Background:
A U.S. manufacturer specializing in safety and security solutions encountered a recurring stall problem while using Namiki Spur gear motors in their electronic wheel gauges. They turned to us, seeking an alternative gear motor solution to replace Namiki motors.
In the customer’s view, Namiki motors lacked the necessary power, causing frequent stalls in their application. They were in search of more robust and powerful motors.
Required Specifications for Gear Motors:
- Nominal voltage: 6V
- No load speed: 65 RPM
- Rated torque: 0.8 kg.cm
- On-load speed: 50 RPM
Work Scenario:
In their electronic wheel gauges, the motors are responsible for moving a probe. The probes continue moving until they make contact with the wheel. Once the probes touch the wheel, they need to return to their initial position immediately. This constitutes a complete duty cycle, and the motors must complete two duty cycles in just two seconds, totaling 30 cycles per minute.
Challenges:
- In their application, the motor would stall every time the probe hit the wheel. Stalling is detrimental to gear motors, resulting in high torque and current that can damage gears and burn out the motors.
- Once the probe makes contact with the wheel, it must immediately reverse its motion. This frequent sudden reversal can be detrimental to gear motors due to inertia.
Upon discussing the challenges mentioned above, the customer held an engineering meeting with us and agreed to implement a current limit to prevent stalls and protect the motors. Simultaneously, they expressed their willingness to test samples and upgrade their design if necessary.
Solution:
Following evaluations by our engineers, the HT-SOG15A spur gear motor perfectly matched the customer’s specifications. Samples were manufactured for their field tests.
Based on customer feedback from the tests, the loaded current was measured at 45mA, significantly lower than the rated current. This indicated that the loaded torque was much less than the required 0.8 kg.cm.
Subsequently, a shorter and more cost-effective spur gear motor, HT-SOG15B, was introduced to the customer. Second-round samples were crafted with precise specifications as follows:
- Nominal voltage: 6V
- No load speed: 65 RPM
- Rated torque: 0.4 kg.cm
- On-load speed: 54 RPM
The customer was highly satisfied with our new gear motor samples. They not only perfectly matched their application but also proved to be more compact and cost-effective.
However, a new issue arose after approximately 1500 duty cycles, with gears showing signs of damage. Our engineering team conducted an analysis of the motor’s performance, working conditions, and customer-provided images. It was concluded that gear damage resulted from the frequent sudden reversals.
Following our advice, the customer implemented a 2-second dwell time in their firmware before the motor switched direction. As expected, this solved the problem, and the motors performed admirably until the battery was depleted.
Conclusion:
Unlike common off-the-shelf commodities, DC gear motors are highly customizable. Finding the ideal gear motors for your design may require several rounds of sampling, especially in new product development. Specifications calculated on paper may not always prove precise or accurate. HOTEC MOTOR boasts experienced and multidisciplinary engineers who can assist you in motor selection, sampling, and more.
