Design and laser cut a parametric construction kit.

I created the below 2-dimensional drawing in Fusion 360 using parametric functions that incorporated laser kerf and the dimensions of roller bearings and acrylic pipe that I had on hand. The use of parametric functions allows instant scaling of the model to any suitable roller bearing and acrylic pipe pairing. I desired an interference fit between components, so I did not include a clearance tolerance in the parametric functions.

The long slender component is one of two forks that notch together to form the shaft of the impeller. After rotating the center cross of the components on the left incrementally, they combine to create the screw portion of the impeller. The larger component to the right is the frame holds the roller bearing to support the impeller shaft.

#1: My initial design contained a major flaw, the designed width of the shaft components was set to the inner diameter of the roller bearings minus the anticipated kerf. This failed to account for the inner race's curvature and the material's thickness. As shown below I needed to apply a little trigonometry to determine the correct parametric formula for the shaft component width.

After refining the parametric width formula to, 2*(sqrt((c^2)-(a^2))+2*kerf), I had success creating an interference fit shaft for the roller bearings.

#2: There where several small sheets of 1/4in plywood that I used to create my model. After changing to a different sheet, I noticed the power necessary to cut through the sheet varied. I suspect this is because the plywood sheets I used had been sitting on the cement floor of my garage for quite some time and likely contained different levels of moisture depending on where it was in the stack. Using a different power effected the kerf of the laser and ultimately the fit of several components. To avoid this in the future I will ensure homogeneity of my material prior to using it for laser cutting.