This is an overview of how to design a wheel using 3DS Max, which I then printed out using an Objet 3D printer. While the buttons may be slightly different in other 3D software packages, the process for doing this should look roughly the same. Follows are step-by-step instructions for creating a 2-part wheel consisting of a hub and a tire. It may seem slightly complicated, but it is a surprisingly straight-forward operation.
I have also included a file for a pivot. If you insert a shaft through the wheel, you can use the pivots to mount it and make it spin. The wheel and pivots can be scaled to meet your needs.
Step 1: Circles
Make a small circle which will be the size of your inner hub.
Make a second larger circle which will indicate the outer boundary of your spokes.
Step 2: Duplicate
Duplicate the inner circle on top of itself, such that you have two.
Step 3: Make a Cut Out
Create an egg-shaped spline (without an outline).
Convert it to an editable spline by right-clicking on it's name in the modifer tab.
Select the red "points" button.
Modify the shape of the egg to your liking. This will be the negative space between the spokes.
Step 4: Change Pivot
Select the Hierarchy tab.
Click on "Affect Pivot Only"
Click the rotation tool, and then change the Z-rotate option to 0.
Unclick "Affect Pivot Only"
Step 5: Create an Array
Under the "Tools" drop-down menu, select "Array"
Change the Z-rotate to roughly 40. If the copies appear to be touching, increase this number
Finally, increase the number of copies until they go all the way around your wheel.
Step 6: Attach
Select the outer circle and then go to the Modifiers tab.
Right-click on the circle's name and make it an "Editable Spline"
Click the "Attach" button.
Next, click on all of the egg-shapes. As you click on them, they should change color.
Also, click on one of the inner, smaller, circles.
Step 7: Extrude
From the Modifiers list, now select "Extrude"
Set the amount of extrusion to be about a value of 1.
Step 8: Create the Inner Hub
Create a smaller circle than any you have created thus far and center it on the wheel.
Select this circle, right-click on it, and make it an editable spline.
Click the "Attach" button and then click on the slightly larger inner hub circle.
Finally, choose "Extrude" from the modifier list and set the height to a value of about 2.
Step 9: Center
Center the extruded hub in the middle of the extruded spokes.
Step 10: Rim
Create a Tube standard primitive shape that slightly overlaps the outer edge of the spokes. This will be the rim the tire sits upon.
Give this a height of 2 and center it upon the wheel.
Step 11: Tire
Finally, make another tube with a height of 2.5. This should slightly overlap the rim (This is ideal for an Objet printer. For other printers, overlap may not be).
Center the tire upon the wheel and your model should be just about done.
Step 12: Attach
The one last thing you will want to do is to select the tube you made for the rim, go the Modifiers tab, and select the "Editable Mesh" modifier.
Click the "attach" button, and then click upon the spokes and inner hub. The entire hub should now be joined as a single shape.
Select the tire and hub individually, and export each separately as an STL file.
Step 13: Pivots
I am not going to go over how I made pivots, but I have included them in the .max file for your printing enjoyment.
In short, I made them using similar techniques to how we made the wheel.
Step 14: Print
I printed out the wheel using an Objet Connex 500 printer.
I imported the two files as an assembly.
The hub was assigned DM_8250_Grey40, which is a larger plastic material. The tire was made DM_9885_Shore85, which is largely rubber.
I printed the optional pivots out of the "ABS-like" resin.