Skelebot Design Process

We wanted the design to mimic an animatronic skull used for Halloween decoration. They typically consist of a realistic-looking skull with moving parts, such as the jaw or eyes, that are controlled by an internal mechanism. The skull would be made from a durable material such as plastic, and is designed to look spooky, with hairline cracks or other signs of wear. 

The mechanism that controls the movement of the skull would be powered by a small motor with an encoder that can be used for speed control. The motor is connected to a series of linkages that translate the rotational motion of the motor into the desired movements of the skull and dispense candy. The skull would also include additional features, such as LED lights that create an eerie glow, or sound effects that add to the overall spooky atmosphere. These features can be controlled by an internal Arduino device and possibly a small music player.

The original designs for Skelebot presented the following desired actions: skull rotation, jaw movement, and candy dispensing. The primary skull body is adapted from an anatomical model in the GrabCAD forum library (https://grabcad.com/library/3-parts-anatomical-skull-model). This skull basis was used to provide a starting point from which the rest of the model could be built around. Skelebot's mechanical components were designed primarily in Siemens NX and Fusion 360.

The primary consideration in the design of Skelebot's components was manufacturability, since the vast majority of the components would need to be manufactured, cut, or printed in-house at the Texas Inventionworks. As such, some of the designs are limited by the capabilities of the space wherein they would be made. For instance, the current base attached to Skelebot, while effective, is very rudimentary and simple since it needed to be something that would be strong and assembled quickly using materials on hand in the space. The base was also designed such that access to the internal components was very easy, since during the prototype process there would be numerous iterations of the wiring, programming, and component location.

Once the skull basis was established, large sections of it were cut out in order to provide space for the integration of the mechanisms. The base of the skull was cut such that there would be ample room to have the candy dispensing system, wiring, and (originally planned) upper reservoir. Additional modifications to the original model were made to integrate the static shaft and bearings for the primary support means of the model, as well as allocate a mounting surface for the Jaw stepper motor. Additional cuts were made on the model to shorten the printing times, since they were a limiting factor in the manufacturing process. With each cut, dowels were added to aid in the placement and securement of the various sections during assembly. The auger was designed using a swept extension along a helical path up the rotating shaft, and then was split into 4 bodies for printing and assembly. The outer components of the candy dispensing mechanisms were designed to use off-the-shelf components from local hardware stores for shapes that would have been too costly or ineffective to manufacture in-house (i.e. PVC Piping and adapters). The crank rocker mechanism (sized and designed in the kinematic analysis section) was designed in Fusion 360 and had multiple iterations during testing that provided additional insight into the design characteristics needed in order to achieve the simulated and calculated motion.