Another major limitation of today’s additive manufacturing techniques is linked to the unidirectional nature of layer orientation, creating an inherent weakness. Additive manufacturing allows for heterogeneous optimized distribution of matter. To take advantage of this, and not succumb to this limitation, we used structural optimization tools to create a second layer of material over the shell. The material is also closely aligned with the direction of stress, finally optimizing both orientation and thickness of the shell structure. The data derived from the structural analysis is then translated into paths for the third and final robot, the Vacuum Robot. Using a vacuum generator this robot attaches to the surface of the previously printed structure. Moving freely over the first shell on its tracks, depositing material on the surface of the shell, enhancing its structural properties. This task can be performed by one robot, or a swarm of robots working in coordination.
Consulting papers below:
The Vacuum robot size 30*27*12 cm, weighs 2.1kg
Tools and materials:
-Dynamixel ax-12 servos *4
-Silver Duct Tape
-700w handheld cyclone vacuum cleaner. We used the Core.
-Foam for CNC milling
-4mm acrylic for laser cutting
-Motor, Axle and wheel mount (aluminum or 3d printed)
The frame of the robot is similar to the first robot, an aluminum mounting affixes the motors and the wheel mechanism to the frame. Whilst the vacuum generator is bolted to the frame. The vacuum generator extracts air from below the robot and a flexible suction cup seals the irregular surface. Negative pressure in the space between the suction cup and the surface attaches the wall climbing robot to vertical and horizontal surfaces. In order to give the robot mobility on double curved surfaces, The suction cup should be adjusted to be lower than the tracks ( approximately 3mm). The frame of the robot should be as rigid as possible and the suction cup should be as soft and malleable as possible. There are other solutions to allow the wheels/tracks to always maintain traction, such as using a suspension system but we found this to be the simplest and most reliable.
The force of the vacuum generator must overcome the weight of the robot. Moreover the power/torque of the motors must overcome the overall weight of the robot, plus friction between the suction cup and the surface. Rubber-like materials produce friction with other surfaces, especially when a force is applied. We experimented with many solutions looking for a rubber-like material or coating to reduce the friction. An alternative solution was found by applying one or two layers of silver duct tape onto the suction cup. We found that this significantly reduces the friction and proving more durable than plastic coatings or lubricant. In practice the tape coating would slowly degrade, however it was easily reparable.
For certain curvature(single curvature or double curvature) the size of the wheel, the distance of the wheels are smaller the better, the weight of the robot should be as light as possible, bigger suction cup gives better suction force. So there is a balance between the weight of the robot and the power of the motors, suction cup size, and robot size.