What is Reliability?

Reliability, within the reasonable life expectation, is a measure of the occurrence of random failures. MTTF is a basic measure of reliability for non-repairable systems. It is the mean time expected until the first failure of a piece of equipment. MTTF is a statistical value and is meant to be the mean over a long period of time and large number of units. For constant failure rate systems, MTTF is the inverse of the failure rate. If failure rate is in failures/million hours, MTTF = 1,000,000 / Failure Rate for components with exponential distributions.

How were the motors tested?

Since the theoretical failure rates of stepper motors range from 25,000 hours to 13,00,000 hours depending on the temperature, we require a minimum number of samples to test for MTTF. The minimum samples for most statistical purposes is set at 24. Since the samples are all homogeneous (they have the same characteristics) the number of samples have to be reduced. Hence, 16 samples were put to test. They were loaded to 70% of their rated torque. Due to economic considerations, chopper drives were not used and the motors were run on voltage drives drawing more current than rated. The motors were run continuously and periodic measurements of temperature were taken.

What was the result?

We are proud to say that all the motors ran for the full length of the test and did not show any sign of wear and tear. Noise level of operation was the same throughout and the motors maintained a constant temperature level. We are sure that the motors will out perform the MTTF figures that we have established.

MTTF Data for our motors (8kb)


The reason for this achievement is our careful selection of all parts and most importantly the winding wires and the bearing. The wires are procured from the best companies in the world and have been put to a lot of tests before they have been accepted by us. The bearings are also procured from reputed companies and their hardness, composition and strength are all tested before being accepted. This process of testing is an integral part of our raw material acceptance procedure. Hence you can be sure of getting a quality product from Precision Motors Private Limited.

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