Planetary Hex Key

Last Updated: 12/6/22

During one of my internships, I was fortunate enough to be able to observe laser alignment for optical systems that would later go into DNA sequencers. Most if not all of the adjustments were made with standard off-the-shelf hex keys. One complaint that the laser alignment technician expressed to me was that he was making micron-level adjustments with very coarse instruments. This lead to loss of efficiency and, more importantly, accuracy when it came to aligning the system. Seeing how this could be improved upon, I conceived of a geared-down hex key. This gearing down would essentially increase the torque of the system while reducing the angular travel of the out hex compared to the input shaft.

The design is currently optimized for 3D printing. The gearbox involves entirely custom designed gears and housing. I believe that the current design could certainly be shrunk in order to house an even smaller envelope if that was desired (and I can certainly see situations where it would be). But as it stands, I tried to design to a comfortable holding diameter. Moving forward, if I chose to work on this more, the next goal would be to create a housing for the gearbox. This would work twofold:

1) It would add more rigidity to the output hex as currently it is only mounted into the output gear. Having another point of contact to counteract cantilevering would be good

2) To provide a more ergonomic grip for the user

Information About Planetary Gearboxes:

Autodesk screenshot of the planetary gear assembly

I find planetary gearboxes very interesting because of there small profile and ease of stacking. This means that a very large gear ratio can be fit into a small envelope. The design is as follows:

1) Ring Gear. The outer ring of this gearbox design features gear teeth

2) Sun Gear. The centermost gear

3) Planetary Gears. These are the gears that surround and "orbit" the sun gear and lie between the sun gear and the ring gear

A very interesting fact about planetary gearboxes is that a singular gearbox can produce three different gear ratio based on which stage is held stationary. This is because the stage is held still becomes an idler gear, and the two gears that are allowed to spin (or move in the planetary gears' case) become the input and output of the gearbox.

Current Main Assembly:

Files:

I would suggest download all of the files from the Google Drive folder if you wish to view the files in Inventor. I also realize that these are Inventor files. I will work on creating a new folder with .STEP folders so that the hex key can be viewed across various CAD software. Hopefully while doing that I can also find the time to create some technical drawing files as well.

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