From geometry to hardware
I first designed each of the components in a top-level CAD model, then we made engineering drawings for all the manufactured parts so that part of our team could start waterjetting and machining relevant parts.
Design for manufacture
Since every component is multiplied by 6, I had to make many decisions that made each of these parts easier to manufacture. Some examples include:
- Adding flats to machined parts so they can be easier to set up in a mill vise
- Making parts out of the same thickness sheet-metal
- Making everything 2D profiles so we can waterjet as many parts as possible
- Minimizing fastener count wherever possible
Assembly breakdown
Here are some of our assembly views:
Platform Assembly
We made the platform out of a nylon frame — to reduce weight, but with an aluminum top plate for wear resistance. We also used threaded inserts so that we could reliably bolt objects to the platform.
Pushrod Assembly
We chose to use aluminum tubes with a high diameter and low wall thickness to maximize stiffness to weight ratio. We picked the diameters such that we could easily tap and die both sides to interface with mating components without any lathe-turning.
Bellcrank Assembly
The bellcranks are two spaced out aluminum plates, allowing us to mount all interfacing components in double shear and to maximize stiffness. The bellcrank is mounted with two thrust bearings secured by a precision shoulder-bolt. I used FEA to make weight reduction cutouts while preserving the majority of its stiffness. The bellcrank has two holes for the actuator to change our motion ratio if needed.
Baseplate
The baseplate is split into three parts connected together by lap joints. This was in an effort to make each baseplate section manufacturable in-house on our waterjet (though we did still exceed its limits slightly, requiring some janky fixes) and to make them easier to carry around.
Finished platform
After all of this design, and a few weeks of strenuous manufacturing, we had a finished motion platform! Only one problem... It didn't move yet. I first needed to figure out the Controls and Electronics.
