Proof-of-Concept Prototype

A proof of concept prototype was constructed to show that the mechanism is capable of the required tool paths in the physical world. The prototype consists of 3 linear motions and 3 rotational motions, as described by the NX6 proof of concept. In the absence of a CNC controller, the motions were controlled manually. The Proof-of-Concept Prototype developed for this project was a bit of a challenge. For construction materials, scrap pieces were used from several sources. While a prototype made from Lego or Mecano would have had a neater presentation, the size and motion limitations of these sets were not suited to a six axis design, particularly when the behavior of a filament band had to be considered. An old workbench was acquired and dismantled. The top wood pieces were used as parts of the axis, while the screw sliders were used for the vertical direction and the mandrel rotator. These pieces allow the robot to move up and down without gravity playing too much into the motion.

Sliders from a desk drawer were used for the horizontal axis as well as the cross feed axis. They provided smooth and quick motion from side to side for the horizontal axis, and back and forth for the cross feed axis.

The next part used was the top of a pop bottle and its lid. These make up the eye rotation, and allow the filament to be fed from the robot to the arm on the mandrel.

Finally, there were several other pieces used to demonstrate that the concept developed is a good choice. Scraps of wood are used to connect all components, as well as screws to join the pieces. A tape dispenser and tape made up the filament and how it was supplied to the robot.

The horizontal axis provided linear motion in the horizontal direction, otherwise known as left to right movement. This part is the most prominent degree of freedom, and is connected to the base.

The vertical axis allows linear motion in the vertical direction (up and down). This axis is very important for winding around the joint end of the link.

The cross-feed axis allows linear motion in the axial direction (backwards and forwards); it allows flexibility with winding filament around different shaped and sized links. Yaw rotation provides motion in the z direction, and is also very important for winding around the end geometry. Finally, the eye rotation is about the y direction and ensures that the filament lies flat on the link and doesn’t become twisted.

The prototype was demonstrated in class on November 23, 2009, and was found to sufficiently show that the design would be capable of producing the tool paths required to integrate a link to the composite robot arm.

There are five degrees of motion in the main robot, and another one that rotates the mandrel, so the filament can be wound around the arm. The filament is wrapped around the arm on the mandrel, as the robot travels down the horizontal axis.

Wrapping around the joint piece is slightly more complex. The robot needs to move up on the vertical axis, increase the yaw rotation angle, and rotate the eye. This position is held for a short while as the filament winds around the end joint of the arm. After the filament has made it around the end, the robot returns to its original position and travels back down the horizontal axis doing simple filament winding.

The proof-of-concept prototype has been used to wind the filament (in this case tape) around the arm successfully. It can be used to demonstrate simple winding as well as complex winding. This is vital in proving the designs validity.

The proof-of-concept prototype allowed the design to be proven feasible. It demonstrated that the joint and link could be integrated using fiber wrapping. The biggest concerns from the customer and instructors were regarding future steps. Specifically what parts would be needed to make the final prototype; this included the type and size of motors and electrical components. Furthermore, the design was in need of refinement. The proof-of-concept prototype could be described as several Lego blocks stuck together, and such more cohesiveness was needed.