MTBF should be used in reference to repairable items, while MTTF should be used for non-repairable items. MTTF is a statistical value and is calculated as the mean over a long period of time and a large number of units. It is the mean time expected until the piece of equipment fails and needs to be replaced. Mean Time To Failure (MTTF) is a measure of reliability for nonrepairable systems. The time required to acquire the new part is also a factor. The actual installation time is only part of the story. Mean Time To Repair (MTTR) is the mean time needed to repair a failed hardware module. If this data is not provided, a manufacturer’s piece of equipment should be immediately disqualified. MTBF data should be a required line item in a request-for-quote (RFQ). MTBF data is not always readily available but, it is worth asking for the information. They may not realize that a product with a short lifespan really is not much of a bargain. Industries and integrators tend to pay close attention to MTBF, but consumers are often price driven. This is the most common parameter used to predict a product’s life span. Mean Time Between Failure (MTBF) is the number of failures per million hours for a product. Understanding the methods used to predict a product life cycle will help you make informed decisions. You should also consider the product’s life expectancy. Please note the attached German and English PDFs which hold all the above information for print-out.Product purchasing decisions should not be based on feature sets alone. Gottschalk, Armin: Qualitäts- und Zuverlässigkeitssicherung elektronischer Bauelemente und Systeme, ISBN, 978-3-8169-2680-1 The MTBF value should not be confused with the minimum service life of a system. For the development engineer, these values allow to validate the failure rates of the complete system in order to select other components if necessary or to start a redesign. The values of the analysis must be considered as pure statistical values. The MTBF value is specified in the chapter "Specifications / Standards" of the "Hardware Reference" corresponding to the controller.Įxample: Extract of chapter "2.5 Standards" of the "EPOS4 Module-Compact 24-1_5 Hardware Reference.pdf" manual: This finally means that the specified total MTBF-value match very precisely the reality. The remaining passive components are calculated according to the MIL-HDBK-217F handbook. That is the reason why we calculate with these effective FIT-values. Active components have a predominant influence on the resulting MTBF-value of a product. These FIT-values are preferred for calculating the MTBF of maxon controllers, because they allow a more accurate calculation than the general values from handbooks. Producers of electronic components identify the effective FIT-value with so-called accelerated tests according to the Arrhenius law. They are based on international standards such as:īased on parts lists, the MTBF value is calculated for each part, considering as well external factors such as ambient temperature, humidity or stress.
#Sequential testing mil reliability mtbf manuals
Manuals are used to get realistic MTBF values close to the later experience in the field. Besides the time for repairing, it includes the time for failure analysis as well. MTTR is the average time needed for repair (= Mean Time to Repair). It is used for systems that cannot be repaired the device directly enters the recycling process. The term MTTF (= Mean Time To Failure) differs only slightly from MTBF. Therefore, MTBF values are determined with the help of manuals that include these conditions. A large influence comes from the ambient conditions such as temperature variations, vibrations, and so on.
#Sequential testing mil reliability mtbf full
Summing the MTBF values of single components or subassemblies gives the MTBF of the full system. The MTBF results from the inverse FIT or λ values. Failure rates are identified by means of life testing experiments and experience from the field. Typical values lie between 300‘000 and 1‘200‘000 hours.
The MTBF value (= Mean Time Between Failure) is defined as the time between two errors of an assembly or device. Phase 3, the deterioration phase, is hardly relevant for electronic components.Īssuming that the failure rate λ is approximately constant, the equation can be simplified as follows: In this second phase, the standard failure rates for electronics components are defined and calculated. In the second phase, the admissible failures are defined, usually with a constant rate over time. In the first phase, one finds the early failure due to weakness in the materials, quality variations in production, handling mistakes and spurious, unconfirmed failures. Where to find the MTBF value of maxon controllers?Įach component has a failure rate curve in the shape of a bath tube, called Weibull distribution.How is reliability calculated for maxon controllers?.
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