UKM-SUM23-PG38+39_Layout 1 27/04/2023 11:19 Page 38
GEARS & GEARBOXES
ENSURING THE LIFETIME OF A DC GEARMOTOR WITH SYSTEMATIC RELIABILITY TESTING
From industrial power tools to surgical robots, through to applications in aerospace and defence, a motion solution that delivers high power density in a small package is a common requirement. However, integrating a gearmotor means an assurance of reliability is crucial. When operational life exceeds the duration allowable for testing, a systematic approach to Reliability Demonstration Testing (RDT) can provide OEMs with 95 per cent certainty that the gearmotors will meet or exceed their required run time. Utpal Rabha, lead engineer, Portescap, explains the RDT procedure...
combines a gearbox that optimises torque, speed, and efficiency requirements. This enables a gearmotor to reduce output speed while increasing torque to the required level, achieving this with a more compact diameter compared to using a higher-rated individual motor alone. With the additional gearbox mechanism, it is imperative that the design of the gearmotor is sufficiently reliable for the duration of its required use. To ensure resilience for real- world conditions, Reliability Demonstration Testing (RDT) is required.
D RDT STAGES
The first task of the planning stage is to establish the reliability objective, which is required to set the RDT parameters. Typical gearmotor characteristics subject to RDT include voltage, current, speed, temperature, noise, and physical integrity. The test models can then be selected to calculate sample size, as well as the test time required. The preference depends on whether the test duration differs from the expected service life; it is needed for a device that operates long- term, compared to a device that might just require single-shot operation. An accepted test tolerance level must also be set. Ideally, testing should take place under actual application conditions, and be continued for the full duration of the intended operational period. However, if time to market requirements do not allow this, such as for long life expectancy gearmotors that might operate for 10 years, an accelerated test method can be used. In this case we would calculate the
38 Summer 2023 UKManufacturing
C gearmotors are designed to meet the torque requirements of specific tasks while ensuring compact dimensions. With an assembly of a brush or brushless DC motor, the device
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