The voind robot was present at the Elephant & Castle Mini Maker Faire which took place in London on November 15th. The overall reaction of the attendees with whom we had the opportunity to talk about the project has been fantastic!
Not only did we receive great input from people in the audio production industry but also from enthusiasts and experts in robotics, electronics, software development and every other field we could think of!
The small animation below was used at the faire to quickly convey the robot action.
After installing needle and ball bearings and a new hardened steel shaft to pivot the voind robot arm, we noticed that the stepper motor shaft was presenting noticeable axial movement when the arm was being accelerated up towards an horizontal position.
A quick calculation revealed the design flaw: the stepper motor is driving a worm/wheel which converts the significant torque of the arm into a 30N axial force on the stepper shaft, 3 times the rated value for this particular motor!
Luckily we discovered the problem before the motor internal bearings were completely destroyed! This was the reason why the robot was unable to perform any rotational arm movements when it was exhibited at the Lisbon Mini Maker Faire.
We then took some time to evaluate a solution for this problem. Two options were considered:
1. Compensate for the torque on the arm shaft using springs and/or a counterweight
2. Reinforce the axial maximum load supported by the stepper motor on its shaft
We chose to go for option 2 using a pair of miniature thrust bearings mounted directly on the motor shaft and pressing against the motor case on both ends:
Through careful adjustment we believe the axial load is now being entirely transferred to these bearings which are more than capable of supporting it leaving the motor with the sole task of driving the worm.
The robot and the acrylic display box has been packaged inside a custom built MDF box which (fingers crossed) will hopefully protect it during the transportation.
Because we couldn’t get any satisfactory answers for our RFP for a suitable box we built it from scratch using 16mm and 10mm thick MDF reinforced with steel corners.
Its dimensions were carefully selected to accommodate the robot and the acrylic display box and a protective layer of bubble wrap padding. An added feature of the box is its ability to be used as a platform for displaying the robot.
The next time we’ll see it again will be in London. Visit us there and see at first hand the robot in action!