Brief
The High Voltage DC Motor (details provided) is a critical part of a high torque actuator mechanism. The mechanism is required to upto 80 kg of axial force. However, this nature of the motor makes it a major liability in case of faliure or motor stall.
Additionally, inefficient meshing of metal gears at high speeds results in excessive noise and available gearbox solutions were not suitable as there was no room to incorporate cost effective safety features. A new gearbox design was needed to tackle these two critical problems, while maintaining the same reduction ratio of 14:1.
The High Voltage DC Motor (details provided) is a critical part of a high torque actuator mechanism. The mechanism is required to upto 80 kg of axial force. However, this nature of the motor makes it a major liability in case of faliure or motor stall.
Additionally, inefficient meshing of metal gears at high speeds results in excessive noise and available gearbox solutions were not suitable as there was no room to incorporate cost effective safety features. A new gearbox design was needed to tackle these two critical problems, while maintaining the same reduction ratio of 14:1.
Conceptualisation
In order to tackle this problem, the proposal was to design and use a plastic gearbox. If designed well meshing plastic gears at high speeds would lead to lower noise.
The optimal and most simple fail safe mechanism would be a solution that allows the gears to slip in case of motor stall. Based on research of existing products that use a similar ‘slip’ mechanism, a rough concept was designed.
In order to tackle this problem, the proposal was to design and use a plastic gearbox. If designed well meshing plastic gears at high speeds would lead to lower noise.
The optimal and most simple fail safe mechanism would be a solution that allows the gears to slip in case of motor stall. Based on research of existing products that use a similar ‘slip’ mechanism, a rough concept was designed.
Solution
Based on the concepts, the final solution was prototyped and tested with the acutating mechanism.
With the restrictions on the gearbox dimensions and based on some preliminary calculations, Nylon 6/10 was the preferred material. Being the strongest polyamide, it’s charecteristics allowed the gearbox to deliver upto 22 kg.cm torque at output.
For the fail safe ‘slip’ mechanism, different spring settings were tested to ensure that in case of stall, the gear slips and jumps.
Based on the concepts, the final solution was prototyped and tested with the acutating mechanism.
With the restrictions on the gearbox dimensions and based on some preliminary calculations, Nylon 6/10 was the preferred material. Being the strongest polyamide, it’s charecteristics allowed the gearbox to deliver upto 22 kg.cm torque at output.
For the fail safe ‘slip’ mechanism, different spring settings were tested to ensure that in case of stall, the gear slips and jumps.
Features & Benefits
The implementation of the slip gear system guaranteed that the motor did not stall. This fail safe mechanism ensured that the motor continued to run within the dictated safe range, without the need for expensive couplings.
Another key feature included the strengthening disc on the output gear. The lead screw was directly attached to this disc and not the plastic gear . In cases of excess loads, the maximum stress would be borne by the metal disc.
The implementation of the slip gear system guaranteed that the motor did not stall. This fail safe mechanism ensured that the motor continued to run within the dictated safe range, without the need for expensive couplings.
Another key feature included the strengthening disc on the output gear. The lead screw was directly attached to this disc and not the plastic gear . In cases of excess loads, the maximum stress would be borne by the metal disc.
