests (ALT’s) explored two failure mechanisms of concern for a product expected to experience a 2-year storage period. Each ALT focused on a specific failure mechanism and required different applied stress.
Making periodic measurements permitted the experiments to illustrate the stability of the performance of the units over the aging process. The life data analysis for each set of data also permitted the calculation of the expected reliability performance of the… Show more

Two accelerated life tests (ALT’s) explored two failure mechanisms of concern for a product expected to experience a 2-year storage period. Each ALT focused on a specific failure mechanism and required different applied stress.
Making periodic measurements permitted the experiments to illustrate the stability of the performance of the units over the aging process. The life data analysis for each set of data also permitted the calculation of the expected reliability performance of the population after two years of storage.
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The way we communicate goals directly impacts the achievement of the goal. Creating and succinctly stating a reliability goal necessary for the leadership it provides an organization when designing a new product.
The reliability goal statement includes four elements: function, environment, probability of success, and duration. The function definition provides one means to define failure conditions. The environment includes elements such as weather and elements related to use frequency… Show more

The way we communicate goals directly impacts the achievement of the goal. Creating and succinctly stating a reliability goal necessary for the leadership it provides an organization when designing a new product.
The reliability goal statement includes four elements: function, environment, probability of success, and duration. The function definition provides one means to define failure conditions. The environment includes elements such as weather and elements related to use frequency.
The probability of success and duration should always be stated in a couplet. Setting more than one probability and duration couplet further defines reliability over the expected lifespan of the product. And setting multiple couplets enables various focuses of the goal that concern different periods of time or constituents.
Setting and stating a clear and complete reliability goal delineates the boundary between a reliable enough product and one that is not. The goal enables the design team to balance the myriad of other design considerations along with product reliability in a meaningful manner.
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Last year we presented a paper on Design for Reliability (DFR), reviewing the benefits of a good DFR program and included some of the essential building blocks of DfR along with pointing out some erroneous practices that people today are using today.
We discussed a good DFR Program having the following attributes:
1. Setting Goals at the beginning of the program and then developing a plan to meet the goals.
2. Having the reliability goals being driven by the design team with the… Show more

Last year we presented a paper on Design for Reliability (DFR), reviewing the benefits of a good DFR program and included some of the essential building blocks of DfR along with pointing out some erroneous practices that people today are using today.
We discussed a good DFR Program having the following attributes:
1. Setting Goals at the beginning of the program and then developing a plan to meet the goals.
2. Having the reliability goals being driven by the design team with the reliability team acting as mentors.
3. Providing metrics so that you have checkpoints on where you are against your goals.
4. Writing a Reliability Plan (not only a test plan) to drive your program.
A Good DFR Program must choose the best tools from each area of the product life cycle
• Identify
• Design
• Analyze
• Verify
• Validate
• Monitor and Control
The DFR Program must then integrate the tools together effectively.
Since then, we have developed a method to calculate the Return on Investment (ROI) from a Design for Reliability (DFR) program, also known as the DFR ROI. In this paper, we will discuss a method we have developed to calculate the Return on Investment (ROI) from a Design for Reliability (DFR) program, also known as the DFR ROI.
There are a number of factors involved in calculating the ROI for your DFR program, including:
1) Improved Warranty Rate (derived from your Reliability Maturity Level)
2) Current Warranty Rate
3) Cost per Repair
4) Cost of New Reliability Program
5) Savings from Losing a Customer
6) Volume
In this paper, we will show you how to calculate each of these to derive your DFR ROI.
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Three-phase inverters are physically large, complex and expensive elements of major solar power generation systems. The inverter converts DC power created by the photovoltaic (PV) panels to AC power suitable for adding to the power grid.
The inverters’ reliability testing is a complex task and relies on reliability block diagrams (RBD), vendor and field data, plus selecting accelerated life tests (ALT) based on critical elements of the product.
This paper illustrates a case study that… Show more

Three-phase inverters are physically large, complex and expensive elements of major solar power generation systems. The inverter converts DC power created by the photovoltaic (PV) panels to AC power suitable for adding to the power grid.
The inverters’ reliability testing is a complex task and relies on reliability block diagrams (RBD), vendor and field data, plus selecting accelerated life tests (ALT) based on critical elements of the product.
This paper illustrates a case study that developed an RBD, used field and vendor data, and includes the design and use of two ALTs. The result is a working framework or model that provides a reasonable estimate of the expected lifetime performance of the inverter. While any project similar to this, is always a work in progress, the examination of the decisions and inputs for the model proves valuable for the continued improvement of the model and resulting life predictions. This project provides an excellent real life example of reliability estimation having a multitude of constraints including: sample size, test duration, and field data, thus having to rely on all sources of available data starting from field and vendor data to theoretical component reliability calculations, ALT plan execution, failure analysis, and finally summarizing the results using RBD to estimate product expected lifetime. At the time of writing this paper, based on completion of system level ALT, an availability of 99.97% is valid over a 10 year period according to southern Ontario weather as the main installation base. This will be revisited once subsystem ALT is completed.
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Reliability is a engineering discipline that encompasses a broad array of tools and techniques useful for answering durability and robustness type questions. Product development teams often rely on reliability engineering professionals to guide, advise and manage reliability programs. Reliability is facet in nearly every function of an organization. This implies the knowledge and skills required for the reliability engineer is comprehensive. The knowledge breadth may span aspects of material… Show more

