We were all given the assignment of designing a 3D printed prop for an educator of our choice here at UNH Manchester. I chose my chemistry lab instructor, who asked for a model of DNA.
In Fusion 360, sketch a 100 x 40 center-point rectangle around the origin on one of the 3 original planes.
Fillet each edge with a fillet radius of 20, then extrude the shape 20 mm above the plane.
Fillet the top face of the figure with a constant radius of 10 mm.
On either of the two other planes not yet worked on, sketch a line from the midpoint of the top, filleted face of this figure and extend it straight up for 150 mm.
First, in a sketch on the flat top surface of the figure, sketch two lines each 30 mm from the origin, starting on the edge of the fillet and extending 12.5 mm on the surface, just over the midpoint. These lines should originate on opposite sides from each other on the surface. From the end point of each line on the surface, sketch a 13.5 x 6.5 center point rectangle, with the center point of each rectangle being the end point of the two lines previously sketched.
The next few steps make the double helix of the structure. I tried a few ways to do this myself but I couldn’t get the helices how I wanted them, so I watched a YouTube video to find an easy way to make them, which you can watch here. In the patch environment, select the two lines and use the sweep command to sweep them along a single path, the vertical line extending from the middle of the figure and adjust the twist angle to be 270°.
In the model environment, select the edge of each helix that originates from the center point of each rectangle, then under sketch select project / include and select include 3D geometry. Then, turn off the two bodies that were created in the previous step, which will leave the helices visible as just a line from the center point of the rectangle.
Sweep each rectangle along its center point helix using the path + guide rail sweep, selecting the rectangle as the profile, the helix as the path, and the center vertical line as the guide rail.
On both planes that were not originally worked on for the base, sketch a circle 9 mm in diameter with the center point being the intersection of the two helices. Extend two lines tangent to the center diameter of the circle so that the lines extend higher than the 3D helices, then close off the lines to make a face and extrude the face 32 mm in each direction cutting into the helices to make a slot for where the nucleobases will sit in the model.
On the work plane separate from the double helix structure, sketch a circle with a diameter of 8.5 and extrude 31.5 mm in each direction, creating two separate bodies that are cylinders of equal dimensions, one situated on top of the other.
When printing the nucleobases, you must use a 3D printer with dual extruders so that they can be printed in two different colors.
Slicer: Cura 3.0
Layer Height: 0.2mm
Infill Density: 20%
Nozzle Size: 0.4 mm
Files for this print can be found here.