Goal: To make a cool gadget for my last Maker Faire at high school.
Background: I found the plans and schematics for this little project on Instructables and it was just the kind of funky, “out there” kind of project I was looking for to make for my last Maker Faire at high school (since I’ll be graduating this Spring). It uses the 3D printed forearm parts from an entire human body robot. For this though, I’ll be following the Instructables and just making the forearm. Basically, flex sensors (resistors) on a glove detect a difference from 22k resistors and that is given a numerical value which the programmed arduino translates into specific servo movement. Each of the five servos have two fishing lines attached to it which move the fingers in a realistic motion. So by putting on a glove that has the flex sensors attached to it and bending my hand, the robotic hand will bend in the same way simultaneously. I thought this project would be especially cool because a lot of students can try it on and play around with it instead of just looking at it and moving on.
The first step was to put all of the .stl files on an SD card and print it all off on the school’s 3D printer, the Ultimaker 2. This was probably the longest step in the project, because there was a LOT of material that had to be printed. I didn’t take a tally of the total number of hours, but it probably totaled to over 300 hours of printing. It took over a month to get it all printed off because the printer is shared by the whole school.
The printer sometimes had a hard time printing everything right. Above is an example of one of the worst prints. Fortunately, after scraping and sanding all of that excess plastic away, these two parts were just fine.
Here is one of the cleaner prints.
Here are most of the printed parts. I took this picture later in the build, so you can see a partly completed hand in the right side.
I apologize for a lot of blurry pictures. I didn’t realize they were out of focus when I took these pictures! Here is the beginnings of the hand parts. You can see where the top four fingers will eventually attach. The thumb will later go on the right side where the rectangular indent is.
The hand starting to come together! I took a trip to the Home Depot the day before to get the bolts to attach these on. The Instructables gives bolt measurements in millimeters but I could not find any matching sizes at the Home Depot and the project was due in just over a week so I couldn’t order them from some far away factory. So I bought the closest measurements I could (in inches) and then used an angle grinder to chop them to the perfect size.
The finger parts are grouped by finger by the 3D printer, but unfortunately when I was cleaning/sanding down all of the parts they all got mismatched. So I spent a class period painstakingly matching and then taping each part with its respective place on each finger. I switched two of them but I later swapped them to their right places I was gluing them down.
I finally received the screws in the mail for the fingers! I quickly screwed and glued the fingers together.
It took about two class periods to screw them all on. If I were 100% focused I probably could have done it in one, but I was working on multiple projects at the same time.
Here is the completed forearm. This will later attach to the hand.
The servo bay. Only one servo is in place in this picture, but four more will go in this section of the forearm and be responsible for the movement of the fingers.
Now for the complicated part: the electronics. I put in the code for the arduino, attached the servos to the arduino, and then attached the flex sensors to the arduino. I did this all on 5/24/17, and when I tested the sensors I got no reaction from the servos. So I am still working on that, but I expect to be done for the Maker Faire next Tuesday.