Reliability is a engineering discipline that encompasses a broad array of tools and techniques useful for answering durability and robustness type questions. Product development teams often rely on reliability engineering professionals to guide, advise and manage reliability programs. Reliability is facet in nearly every function of an organization. This implies the knowledge and skills required for the reliability engineer is comprehensive. The knowledge breadth may span aspects of material science to design constraints to warranty reverse logistics.

How do engineers become reliability professionals? What are the knowledge transfer options available to the reliability profession. How do we get started and maintain our knowledge? In this short paper, I plan on summarizing what’s available, a couple of common paths taken to become a reliability professional, and highlight the strengths and a few weaknesses concerning reliability education. This is my view of the state of reliability education.

What is available?
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Over the many years of development concerning accelerated life testing (ALT), our peers have found many ways to take advantage of the interaction of stress and failure mechanisms [1-15]. In an ideal situation, the reliability engineer will have ample time, samples, test resources and knowledge to conduct an ALT. This is often not the case.
Trading off the risks in conducting the ALT and fitting within the myriad of constraints and expectations is a challenge. Understanding the basics of ALT… Show more

Over the many years of development concerning accelerated life testing (ALT), our peers have found many ways to take advantage of the interaction of stress and failure mechanisms [1-15]. In an ideal situation, the reliability engineer will have ample time, samples, test resources and knowledge to conduct an ALT. This is often not the case.
Trading off the risks in conducting the ALT and fitting within the myriad of constraints and expectations is a challenge. Understanding the basics of ALT approaches and associated assumptions, permits one to select the right ALT. ‘Right’ being the ALT that provides meaningful results in time for technical and business decisions, plus meets the budget and risk tolerance limits.
There is no one-way to design an ALT that will meet the specific set of conditions presented to the test designer. Being able to clearly articulate the tradeoffs involved permits the entire design team to fully understand the results when produced. The ‘best’ ALT is one that adds value to the design process.
The most accurate results involve testing all of the production units in actual customer application or use until they all have failed. While this is clearly not practical, neither is the simple-minded approach guessing at the results. In between these two extremes lies an optimal value: being the most efficient ALT that provides meaningful results. When the results provide information to make design or program decisions, the ALT adds value.
Reducing ALT costs by reducing sample size or test duration is possible, yet may significantly increase uncertainly around the results. Running the test longer to achieve more accurate results is often constrained by the timeline to make decisions. It is this and similar tradeoffs that force us to carefully design each ALT and determine the best path forward.
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In some cases the use of reliability testing to sample the products at the end of assembly provides an effective means to detect shifts in materials and processes that adversely impact product reliability. Ongoing Reliability Test (ORT) design is a balance considering cost, timeliness, resolution, and accuracy. A poor ORT is costly and may increase the risk of significant field failure by falsely building management confidence. Or, the testing may be unable to detect even major adverse changes… Show more

In some cases the use of reliability testing to sample the products at the end of assembly provides an effective means to detect shifts in materials and processes that adversely impact product reliability. Ongoing Reliability Test (ORT) design is a balance considering cost, timeliness, resolution, and accuracy. A poor ORT is costly and may increase the risk of significant field failure by falsely building management confidence. Or, the testing may be unable to detect even major adverse changes in the field failure rates by not evaluating the appropriate risks or with insufficient sampling.
This paper steps through the design of an effective product ORT program for a high volume consumer product. The analysis includes business objectives, design risk, vendor variability, and accelerated life testing considerations, while also considering the real factory constraints concerning equipment, skill, and time.
Considering the constraints and the major decisions based on the testing results permits the ORT to become an effective part of process control while providing protection from unwanted field failures. An effective ORT evaluates sufficient number of samples, with a set of stresses that accelerate the appropriate failure mechanisms and produces test results in a timely and informative manner
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Selecting the right tool, or the right investment for a specific reliability task is often left to the judgment of the reliability professional. With experience these choices become simpler, yet in many cases the task can be daunting. By examining the decision process we explore a means to determine the most cost effective reliability activities for specific situations.
Not all reliability tools provide useful information or timely results in every situation, yet how does one choose the… Show more

