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Introduction

MTBF certification refers to the certification of the average time between failures of a product, and its full English name is "Mean Time Between Failure". Actually, MTBF refers to the MTBF testing report, which is a report on the prediction of product reliability. MTBF is a reliability indicator for measuring a product (especially electrical products). The unit is' hour '. It reflects the time quality of the product and is an ability to maintain its functionality within a specified time. Specifically, it refers to the average working time between two adjacent faults, also known as the average fault interval. In summary, a product with fewer failures has higher reliability, and the ratio of the total number of failures to the total number of life units is called the "failure rate". It is only applicable to repairable products. At the same time, it is also stipulated that the ratio of the cumulative working time to the number of failures during the total usage phase of the product is MTBF. The MTBF of disk array products generally cannot be less than 50000 hours.

MTBF data calculation

Assuming the MTBF of a computer is 30000 hours, is it possible to detect the continuous operation of this computer for 30000 hours? Of course not, otherwise there are so many products that cannot be tested for decades. The most commonly used authoritative standards for calculating MTBF values are MIL-HDBK-217 (proposed by the Reliability Analysis Center and Rome Laboratory of the US Department of Defense and became an industry standard specifically for military products), GJB/Z299B (Chinese military standard), and Bellcore (proposed by AT&T Bell Laboratory and became an industry standard for MTBF of civilian products).

The main consideration in MTBF calculation is the failure rate of each component in the product. However, due to the significant differences in failure rates of devices under different environments and usage conditions, these factors must be considered when calculating reliability indicators. And these factors are almost impossible to calculate manually, but with the help of software such as MTBFcal and its vast parameter library, MTBF values can be easily obtained. If a factory that works three shifts a day requires 24-hour continuous operation and a failure free rate P (t) of 99% or more, the MTBF of the machine tool must be greater than 4500 hours. The MTBF of 5000 hours requires a higher and more complex production line composed of different numbers of CNC machine tools. Here, we will only discuss a single machine tool:

If the ratio of failure rate between the host and the CNC system is 10:1 (the reliability of the CNC system is one order of magnitude higher than that of the host), the MTBF of the CNC system must be greater than 50000 hours, and the MTBF of the main parts such as the CNC device, spindle, and drive must be greater than 100000 hours.

MTBF is not detected in actual operation, it is converted through national standard detection algorithms. For example, the 60000 hour MTBF of Lenovo Yangtian was obtained by testing 192 Lenovo Yangtian computers and applying comprehensive environmental stresses such as voltage, temperature, and humidity to the tested products at a specific frequency during a 40 day experimental period. Based on the correspondence between the reliability and time characteristics of electronic products, the experimental results were converted using a standard data model. Similarly, the 100000 hours MTBF of Tongfang exceeding E350 was calculated based on 18 days of testing results from 400 computers.

In fact, we don't need to pay attention to how the MTBF value is calculated, as long as we know that choosing products with high MTBF values will bring us higher competitiveness. Of course, the higher the MTBF value, the better, and the higher the reliability, the higher the machine tool cost. Choosing moderate reliability according to actual needs is enough.

The purpose of MTBF analysis

1. Key countermeasures for high-frequency faulty parts and technical transformation basis for extending part life.

2. Calculate the life cycle of parts and prepare the optimal maintenance plan.

3. Regarding the selection of inspection objects and projects, as well as the setting and improvement of inspection benchmarks.

4. Used to guide the allocation of internal and external maintenance work. Based on the evaluation of the company's equipment repair capability, the risk of internal maintenance quality and equipment efficiency is determined by the different types of equipment and job types, which serves as an important reference for maintenance outsourcing.

5. Set standards for spare parts. The reserve items and basic inventory quantities of mechanical and electrical components should be determined based on the analysis of MTBF records to achieve the most economical inventory level.

6. As a reference for selecting maintenance technology methods to improve key areas. In order to improve the equipment operation rate, it is necessary to shorten the time for long-term maintenance operations, engineering adjustments, and switching related to equipment shutdown. Therefore, it is necessary to inspect the maintenance operation methods, and the selection of inspection items, priority order, and other basic information need to be based on the MTBF analysis record table.

7. Research on the establishment of estimated operating time standards for equipment objects, as well as the selection of maintenance tasks and maintenance time standards. The setting of estimated time standards for maintenance plans and the selection of maintenance operations must consider factors such as equipment maintenance repetition cycles or differences between standard time values and actual maintenance times, as well as corresponding maintenance operation characteristics. Therefore, MTBF analysis tables are essential.

8. Reference for pattern organization and reselection of key equipment or parts. The analysis record table of MTBF records information on equipment parts modification projects or friction deterioration, as well as equipment drawing modifications or pre production situations. By regularly conducting analysis and inspection, and managing importance rankings, engineering drawing management can be made easier.

9. Setting, revising, and determining the responsibility allocation for equipment maintenance operations based on operational standards.

10. Provide technical data on the reliability and maintainability design of the equipment. The most important aspect of maintenance technology is to collect technical information on the reliability and maintainability design of equipment based on the MTBF analysis table, in order to provide reference for the design department when designing equipment.

MTBF reference standard

MTBF usually corresponds to the following reference standards:

Telcordia SR 232

US military standard MIL-HDBK-217

National Army Standard GJB/Z 299B

Apply for MTBF documentation

Product BOM

Product Specification

Product usage conditions

Conduct corresponding tests to obtain data on temperature rise, current, or voltage