To ease fabrication, given the materials and fabrication methods available, the initial CAD model was modified as shown below:
The links, guide arm, gears and carriage were additively manufactured (with Fused Deposition Modelling - FDM). This greatly simplified the task of fabricating the complex geometry of the guide arms in addition to reducing machining time required. PLA was the fabrication material of choice as it is less susceptible to warping compared to other materials available for fabricating with FDM. Also, it provided enough strength and smoothness for the sliding of the rollers on the guide arms. The dimensions of the driver and driven gears transferring motion from the motor were chosen to amplify the motor's torque output (MA>1).
Mounting hubs, set screws and additively-manufactured retention rings were used to achieve tight-fits between the shafts and bearings.
The final assembly is shown below:
