Omni wheel design (3D print)¶
Created the wheels based on the reference 3D model in thingiverse made by 3D printer. 3D print fabrication procedures are followed from the lesson of 3D scanning and printing week.
The 1st iteration’s problems are,
1. Plastic rollers on wheel was slippery, less grip.
2. Introduced 5x24 mm stainless pin as common commercial parts but not easy to purchase here.
The solutions are,
1. Solved by using heat shrinking tube for the rollers.
2. Purchased 5mm stainless rod of 1.5m in hardware house, then cut the piece of 24mm length by Machine workshop in Oulu University (located next to Fablab Oulu).
Applying the heat shrink tube rubber coating on the rollers, also problems were appeared.
- Roller hits the rim.
- Double roller structure, the gap of the rim and another rim became small, no margin.
To solve above problem, the original 3D model design files were modified with offset the faces and changed the roller mounting direction.
Below picture is the after the improvements. It can work as wheel with enough grip with rubber coating.
Compared with commercial 60mm Omni wheel. Big!
And the hub connecting the wheel into the stepper motor shaft, the first iteration made by Stratasys ABS material, but the hub cannot connect totally with the rim of wheel. FDM print made a bigger size than data, contacted faces needs more margins. Then the second iteration, the Hub was made by Form Lab Form3 by resin printing. This was produced with more precise scales, then nicely attached to the rim.
However, the Formlab’s resign printed hub had a problem after integration everything and run as a robot. Because of less rigid mechanically, easily shaking and made vibration into the wheel when the machine is running.
I made it again as the third iteration with proper margin and bigger size for contacted face with rim, this hub could assemble firmly and no vibration on the wheel when the machine is running.