Selecting the right tool, or the right investment for a specific reliability task is often left to the judgment of the reliability professional. With experience these choices become simpler, yet in many cases the task can be daunting. By examining the decision process we explore a means to determine the most cost effective reliability activities for specific situations.
Not all reliability tools provide useful information or timely results in every situation, yet how does one choose the best activities for a given situation. After conducting over 100 reliability program assessments and working with dozens of design teams to build effective reliability programs, the author lays out an means to trade-off the cost and benefits for the appropriate selections of reliability activities.
Considering the constraints and the objectives - there is a best set of tools to employ during the development process to produce a reliable product. This paper explore the cost/benefit equation in three different cases: High cost low volume, low cost high volume and brand new technology product development situations. Considerations include risk, models, processes, and technology along with customer or market expectations. Another significant consideration is the reliability maturity of the organization.
There isn't a single set of tools or activities that will always produce a reliable product in a cost effective manner. Carefully, considering the current situation and capabilities permit the team to select the right tools to make significant progress toward a reliable product.
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MTBF is widely used to describe the reliability of a component or system. It is also often misunderstood and used incorrectly. In some sense, the very name “mean time between failures” contributes to the misunderstanding. The objective of this paper is to explore the nature of the MTBF misunderstandings and the impact on decision-making and program costs.

Reliability is an engineering discipline that encompasses a broad array of tools and techniques useful for answering durability and robustness type questions. Product development teams often rely on reliability engineering professionals to guide, advise and manage reliability programs. Reliability is a facet in nearly every function of an organization. This implies the knowledge and skills required for the reliability engineer is comprehensive and the knowledge breadth may have to span aspects… Show more

Reliability is an engineering discipline that encompasses a broad array of tools and techniques useful for answering durability and robustness type questions. Product development teams often rely on reliability engineering professionals to guide, advise and manage reliability programs. Reliability is a facet in nearly every function of an organization. This implies the knowledge and skills required for the reliability engineer is comprehensive and the knowledge breadth may have to span aspects of material science in design constraint considerations to warranty reverse logistics.
How do engineers become reliability professionals? What are the knowledge transfer options available to the reliability profession? How do we get started and maintain our knowledge? In this short paper, I summarize what’s available, a couple of common paths taken to become a reliability professional, and highlight the strengths and a few weaknesses concerning reliability education. Note: This is my view of the state of reliability education.
Show less

Tracking bottling equipment line uptime and downtime is a common metric for bottling production lines. The runtime and downtime along with reasons for being down are routinely and semi-automatically recorded. The data is often summarized using the exponential distribution and reported as MTBF and MTTR.
During the design of a new bottling line, the design team used the recorded data from existing lines and equipment to estimate the proposed line availability. If the new line could shorten the… Show more

Tracking bottling equipment line uptime and downtime is a common metric for bottling production lines. The runtime and downtime along with reasons for being down are routinely and semi-automatically recorded. The data is often summarized using the exponential distribution and reported as MTBF and MTTR.
During the design of a new bottling line, the design team used the recorded data from existing lines and equipment to estimate the proposed line availability. If the new line could shorten the run time to accommodate a high mix of products and improve the line availability and thus throughput, the new line would permit significant warehouse savings.
The experienced operator, maintenance and engineering teams knew that the line availability improved as the run duration increased. After the initial setup, the line operator and maintenance crew continued to adjust and improve the operation of the bottling line, thus, overtime improving the line availability. It was not a constant value independent of the run duration. And, the existing calculations based on MTBF and MTTR did not reflect this behavior.
This paper examines the use of expected values of the fitted distributions for uptime and downtime, rather than using MTBF and MTTR. The expected values permit the analysis to study the changes in availability as the run duration changes. The result was the design team’s analysis could tradeoff the run duration and associated throughput with the expected warehouse requirements and cost savings for an optimal bottling line design. This paper primarily explores the equipment analysis and availability calculations.
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An assessment of product development teams reveals that few have efficient and cost effective reliability programs critical to making systematic program improvement. It is shown that a proactive approach, statistical thinking, fact based decision making, and integrated reliability tools can make a difference in the effectiveness of an organization's reliability program. Key traits that separate good from outstanding reliability programs are explored.

Engineering degradation tests allow industry to assess the potential life span of long-life products that do not fail readily under accelerated conditions in life tests. A general statistical model is presented here for performance degradation of an item of equipment. The degradation process in the model is taken to be a Wiener diffusion process with a time scale transformation. The model incorporates Arrhenius extrapolation for high stress testing. The lifetime of an item is defined as the… Show more

Engineering degradation tests allow industry to assess the potential life span of long-life products that do not fail readily under accelerated conditions in life tests. A general statistical model is presented here for performance degradation of an item of equipment. The degradation process in the model is taken to be a Wiener diffusion process with a time scale transformation. The model incorporates Arrhenius extrapolation for high stress testing. The lifetime of an item is defined as the time until performance deteriorates to a specified failure threshold. The model can be used to predict the lifetime of an item or the extent of degradation of an item at a specified future time. Inference methods for the model parameters, based on accelerated degradation test data, are presented. The model and inference methods are illustrated with a case application involving self-regulating heating cables. The paper also discusses a number of practical issues encountered in applications. Show less