“Reliability is quality for a time”
Reliability management means defining reliability specifications and monitoring their development in the sense of reliability growth. This means that all optimisation, demonstration, assessment and predetermination activities have to be defined as corporate goals and both the responsibility as well as the competence in the sense of a “reliability culture” within the company have to be implemented on all levels – and this throughout the entire product life-cycle. It is the content of standards and guidelines such as VDI 4004, DIN 60300 or VDA 3.1 and 3.2.
Reliability management can hereby be split into a preventive and a reactive branch. Both of these branches are intertwined, exchange information in an ideal case and ensure an integrated approach to reliability management.
Preventive reliability management
Preventive reliability management deals with questions of reliability during the product development process (PDP) to identify potential and errors as early as possible and to remedy these cost-efficiently. The goal is to design a highly reliable and safe product that is characterised by minimum failures in the field and consequently low guarantee and warranty costs. What’s more, reliability growth should also be ensured.
The following steps should be dealt with in preventive reliability management:
- Reliability requirements and goals (empirical values, competition data, normative requirements, customer requirements , etc.)
- Reliability specifications (incl. test and inspection planning, specifications for suppliers)
- Reliability prediction and assessment (incl. development tests, system models)
- Reliability verification (prototype test)
- Reliability testing (pre-series test)
- Record of ACTUAL reliability (production tests, field data analysis > reactive methods)
The following figure shows an integrated reliability process, the likes of which has already been implemented by IQZ staff for well-known companies.
The following methods are suitable for use in preventive reliability management:
FMEA, FMECA, RBD, FBA/FTA, Markov models, Weibayes, MTTF/MTBF, Success-Run, Sudden Death, EOL-Test, acceleration method.
Reactive reliability management
Reactive reliability management relates to all phases of the product life cycle following delivery of the product to the customer.
An attempt is hereby made to make statements on the reliability of the corresponding products on the basis of real field data. Methods also exist that can be used to determine key errors from data. These should always precede a reliability analysis of field data to focus the later analytical work on critical problem cases. This means that financial as well as personnel capacities are not spread evenly over all products according to scattergun approach but can be deployed selectively.
The results of field data analyses – e.g. from a reliability forecast – are ideal to support preventive reliability management. Reliability requirements and thus goals can be formulated with these, amongst other things, and these constitute an important basis for the development process. Field data analyses remain a suitable aid in guarantee and warranty management. They can be used to forecast guarantee costs, estimate the risks of extended warranties or verify recall campaigns. In addition, field data analyses supply decision-making aids when calculating the replacement demand for series or final stockpiling. They are thus an important part of obsolescence and spare parts management.
The following methods are suitable for use in reactive reliability management:
Pareto analyses, layer line diagrams, load distributions (e.g. performance, load cycles, etc.), Weibull analyses, reliability forecasts, MTTF/MTBF, Monte-Carlo simulation