While working on the HL2 Turret project I made myself some tea. Heat up water, add tea bag, forget tea bag in said water, drink horribly bitter tea. After repeating this process several times I got a bit fed up and decided it was time to fire up the printer and solve this very /r/Britishproblem. Luckily I had some terrible 9g servos and an Arduino Pro Mini to use.
Not having a lot of time on my hands, I decided to limit the design process to only two hours. if it could be done, great, if not, drop the project. Granted, I gave myself one hour before that to think about how this tea steeper should look and work. The good news is, I managed in only 1.5 hours but some mistakes were made.
The red servo horn is designed with ‘tabs’ because I thought it would be a good idea to file the axle of the servo to get better torque transmission through the joint. Bad idea. There is no torque to speak of in this design. It’s a damn tea bag. I drilled out the holes and it’s just an interference fit with screws now. This way the initial position of the horn is also adjustable. Another thing is that I made a hole in the purple case for the servo cables to go through. Never thought about the connectors and they didn’t fit. I filed the hole bigger and eventually cut off the connectors because they wouldn’t fit in the case anyway. D’oh!
While the parts were printing I decided to get started on the software side. After 3.5 hours of trying and failing to correctly calculate the inverse kinematics I was already tired and decided to just used predefined angles for the home position, lifted position for tying the bag to the servo horn and the dunked position. There also is an intermediate position for repeatedly lifting and lowering the bag to get it to fill up and stay vertical.
Once the print was done I acetone welded all the parts together and thankfully it came out great.
Basically, when powered on, it waits for you to hang the tea bag on it, then dunks it three times then waits for three minutes and lifts the bag up to let it drip. Perfect tea every time!
All in all, I used only 8 hours for this project. Which isn’t too bad. Future improvements include an LED or RGB LED to indicate status or time remaining to brew, and inverse kinematics for the servo positioning.
If anyone is interested, I’ll publish the CAD files also (Fusion 360 and STLs), and maybe the sketch (although it’s not really well made).
Edit: Get the .Step file here.
Your Majesty, I am ready to be knighted!